- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Assert that interrupts are enabled in the trap handlers on x86 before
calling generic code to deliver signals.

Discussed with: bde
Tested by: pho
MFC after: 1 week

MFamd64: when printing the trap information, show the %esp value.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week

MFamd64: add machdep.uprintf_signal.

MFC after: 1 week

userret() already checks for td_locks when INVARIANTS is enabled, so
there is no need to check if Giant is acquired after it.

Reviewed by: kib
MFC after: 1 week

MFamd64 r238623:
Introduce curpcb magic variable.

Requested and reviewed by: bde
MFC after: 3 weeks

MFCamd64 r238598:
Provide siginfo.si_code for floating point errors when error occurs
using the SSE math processor.

MFC after: 3 weeks

Make machine check exception logging more readable. On newer Intel systems,
an uncorrected ECC error tends to fire on all CPUs in a package
simultaneously and the current printf hacks are not sufficient to make
the messages legible. Instead, use the existing mca_lock spinlock to
serialize calls to mca_log() and change the machine check code to panic
directly when an unrecoverable error is encoutered rather than falling
back to a trap_fatal() call in trap() (which adds nearly a screen-full of
logging messages that aren't useful for machine checks).

MFC after: 2 weeks

Add software PMC support.

New kernel events can be added at various location for sampling or counting.
This will for example allow easy system profiling whatever the processor is
with known tools like pmcstat(8).

Simultaneous usage of software PMC and hardware PMC is possible, for example
looking at the lock acquire failure, page fault while sampling on
instructions.

Sponsored by: NETASQ
MFC after: 1 month

Handle spurious page faults that may occur in no-fault sections of the
kernel.

When access restrictions are added to a page table entry, we flush the
corresponding virtual address mapping from the TLB. In contrast, when
access restrictions are removed from a page table entry, we do not
flush the virtual address mapping from the TLB. This is exactly as
recommended in AMD's documentation. In effect, when access
restrictions are removed from a page table entry, AMD's MMUs will
transparently refresh a stale TLB entry. In short, this saves us from
having to perform potentially costly TLB flushes. In contrast,
Intel's MMUs are allowed to generate a spurious page fault based upon
the stale TLB entry. Usually, such spurious page faults are handled
by vm_fault() without incident. However, when we are executing
no-fault sections of the kernel, we are not allowed to execute
vm_fault(). This change introduces special-case handling for spurious
page faults that occur in no-fault sections of the kernel.

In collaboration with: kib
Tested by: gibbs (an earlier version)

I would also like to acknowledge Hiroki Sato's assistance in
diagnosing this problem.

MFC after: 1 week

Simplify the error checking in one branch of trap_pfault() and update
the nearby comment.

Correct the style of two return statements in trap_pfault().

Merge a comment from amd64's trap_pfault().

MFamd64: Don't whine about interrupts being disabled for an NMI.

Attempt to improve formatting and content of several comments for
amd64 and i386 MD code.

Based on suggestions by: bde
MFC after: 1 week

Fix the DTrace pid return trap interrupt vector. Previously we were using
31, but that vector is reserved.

Without this fix, running dtrace -p <pid> would either cause the target
process to crash or the kernel to page fault.

Obtained from: rpaulo
MFC after: 3days

Revert rev. 226893: subr_syscall.c is being included from C files and
on amd64 with FREEBSD32 enabled, this means that systrace_probe_func
gets defined twice.

Define systrace_probe_func in subr_syscall.c where it's used, instead
of defining it in MD code. This eliminates porting to other architectures.

Do not allow the kernel to access usermode pages without installed
fault handler. Panic immediately in such situation, on i386 and amd64.

Reviewed by: avg, jhb
MFC after: 1 week

In order to maximize the re-usability of kernel code in user space this
patch modifies makesyscalls.sh to prefix all of the non-compatibility
calls (e.g. not linux_, freebsd32_) with sys_ and updates the kernel
entry points and all places in the code that use them. It also
fixes an additional name space collision between the kernel function
psignal and the libc function of the same name by renaming the kernel
psignal kern_psignal(). By introducing this change now we will ease future
MFCs that change syscalls.

Reviewed by: rwatson
Approved by: re (bz)

Inline the syscallenter() and syscallret(). This reduces the time measured
by the syscall entry speed microbenchmarks by ~10% on amd64.

Submitted by: jhb
Approved by: re (bz)
MFC after: 2 weeks

Add tunables that mirror the functionality of sysctls machdep.panic_on_nmi
and machdep.kdb_on_nmi.

Approved by: emaste (mentor)
MFC after: 1 week

Fix typos - remove duplicate "the".

PR: bin/154928
Submitted by: Eitan Adler <lists at eitanadler.com>
MFC after: 3 days

To avoid excessive code duplication create wrapper for fill regs
from stack frame. Change the trap() code to use newly created function
instead of explicit regs assignment.

Do not use __FreeBSD_version prefix for the special osrel version.
The ports/Mk/bsd.port.mk uses sys/param.h to fetch osrel, and cannot
grok several constants with the prefix.

Reported and tested by: swell.k gmail com
MFC after: 1 week

Use symbolic names instead of hardcoding values for magic p_osrel constants.

MFC after: 1 week

Move the <machine/mca.h> header to <x86/mca.h>.

Sync DTrace bits with amd64 and fix the build.

Sponsored by: The FreeBSD Foundation

Call the necessary DTrace function pointers when we have different kinds
of traps.

Sponsored by: The FreeBSD Foundation

Remove unused KTRACE includes.

Introduce the x86 kernel interfaces to allow kernel code to use
FPU/SSE hardware. Caller should provide a save area that is chained
into the stack of the areas; pcb save_area for usermode FPU state is
on top. The pcb now contains a pointer to the current FPU saved area,
used during FPUDNA handling and context switches. There is also a
facility to allow the kernel thread to use pcb save_area.

Change the dreaded warnings "npxdna in kernel mode!" into the panics
when FPU usage is not registered.

KPI discussed with: fabient
Tested by: pho, fabient
Hardware provided by: Sentex Communications
MFC after: 1 month

Reorganize syscall entry and leave handling.

Extend struct sysvec with three new elements:
sv_fetch_syscall_args - the method to fetch syscall arguments from
usermode into struct syscall_args. The structure is machine-depended
(this might be reconsidered after all architectures are converted).
sv_set_syscall_retval - the method to set a return value for usermode
from the syscall. It is a generalization of
cpu_set_syscall_retval(9) to allow ABIs to override the way to set a
return value.
sv_syscallnames - the table of syscall names.

Use sv_set_syscall_retval in kern_sigsuspend() instead of hardcoding
the call to cpu_set_syscall_retval().

The new functions syscallenter(9) and syscallret(9) are provided that
use sv_*syscall* pointers and contain the common repeated code from
the syscall() implementations for the architecture-specific syscall
trap handlers.

Syscallenter() fetches arguments, calls syscall implementation from
ABI sysent table, and set up return frame. The end of syscall
bookkeeping is done by syscallret().

Take advantage of single place for MI syscall handling code and
implement ptrace_lwpinfo pl_flags PL_FLAG_SCE, PL_FLAG_SCX and
PL_FLAG_EXEC. The SCE and SCX flags notify the debugger that the
thread is stopped at syscall entry or return point respectively. The
EXEC flag augments SCX and notifies debugger that the process address
space was changed by one of exec(2)-family syscalls.

The i386, amd64, sparc64, sun4v, powerpc and ia64 syscall()s are
changed to use syscallenter()/syscallret(). MIPS and arm are not
converted and use the mostly unchanged syscall() implementation.

Reviewed by: jhb, marcel, marius, nwhitehorn, stas
Tested by: marcel (ia64), marius (sparc64), nwhitehorn (powerpc),
stas (mips)
MFC after: 1 month

Change printf() calls to uprintf() for sigreturn() and trap() complaints
about inacessible or wrong mcontext, and for dreaded "kernel trap with
interrupts disabled" situation. The later is changed when trap is
generated from user mode (shall never be ?).

Normalize the messages to include both pid and thread name.

MFC after: 1 week

Merge r197455 from amd64:

Add a backtrace to the "fpudna in kernel mode!" case, to help track down
where this comes from.

Reviewed by: bde

For PT_TO_SCE stop that stops the ptraced process upon syscall entry,
syscall arguments are collected before ptracestop() is called. As a
consequence, debugger cannot modify syscall or its arguments.

For i386, amd64 and ia32 on amd64 MD syscall(), reread syscall number
and arguments after ptracestop(), if debugger modified anything in the
process environment. Since procfs stopeven requires number of syscall
arguments in p_xstat, this cannot be solved by moving stop/trace point
before argument fetching.

Move the code to read arguments into separate function
fetch_syscall_args() to avoid code duplication. Note that ktrace point
for modified syscall is intentionally recorded twice, once with original
arguments, and second time with the arguments set by debugger.

PT_TO_SCX stop is executed after cpu_syscall_set_retval() already.

Reported by: Ali Polatel <alip exherbo org>
Briefly discussed with: jhb
MFC after: 3 weeks

Simplify the invocation of vm_fault(). Specifically, eliminate the flag
VM_FAULT_DIRTY. The information provided by this flag can be trivially
inferred by vm_fault().

Discussed with: kib

Extract the code that records syscall results in the frame into MD
function cpu_set_syscall_retval().

Suggested by: marcel
Reviewed by: marcel, davidxu
PowerPC, ARM, ia64 changes: marcel
Sparc64 tested and reviewed by: marius, also sunv reviewed
MIPS tested by: gonzo
MFC after: 1 month

If CPU happens to be in usermode when a T_RESERVED trap occured,
then trapsignal is called with ksi.ksi_signo = 0. For debugging kernels,
that should end up in panic, for non-debugging kernels behaviour is
undefined.

Do panic regardeless of execution mode at the moment of trap.

Reviewed by: jhb
MFC after: 1 month

Fix handling of .note.ABI-tag section for GNU systems [1].
Handle GNU/Linux according to LSB Core Specification 4.0,
Chapter 11. Object Format, 11.8. ABI note tag.

Also check the first word of desc, not only name, according to
glibc abi-tags specification to distinguish between Linux and
kFreeBSD.

Add explicit handling for Debian GNU/kFreeBSD, which runs
on our kernels as well [2].

In {amd64,i386}/trap.c, when checking osrel of the current process,
also check the ABI to not change the signal behaviour for Linux
binary processes, now that we save an osrel version for all three
from the lists above in struct proc [2].

These changes make it possible to run FreeBSD, Debian GNU/kFreeBSD
and Linux binaries on the same machine again for at least i386 and
amd64, and no longer break kFreeBSD which was detected as GNU(/Linux).

PR: kern/135468
Submitted by: dchagin [1] (initial patch)
Suggested by: kib [2]
Tested by: Petr Salinger (Petr.Salinger seznam.cz) for kFreeBSD
Reviewed by: kib
MFC after: 3 days

* Completely Remove the option STOP_NMI from the kernel. This option
has proven to have a good effect when entering KDB by using a NMI,
but it completely violates all the good rules about interrupts
disabled while holding a spinlock in other occasions. This can be the
cause of deadlocks on events where a normal IPI_STOP is expected.
* Adds an new IPI called IPI_STOP_HARD on all the supported architectures.
This IPI is responsible for sending a stop message among CPUs using a
privileged channel when disponible. In other cases it just does match a
normal IPI_STOP.
Right now the IPI_STOP_HARD functionality uses a NMI on ia32 and amd64
architectures, while on the other has a normal IPI_STOP effect. It is
responsibility of maintainers to eventually implement an hard stop
when necessary and possible.
* Use the new IPI facility in order to implement a new userend SMP kernel
function called stop_cpus_hard(). That is specular to stop_cpu() but
it does use the privileged channel for the stopping facility.
* Let KDB use the newly introduced function stop_cpus_hard() and leave
stop_cpus() for all the other cases
* Disable interrupts on CPU0 when starting the process of APs suspension.
* Style cleanup and comments adding

This patch should fix the reboot/shutdown deadlocks many users are
constantly reporting on mailing lists.

Please don't forget to update your config file with the STOP_NMI
option removal

Reviewed by: jhb
Tested by: pho, bz, rink
Approved by: re (kib)

Implement simple machine check support for amd64 and i386.
- For CPUs that only support MCE (the machine check exception) but not MCA
(i.e. Pentium), all this does is print out the value of the machine check
registers and then panic when a machine check exception occurs.
- For CPUs that support MCA (the machine check architecture), the support is
a bit more involved.
- First, there is limited support for decoding the CPU-independent MCA
error codes in the kernel, and the kernel uses this to output a short
description of any machine check events that occur.
- When a machine check exception occurs, all of the MCx banks on the
current CPU are scanned and any events are reported to the console
before panic'ing.
- To catch events for correctable errors, a periodic timer kicks off a
task which scans the MCx banks on all CPUs. The frequency of these
checks is controlled via the "hw.mca.interval" sysctl.
- Userland can request an immediate scan of the MCx banks by writing
a non-zero value to "hw.mca.force_scan".
- If any correctable events are encountered, the appropriate details
are stored in a 'struct mca_record' (defined in <machine/mca.h>).
The "hw.mca.count" is a count of such records and each record may
be queried via the "hw.mca.records" tree by specifying the record
index (0 .. count - 1) as the next name in the MIB similar to using
PIDs with the kern.proc.* sysctls. The idea is to export machine
check events to userland for more detailed processing.
- The periodic timer and hw.mca sysctls are only present if the CPU
supports MCA.

Discussed with: emaste (briefly)
MFC after: 1 month

Trim comments about the MP-safety of various bits of the amd64/i386
system call entry path and i386 IP checksum generation: we now assume
all code is MPSAFE unless explicitly marked otherwise. Remove XXX
Giant comments along similar lines: the code by the comments either
doesn't need or doesn't want Giant (especially the NMI handler).

MFC after: 3 days

remove gratuitous XEN define

GC gratuitous XEN defines

Integrate support for xen in to i386 common code.

MFC after: 1 month

In the case of POWERFAIL_NMI, remove the Giant acquisitions because they
can lead to a deadlock if the thread owning the Giant lock is interrupted
by the NMI.
Instead, tollerate a small race on the x86 architecture.

Add the DTrace hooks for exception handling (Function boundary trace
-fbt- provider), cyclic clock and syscalls.

The "free-lance" timer in the i8254 is only used for the speaker
these days, so de-generalize the acquire_timer/release_timer api
to just deal with speakers.

The new (optional) MD functions are:
timer_spkr_acquire()
timer_spkr_release()
and
timer_spkr_setfreq()

the last of which configures the timer to generate a tone of a given
frequency, in Hz instead of 1/1193182th of seconds.

Drop entirely timer2 on pc98, it is not used anywhere at all.

Move sysbeep() to kern/tty_cons.c and use the timer_spkr*() if
they exist, and do nothing otherwise.

Remove prototypes and empty acquire-/release-timer() and sysbeep()
functions from the non-beeping archs.

This eliminate the need for the speaker driver to know about
i8254frequency at all. In theory this makes the speaker driver MI,
contingent on the timer_spkr_*() functions existing but the driver
does not know this yet and still attaches to the ISA bus.

Syscons is more tricky, in one function, sc_tone(), it knows the hz
and things are just fine.

In the other function, sc_bell() it seems to get the period from
the KDMKTONE ioctl in terms if 1/1193182th second, so we hardcode
the 1193182 and leave it at that. It's probably not important.

Change a few other sysbeep() uses which obviously knew that the
argument was in terms of i8254 frequency, and leave alone those
that look like people thought sysbeep() took frequency in hertz.

