Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Add a convenience macro for the returns_twice attribute, and apply it to
the prototypes of the appropriate functions (getcontext, savectx,
setjmp, sigsetjmp and vfork).

MFC after: 2 weeks

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

Convert the remainder of the low hanging fruits regarding including
headers in .S directly rather than getting to their macros through
genassym.c/assym.s so there are less headers genassym.c has to be
kept in sync with.
While at it fix some stytle(9) bugs (indentation, prototype format,
sort headers, etc) and remove trailing whitespace.

Implement makectx(). The makectx() function is used by KDB to create
a PCB from a trapframe for purposes of unwinding the stack. The PCB
is used as the thread context and all but the thread that entered the
debugger has a valid PCB.
This function can also be used to create a context for the threads
running on the CPUs that have been stopped when the debugger got
entered. This however is not done at the time of this commit.

- Add space for kernel floating point registers to the pcb. These will be
used to support block copy and zero operations in the kernel which use the
floating point registers.
- While I'm changing the size, improve the layout of struct pcb, sort by size,
then alphabetical etc.
- Add some assertions to validate assumptions made about how the pcb is
allocated.

- Add a flags field to struct pcb. Use this to keep track of wether or
not the pcb has floating point registers saved in it.
- Implement get_mcontext and set_mcontext.

- Rename pcb_fpstate to pcb_ufp (user floating point), and change it to
a simple array of 64 ints.
- Use a critical section when saving floating point state in cpu_fork
instead of sched_lock.

Rename pcb_fp to pcb_sp, so as to not be confused with floating point
state.

Explicitely specify an alignment for struct pcb. While all regular pcb's
are positioned and aligned by md code, dumppcb is just a static
variable and requires this.

The a.out md_coredump stuff isn't referenced anywhere anymore, and
hasn't been filled in for ages.. Nuked.

Demark sections of code that need special fault handling with labels.
Check if the trapped pc is inside of the demarked sections to implement
fault recovery for copyin etc, instead of pcb_onfault. Handle recovery
from data access exceptions as well as page faults.

Inspired by: bde's sys.dif

Remove pcb_y. It has moved to trapframe.

1. Convert the tstate saved in the pcb to a pstate and test for PSTATE_PEF
to determine if a process is using floating point. in order to avoid
sign extending a 13 bit immediate.
2. We don't need to context switch cwp anymore, it is better to just
fiddle the save tstate on return from traps. See exception.s 1.10
and 1.12.
3. Completely remove pcb_cwp.
4. Implement vmapbuf, vunmapbuf and vm_fault_quick. Completely remove
TODOs from vm_machdep.c (yay!).

Submitted by: tmm (1, 3, 4)
Obtained from: existing archs (4)

style(9) the structure definitions.

Implement a slightly different window spill/fill algorithm for dealing
with user windows in kernel mode. We split the windows using %otherwin,
but instead of spilling user window directly to the pcb, we attempt to
spill to user space. If this fails because a stack page is not resident
(or the stack is smashed), the fault handler at tl 2 will detect the
situation and resume at tl 1 again where recovery code can spill to the
pcb. Any windows that have been saved to the pcb will be copied out to
the user stack on return from kernel mode.

Add a first stab at 32 bit window handling. This uses much of the same
recovery code as above because the alignment of the stack pointer is used
to detect 32 bit code. Attempting to spill a 32 bit window to a 64 bit
stack, or vice versa, will cause an alignment fault. The recovery code
then changes the window state to vector to a 32 bit spill/fill handler
and retries the faulting instruction.

Add ktr traces in useful places during trap processing.

Adjust comments to reflect new code and add many more.

Add support for splitting the register windows on entry to the
kernel from usermode. The remaining user windows are spilled
to the pcb as necessary. The user land window fault handlers
fill directly from the pcb on return.
Add system call entry points.

Submitted by: tmm

The author isn't a [UC] Regents. Correct the copyright language.

Add floating point context switching code for sparc64.

Reviewed by: jake

Flesh out the sparc64 port considerably. This contains:
- mostly complete kernel pmap support, and tested but currently turned
off userland pmap support
- low level assembly language trap, context switching and support code
- fully implemented atomic.h and supporting cpufunc.h
- some support for kernel debugging with ddb
- various header tweaks and filling out of machine dependent structures

Add skeleton machine dependent headers and c files for a port of freebsd
to a new architecture. This is the base of the sparc64 port, but contains
limited machine dependent code, and can be used a base for ports. Included
are:
- standard machine dependent headers, tweaked for a 64 bit, big endian
architecture, including empty versions of all the machine dependent
structures
- a machine independent atomic.h, which can be used until a port has
support for interrupts and the operations really need to be atomic
- stub versions of all the machine dependent functions, which panic
when called and print out the name of the function that needs to
be implemented. functions which are normally in assembly files are
not included, but this should reduce the number of different undefined
references on the first few compiles from hundreds to 5 or 6
Given minimal startup code and console support it should be trivial to
make this compile and run the first few sysinits on almost any architecture.

Requested by: alfred, imp, jhb