This eliminates the knowledge of i8254_freq from all but the actual
clock.c code and the prof_machdep.c on amd64 and i386, where I think
it would be smart to ask for help from the timecounters anyway [TBD].

Remove kernel support for M:N threading.

While the KSE project was quite successful in bringing threading to
FreeBSD, the M:N approach taken by the kse library was never developed
to its full potential. Backwards compatibility will be provided via
libmap.conf for dynamically linked binaries and static binaries will
be broken.

Kernel and hwpmc(4) support for callchain capture.

Sponsored by: FreeBSD Foundation and Google Inc.

Fix the ABI change of the signal delivered on the access to the page
with insufficient protection mode.

For the i386 and amd64, create the tunable, machdep.prot_fault_translation,
with the following behaviour:
0 = autodetect the signal to be delivered on KERN_PROTECTION_FAILURE
from vm_fault based on the ELF OSABI note:
no note or __FreeBSD_version < 700004 - SIGBUS/BUS_PAGE_FAULT
note, and __FreeBSD_version >= 700004 - SIGSEGV/SEGV_ACCERR
1 = always SIGBUS/BUS_PAGE_FAULT
2 = always SIGSEGV/SEGV_ACCERR

This would do mostly automatic correction of ABI breakage, with the exception
of the untaged binaries for 7-CURRENT/RELENG_7 before the note is fixed. For
them, sysctl would allow to run the binary with manual settings.

Discussed with: portmgr (kris)
PR: kern/118304
MFC after: 3 days

A bunch more files that should probably print out a thread name
instead of a process name.

generally we are interested in what thread did something as
opposed to what process. Since threads by default have teh name of the
process unless over-written with more useful information, just print the
thread name instead.

If the trap number stored in the trapframe is corrupted into a negative
value, then we would use a negative index into the trap_msg[] array
resulting in a nested page fault. Make the 'type' variable holding the
trap number unsigned to avoid this.

MFC after: 2 weeks
Approved by: re (rwatson)

Don't clobber tf_err with the eva from a page fault as the page fault
address is saved in ksi_addr already.

PR: i386/101379
Submitted by: Tijl Coosemans : tijl ulyssis org

Optimize vmmeter locking.
In particular:
- Add an explicative table for locking of struct vmmeter members
- Apply new rules for some of those members
- Remove some unuseful comments

Heavily reviewed by: alc, bde, jeff
Approved by: jeff (mentor)

Rework the PCPU_* (MD) interface:
- Rename PCPU_LAZY_INC into PCPU_INC
- Add the PCPU_ADD interface which just does an add on the pcpu member
given a specific value.

Note that for most architectures PCPU_INC and PCPU_ADD are not safe.
This is a point that needs some discussions/work in the next days.

Reviewed by: alc, bde
Approved by: jeff (mentor)

Remove "XXX Giant" comments before calls to kdb_trap() -- the kernel
debugger is quite capable of handling Giant-free execution at this
point. Several other similar comments remain in trap.c on both i386
and amd64 awaiting analysis.

Don't check curproc->p_comm for NULL as it is an array allocated as part of
struct proc.

Found with: Coverity Prevent(tm)
CID: 2096

Add the PG_NX support for i386/PAE.

Reviewed by: alc

Remove unnecessary giant acquisition around panic in #ifdef DIAGNOSTIC
code.

# There is some question about whether this code is even relevant any
# longer (it dates back to prehistoric times, i.e. present in r1.1),
# especially on amd64.

Reviewed by: jhb

Over NFS, an open() call could result in multiple over-the-wire
GETATTRs being generated - one from lookup()/namei() and the other
from nfs_open() (for cto consistency). This change eliminates the
GETATTR in nfs_open() if an otw GETATTR was done from the namei()
path. Instead of extending the vop interface, we timestamp each attr
load, and use this to detect whether a GETATTR was done from namei()
for this syscall. Introduces a thread-local variable that counts the
syscalls made by the thread and uses <pid, tid, thread syscalls> as
the attrload timestamp. Thanks to jhb@ and peter@ for a discussion on
thread state that could be used as the timestamp with minimal overhead.

Evidently FreeBSD has long relied on the compiler to treat structures
passed by value (trap frames) as if they were in fact being passed by
reference. For better or worse, this incorrect behaviour is no longer
present in gcc 4.1. In this patch I convert all trapframe arguments to
be explicitly pass by reference. I also remove vm86_initflags, pushing
the very little work that it actually does up into vm86_prepcall.

Reviewed by: kan
Tested by: kan

Make KSE a kernel option, turned on by default in all GENERIC
kernel configs except sun4v (which doesn't process signals properly
with KSE).

Reviewed by: davidxu@

Eliminate an unnecessary initialization from trap_pfault() that also
happens to contain a style error.

Retire SYF_ARGMASK and remove both SYF_MPSAFE and SYF_ARGMASK. sy_narg is
now back to just being an argument count.

Now that all system calls are MPSAFE, retire the SYF_MPSAFE flag used to
mark system calls as being MPSAFE:
- Stop conditionally acquiring Giant around system call invocations.
- Remove all of the 'M' prefixes from the master system call files.
- Remove support for the 'M' prefix from the script that generates the
syscall-related files from the master system call files.
- Don't explicitly set SYF_MPSAFE when registering nfssvc.

Unify the checking for lock misbehavior in the various syscall()
implementations and adjust some of the checks while I'm here:
- Add a new check to make sure we don't return from a syscall in a critical
section.
- Add a new explicit check before userret() to make sure we don't return
with any locks held. The advantage here is that we can include the
syscall number and name in syscall() whereas that info is not available
in userret().
- Drop the mtx_assert()'s of sched_lock and Giant. They are replaced by
the more general checks just added.

MFC after: 2 weeks

We no longer need to disable interrupts in MD trap machinery
when we're about to call kdb_trap() because the latter MI
function can disable interrupts by itself now.

Pointed out by: bde
X-MFC remark: depends on kern/subr_kdb.c#1.18
Sponsored by: RiNet (Cronyx Plus LLC)

Fix style while I'm here.

The i386 "call" instruction works as follows: it pushes
the return address on the stack and only then "dereferences" %pc.
Therefore, in the case of a call to an invalid address, we arrive
to the trap handler with the invalid value in tf_eip. This used
to prevent db_backtrace() from assigning the most recent and interesting
frame on the stack to the right spot in the right function, from
which the invalid call was attempted.

Try to detect and work around that by recovering the return address
from the stack.

The work-around requires the fault address be passed to db_backtrace().
Smuggle it as tf_err.

MFC after: 1 month
Sponsored by: RiNet (Cronyx Plus LLC)

Simplify system time accounting for profiling.

Rename struct thread's td_sticks to td_pticks, we will need the
other name for more appropriately named use shortly. Reduce it
from uint64_t to u_int.

Clear td_pticks whenever we enter the kernel instead of recording
its value as reference for userret(). Use the absolute value of
td->pticks in userret() and eliminate third argument.

Hook up the audit system to system call entry and exit. System calls will
now be audited.

Obtained from: TrustedBSD Project
Approved by: rwatson (mentor)

Call WITNESS_CHECK() in the page fault handler and immediately assume it
is a fatal fault if we are holding any non-sleepable locks. This should
cut down on the number of bogus LORs we currently get when the kernel
panics due to a NULL (or bogus) pointer dereference that goes wandering
off into the VM system which tries to acquire locks and then kicks off
the spurious LORs. This should probably be ported to all the archs at
some point.

Tested on: i386

Fix various places that were testing td_critnest to see if interrupts
should remain disabled during a trap or not to check
td_md.md_spinlock_count instead.

- Always print the trap number so that we have something to start with for
mystery traps. If we don't have a message for a given trap, just use
UNKNOWN for the message.
- Add trap messages for T_XMMFLT and T_RESERVED.

MFC after: 1 week

Unbreak !SMP kernels

Rename the KDB_STOP_NMI kernel option to STOP_NMI and make it apply to all
IPI_STOP IPIs.
- Change the i386 and amd64 MD IPI code to send an NMI if STOP_NMI is
enabled if an attempt is made to send an IPI_STOP IPI. If the kernel
option is enabled, there is also a sysctl to change the behavior at
runtime (debug.stop_cpus_with_nmi which defaults to enabled). This
includes removing stop_cpus_nmi() and making ipi_nmi_selected() a
private function for i386 and amd64.
- Fix ipi_all(), ipi_all_but_self(), and ipi_self() on i386 and amd64 to
properly handle bitmapped IPIs as well as IPI_STOP IPIs when STOP_NMI is
enabled.
- Fix ipi_nmi_handler() to execute the restart function on the first CPU
that is restarted making use of atomic_readandclear() rather than
assuming that the BSP is always included in the set of restarted CPUs.
Also, the NMI handler didn't clear the function pointer meaning that
subsequent stop and restarts could execute the function again.
- Define a new macro HAVE_STOPPEDPCBS on i386 and amd64 to control the use
of stoppedpcbs[] and always enable it for i386 and amd64 instead of
being dependent on KDB_STOP_NMI. It works fine in both the NMI and
non-NMI cases.

1. Change prototype of trapsignal and sendsig to use ksiginfo_t *, most
changes in MD code are trivial, before this change, trapsignal and
sendsig use discrete parameters, now they uses member fields of
ksiginfo_t structure. For sendsig, this change allows us to pass
POSIX realtime signal value to user code.

2. Remove cpu_thread_siginfo, it is no longer needed because we now always
generate ksiginfo_t data and feed it to libpthread.

3. Add p_sigqueue to proc structure to hold shared signals which were
blocked by all threads in the proc.

4. Add td_sigqueue to thread structure to hold all signals delivered to
thread.

5. i386 and amd64 now return POSIX standard si_code, other arches will
be fixed.

6. In this sigqueue implementation, pending signal set is kept as before,
an extra siginfo list holds additional siginfo_t data for signals.
kernel code uses psignal() still behavior as before, it won't be failed
even under memory pressure, only exception is when deleting a signal,
we should call sigqueue_delete to remove signal from sigqueue but
not SIGDELSET. Current there is no kernel code will deliver a signal
with additional data, so kernel should be as stable as before,
a ksiginfo can carry more information, for example, allow signal to
be delivered but throw away siginfo data if memory is not enough.
SIGKILL and SIGSTOP have fast path in sigqueue_add, because they can
not be caught or masked.
The sigqueue() syscall allows user code to queue a signal to target
process, if resource is unavailable, EAGAIN will be returned as
specification said.
Just before thread exits, signal queue memory will be freed by
sigqueue_flush.
Current, all signals are allowed to be queued, not only realtime signals.

Earlier patch reviewed by: jhb, deischen
Tested on: i386, amd64

Big polling(4) cleanup.

o Axe poll in trap.

o Axe IFF_POLLING flag from if_flags.

o Rework revision 1.21 (Giant removal), in such a way that
poll_mtx is not dropped during call to polling handler.
This fixes problem with idle polling.

o Make registration and deregistration from polling in a
functional way, insted of next tick/interrupt.

o Obsolete kern.polling.enable. Polling is turned on/off
with ifconfig.

Detailed kern_poll.c changes:
- Remove polling handler flags, introduced in 1.21. The are not
needed now.
- Forget and do not check if_flags, if_capenable and if_drv_flags.
- Call all registered polling handlers unconditionally.
- Do not drop poll_mtx, when entering polling handlers.
- In ether_poll() NET_LOCK_GIANT prior to locking poll_mtx.
- In netisr_poll() axe the block, where polling code asks drivers
to unregister.
- In netisr_poll() and ether_poll() do polling always, if any
handlers are present.
- In ether_poll_[de]register() remove a lot of error hiding code. Assert
that arguments are correct, instead.
- In ether_poll_[de]register() use standard return values in case of
error or success.
- Introduce poll_switch() that is a sysctl handler for kern.polling.enable.
poll_switch() goes through interface list and enabled/disables polling.
A message that kern.polling.enable is deprecated is printed.

Detailed driver changes:
- On attach driver announces IFCAP_POLLING in if_capabilities, but
not in if_capenable.
- On detach driver calls ether_poll_deregister() if polling is enabled.
- In polling handler driver obtains its lock and checks IFF_DRV_RUNNING
flag. If there is no, then unlocks and returns.
- In ioctl handler driver checks for IFCAP_POLLING flag requested to
be set or cleared. Driver first calls ether_poll_[de]register(), then
obtains driver lock and [dis/en]ables interrupts.
- In interrupt handler driver checks IFCAP_POLLING flag in if_capenable.
If present, then returns.This is important to protect from spurious
interrupts.

Reviewed by: ru, sam, jhb

Back out alpha/alpha/trap.c:1.124, osf1_ioctl.c:1.14, osf1_misc.c:1.57,
osf1_signal.c:1.41, amd64/amd64/trap.c:1.291, linux_socket.c:1.60,
svr4_fcntl.c:1.36, svr4_ioctl.c:1.23, svr4_ipc.c:1.18, svr4_misc.c:1.81,
svr4_signal.c:1.34, svr4_stat.c:1.21, svr4_stream.c:1.55,
svr4_termios.c:1.13, svr4_ttold.c:1.15, svr4_util.h:1.10,
ext2_alloc.c:1.43, i386/i386/trap.c:1.279, vm86.c:1.58,
unaligned.c:1.12, imgact_elf.c:1.164, ffs_alloc.c:1.133:

Now that Giant is acquired in uprintf() and tprintf(), the caller no
longer leads to acquire Giant unless it also holds another mutex that
would generate a lock order reversal when calling into these functions.
Specifically not backed out is the acquisition of Giant in nfs_socket.c
and rpcclnt.c, where local mutexes are held and would otherwise violate
the lock order with Giant.

This aligns this code more with the eventual locking of ttys.

Suggested by: bde

Add GIANT_REQUIRED and WITNESS sleep warnings to uprintf() and tprintf(),
as they both interact with the tty code (!MPSAFE) and may sleep if the
tty buffer is full (per comment).

Modify all consumers of uprintf() and tprintf() to hold Giant around
calls into these functions. In most cases, this means adding an
acquisition of Giant immediately around the function. In some cases
(nfs_timer()), it means acquiring Giant higher up in the callout.

With these changes, UFS no longer panics on SMP when either blocks are
exhausted or inodes are exhausted under load due to races in the tty
code when running without Giant.

NB: Some reduction in calls to uprintf() in the svr4 code is probably
desirable.

NB: In the case of nfs_timer(), calling uprintf() while holding a mutex,
or even in a callout at all, is a bad idea, and will generate warnings
and potential upset. This needs to be fixed, but was a problem before
this change.

NB: uprintf()/tprintf() sleeping is generally a bad ideas, as is having
non-MPSAFE tty code.

MFC after: 1 week

Use an interrupt gate for the NMI handler and prevent too-early
enabling of interrupts inside of trap(). Fix a typo in a comment.

Revert rev 1.113 of "sys/i386/i386/exception.s" as it is no longer
needed.

Reviewed by: bde
MFC after: 3 days

Move the KDB_STOP_NMI option from opt_global.h to opt_kdb.h

Approved by: re

Disable the interrupts in trap_fatal before calling kdb_trap.
(required now that critical sections no longer block interrupts)

Reviewed by: jhb@
Approved by: re (scottl)
Tested by: kris@,glebius@

Move HWPMC_HOOKS into its own opt_hwpmc_hooks.h file. It doesn't merit
being in opt_global.h and forcing a global recompile when only a few files
reference it.

Approved by: re

Kernel hooks to support PMC sampling modes.

Reviewed by: alc

Implement an alternate method to stop CPUs when entering DDB. Normally we use
a regular IPI vector, but this vector is blocked when interrupts are disabled.
With "options KDB_STOP_NMI" and debug.kdb.stop_cpus_with_nmi set, KDB will
send an NMI to each CPU instead. The code also has a context-stuffing
feature which helps ddb extract the state of processes running on the
stopped CPUs.

KDB_STOP_NMI is only useful with SMP and complains if SMP is not defined.
This feature only applies to i386 and amd64 at the moment, but could be
used on other architectures with the appropriate MD bits.

Submitted by: ups

Don't enter the debugger if KDB_UNATTENDED is set or if
debug.debugger_on_panic=0.

MFC after: 2 weeks

Use PCPU_LAZY_INC() for cnt.v_{intr,trap,syscalls} rather than atomic
operations in some places and simple non-per CPU math in others.

Initiate deorbit burn sequence for 80386 support in FreeBSD: Remove
80386 (I386_CPU) support from the kernel.

Remove an unneeded argument..
The removed argument could trivially be derived from the remaining one.
That in turn should be the same as curthread, but it is possible that curthread could be expensive to derive on some syste,s so leave it as an argument.
Having both proc and thread as an argumen tjust gives an opportunity for
them to get out sync.

MFC after: 3 days

Remove sched_free_thread() which was only used
in diagnostics. It has outlived its usefulness and has started
causing panics for people who turn on DIAGNOSTIC, in what is otherwise
good code.

MFC after: 2 days

Generate KTR trace records for syscall enter and exit in i386 system
calls. Note that the information included is a bit different from the
existing KTR traces generated on powerpc, as I'm primarily interested
in kernel context (thread, syscall #, proc, etc), not the user
arguments to the system call. Some convergence would be useful here.

Update for the KDB framework:
o s/ddb_on_nmi/kdb_on_nmi/g
o Rename sysctl machdep.ddb_on_nmi to machdep.kdb_on_nmi
o Make debugging support conditional upon KDB instead of DDB.
o Call kdb_reenter() when kdb_active is non-zero.
o Call kdb_trap() to enter the debugger when not already active.
o Update comments accordingly.
o Remove misplaced prototype of kdb_trap().

Move TDF_SA from td_flags to td_pflags (and rename it accordingly)
so that it is no longer necessary to hold sched_lock while
manipulating it.

Reviewed by: davidxu

Remove stale or broken call to kdb_trap() and protected by the non-
option KDB. Besides being wrong, it also interferes with ongoing
work.

Removed bogus checks that (PCPU_GET(curpcb) != NULL). Rev.1.586 of
machdep.c fixed the missing early initialization of curpcb, so curpcb
is now always set together with curthread and it cannot be NULL except
before the IDT has been set up (so trap() is unreachable) or after a
memory error. In any case, it was often used without checking.

curcpb shouldn't exist anyway. It doesn't exist for most non-i386 arches.
It just caches curthread->td_pcb in a global. This was a better idea
before it was per-cpu. trap() and some other places can get at it more
efficiently using td->td_pcb instead of PCPU_GET(curpcb). The main
exception is support.s which mostly wants only curpcb->pcb_onfault.

Remove process lock XXX's, fixed in src/sys/sys/proc.h:1.366.

Stick two XXX's in the syscall() code: we call STOPEVENT() twice for
every system call, and that grabs and release the process lock each
time. Don't fix it (yet), but document it so we know to fix it.
Also should be a 5.3-RELEASE todo item.

New APIC support code:

- The apic interrupt entry points have been rewritten so that each entry
point can serve 32 different vectors. When the entry is executed, it
uses one of the 32-bit ISR registers to determine which vector in its
assigned range was triggered. Thus, the apic code can support 159
different interrupt vectors with only 5 entry points.
- We now always to disable the local APIC to work around an errata in
certain PPros and then re-enable it again if we decide to use the APICs
to route interrupts.
- We no longer map IO APICs or local APICs using special page table
entries. Instead, we just use pmap_mapdev(). We also no longer
export the virtual address of the local APIC as a global symbol to
the rest of the system, but only in local_apic.c. To aid this, the
APIC ID of each CPU is exported as a per-CPU variable.
- Interrupt sources are provided for each intpin on each IO APIC.
Currently, each source is given a unique interrupt vector meaning that
PCI interrupts are not shared on most machines with an I/O APIC.
That mapping for interrupt sources to interrupt vectors is up to the
APIC enumerator driver however.
- We no longer probe to see if we need to use mixed mode to route IRQ 0,
instead we always use mixed mode to route IRQ 0 for now. This can be
disabled via the 'NO_MIXED_MODE' kernel option.
- The npx(4) driver now always probes to see if a built-in FPU is present
since this test can now be performed with the new APIC code. However,
an SMP kernel will panic if there is more than one CPU and a built-in
FPU is not found.
- PCI interrupts are now properly routed when using APICs to route
interrupts, so remove the hack to psuedo-route interrupts when the
intpin register was read.
- The apic.h header was moved to apicreg.h and a new apicvar.h header
that declares the APIs used by the new APIC code was added.

Try to fetch thread mailbox address in page fault trap, so when thread
blocks in page fault hanlder, and upcall thread can be scheduled. It is
useful if process is doing lots of mmap based I/O.

Implement preliminary support for the PT_SYSCALL command to ptrace(2).

Don't forget to reenable interrupts after a breakpoint and trace traps from
user mode. This goes with rev.1.468 of machdep.c which changed the gates
for these traps to interrupt gates. Having the interrupts disabled for
these traps from user mode is just an unwanted side effect.

This fixes at least 1 case of "panic: absolutely cannot call
smp_ipi_shootdown with interrupts already disabled". Too much code was
run with interrupts disabled, and it sometimes hit a sanity check.

Fix verified by: deischen

- Remove redundant <sys/sysctl.h> include.
- Move the <machine/vm86.h> include up to the other <machine/*> includes.

Initiate de-orbit burn for fpu-less operation. 386+387 is still
theoretically supportable, but you'd really be happier with FreeBSD 2.1.8
on it.

Rename P_THREADED to P_SA. P_SA means a process is using scheduler
activations.

Use __FBSDID().

The per-CPU spinlocks list is only maintained when WITNESS is enabled.
Thus, treat all page faults while in a critical section as fatal rather
than just those that occur with a non-empty spinlocks list. All such page
faults are fatal anyways. Calling trap_fatal() earlier increases the
chances of getting more useful panic messages and a possible DDB prompt.

Approved by: re (scottl)

Range check the syscall number before looking it up in the syscallnames[]
array.

Submitted by: pho

Don't print anything for fault at cpu_switch_load_gs, just like other
code to recover fault in doreti because of invalid segment registers,
silently push error to userland.

Move down intr level testing code a bit, cpu_switch_load_gs fault can be at
interrupt nested time.

Fix some problems for cpu_switch_load_gs. when fault address is at
cpu_switch_load_gs, cpu is in context switch, so don't enable interrupt.
because it is in context switch, it is expected sched_lock was held,
so don't PROC_LOCK(p) and psignal, it is LOR, probably we can
set a P_XSIGBUS like flag in p_sflags, and set TDF_ASTPENDING in
td_flags, in ast(), post a SIGBUS to process if P_XSIGBUS was set.

Remove single threading detecting code, these code really should be
replaced by thread_user_enter(), but current we don't want to enable
this in trap.

Use the proc lock to protect p_singlethread and a P_WEXIT test. This
fixes a couple of potential KSE panics on non-i386 arch's that weren't
holding the proc lock when calling thread_exit().

- Fix two calls to trapsignal() that were still passing in 'struct proc'.
These were missed in my last commit.

Replace calls to WITNESS_SLEEP() and witness_list() with equivalent calls
to WITNESS_WARN().

Change the process flags P_KSES to be P_THREADED.
This is just a cosmetic change but I've been meaning to do it for about a year.

Better to not know anything about KSE.

Remove an unsafe KASSERT.

- Move ke_sticks, ke_iticks, ke_uticks, ke_uu, ke_su, and ke_iu back into
the proc. These counters are only examined through calcru.

Submitted by: davidxu
Tested on: x86, alpha, UP/SMP

Reversion of commit by Davidxu plus fixes since applied.

I'm not convinced there is anything major wrong with the patch but
them's the rules..

I am using my "David's mentor" hat to revert this as he's
offline for a while.

Move UPCALL related data structure out of kse, introduce a new
data structure called kse_upcall to manage UPCALL. All KSE binding
and loaning code are gone.

A thread owns an upcall can collect all completed syscall contexts in
its ksegrp, turn itself into UPCALL mode, and takes those contexts back
to userland. Any thread without upcall structure has to export their
contexts and exit at user boundary.

Any thread running in user mode owns an upcall structure, when it enters
kernel, if the kse mailbox's current thread pointer is not NULL, then
when the thread is blocked in kernel, a new UPCALL thread is created and
the upcall structure is transfered to the new UPCALL thread. if the kse
mailbox's current thread pointer is NULL, then when a thread is blocked
in kernel, no UPCALL thread will be created.

Each upcall always has an owner thread. Userland can remove an upcall by
calling kse_exit, when all upcalls in ksegrp are removed, the group is
atomatically shutdown. An upcall owner thread also exits when process is
in exiting state. when an owner thread exits, the upcall it owns is also
removed.

KSE is a pure scheduler entity. it represents a virtual cpu. when a thread
is running, it always has a KSE associated with it. scheduler is free to
assign a KSE to thread according thread priority, if thread priority is changed,
KSE can be moved from one thread to another.

When a ksegrp is created, there is always N KSEs created in the group. the
N is the number of physical cpu in the current system. This makes it is
possible that even an userland UTS is single CPU safe, threads in kernel still
can execute on different cpu in parallel. Userland calls kse_create to add more
upcall structures into ksegrp to increase concurrent in userland itself, kernel
is not restricted by number of upcalls userland provides.

The code hasn't been tested under SMP by author due to lack of hardware.

Reviewed by: julian

1.Fix smp race between kernel vm86 BIOS calling and userland vm86 mode code,
remove global variable in_vm86call, set vm86 calling flag in PCB flags.

2.Fix vm86 BIOS calling preempted problem by changing vm86_lock mutex type
from MTX_DEF to MTX_SPIN. vm86pcb is not remembered in thread struct,
when the thread calling vm86 BIOS is preempted by interrupt thread,
and later switching back to the thread would cause incorrect context be
loaded into CPU registers, this leads to kernel crash.

Extract out KSE specific code from machine specific code
so that there is ony one copy of it. Fix that one copy
so that KSEs with no mailbox in a KSE program are not a cause
of page faults (this can legitmatly happen).

Submitted by: (parts) davidxu

Round out the facilty for a 'bound' thread to loan out its KSE
in specific situations. The owner thread must be blocked, and the
borrower can not proceed back to user space with the borrowed KSE.
The borrower will return the KSE on the next context switch where
teh owner wants it back. This removes a lot of possible
race conditions and deadlocks. It is consceivable that the
borrower should inherit the priority of the owner too.
that's another discussion and would be simple to do.

Also, as part of this, the "preallocatd spare thread" is attached to the
thread doing a syscall rather than the KSE. This removes the need to lock
the scheduler when we want to access it, as it's now "at hand".

DDB now shows a lot mor info for threaded proceses though it may need
some optimisation to squeeze it all back into 80 chars again.
(possible JKH project)

Upcalls are now "bound" threads, but "KSE Lending" now means that
other completing syscalls can be completed using that KSE before the upcall
finally makes it back to the UTS. (getting threads OUT OF THE KERNEL is
one of the highest priorities in the KSE system.) The upcall when it happens
will present all the completed syscalls to the KSE for selection.

Be consistent about "static" functions: if the function is marked
static in its prototype, mark it static at the definition too.

Inspired by: FlexeLint warning #512

Add kernel support needed for the KSE-aware libpthread:
- Maintain fpu state across signals.
- Use ucontext_t's to store KSE thread state.
- Synthesize state for the UTS upon each upcall, rather than
saving and copying a trapframe.
- Save and restore FPU state properly in ucontext_t's.

Reviewed by: deischen, julian
Approved by: -arch

Replace various spelling with FALLTHROUGH which is lint()able

Add some locking asserts and some comments

Add additional cred_free_thread() calls that I had missed the first time.

Pointed out by: jhb

Fix reverse ordering of locks. add a comment about locks on some platforms.

Submitted by: jhb@freebsd.org

Part 1 of KSE-III

The ability to schedule multiple threads per process
(one one cpu) by making ALL system calls optionally asynchronous.
to come: ia64 and power-pc patches, patches for gdb, test program (in tools)

Reviewed by: Almost everyone who counts
(at various times, peter, jhb, matt, alfred, mini, bernd,
and a cast of thousands)

NOTE: this is still Beta code, and contains lots of debugging stuff.
expect slight instability in signals..

userout -> out. These two labels are now identical.

Approved by: alfred

Remove unused diagnostic function cread_free_thread().

Approved by: alfred

If trap() is called when ddb is active, then go directly to trap_fatal();
do not blunder around enabling interrupts and running trap handlers.
trap_pfault() will normally pass control to ddb's fault handler which
will normally do the right thing.

This bug is very old. but in old versions of FreeBSD it is probably only
serious for trap handling that involves sleeping. In -current, attempting
to examine unmapped memory while stopped at a breakpoint at mi_switch()
was always fatal.

- Fixup / remove obsolete comments.
- ktrace no longer requires Giant so do ktrace syscall events before and
after acquiring and releasing Giant, respectively.
- For i386, ia32 syscalls on ia64, powerpc, and sparc64, get rid of the
goto bad hack and instead use the model on ia64 and alpha were we
skip the actual syscall invocation if error != 0. This fixes a bug
where if we the copyin() of the arguments failed for a syscall that
was not marked MP safe, we would try to release Giant when we had
not acquired it.

Don't call vm_map_growstack() from trapwrite() as vm_fault() now performs
this automatically.

o Call vm_map_growstack() from vm_fault() if vm_map_lookup() has failed
due to conditions that suggest the possible need for stack growth.
This has two beneficial effects: (1) we can
now remove calls to vm_map_growstack() from the MD trap handlers and (2)
simple page faults are faster because we no longer unnecessarily perform
vm_map_growstack() on every page fault.
o Remove vm_map_growstack() from the i386's trap_pfault().
o Remove the acquisition and release of Giant from i386's trap_pfault().
(vm_fault() still acquires it.)

Embed a struct vmmeter in the per-cpu structure and add a macro,
PCPU_LAZY_INC() which increments elements in it for cases where we
can afford the occassional inaccuracy. Use of per-cpu stats counters
avoids significant cache stalls in various critical paths that would
otherwise severely limit our cpu scaleability.

Adjust all sysctl's accessing cnt.* elements to now use a procedure
which aggregates the requested field for all cpus and for the global
vmmeter.

The global vmmeter is retained, since some stats counters, like v_free_min,
cannot be made per-cpu. Also, this allows us to convert counters from
the global vmmeter to the per-cpu vmmeter in a piecemeal fashion, so
have at it!

o Use the MI vm_map_growstack() instead of grow_stack() in trap_pfault()
and trapwrite().
o On i386/pc98, remove the (now) unused grow_stack().

Change the way we ensure td_ucred is NULL if DIAGNOSTIC is defined.
Instead of caching the ucred reference, just go ahead and eat the
decerement and increment of the refcount. Now that Giant is pushed down
into crfree(), we no longer have to get Giant in the common case. In the
case when we are actually free'ing the ucred, we would normally free it on
the next kernel entry, so the cost there is not new, just in a different
place. This also removse td_cache_ucred from struct thread. This is
still only done #ifdef DIAGNOSTIC.

Tested on: i386, alpha

Remove __P.

Condition the compilation of trapwrite() on I386_CPU.

- Move a comment from being on the same line as a #ifdef to the line
following it. This should have gone in the previous commit, but
misviewed Bruce's patch.

Requested by: bde

- trap -> trap() in panic() string.
- Translate the message into some sort of understandable english.
- Fix a couple near-by style nits.

Submitted by: bde

- Insert a space in the panic() string in order more clearly show the
message.

Add some DIAGNOSTIC code.
While in userland, keep the thread's ucred reference in a shadow
field so that the usual place to store it is NULL.
If DIAGNOSTIC is not set, the thread ucred is kept valid until the next
kernel entry, at which time it is checked against the process cred
and possibly corrected. Produces a BIG speedup in
kernels with INVARIANTS set. (A previous commit corrected it
for the non INVARIANTS case already)

Reviewed by: dillon@freebsd.org

If the credential on an incoming thread is correct, don't bother
reaquiring it. In the same vein, don't bother dropping the thread cred
when goinf ot userland. We are guaranteed to nned it when we come back,
(which we are guaranteed to do).

Reviewed by: jhb@freebsd.org, bde@freebsd.org (slightly different version)

Clear the single-step flag for signal handlers. This fixes bogus trace
traps on the first instruction of signal handlers.

In trap.c:syscall(), fake a trace trap if the single-step flag was set
on entry to the kernel, not if it will be set on exit from the kernel.
This fixes bogus trace traps after the last instruction of signal handlers.

gdb-4.18 (the version in FreeBSD) still has problems with the program in
the PR. These seem to be due to bugs in gdb and not in FreeBSD, and are
fixed in gdb-5.1 (the distribution version).

PR: 33262
Tested by: k Macy <kip_macy@yahoo.com>
MFC after: 1 day

GC an alternate trap_pfault() which has rotted away behind an "#ifdef notyet"
since 21-Mar-95 .

Device Polling code for -current.

Non-SMP, i386-only, no polling in the idle loop at the moment.

To use this code you must compile a kernel with

options DEVICE_POLLING

and at runtime enable polling with

sysctl kern.polling.enable=1

The percentage of CPU reserved to userland can be set with

sysctl kern.polling.user_frac=NN (default is 50)

while the remainder is used by polling device drivers and netisr's.
These are the only two variables that you should need to touch. There
are a few more parameters in kern.polling but the default values
are adequate for all purposes. See the code in kern_poll.c for
more details on them.

Polling in the idle loop will be implemented shortly by introducing
a kernel thread which does the job. Until then, the amount of CPU
dedicated to polling will never exceed (100-user_frac).
The equivalent (actually, better) code for -stable is at

http://info.iet.unipi.it/~luigi/polling/

and also supports polling in the idle loop.

NOTE to Alpha developers:
There is really nothing in this code that is i386-specific.
If you move the 2 lines supporting the new option from
sys/conf/{files,options}.i386 to sys/conf/{files,options} I am
pretty sure that this should work on the Alpha as well, just that
I do not have a suitable test box to try it. If someone feels like
trying it, I would appreciate it.

NOTE to other developers:
sure some things could be done better, and as always I am open to
constructive criticism, which a few of you have already given and
I greatly appreciated.
However, before proposing radical architectural changes, please
take some time to possibly try out this code, or at the very least
read the comments in kern_poll.c, especially re. the reason why I
am using a soft netisr and cannot (I believe) replace it with a
simple timeout.

Quick description of files touched by this commit:

sys/conf/files.i386
new file kern/kern_poll.c
sys/conf/options.i386
new option
sys/i386/i386/trap.c
poll in trap (disabled by default)
sys/kern/kern_clock.c
initialization and hardclock hooks.
sys/kern/kern_intr.c
minor swi_net changes
sys/kern/kern_poll.c
the bulk of the code.
sys/net/if.h
new flag
sys/net/if_var.h
declaration for functions used in device drivers.
sys/net/netisr.h
NETISR_POLL
sys/dev/fxp/if_fxp.c
sys/dev/fxp/if_fxpvar.h
sys/pci/if_dc.c
sys/pci/if_dcreg.h
sys/pci/if_sis.c
sys/pci/if_sisreg.h
device driver modifications

- Don't enable interrupts in trap() if we trapped while holding a spin
lock as this usually makes the problem worse.
- If we get a page fault while holding a spin lock, treat it as a fatal
trap and don't even bother calling into the VM since calling into the
VM will panic when trying to lock Giant before we can get a useful
message anyways.

Add a per-thread ucred reference for syscalls and synchronous traps from
userland. The per thread ucred reference is immutable and thus needs no
locks to be read. However, until all the proc locking associated with
writes to p_ucred are completed, it is still not safe to use the per-thread
reference.

Tested on: x86 (SMP), alpha, sparc64

- Clean up the comments slightly here to make them more readable.
- Set the type and trapframe number for the F00F workaround since type
can be used later by sv_transtrap(). Debuggers might also want to look
at the type in the trapframe.

Submitted by: bde (mostly)

Set the code and signal for the F00F hack fault directly instead of
changing the code in the trapframe and looping back to the top of trap
again.

Tested by: cjc

Oops, these already included sys/lock.h, they just did so after
sys/mutex.h which is too late.

Add missing includes of sys/lock.h.

KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after: ha ha ha ha

Remove the MPSAFE keyword from the parser for syscalls.master.
Instead introduce the [M] prefix to existing keywords. e.g.
MSTD is the MP SAFE version of STD. This is prepatory for a
massive Giant lock pushdown. The old MPSAFE keyword made
syscalls.master too messy.

Begin comments MP-Safe procedures with the comment:
/*
* MPSAFE
*/
This comments means that the procedure may be called without
Giant held (The procedure itself may still need to obtain
Giant temporarily to do its thing).

sv_prepsyscall() is now MP SAFE and assumed to be MP SAFE
sv_transtrap() is now MP SAFE and assumed to be MP SAFE

ktrsyscall() and ktrsysret() are now MP SAFE (Giant Pushdown)
trapsignal() is now MP SAFE (Giant Pushdown)

Places which used to do the if (mtx_owned(&Giant)) mtx_unlock(&Giant)
test in syscall[2]() in */*/trap.c now do not. Instead they
explicitly unlock Giant if they previously obtained it, and then
assert that it is no longer held to catch broken system calls.

Rebuild syscall tables.

Remove references to the old giant kernel lock in various comments.

Push down Giant some in trap_pfault() so we don't grab Giant around
trap_fatal() to make restarting from panic's slightly easier. Before if
one did 'w 0 0' in ddb, the longjmp in ddb inside of trap_fatal() would
result in Giant being held (or recursed one level deeper) which led to
problems later on. You can now drop to teh debugger, do 'w 0 0', and
continue w/o a problem.

- Close races with signals and other AST's being triggered while we are in
the process of exiting the kernel. The ast() function now loops as long
as the PS_ASTPENDING or PS_NEEDRESCHED flags are set. It returns with
preemption disabled so that any further AST's that arrive via an
interrupt will be delayed until the low-level MD code returns to user
mode.
- Use u_int's to store the tick counts for profiling purposes so that we
do not need sched_lock just to read p_sticks. This also closes a
problem where the call to addupc_task() could screw up the arithmetic
due to non-atomic reads of p_sticks.
- Axe need_proftick(), aston(), astoff(), astpending(), need_resched(),
clear_resched(), and resched_wanted() in favor of direct bit operations
on p_sflag.
- Fix up locking with sched_lock some. In addupc_intr(), use sched_lock
to ensure pr_addr and pr_ticks are updated atomically with setting
PS_OWEUPC. In ast() we clear pr_ticks atomically with clearing
PS_OWEUPC. We also do not grab the lock just to test a flag.
- Simplify the handling of Giant in ast() slightly.

Reviewed by: bde (mostly)

Quiet a variable format-string warning.

MFC after: 1 week

Activate SSE/SIMD. This is the extra context switching support that
we are required to do if we let user processes use the extra 128 bit
registers etc.

This is the base part of the diff I got from:
http://www.issei.org/issei/FreeBSD/sse.html
I believe this is by: Mr. SUZUKI Issei <issei@issei.org>
SMP support apparently by: Takekazu KATO <kato@chino.it.okayama-u.ac.jp>
Test code by: NAKAMURA Kazushi <kaz@kobe1995.net>, see
http://kobe1995.net/~kaz/FreeBSD/SSE.en.html

I have fixed a couple of style(9) deviations. I have some followup
commits to fix a couple of non-style things.

Quiet warning by removing ast() prototype.

Forgotten by: jhb (me)

Move ast() and userret() to sys/kern/subr_trap.c now that they are MI.

Add a new MI pointer to the process' trapframe p_frame instead of using
various differently named pointers buried under p_md.

Reviewed by: jake (in principle)

Grab Giant around trap_pfault() for now.

- Grab the proc lock around CURSIG and postsig(). Don't release the proc
lock until after grabbing the sched_lock to avoid CURSIG racing with
psignal.
- Don't grab Giant for addupc_task() as it isn't needed.

Reported by: tegge (signal race), bde (addupc_task a while back)

Don't hold sched_lock across addupc_task().

Reported by: David Taylor <davidt@yadt.co.uk>
Submitted by: bde

Don't acquire Giant just to call trap_fatal(), we are about to panic
anyway so we'd rather see the printf's then block if the system is
hosed.

Convert npx interrupts into traps instead of vice versa. This is much
simpler for npx exceptions that start as traps (no assembly required...)
and works better for npx exceptions that start as interrupts (there is
no longer a problem for nested interrupts).

Submitted by: original (pre-SMPng) version by luoqi

Introduce a global lock for the vm subsystem (vm_mtx).

vm_mtx does not recurse and is required for most low level
vm operations.

faults can not be taken without holding Giant.

Memory subsystems can now call the base page allocators safely.

Almost all atomic ops were removed as they are covered under the
vm mutex.

Alpha and ia64 now need to catch up to i386's trap handlers.

FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).

Reviewed (partially) by: jake, jhb

Remove unneeded includes of sys/ipl.h and machine/ipl.h.

Simplify the vm fault trap handling code a bit by using if-else instead of
duplicating code in the then case and then using a goto to jump around
the else case.

Overhaul of the SMP code. Several portions of the SMP kernel support have
been made machine independent and various other adjustments have been made
to support Alpha SMP.

- It splits the per-process portions of hardclock() and statclock() off
into hardclock_process() and statclock_process() respectively. hardclock()
and statclock() call the *_process() functions for the current process so
that UP systems will run as before. For SMP systems, it is simply necessary
to ensure that all other processors execute the *_process() functions when the
main clock functions are triggered on one CPU by an interrupt. For the alpha
4100, clock interrupts are delievered in a staggered broadcast fashion, so
we simply call hardclock/statclock on the boot CPU and call the *_process()
functions on the secondaries. For x86, we call statclock and hardclock as
usual and then call forward_hardclock/statclock in the MD code to send an IPI
to cause the AP's to execute forwared_hardclock/statclock which then call the
*_process() functions.
- forward_signal() and forward_roundrobin() have been reworked to be MI and to
involve less hackery. Now the cpu doing the forward sets any flags, etc. and
sends a very simple IPI_AST to the other cpu(s). AST IPIs now just basically
return so that they can execute ast() and don't bother with setting the
astpending or needresched flags themselves. This also removes the loop in
forward_signal() as sched_lock closes the race condition that the loop worked
around.
- need_resched(), resched_wanted() and clear_resched() have been changed to take
a process to act on rather than assuming curproc so that they can be used to
implement forward_roundrobin() as described above.
- Various other SMP variables have been moved to a MI subr_smp.c and a new
header sys/smp.h declares MI SMP variables and API's. The IPI API's from
machine/ipl.h have moved to machine/smp.h which is included by sys/smp.h.
- The globaldata_register() and globaldata_find() functions as well as the
SLIST of globaldata structures has become MI and moved into subr_smp.c.
Also, the globaldata list is only available if SMP support is compiled in.

Reviewed by: jake, peter
Looked over by: eivind

- Release Giant a bit earlier on syscall exit.
- Don't try to grab Giant before postsig() in userret() as it is no longer
needed.
- Don't grab Giant before psignal() in ast() but get the proc lock instead.

- Rename the lcall system call handler from Xsyscall to Xlcall_syscall
to be more like Xint0x80_syscall and less like c function syscall().
- Reduce code duplication between the int0x80 and lcall handlers by
shuffling the elfags into the right place, saving the sizeof the
instruction in tf_err and jumping into the common int0x80 code.

Reviewed by: peter

The p_md.md_regs member of proc is used in signal handling to reference
the the original trapframe of the syscall, trap, or interrupt that entered
the kernel. Before SMPng, ast's were handled via a psuedo trap at the
end of doerti. With the SMPng commit, ast's were broken out into a
separate ast() function that was called from doreti to match the behavior
of other architectures. Unfortunately, when this was done, the
p_md.md_regs member of curproc was not updateda in ast(), thus when
signals are handled by userret() after an interrupt that returns to
userland, we end up using a stale trapframe that will result in the
registers from the old trapframe overwriting the real trapframe and
smashing all the registers right before we return to usermode. The saved
%cs:%eip from where we were in usermode are saved in the trapframe for
example.

- Change ast() to take a pointer to a trapframe like other architectures.
- Don't use an atomic operation to update cnt.v_soft in ast(). This is
the only place the variable is written to, and sched_lock is always
held when it is written, so it is already protected and the mutex release
of sched_lock asserts a memory barrier that ensures the value will be
updated in a timely fashion.

- Use TRAPF_PC() on the alpha to acess the PC in the trap frame.
- Don't hold sched_lock around addupc_task() as this apparently breaks
profiling badly due to sched_lock being held across copyin().

Reported by: bde (2)

- Don't call clear_resched() in userret(), instead, clear the resched flag
in mi_switch() just before calling cpu_switch() so that the first switch
after a resched request will satisfy the request.
- While I'm at it, move a few things into mi_switch() and out of
cpu_switch(), specifically set the p_oncpu and p_lastcpu members of
proc in mi_switch(), and handle the sched_lock state change across a
context switch in mi_switch().
- Since cpu_switch() no longer handles the sched_lock state change, we
have to setup an initial state for sched_lock in fork_exit() before we
release it.

Removed all traces of T_ASTFLT (except for gaps where it was). It became
unused except in dead code when ast() was split off from trap().

Changed the aston() family to operate on a specified process instead of
always on curproc. This is needed to implement signal delivery properly
(see a future log message for kern_sig.c).

Debogotified the definition of aston(). aston() was defined in terms
of signotify() (perhaps because only the latter already operated on
a specified process), but aston() is the primitive.

Similar changes are needed in the ia64 versions of cpu.h and trap.c.
I didn't make them because the ia64 is missing the prerequisite changes
to make astpending and need_resched per-process and those changes are
too large to make without testing.

Implement a unified run queue and adjust priority levels accordingly.

- All processes go into the same array of queues, with different
scheduling classes using different portions of the array. This
allows user processes to have their priorities propogated up into
interrupt thread range if need be.
- I chose 64 run queues as an arbitrary number that is greater than
32. We used to have 4 separate arrays of 32 queues each, so this
may not be optimal. The new run queue code was written with this
in mind; changing the number of run queues only requires changing
constants in runq.h and adjusting the priority levels.
- The new run queue code takes the run queue as a parameter. This
is intended to be used to create per-cpu run queues. Implement
wrappers for compatibility with the old interface which pass in
the global run queue structure.
- Group the priority level, user priority, native priority (before
propogation) and the scheduling class into a struct priority.
- Change any hard coded priority levels that I found to use
symbolic constants (TTIPRI and TTOPRI).
- Remove the curpriority global variable and use that of curproc.
This was used to detect when a process' priority had lowered and
it should yield. We now effectively yield on every interrupt.
- Activate propogate_priority(). It should now have the desired
effect without needing to also propogate the scheduling class.
- Temporarily comment out the call to vm_page_zero_idle() in the
idle loop. It interfered with propogate_priority() because
the idle process needed to do a non-blocking acquire of Giant
and then other processes would try to propogate their priority
onto it. The idle process should not do anything except idle.
vm_page_zero_idle() will return in the form of an idle priority
kernel thread which is woken up at apprioriate times by the vm
system.
- Update struct kinfo_proc to the new priority interface. Deliberately
change its size by adjusting the spare fields. It remained the same
size, but the layout has changed, so userland processes that use it
would parse the data incorrectly. The size constraint should really
be changed to an arbitrary version number. Also add a debug.sizeof
sysctl node for struct kinfo_proc.

Clear the reschedule flag after finding it set in userret(). This
used to be in cpu_switch(), but I don't see any difference between
doing it here.

- Make astpending and need_resched process attributes rather than CPU
attributes. This is needed for AST's to be properly posted in a preemptive
kernel. They are backed by two new flags in p_sflag: PS_ASTPENDING and
PS_NEEDRESCHED. They are still accesssed by their old macros:
aston(), astoff(), etc. For completeness, an astpending() macro has been
added to check for a pending AST, and clear_resched() has been added to
clear need_resched().
- Rename syscall2() on the x86 back to syscall() to be consistent with
other architectures.

Change and clean the mutex lock interface.

mtx_enter(lock, type) becomes:

mtx_lock(lock) for sleep locks (MTX_DEF-initialized locks)
mtx_lock_spin(lock) for spin locks (MTX_SPIN-initialized)

similarily, for releasing a lock, we now have:

mtx_unlock(lock) for MTX_DEF and mtx_unlock_spin(lock) for MTX_SPIN.
We change the caller interface for the two different types of locks
because the semantics are entirely different for each case, and this
makes it explicitly clear and, at the same time, it rids us of the
extra `type' argument.

The enter->lock and exit->unlock change has been made with the idea
that we're "locking data" and not "entering locked code" in mind.

Further, remove all additional "flags" previously passed to the
lock acquire/release routines with the exception of two:

MTX_QUIET and MTX_NOSWITCH

The functionality of these flags is preserved and they can be passed
to the lock/unlock routines by calling the corresponding wrappers:

mtx_{lock, unlock}_flags(lock, flag(s)) and
mtx_{lock, unlock}_spin_flags(lock, flag(s)) for MTX_DEF and MTX_SPIN
locks, respectively.

Re-inline some lock acq/rel code; in the sleep lock case, we only
inline the _obtain_lock()s in order to ensure that the inlined code
fits into a cache line. In the spin lock case, we inline recursion and
actually only perform a function call if we need to spin. This change
has been made with the idea that we generally tend to avoid spin locks
and that also the spin locks that we do have and are heavily used
(i.e. sched_lock) do recurse, and therefore in an effort to reduce
function call overhead for some architectures (such as alpha), we
inline recursion for this case.

Create a new malloc type for the witness code and retire from using
the M_DEV type. The new type is called M_WITNESS and is only declared
if WITNESS is enabled.

Begin cleaning up some machdep/mutex.h code - specifically updated the
"optimized" inlined code in alpha/mutex.h and wrote MTX_LOCK_SPIN
and MTX_UNLOCK_SPIN asm macros for the i386/mutex.h as we presently
need those.

Finally, caught up to the interface changes in all sys code.

Contributors: jake, jhb, jasone (in no particular order)

Don't enable interrupts for a kernel breakpoint or trace trap. Otherwise,
this negates the explicit disabling of interrupts when entering the
debugger in Debugger().

Fix typo: seperate -> separate.

Seperate does not exist in the english language.

Send "#if NISA > 0" to the bit-bucket and replace it with an option.
These were compile-time "is the isa code present?" tests and not
'how many isa busses' tests.

Push Giant down into the trap handlers that need it, instead of
acquiring it unconditionally.

Reviewed by: jhb

- Kill the have_giant parameter to userret() along with all instances of
that name as a variable. Use mtx_owned(&Giant) where appropriate
instead.
- Proc locking.
- P_FOO -> PS_FOO.
- Update comments about enable interrupts during trap and why this may be
bad if we trap while holding a spin mutex.
- Don't bother resetting p to curproc in syscall() in case we are the child
returning from fork. The child hasn't returned from fork through syscall
in a while.
- Remove fork_return() as it has been superseded by the MI version.

Make intr_nesting_level per-process, rather than per-cpu. Setup
interrupt threads to run with it always >= 1, so that malloc can
detect M_WAITOK from "interrupt" context. This is also necessary
in order to context switch from sched_ithd() directly.

Reviewed By: peter

Use #ifdef DEV_NPX from opt_npx.h instead of #if NNPX > 0 from npx.h

Use PCPU_GET, PCPU_PTR and PCPU_SET to access all per-cpu variables
other then curproc.

If we fail to emulate a vm86 trap in kernel mode, then we use
vm86_trap() to return to the calling program directly. vm86_trap()
doesn't return, thus it was never returning to trap() to release
Giant. Thus, release Giant before calling vm86_trap().

- Add code to detect if a system call returns with locks other than Giant
held and panic if so (conditional on witness).
- Change witness_list to return the number of locks held so this is easier.
- Add kern/syscalls.c to the kernel build if witness is defined so that the
panic message can contain the name of the offending system call.
- Add assertions that Giant and sched_lock are not held when returning from
a system call, which were missing for alpha and ia64.

- Split the run queue and sleep queue linkage, so that a process
may block on a mutex while on the sleep queue without corrupting
it.
- Move dropping of Giant to after the acquire of sched_lock.

Tested by: John Hay <jhay@icomtek.csir.co.za>
jhb

Don't release and acquire Giant in mi_switch(). Instead, release and
acquire Giant as needed in functions that call mi_switch(). The releases
need to be done outside of the sched_lock to avoid potential deadlocks
from trying to acquire Giant while interrupts are disabled.

Submitted by: witness

Catch up to moving headers:
- machine/ipl.h -> sys/ipl.h
- machine/mutex.h -> sys/mutex.h

- Change fast interrupts on x86 to push a full interrupt frame and to
return through doreti to handle ast's. This is necessary for the
clock interrupts to work properly.
- Change the clock interrupts on the x86 to be fast instead of threaded.
This is needed because both hardclock() and statclock() need to run in
the context of the current process, not in a separate thread context.
- Kill the prevproc hack as it is no longer needed.
- We really need Giant when we call psignal(), but we don't want to block
during the clock interrupt. Instead, use two p_flag's in the proc struct
to mark the current process as having a pending SIGVTALRM or a SIGPROF
and let them be delivered during ast() when hardclock() has finished
running.
- Remove CLKF_BASEPRI, which was #ifdef'd out on the x86 anyways. It was
broken on the x86 if it was turned on since cpl is gone. It's only use
was to bogusly run softclock() directly during hardclock() rather than
scheduling an SWI.
- Remove the COM_LOCK simplelock and replace it with a clock_lock spin
mutex. Since the spin mutex already handles disabling/restoring
interrupts appropriately, this also lets us axe all the *_intr() fu.
- Back out the hacks in the APIC_IO x86 cpu_initclocks() code to use
temporary fast interrupts for the APIC trial.
- Add two new process flags P_ALRMPEND and P_PROFPEND to mark the pending
signals in hardclock() that are to be delivered in ast().

Submitted by: jakeb (making statclock safe in a fast interrupt)
Submitted by: cp (concept of delaying signals until ast())

Various whitespace cleanups after the SMPng commit, which jumbled things
around a bit in the trap handling code.

Don't treat a kernel stack fault the same as a general protect fault or
a segment not present fault in the non-vm86 case.

Fixed hang on booting with -d. mtx_enter() was called on an uninitialized
lock. The quick fix in trap.c was not quite the version tested and had no
effect; back it out.

Quick fix for hang on booting with -d. mtx_enter() was called before
curproc was initialized. curproc == NULL was interpreted as matching
the process holding Giant... Just skip mtx_enter() and mtx_exit() in
trap() if (curproc == NULL && cold) (&& cold for safety).

Major update to the way synchronization is done in the kernel. Highlights
include:

* Mutual exclusion is used instead of spl*(). See mutex(9). (Note: The
alpha port is still in transition and currently uses both.)

* Per-CPU idle processes.

* Interrupts are run in their own separate kernel threads and can be
preempted (i386 only).

Partially contributed by: BSDi (BSD/OS)
Submissions by (at least): cp, dfr, dillon, grog, jake, jhb, sheldonh

Change the behavior of isa_nmi to log an error message instead of
panicing and return a status so that we can decide whether to drop
into DDB or panic. If the status from isa_nmi is true, panic the
kernel based on machdep.panic_on_nmi, otherwise if DDB is
enabled, drop to DDB based on machdep.ddb_on_nmi.

Reviewed by: peter, phk

Handle write page faults (both write only or read-modify-write) as MI vm
write-only faults. This would allow write-only mmapped regions to function
correctly.

Change the way NMI's are handled. Before, if DDB was enabled and
a NMI occured, you could type continue in DDB and the kernel would
not attempt to detect what type of NMI was recieved. Now we check
for the type of NMI first and then go to DDB if it is enabled.

This will solve the problem with having DDB enabled and getting an
NMI due to some possibly bad error and being able to continue the
operation of the kernel when you really want to panic and know
what happened.

Submitted by: jhb

Fix my own style bugs (use of spaces instead of tabs for indentation).
This is a style-only change.

Commit major SMP cleanups and move the BGL (big giant lock) in the
syscall path inward. A system call may select whether it needs the MP
lock or not (the default being that it does need it).

A great deal of conditional SMP code for various deadended experiments
has been removed. 'cil' and 'cml' have been removed entirely, and the
locking around the cpl has been removed. The conditional
separately-locked fast-interrupt code has been removed, meaning that
interrupts must hold the CPL now (but they pretty much had to anyway).
Another reason for doing this is that the original separate-lock for
interrupts just doesn't apply to the interrupt thread mechanism being
contemplated.

Modifications to the cpl may now ONLY occur while holding the MP
lock. For example, if an otherwise MP safe syscall needs to mess with
the cpl, it must hold the MP lock for the duration and must (as usual)
save/restore the cpl in a nested fashion.

This is precursor work for the real meat coming later: avoiding having
to hold the MP lock for common syscalls and I/O's and interrupt threads.
It is expected that the spl mechanisms and new interrupt threading
mechanisms will be able to run in tandem, allowing a slow piecemeal
transition to occur.

This patch should result in a moderate performance improvement due to
the considerable amount of code that has been removed from the critical
path, especially the simplification of the spl*() calls. The real
performance gains will come later.

Approved by: jkh
Reviewed by: current, bde (exception.s)
Some work taken from: luoqi's patch

I applied the wrong patch set. Back out anything associated
with the known bogus currtpriority. This undoes the previous changes to
sys/i386/i386/trap.c, sys/alpha/alpha/trap.c, sys/sys/systm.h

Now we have the patch set approved by bde.

Approved by: bde

Patches that eliminate extra context switches in FIFO case.
Fixes p1003_1b regression test in the simple case of no RR and
FIFO processes competing.

Reviewed by: jkh, bde

Don't forget to reset the hardware debug registers when a process that
was using them exits.

Don't allow a user process to cause the kernel to take a TRCTRAP on a
user space address.

Reviewed by: jlemon, sef
Approved by: jkh

Add a new mechanism, cndbctl(), to tell the console driver that
ddb is entered. Don't refer to `in_Debugger' to see if we
are in the debugger. (The variable used to be static in Debugger()
and wasn't updated if ddb is entered via traps and panic anyway.)

- Don't refer to `in_Debugger'.
- Add `db_active' to i386/i386/db_interface.d (as in
alpha/alpha/db_interface.c).
- Remove cnpollc() stub from ddb/db_input.c.
- Add the dbctl function to syscons, pcvt, and sio. (The function for
pcvt and sio is noop at the moment.)

Jointly developed by: bde and me

(The final version was tweaked by me and not reviewed by bde. Thus,
if there is any error in this commit, that is entirely of mine, not
his.)

Some changes were obtained from: NetBSD

Passing "0" or "FALSE" as the fourth argument to vm_fault is wrong. It
should be "VM_FAULT_NORMAL".

useracc() the prequel:

Merge the contents (less some trivial bordering the silly comments)
of <vm/vm_prot.h> and <vm/vm_inherit.h> into <vm/vm.h>. This puts
the #defines for the vm_inherit_t and vm_prot_t types next to their
typedefs.

This paves the road for the commit to follow shortly: change
useracc() to use VM_PROT_{READ|WRITE} rather than B_{READ|WRITE}
as argument.

$Id$ -> $FreeBSD$

On FPU exceptions, pass a useful error code (one of the FPE_...
macros) to the signal handler, for old-style BSD signal handlers as
the second (int) argument, for SA_SIGINFO signal handlers as
siginfo_t->si_code. This is source-compatible with Solaris, except
that we have no <siginfo.h> (which isn't even mentioned in POSIX
1003.1b).

An rather complete example program is at
http://www3.cons.org/cracauer/freebsd-signal.c
This will be added to the regression tests in src/.

This commit also adds code to disable the (hardware) FPU from
userconfig, so that you can use a software FP emulator on a machine
that has hardware floating point. See LINT.

Changed the global `idt' from an array to a pointer so that npx.c
automatically hacks on the active copy of the IDT if f00f_hack()
has changed it. This also allows simplifications in setidt().
This fixes breakage of FP exception handling by rev.1.55 of
sys/kernel.h. FP exceptions were sent to npx.c's probe handlers
because npx.c "restored" the old handlers to the wrong copy of the
IDT. The SYSINIT for f00f_hack() was purposely run quite late to
avoid problems like this, but it is bogusly associated with the
SYSINIT for proc0 so it was moved with the latter.

Problem reported and fix tested by: Martin Cracauer <cracauer@cons.org>

Unifdef VM86.

Reviewed by: silence on on -current

Add sufficient braces to keep egcs happy about potentially ambiguous
if/else nesting.

Enable vmspace sharing on SMP. Major changes are,
- %fs register is added to trapframe and saved/restored upon kernel entry/exit.
- Per-cpu pages are no longer mapped at the same virtual address.
- Each cpu now has a separate gdt selector table. A new segment selector
is added to point to per-cpu pages, per-cpu global variables are now
accessed through this new selector (%fs). The selectors in gdt table are
rearranged for cache line optimization.
- fask_vfork is now on as default for both UP and SMP.
- Some aio code cleanup.

Reviewed by: Alan Cox <alc@cs.rice.edu>
John Dyson <dyson@iquest.net>
Julian Elischer <julian@whistel.com>
Bruce Evans <bde@zeta.org.au>
David Greenman <dg@root.com>

unifdef -DVM_STACK - it's been on for a while for x86 and was checked
and appeared to be working for the Alpha some time ago.

Make TIMER_FREQ a normal, undocumented option. Raise confusion to
a higher level with example in LINT.

Clarify comment about PPS_SYNC. Ignore for now that it doesn't
work in FLL mode, it will in a few days.

Add (but don't activate) code for a special VM option to make
downward growing stacks more general.
Add (but don't activate) code to use the new stack facility
when running threads, (specifically the linux threads support).
This allows people to use both linux compiled linuxthreads, and also the
native FreeBSD linux-threads port.

The code is conditional on VM_STACK. Not using this will
produce the old heavily tested system.

Submitted by: Richard Seaman <dick@tar.com>

Improved DDB_UNATTENDED behaviour. From the submitter:

There's something that's been bugging me for a while, so I decided to fix it.
FreeBSD now will DTRT WRT DDB and DDB_UNATTENDED (!debugger_on_panic), at least
in my opinion. The behavior change is such that:

1. Nothing changes when debugger_on_panic != 0.
2. When DDB_UNATTENDED (!debugger_on_panic), if a panic occurs, the
machine will reboot. Also, if a trap occurs, the machine will
panic and reboot, unlike how it broke to DDB before. HOWEVER,
a trap inside DDB will not cause a panic, allowing full use
of DDB without having to worry about the machine being stuck
at a DDB prompt if something goes wrong during the day.
Patches for this behavior follow my signature, and it would
be a boon to anyone (like me) who uses DDB_UNATTENDED, but
actually wants the machine to panic on a trap (otherwise,
what's the use, if the machine causes a fatal trap rather than
a true panic, of debugger_on_panic?). The changes cause no
adverse behavior, but do involve two symbols becoming global

Submitted by: Brian Feldman <green@unixhelp.org>

Removed bogus casts of USRSTACK and/or the other operand in binary
expressions involving USRSTACK.

Avoid compiler warning (printf arg type mismatch) when compiling #ifdef DEBUG

- For some old Cyrix CPUs, %cr2 is clobbered by interrupts. This
problem is worked around by using an interrupt gate for the page
fault handler. This code was originally made for NetBSD/pc98 by
Naofumi Honda <honda@kururu.math.sci.hokudai.ac.jp> and has already
been in PC98 tree. Because of this bug, trap_fatal cannot show
correct page fault address if %cr2 is obtained in this function.
Therefore, trap_fatal uses the value from trap() function.
- The trap handler always enables interruption when buggy application
or kernel code has disabled interrupts and then trapped. This code
was prepared by Bruce Evans <bde@FreeBSD.org>.

Submitted by: Bruce Evans <bde@FreeBSD.org>
Naofumi Honda <honda@kururu.math.sci.hokudai.ac.jp>

Fixed printf format errors.

Translate T_PROTFLT to SIGSEGV instead of SIGBUS when running under
Linux emulation. This make Allegro Common Lisp 4.3 work under
FreeBSD!

Submitted by: Fred Gilham <gilham@csl.sri.com>
Commented on by: bde, dg, msmith, tg
Hoping he got everything right: eivind

Support compiling with `gcc -ansi'.

Eradicate the variable "time" from the kernel, using various measures.
"time" wasn't a atomic variable, so splfoo() protection were needed
around any access to it, unless you just wanted the seconds part.

Most uses of time.tv_sec now uses the new variable time_second instead.

gettime() changed to getmicrotime(0.

Remove a couple of unneeded splfoo() protections, the new getmicrotime()
is atomic, (until Bruce sets a breakpoint in it).

A couple of places needed random data, so use read_random() instead
of mucking about with time which isn't random.

Add a new nfs_curusec() function.

Mark a couple of bogosities involving the now disappeard time variable.

Update ffs_update() to avoid the weird "== &time" checks, by fixing the
one remaining call that passwd &time as args.

Change profiling in ncr.c to use ticks instead of time. Resolution is
the same.

Add new function "tvtohz()" to avoid the bogus "splfoo(), add time, call
hzto() which subtracts time" sequences.

Reviewed by: bde

Moved some #includes from <sys/param.h> nearer to where they are actually
used.

Add the ability to make real-mode BIOS calls from the kernel. Currently,
everything is contained inside #ifdef VM86, so this option must be
present in the config file to use this functionality.

Thanks to Tor Egge, these changes should work on SMP machines. However,
it may not be throughly SMP-safe.

Currently, the only BIOS calls made are memory-sizing routines at bootup,
these replace reading the RTC values.

Back out DIAGNOSTIC changes.

Turn DIAGNOSTIC into a new-style option.

Make POWERFAIL_NMI, PPS_SYNC and NATM new style options.

This also fixes a couple of defunct options; submitted by bde.

Changes to allow event-based process monitoring and control.

document and make the NO_F00F_HACK a proper option...

also, sort some option includes while I'm here..

Forgotten by: sef

After consultation with David, change
#ifndef NO_F00F_HACK
to
#if defined(I586_CPU) && !defined(NO_F00F_HACK)

Work around for the Intel Pentium F00F bug; this is Intel's recommended
workaround. Note that this currently eats up two pages extra in the system;
this could be alleviated by aligning idt correctly, and then only dealing with
that (as opposed to the current method of allocated two pages and copying the
IDT table to that, and then setting that to be the IDT table).

Fixed some #include messes.

Hid the check of the user %cs in syscall() under `#ifdef DIAGNOSTIC'.

Move the "retval" (3rd) parameter from all syscall functions and put
it in struct proc instead.

This fixes a boatload of compiler warning, and removes a lot of cruft
from the sources.

I have not removed the /*ARGSUSED*/, they will require some looking at.

libkvm, ps and other userland struct proc frobbing programs will need
recompiled.

Compensate for pcb.h tweaks.

(Bruce pointed out the nesting)

Convert the VM86 option from a global option to an option only depended
on by the files that use it. Changing the VM86 option now only causes
a recompile of a dozen files or so rather than the entire kernel.

autoconf.c:
Add cpu_rootconf and cpu_dumpconf so that configuring these
two devices can be better controlled by the MI configuration
code.

machdep.c:
MD initialization code for the new callout interface.

trap.c:
Add support for printing out whether cam interrupts are masked
during a panic.

Cosmetic adjustment for the trap/double fault/panic cpu id listing.
It now prints the apic id in hex rather than decimal.

Remove the vm86 support as an LKM, and link it directly into the kernel
if 'options "VM86"' is in the config file. The LKM was really for
development, and has probably outlived its usefulness.

Clean up the SMP AP bootstrap and eliminate the wretched idle procs.

- We now have enough per-cpu idle context, the real idle loop has been
revived (cpu's halt now with nothing to do).
- Some preliminary support for running some operations outside the
global lock (eg: zeroing "free but not yet zeroed pages") is present
but appears to cause problems. Off by default.
- the smp_active sysctl now behaves differently. It's merely a 'true/false'
option. Setting smp_active to zero causes the AP's to halt in the idle
loop and stop scheduling processes.
- bootstrap is a lot safer. Instead of sharing a statically compiled in
stack a number of times (which has caused lots of problems) and then
abandoning it, we use the idle context to boot the AP's directly. This
should help >2 cpu support since the bootlock stuff was in doubt.
- print physical apic id in traps.. helps identify private pages getting
out of sync. (You don't want to know how much hair I tore out with this!)

More cleanup to follow, this is more of a checkpoint than a
'finished' thing.

Revert my previous commit about using CS_SECURE macro.
Requested by: Bruce.

Preperation for moving cpl into critical region access.
Several new fine-grained locks.
New FAST_INTR() methods:
- separate simplelock for FAST_INTR, no more giant lock.
- FAST_INTR()s no longer checks ipending on way out of ISR.
sio made MP-safe (I hope).

Use CS_SECURE macro.
Reviewed by: John Dyson

Back out a part of the disk scheduling "improvements" :-(. Let me know
how the system works now!!!

Modify the scheduling policy to take into account disk I/O waits
as chargeable CPU usage. This should mitigate the problem of processes
doing disk I/O hogging the CPU. Various users have reported the
problem, and test code shows that the problem should now be gone.

VM86 kernel support.
Work done by BSDI, Jonathan Lemon <jlemon@americantv.com>,
Mike Smith <msmith@gsoft.com.au>, Sean Eric Fagan <sef@kithrup.com>,
and probably alot of others.
Submitted by: Jnathan Lemon <jlemon@americantv.com>

Removed unused #includes.

Preliminary support for per-cpu data pages.

This eliminates a lot of #ifdef SMP type code. Things like _curproc reside
in a data page that is unique on each cpu, eliminating the expensive macros
like: #define curproc (SMPcurproc[cpunumber()])

There are some unresolved bootstrap and address space sharing issues at
present, but Steve is waiting on this for other work. There is still some
strictly temporary code present that isn't exactly pretty.

This is part of a larger change that has run into some bumps, this part is
standalone so it should be safe. The temporary code goes away when the
full idle cpu support is finished.

Reviewed by: fsmp, dyson

Preserve %fs and %gs across context switches. This has a relatively low
cost since it is only done in cpu_switch(), not for every exception.
The extra state is kept in the pcb, and handled much like the npx state,
with similar deficiencies (the state is not preserved across signal
handlers, and error handling loses state).

Move interrupt handling code from isa.c to a new file. This should make
isa.c (slightly) more portable and will make my life developing the really
portable version much easier.

Reviewed by: peter, fsmp

Include file updates.. <machine/spl.h> -> <machine/ipl.h>, add
<machine/ipl.h> to those files that were depending on getting SWI_*
implicitly via <machine/cpufunc.h>

remove opt_smp.h and fix the reason it was needed.

md_regs is now a struct trapframe *

Make sure that *fork() always returns with %edx == 1 in the
child. This was sometimes not happening correctly during my
threads code work.

Man the liferafts! Here comes the long awaited SMP -> -current merge!

There are various options documented in i386/conf/LINT, there is more to
come over the next few days.

The kernel should run pretty much "as before" without the options to
activate SMP mode.

There are a handful of known "loose ends" that need to be fixed, but
have been put off since the SMP kernel is in a moderately good condition
at the moment.

This commit is the result of the tinkering and testing over the last 14
months by many people. A special thanks to Steve Passe for implementing
the APIC code!

Fixed printing of registers in dbflalt_handler(). The registers
were always in a tss; that tss just changed from the one in the
pcb to common_tss (who knows where it was when there was no curpcb?).
Not using the pcb also fixed the problem that there is no pcb in
idle(), so we now always get useful register values.

The biggie: Get rid of the UPAGES from the top of the per-process address
space. (!)

Have each process use the kernel stack and pcb in the kvm space. Since
the stacks are at a different address, we cannot copy the stack at fork()
and allow the child to return up through the function call tree to return
to user mode - create a new execution context and have the new process
begin executing from cpu_switch() and go to user mode directly.
In theory this should speed up fork a bit.

Context switch the tss_esp0 pointer in the common tss. This is a lot
simpler since than swithching the gdt[GPROC0_SEL].sd.sd_base pointer
to each process's tss since the esp0 pointer is a 32 bit pointer, and the
sd_base setting is split into three different bit sections at non-aligned
boundaries and requires a lot of twiddling to reset.

The 8K of memory at the top of the process space is now empty, and unmapped
(and unmappable, it's higher than VM_MAXUSER_ADDRESS).

Simplity the pmap code to manage process contexts, we no longer have to
double map the UPAGES, this simplifies and should measuably speed up fork().

The following parts came from John Dyson:

Set PG_G on the UPAGES that are now in kernel context, and invalidate
them when swapping them out.

Move the upages object (upobj) from the vmspace to the proc structure.

Now that the UPAGES (pcb and kernel stack) are out of user space, make
rfork(..RFMEM..) do what was intended by sharing the vmspace
entirely via reference counting rather than simply inheriting the mappings.

No longer use an i386tss as the basis of our pcb - it wasn't particularly
convenient and makes life difficult for my next commit. We still need
an i386tss to point to for the tss slot in the gdt, so we use a common
tss shared between all processes.

Note that this is going to break debugging until this series of commits
is finished. core dumps will change again too. :-( we really need
a more modern core dump format that doesn't depend on the pcb/upages.

This change makes VM86 mode harder, but the following commits will remove
a lot of constraints for the VM86 system, including the possibility of
extending the pcb for an IO port map etc.

Obtained from: bde

Fix the gdb executable modify problem. Thanks to the detective work
by Alan Cox <alc@cs.rice.edu>, and his description of the problem.

The bug was primarily in procfs_mem, but the mistake likely happened
due to the lack of vm system support for the operation. I added
better support for selective marking of page dirty flags so that
vm_map_pageable(wiring) will not cause this problem again.

The code in procfs_mem is now less bogus (but maybe still a little
so.)

Back out part 1 of the MCFH that changed $Id$ to $FreeBSD$. We are not
ready for it yet.

This is the kernel Lite/2 commit. There are some requisite userland
changes, so don't expect to be able to run the kernel as-is (very well)
without the appropriate Lite/2 userland changes.

The system boots and can mount UFS filesystems.

Untested: ext2fs, msdosfs, NFS
Known problems: Incorrect Berkeley ID strings in some files.
Mount_std mounts will not work until the getfsent
library routine is changed.

Reviewed by: various people
Submitted by: Jeffery Hsu <hsu@freebsd.org>

Remove some dead code from trapwrite.
Submitted by: Stephen McKay <syssgm@devetir.qld.gov.au>

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

Only handle copyin/out/etc faults when not in an interrupt handler.
This makes unexpected faults (in an interrupt handler) more likely
to crash properly. It could be done even better (more robustly and
more efficiently) using lazy fault handling.

Updated #includes to 4.4Lite style.

Change an splclock that needs to be an splhigh into an splhigh.

Reviewed by: bde

Add support for i686 machine check trap.

Fixed cloned comments about npx traps to match context.

trap.c:
Fixed profiling of system times. It was pre-4.4Lite and didn't support
statclocks. System times were too small by a factor of 8.

Handle deferred profiling ticks the 4.4Lite way: use addupc_task() instead
of addupc(). Call addupc_task() directly instead of using the ADDUPC()
macro.

Removed vestigial support for PROFTIMER.

switch.s:
Removed addupc().

resourcevar.h:
Removed ADDUPC() and declarations of addupc().

cpu.h:
Updated a comment. i386's never were tahoe's, and the deferred profiling
tick became (possibly) multiple ticks in 4.4Lite.

Obtained from: mostly from NetBSD

A fast memory copy for Pentiums using floating point registers.
It is called from copyin and copyout.

The new routine is conditioned on I586_CPU and I586_FAST_BCOPY, so you
need

options "I586_FAST_BCOPY"

(quotes essenstial) in your kernel config file.

Also, if you have other kernel types configured in your kernel, an
additional check to make sure it is running on a Pentium is inserted.
(It is not clear why it doesn't help on P6s, it may be just that the
Orion chipset doesn't prefetch as efficiently as Tritons and friends.)

Bruce can now hack this away. :)

Clean up -Wunused warnings.

Reviewed by: bde

This set of commits to the VM system does the following, and contain
contributions or ideas from Stephen McKay <syssgm@devetir.qld.gov.au>,
Alan Cox <alc@cs.rice.edu>, David Greenman <davidg@freebsd.org> and me:

More usage of the TAILQ macros. Additional minor fix to queue.h.
Performance enhancements to the pageout daemon.
Addition of a wait in the case that the pageout daemon
has to run immediately.
Slightly modify the pageout algorithm.
Significant revamp of the pmap/fork code:
1) PTE's and UPAGES's are NO LONGER in the process's map.
2) PTE's and UPAGES's reside in their own objects.
3) TOTAL elimination of recursive page table pagefaults.
4) The page directory now resides in the PTE object.
5) Implemented pmap_copy, thereby speeding up fork time.
6) Changed the pv entries so that the head is a pointer
and not an entire entry.
7) Significant cleanup of pmap_protect, and pmap_remove.
8) Removed significant amounts of machine dependent
fork code from vm_glue. Pushed much of that code into
the machine dependent pmap module.
9) Support more completely the reuse of already zeroed
pages (Page table pages and page directories) as being
already zeroed.
Performance and code cleanups in vm_map:
1) Improved and simplified allocation of map entries.
2) Improved vm_map_copy code.
3) Corrected some minor problems in the simplify code.
Implemented splvm (combo of splbio and splimp.) The VM code now
seldom uses splhigh.
Improved the speed of and simplified kmem_malloc.
Minor mod to vm_fault to avoid using pre-zeroed pages in the case
of objects with backing objects along with the already
existant condition of having a vnode. (If there is a backing
object, there will likely be a COW... With a COW, it isn't
necessary to start with a pre-zeroed page.)
Minor reorg of source to perhaps improve locality of ref.

Remove a now unnecessary prototype from pmap.c. Also remove now
unnecessary vm_fault's of page table pages in trap.c.

Print stack pointer and frame pointer in trap messages.

Fixed "trace/trap" message.

Reviewed by: davidg

Mega-commit for Linux emulator update.. This has been stress tested under
netscape-2.0 for Linux running all the Java stuff. The scrollbars are now
working, at least on my machine. (whew! :-)

I'm uncomfortable with the size of this commit, but it's too
inter-dependant to easily seperate out.

The main changes:

COMPAT_LINUX is *GONE*. Most of the code has been moved out of the i386
machine dependent section into the linux emulator itself. The int 0x80
syscall code was almost identical to the lcall 7,0 code and a minor tweak
allows them to both be used with the same C code. All kernels can now
just modload the lkm and it'll DTRT without having to rebuild the kernel
first. Like IBCS2, you can statically compile it in with "options LINUX".

A pile of new syscalls implemented, including getdents(), llseek(),
readv(), writev(), msync(), personality(). The Linux-ELF libraries want
to use some of these.

linux_select() now obeys Linux semantics, ie: returns the time remaining
of the timeout value rather than leaving it the original value.

Quite a few bugs removed, including incorrect arguments being used in
syscalls.. eg: mixups between passing the sigset as an int, vs passing
it as a pointer and doing a copyin(), missing return values, unhandled
cases, SIOC* ioctls, etc.

The build for the code has changed. i386/conf/files now knows how
to build linux_genassym and generate linux_assym.h on the fly.

Supporting changes elsewhere in the kernel:

The user-mode signal trampoline has moved from the U area to immediately
below the top of the stack (below PS_STRINGS). This allows the different
binary emulations to have their own signal trampoline code (which gets rid
of the hardwired syscall 103 (sigreturn on BSD, syslog on Linux)) and so
that the emulator can provide the exact "struct sigcontext *" argument to
the program's signal handlers.

The sigstack's "ss_flags" now uses SS_DISABLE and SS_ONSTACK flags, which
have the same values as the re-used SA_DISABLE and SA_ONSTACK which are
intended for sigaction only. This enables the support of a SA_RESETHAND
flag to sigaction to implement the gross SYSV and Linux SA_ONESHOT signal
semantics where the signal handler is reset when it's triggered.

makesyscalls.sh no longer appends the struct sysentvec on the end of the
generated init_sysent.c code. It's a lot saner to have it in a seperate
file rather than trying to update the structure inside the awk script. :-)

At exec time, the dozen bytes or so of signal trampoline code are copied
to the top of the user's stack, rather than obtaining the trampoline code
the old way by getting a clone of the parent's user area. This allows
Linux and native binaries to freely exec each other without getting
trampolines mixed up.

Fix a problem with tracking the modified bit. Eliminate the
ugly inline-asm code, and speed up the page-table-page tracking.

Eliminated many redundant vm_map_lookup operations for vm_mmap.
Speed up for vfs_bio -- addition of a routine bqrelse to greatly diminish
overhead for merged cache.
Efficiency improvement for vfs_cluster. It used to do alot of redundant
calls to cluster_rbuild.
Correct the ordering for vrele of .text and release of credentials.
Use the selective tlb update for 486/586/P6.
Numerous fixes to the size of objects allocated for files. Additionally,
fixes in the various pagers.
Fixes for proper positioning of vnode_pager_setsize in msdosfs and ext2fs.
Fixes in the swap pager for exhausted resources. The pageout code
will not as readily thrash.
Change the page queue flags (PG_ACTIVE, PG_INACTIVE, PG_FREE, PG_CACHE) into
page queue indices (PQ_ACTIVE, PQ_INACTIVE, PQ_FREE, PQ_CACHE),
thereby improving efficiency of several routines.
Eliminate even more unnecessary vm_page_protect operations.
Significantly speed up process forks.
Make vm_object_page_clean more efficient, thereby eliminating the pause
that happens every 30seconds.
Make sequential clustered writes B_ASYNC instead of B_DELWRI even in the
case of filesystems mounted async.
Fix a panic with busy pages when write clustering is done for non-VMIO
buffers.

Convert DDB to new-style option.

Converted two options over to the new scheme: USER_LDT and KTRACE.

Corrected a typo in a comment.

Implemented a (sorely needed for years) double fault handler to catch stack
overflows.
It sure would be nice if there was an unmapped page between the PCB and
the stack (and that the size of the stack was configurable!). With the
way things are now, the PCB will get clobbered before the double fault
handler gets control, making somewhat of a mess of things. Despite this,
it is still fairly easy to poke around in the overflowed stack to figure
out the cause.

GENERIC/LINT: Remove redundant quoting on some option lines.
LINT: add a couple of new/missing/undocumented options
files.i386: add linux code so that you can compile a kernel with static
linux emulation ("options LINUX")
i386/*: use #if defined(COMPAT_LINUX) || defined(LINUX) to enable static
support of linux emulation (just like "IBCS2" makes ibcs2 static)

The main thing this is going to make obvious, is that the LINUX code
(when compiled from LINT) has a lot of warnings, some of which dont look
too pleasant..

Make math_emulators LKMable.

Remove various unused symbols and procedures.

Untangled the vm.h include file spaghetti.

Remove unused functions and variables, make things static, and other cleanups.

Fix tracing of syscalls. The previous fix required the undocumented
option DDB_NO_LCALLS to stop ddb getting control and broke all ddb
tracing. Now there is no option and no way for ddb to trace at
address _Xsyscall or to _Xsyscall, but tracing everywhere else
works. The previous fix did unnecessary things for Linux syscalls.

Don't bother checking that syscall frames are for user mode.

Make debugger traps inside the kernel (except at addresses _Xsyscall
and _Xsyscall+1) fatal if ddb is not configured. They "can't happen".

Add prototypes.

Remove stupid comments, e.g., /*ARGSUSED*/ for args that are used.

Submitted by: Juergen Lock <nox@jelal.hb.north.de>
Obtained from: other people on the net ?

1. stepping over syscalls (gdb ni) sends you to DDB, and returned
to the wrong address afterwards, with or without DDB. patch in
i386/i386/trap.c below.

2. the linux emulator (modload'ed) still causes panics with DIAGNOSTIC,
re-applied a patch posted to one of the lists...

A couple of micro optimizations to improve NULL syscall performance by
about 2%.

Fix a bug in my disabled version of trap_pfault()...curpcb may be NULL even
when curproc isn't. This condition occurs at system startup and perhaps
at other times.

This fixes a compiler warning, and a cosmetic problem with the linux
emul code when compiling with "options KTRACE".
ktrsyscall() was expecting an array of integers, this was passing the
address of a structure containing an array of integers..
The cosmetic problem was that it was calling the "enter syscall"
trace hook twice - this looks like a cut/paste error/typo.

Include ``options POWERFAIL_NMI'' for owners of older (non-apm)
notebooks where a powerfail condition (external power drop; battery
state low) is signalled by an NMI. Makes it beep instead of panicing.

Reviewed by: davidg

Truncate the fault address to a page boundry when calling vm_fault(). The
last change to fix the fault-twice bug with page tables wasn't quite
complete.

Fixed bug that caused page tables to be faulted twice instead of once.

Submitted by: John Dyson

Merge RELENG_2_0_5 into HEAD

Remove trailing whitespace.

Added a new version of trap_pfault() that disallows kernel page faults
to the user address space unless pcb_onfault is set. The code is currently
commented out because iBCS2 and process debugging parts of the kernel
need to be changed/fixed first.

Changed some #ifdef DIAGNOSTIC code that I added to be #ifdef DEBUG.

Add and move declarations to fix all of the warnings from `gcc -Wimplicit'
(except in netccitt, netiso and netns) and most of the warnings from
`gcc -Wnested-externs'. Fix all the bugs found. There were no serious
ones.

First attempt to run linux binaries. This is only the changes needed to
the generic kernel. The actual emulator is a separate LKM. (not finished
yet, sorry).
Submitted by: sos@freebsd.org & sef@kithrup.com

Removed unnecessary check for pr_scale in the AST/OWEUPC case.

Check P_PROFIL flag for profiling rather than pr_scale as it makes more
sense.

Changed buffer allocation policy (machdep.c)
Moved various pmap 'bit' test/set functions back into real functions; gcc
generates better code at the expense of more of it. (pmap.c)
Fixed a deadlock problem with pv entry allocations (pmap.c)
Added a new, optional function 'pmap_prefault' that does clustered page
table preloading (pmap.c)
Changed the way that page tables are held onto (trap.c).

Submitted by: John Dyson

Fix security holes in sigreturn(), ptrace() and procfs. sigreturn()
attempted to check for insecure and fatal eflags and segment
selectors, but missed many cases and got the IOPL check back to
front. The other syscalls didn't check at all.

sys_process.c, machdep.c:
Only allow PT_WRITE_U to write to the registers (ordinary and FP).

psl.h, locore.s, machdep.c:
Eliminate PSL_MBZ, PSL_MBO and PSL_USERCLR. We are not supposed
to assume anything about the reserved bits. Use PSL_USERCHANGE
and PSL_KERNEL instead. Rename PSL_USERSET to PSL_USER.

exception.s:
Define a private label for use by doreti when returning to user
mode fails.

machdep.c:
In syscalls, allow changing only the eflags that can be changed on
486's in user mode (no longer attempt to allow benign IOPL changes;
allow changing the nasty PSL_NT; don't allow changing the i586
bits).

Don't attempt to check all the cases involving invalid selectors
and %eip's. Just check for privilege violations and let the invalid
things cause a trap.

procfs_machdep.c:
Call the ptrace register functions to do all the work for reading
and writing ordinary registers and for single stepping.

trap.c:
Ignore traps caused by PSL_NT being set. Previously, users could
cause a fatal trap in user mode by setting PSL_NT and executing an
iret, and a fatal trap in kernel mode by setting PSL_NT and making
a syscall. PSL_NT was cleared too late and not in enough modes to
fix the problem.

Make all traps in user mode (except T_NMI) nonfatal.

Recover from traps caused by attempting to load invalid user
registers in doreti by restarting the traps so that they appear to
occur in user mode.
---

Fix bogons that I noticed while fixing the above:

psl.h:
Fix some comments.

Uniformize idempotency ifdef.

exception.s, machdep.c:
Remove rsvd[0-14]. rsvd0 hasn't been reserved since the 486 came
out. Replace rsvd0 by `align'. rsvd[0-11] used wrong (magic
non-unique) trap numbers. Replace rsvd[1-14] by rsvd.

locore.s:
Enable alignment check flag on 486's and 586's.

machdep.c:
Use a better type for kstack[].

Use TFREGP() to find the registers.

Reformat ptrace functions from SEF to something closer to KNF.

procfs_machdep.c:
The wrong pointer to the registers got fixed as a side effect.

Implement reading and writing of FP registers.

/proc/*/*regs now work (only) for processes that are in memory.

Clean up comments.

trap.c, trap.h:
Remove unused trap types.

These changes embody the support of the fully coherent merged VM buffer cache,
much higher filesystem I/O performance, and much better paging performance. It
represents the culmination of over 6 months of R&D.

The majority of the merged VM/cache work is by John Dyson.

The following highlights the most significant changes. Additionally, there are
(mostly minor) changes to the various filesystem modules (nfs, msdosfs, etc) to
support the new VM/buffer scheme.

vfs_bio.c:
Significant rewrite of most of vfs_bio to support the merged VM buffer cache
scheme. The scheme is almost fully compatible with the old filesystem
interface. Significant improvement in the number of opportunities for write
clustering.

vfs_cluster.c, vfs_subr.c
Upgrade and performance enhancements in vfs layer code to support merged
VM/buffer cache. Fixup of vfs_cluster to eliminate the bogus pagemove stuff.

vm_object.c:
Yet more improvements in the collapse code. Elimination of some windows that
can cause list corruption.

vm_pageout.c:
Fixed it, it really works better now. Somehow in 2.0, some "enhancements"
broke the code. This code has been reworked from the ground-up.

vm_fault.c, vm_page.c, pmap.c, vm_object.c
Support for small-block filesystems with merged VM/buffer cache scheme.

pmap.c vm_map.c
Dynamic kernel VM size, now we dont have to pre-allocate excessive numbers of
kernel PTs.

vm_glue.c
Much simpler and more effective swapping code. No more gratuitous swapping.

proc.h
Fixed the problem that the p_lock flag was not being cleared on a fork.

swap_pager.c, vnode_pager.c
Removal of old vfs_bio cruft to support the past pseudo-coherency. Now the
code doesn't need it anymore.

machdep.c
Changes to better support the parameter values for the merged VM/buffer cache
scheme.

machdep.c, kern_exec.c, vm_glue.c
Implemented a seperate submap for temporary exec string space and another one
to contain process upages. This eliminates all map fragmentation problems
that previously existed.

ffs_inode.c, ufs_inode.c, ufs_readwrite.c
Changes for merged VM/buffer cache. Add "bypass" support for sneaking in on
busy buffers.

Submitted by: John Dyson and David Greenman

Obtained from: 1.1.5

Fix single-stepping of emulated FPU instructions.

Don't panic if an FPU instruction is attempted but there is no FPU
and no FPU emulator is configured.

Fix selector arg to match the (missing) prototype for sdtossd().
Cosmetic.

Return from trap() if trap_fatal() returns. trap_fatal() isn't
fatal if you have ddb. Returning from trap() is usually the right
thing to do and much better than falling through.

Make my ALLDEVS kernel compile (basically, LINT minus a lot of options).

Ouch, fixed bug in errno translation (ibcs2 support).

Hmm, only translate errno when doing an actual return.

Reviewed by: sef@freefall.cdrom.com

Updated to convert errno return in syscall if conversion tabel present.

db_disasm.c: Unused var zapped.
pmap.c: tons of unused vars zapped, various other warnings silenced.
trap.c: unused vars zapped.
vm_machdep.c: A wrong argument, which by chance did the right thing, was
corrected.

Laptop Advanced Power Management support by HOSOKAWA Tatsumi.

Submitted by: HOSOKAWA Tatsumi

Be more careful about dereferencing curproc, p_vmspace, and curpcb,
otherwise the machine will overflow the stack in a recursive fault loop
(causing the machine to spontaneously reboot because of the stack fault
that ultimately happens).

Submitted by: Inspired by Bruce Evans, but this change is different
than what he suggested.

Remove <machine/eflags.h> and all dependencies on it. eflags.h is just
the Mach/i386 version of the BSD/vax(?) <machine/psl.h>. The Mach
version has slightly better names for many macros but is now out of
date and little used. It was originally used even less (for spelling
PSL_T as EFL_TF in <machine/db_machdep.h>).

Don't test if a u_int is < 0. The remaining test is sufficient and the
extra one caused a warning.

1) Changed ddb into a option rather than a pseudo-device (use options DDB
in your kernel config now).
2) Added ps ddb function from 1.1.5. Cleaned it up a bit and moved into its
own file.
3) Added \r handing in db_printf.
4) Added missing memory usage stats to statclock().
5) Added dummy function to pseudo_set so it will be emitted if there
are no other pseudo declarations.

Changes preparing for iBCS support
Reviewed by:
Submitted by:

Fix up some sloppy coding practices:

- Delete redundant declarations.
- Add -Wredundant-declarations to Makefile.i386 so they don't come back.
- Delete sloppy COMMON-style declarations of uninitialized data in
header files.
- Add a few prototypes.
- Clean up warnings resulting from the above.

NB: ioconf.c will still generate a redundant-declaration warning, which
is unavoidable unless somebody volunteers to make `config' smarter.

Handle NMI's in accordance with data in van Gilluwe book.

Removed all code related to the pagescan daemon, and changed 'act_count'
adjustments to compensate for a world without the pagescan daemon.

Fixed minor spelling error.

trap.c:
Vastly improved trap.c from me. This rewritten version has a variety of
features, amoung them: higher performance and much higher code quality.

support.s, cpufunc.h:
No longer use gs override to enforce range limits - compare directly
against VM_MAXUSER_ADDRESS instead. The old way caused problems in
preserving the gs selector...and this method is just as fast or faster.

The big 4.4BSD Lite to FreeBSD 2.0.0 (Development) patch.

Reviewed by: Rodney W. Grimes
Submitted by: John Dyson and David Greenman

Added ifdef for GPL_MATH_EMULATE to keep the sytem from panicing when
using it.

Make Bruce happy: silently enter ddb on a BPT or trace trap if ddb is
configured in the kernel.

New interrupt code from Bruce Evans. In additional to Bruce's attached
list of changes, I've made the following additional changes:

1) i386/include/ipl.h renamed to spl.h as the name conflicts with the
file of the same name in i386/isa/ipl.h.
2) changed all use of *mask (i.e. netmask, biomask, ttymask, etc) to
*_imask (net_imask, etc).
3) changed vestige of splnet use in if_is to splimp.
4) got rid of "impmask" completely (Bruce had gotten rid of netmask),
and are now using net_imask instead.
5) dozens of minor cruft to glue in Bruce's changes.

These require changes I made to config(8) as well, and thus it must
be rebuilt.

-DG

from Bruce Evans:

sio:
o No diff is supplied. Remove the define of setsofttty(). I hope
that is enough.

*.s:
o i386/isa/debug.h no longer exists. The event counters became too
much trouble to maintain. All function call entry and exception
entry counters can be recovered by using profiling kernel (the new
profiling supports all entry points; however, it is too slow to
leave enabled all the time; it also). Only BDBTRAP() from debug.h
is now used. That is moved to exception.s. It might be worth
preserving SHOW_BITS() and calling it from _mcount() (if enabled).
o T_ASTFLT is now only set just before calling trap().
o All exception handlers set SWI_AST_MASK in cpl as soon as possible
after entry and arrange for _doreti to restore it atomically with
exiting. It is not possible to set it atomically with entering
the kernel, so it must be checked against the user mode bits in
the trap frame before committing to using it. There is no place
to store the old value of cpl for syscalls or traps, so there are
some complications restoring it.

Profiling stuff (mostly in *.s):
o Changes to kern/subr_mcount.c, gcc and gprof are not supplied yet.
o All interesting labels `foo' are renamed `_foo' and all
uninteresting labels `_bar' are renamed `bar'. A small change
to gprof allows ignoring labels not starting with underscores.
o MCOUNT_LABEL() is to provide names for counters for times spent
in exception handlers.
o FAKE_MCOUNT() is a version of MCOUNT() suitable for exception
handlers. Its arg is the pc where the exception occurred. The
new mcount() pretends that this was a call from that pc to a
suitable MCOUNT_LABEL().
o MEXITCOUNT is to turn off any timer started by MCOUNT().

/usr/src/sys/i386/i386/exception.s:
o The non-BDB BPTTRAP() macros were doing a sti even when interrupts
were disabled when the trap occurred. The sti (fixed) sti is
actually a no-op unless you have my changes to machdep.c that make
the debugger trap gates interrupt gates, but fixing that would
make the ifdefs messier. ddb seems to be unharmed by both
interrupts always disabled and always enabled (I had the branch in
the fix back to front for some time :-().
o There is no known pushal bug.
o tf_err can be left as garbage for syscalls.

/usr/src/sys/i386/i386/locore.s:
o Fix and update BDE_DEBUGGER support.
o ENTRY(btext) before initialization was dangerous.
o Warm boot shot was longer than intended.

/usr/src/sys/i386/i386/machdep.c:
o DON'T APPLY ALL OF THIS DIFF. It's what I'm using, but may require
other changes.
Use the following:
o Remove aston() and setsoftclock().
Maybe use the following:
o No netisr.h.
o Spelling fix.
o Delay to read the Rebooting message.
o Fix for vm system unmapping a reduced area of memory
after bounds_check_with_label() reduces the size of
a physical i/o for a partition boundary. A similar
fix is required in kern_physio.c.
o Correct use of __CONCAT. It never worked here for non-
ANSI cpp's. Is it time to drop support for non-ANSI?
o gdt_segs init. 0xffffffffUL is bogus because ssd_limit
is not 32 bits. The replacement may have the same
value :-), but is more natural.
o physmem was one page too low. Confusing variable names.
Don't use the following:
o Better numbers of buffers. Each 8K page requires up to
16 buffer headers. On my system, this results in 5576
buffers containing [up to] 2854912 bytes of memory.
The usual allocation of about 384 buffers only holds
192K of disk if you use it on an fs with a block size
of 512.
o gdt changes for bdb.
o *TGT -> *IDT changes for bdb.
o #ifdefed changes for bdb.

/usr/src/sys/i386/i386/microtime.s:
o Use the correct asm macros. I think asm.h was copied from Mach
just for microtime and isn't used now. It certainly doesn't
belong in <sys>. Various macros are also duplicated in
sys/i386/boot.h and libc/i386/*.h.
o Don't switch to and from the IRR; it is guaranteed to be selected
(default after ICU init and explicitly selected in isa.c too, and
never changed until the old microtime clobbered it).

/usr/src/sys/i386/i386/support.s:
o Non-essential changes (none related to spls or profiling).
o Removed slow loads of %gs again. The LDT support may require
not relying on %gs, but loading it is not the way to fix it!
Some places (copyin ...) forgot to load it. Loading it clobbers
the user %gs. trap() still loads it after certain types of
faults so that fuword() etc can rely on it without loading it
explicitly. Exception handlers don't restore it. If we want
to preserve the user %gs, then the fastest method is to not
touch it except for context switches. Comparing with
VM_MAXUSER_ADDRESS and branching takes only 2 or 4 cycles on
a 486, while loading %gs takes 9 cycles and using it takes
another.
o Fixed a signed branch to unsigned.

/usr/src/sys/i386/i386/swtch.s:
o Move spl0() outside of idle loop.
o Remove cli/sti from idle loop. sw1 does a cli, and in the
unlikely event of an interrupt occurring and whichqs becoming
zero, sw1 will just jump back to _idle.
o There's no spl0() function in asm any more, so use splz().
o swtch() doesn't need to be superaligned, at least with the
new mcounting.
o Fixed a signed branch to unsigned.
o Removed astoff().

/usr/src/sys/i386/i386/trap.c:
o The decentralized extern decls were inconsistent, of course.
o Fixed typo MATH_EMULTATE in comments. */
o Removed unused variables.
o Old netmask is now impmask; print it instead. Perhaps we
should print some of the new masks.
o BTW, trap() should not print anything for normal debugger
traps.

/usr/src/sys/i386/include/asmacros.h:
o DON'T APPLY ALL OF THIS DIFF. Just use some of the null macros
as necessary.

/usr/src/sys/i386/include/cpu.h:
o CLKF_BASEPRI() changes since cpl == SWI_AST_MASK is now normal
while the kernel is running.
o Don't use var++ to set boolean variables. It fails after a mere
4G times :-) and is slower than storing a constant on [3-4]86s.

/usr/src/sys/i386/include/cpufunc.h:
o DON'T APPLY ALL OF THIS DIFF. You need mainly the include of
<machine/ipl.h>. Unfortunately, <machine/ipl.h> is needed by
almost everything for the inlines.

/usr/src/sys/i386/include/ipl.h:
o New file. Defines spl inlines and SWI macros and declares most
variables related to hard and soft interrupt masks.

/usr/src/sys/i386/isa/icu.h:
o Moved definitions to <machine/ipl.h>

/usr/src/sys/i386/isa/icu.s:
o Software interrupts (SWIs) and delayed hardware interrupts (HWIs)
are now handled uniformally, and dispatching them from splx() is
more like dispatching them from _doreti. The dispatcher is
essentially *(handler[ffs(ipending & ~cpl)]().
o More care (not quite enough) is taken to avoid unbounded nesting
of interrupts.
o The interface to softclock() is changed so that a trap frame is
not required.
o Fast interrupt handlers are now handled more uniformally.
Configuration is still too early (new handlers would require
bits in <machine/ipl.h> and functions to vector.s).
o splnnn() and splx() are no longer here; they are inline functions
(could be macros for other compilers). splz() is the nontrivial
part of the old splx().

/usr/src/sys/i386/isa/ipl.h
o New file. Supposed to have only bus-dependent stuff. Perhaps
the h/w masks should be declared here.

/usr/src/sys/i386/isa/isa.c:
o DON'T APPLY ALL OF THIS DIFF. You need only things involving
*mask and *MASK and comments about them. netmask is now a pure
software mask. It works like the softclock mask.

/usr/src/sys/i386/isa/vector.s:
o Reorganize AUTO_EOI* macros.
o Option FAST_INTR_HANDLER_USERS_ES for people who don't trust
fastintr handlers.
o fastintr handlers need to metamorphose into ordinary interrupt
handlers if their SWI bit has become set. Previously, sio had
unintended latency for handling output completions and input
of SLIP framing characters because this was not done.

/usr/src/sys/net/netisr.h:
o The machine-dependent stuff is now imported from <machine/ipl.h>.

/usr/src/sys/sys/systm.h
o DON'T APPLY ALL OF THIS DIFF. You need mainly the different
splx() prototype. The spl*() prototypes are duplicated as
inlines in <machine/ipl.h> but they need to be duplicated here
in case there are no inlines. I sent systm.h and cpufunc.h
to Garrett. We agree that spl0 should be replaced by splnone
and not the other way around like I've done.

/usr/src/sys/kern/kern_clock.c
o splsoftclock() now lowers cpl so the direct call to softclock()
works as intended.
o softclock() interface changed to avoid passing the whole frame
(some machines may need another change for profile_tick()).
o profiling renamed _profiling to avoid ANSI namespace pollution.
(I had to improve the mcount() interface and may as well fix it.)
The GUPROF variant doesn't actually reference profiling here,
but the 'U' in GUPROF should mean to select the microtimer
mcount() and not change the interface.

From John Dyson: performance improvements to the new bounce buffer
code.

Performance improvements from John Dyson.

1) A new mechanism has been added to prevent pages from being paged
out called "vm_page_hold". Similar to vm_page_wire, but
much lower overhead.
2) Scheduling algorithm has been changed to improve interactive
performance.
3) Paging algorithm improved.
4) Some vnode and swap pager bugs fixed.

1) "Pre-faulting" in of pages into process address space
Eliminates vm_fault overhead on process startup and
mmap referenced data for in-memory pages.

(process startup time using in-memory segments *much* faster)

2) Even more efficient pmap code. Code partially cleaned up.
More comments yet to follow.

(generally more efficient pte management)

3) Pageout clustering ( in addition to the FreeBSD V1.1 pagein
clustering.)

(much faster paging performance on non-write behind disk
subsystems, slightly faster performance on other systems.)

4) Slightly changed vm_pageout code for more efficiency and
better statistics. Also, resist swapout a little more.

(less likely to pageout a recently used page)

5) Slight improvement to the page table page trap efficiency.

(generally faster system VM fault performance)

6) Defer creation of unnamed anonymous regions pager until needed.

(speeds up shared memory bss creation)

7) Remove possible deadlock from swap_pager initialization.

8) Enhanced procfs to provide "vminfo" about vm objects and user
pmaps.

9) Increased MCLSHIFT/MCLBYTES from 2K to 4K to improve net &
socket performance and to prepare for things to come.

John Dyson
dyson@implode.root.com
David Greenman
davidg@root.com

Fixed bugs in stack grow code, and moved it back into a seperate function
like it was originally. Also added back call to "grow" in sendsig now
that this routine actually works.

Minor cleanup. Decode state information better in the case of a fatal
trap.

Improvements mostly from John Dyson, with a little bit from me.

* Removed pmap_is_wired
* added extra cli/sti protection in idle (swtch.s)
* slight code improvement in trap.c
* added lots of comments
* improved paging and other algorithms in VM system

"New" VM system from John Dyson & myself. For a run-down of the
major changes, see the log of any effected file in the sys/vm
directory (swap_pager.c for instance).

Convert syscall to trapframe. Based on work done by John Brezak.

Make everything compile with -Wtraditional. Make it easier to distribute
a binary link-kit. Make all non-optional options (pagers, procfs) standard,
and update LINT to reflect new symtab requirements.

NB: -Wtraditional will henceforth be forgotten. This editing pass was
primarily intended to detect any constructions where the old code might
have been relying on traditional C semantics or syntax. These were all
fixed, and the result of fixing some of them means that -Wall is now a
realistic possibility within a few weeks.

1) Added proc file system from Paul Kranenburg with changes from
John Dyson to make it reliably work under FreeBSD.
2) Added and enabled PROCFS in the GENERICxx and LINT kernels.
3) New execve() from me. Still work to be done here, but this version
works well and is needed before other changes can be made. For
a description of the design behind this, see freebsd-arch or
ask me.
4) Rewrote stack fault code; made user stack VM grow as needed rather
than all up front; improves performance a little and reduces
process memory requirements.
5) Incorporated fix from Gene Stark to fault/wire a user page table
page to fix a problem in copyout. This is a temporary fix and
is not appropriate for pageable page tables. For a description
of the problem, see Gene's post to the freebsd-hackers mailing
list.
6) Tighten up vm_page struct to reduce memory requirements for it. ifdef
pager page lock code as it's not being used currently.
7) Introduced new element to vmspace struct - vm_minsaddr; initial
(minimum) stack address. Compliment to vm_maxsaddr.
8) Added a panic if the allocation for process u-pages fails.
9) Improve performance and accuracy of kernel profiling by putting in
a little inline assembly instead of spl().
10) Made serial console with sio driver work. Still has problems with
serial input, but is almost useable.
11) Added -Bstatic to SYSTEM_LD in Makefile.i386 so that kernels will
build properly with the new ld.

From: Jeffrey Hsu <hsu@soda.berkeley.edu>

The following patch adds the addr argument to signal handlers.

The kernel with the patch is no more and no less in compliance or in
violation of POSIX and ANSI C than the kernel before the patch.

The added functionality this addr argument provides is quite useful. It
enables an entire class of algorithms which use mprotect to trace memory
references. Beside garbage collectors, I have heard of this technique being
applied to debuggers and profilers. The only benchmarking I've performed is
using akcl to compile maxima: without the kernel patch, it takes 7 hours to
compile maxima, while with stratified garbage collection, it only takes 50
minutes.

Basically, I can't think of a reason not to add the addr argument and there
is a compelling need for it.

If you find the patch acceptable, please let me know so I can send my
FreeBSD akcl config files to wfs for inclusion in the core akcl release.
The old 386BSD config files there won't work on either NetBSD or FreeBSD.