Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r253604: rename scheduler->swapper and SI_SUB_RUN_SCHEDULER->SI_SUB_LAST

Toss bogus mergeinfo.

MFC 234190,234196,234280:
- Extend the KDB interface to add a per-debugger callback to print a
backtrace for an arbitrary thread (rather than the calling thread).
A kdb_backtrace_thread() wrapper function uses the configured debugger
if possible, otherwise it falls back to using stack(9) if that is
available.
- Replace a direct call to db_trace_thread() in propagate_priority()
with a call to kdb_backtrace_thread() instead.

MFC r235634

Fix and update battery status bits according to linux driver

MFC r228631: kern cons: introduce infrastructure for console grabbing by
kernel

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Modify kdb_trap() so that it re-calls the dbbe_trap function as long as
the debugger back-end has changed. This means that switching from ddb
to gdb no longer requires a "step" which can be dangerous on an
already-crashed kernel.

Also add a capability to get from the gdb back-end back to ddb, by
typing ^C in the console window.

While here, simplify kdb_sysctl_available() by using
sbuf_new_for_sysctl(), and use strlcpy() instead of strncpy() since the
strlcpy semantic is desired.

MFC after: 1 month

there must be only one SYSINIT with SI_SUB_RUN_SCHEDULER+SI_ORDER_ANY order

SI_SUB_RUN_SCHEDULER+SI_ORDER_ANY should only be used to call
scheduler() function which turns the initial thread into swapper proper
and thus there is no further SYSINIT processing.
Other SYSINITs with SI_SUB_RUN_SCHEDULER+SI_ORDER_ANY may get ordered
after scheduler() and thus never executed. That particular relative
order is semi-arbitrary.

Thus, change such places to use SI_ORDER_MIDDLE.
Also, use SI_ORDER_MIDDLE instead of correct, but less appealing,
SI_ORDER_ANY - 1.

MFC after: 1 week

Commit SYSINIT() ;-adding patch missed in previous pass.

MFC after: 1 month
Caught by: tinderbox

Add support for kgdb's 'detach' command.

Reviewed by: marcel
Sponsored by: Network Appliance

Add kdb_cpu_sync_icache(), intended to synchronize instruction
caches with data caches after writing to memory. This typically
is required to make breakpoints work on ia64 and powerpc. For
those architectures the function is implemented.

Convert to new console api

Eliminate gdb_checkc member from GDB_DBGPORT(), it is never used.

Use polling behaviour for gdb_getc() where convenient, this edges us
closer to the console code.

Don't use GDB_DBGPORT() macro to fill in dummy element in gdb_dbgport_set.

Wrap our drivers gdb_getc() function so that if it returns -1 we
try again. This way it matches the console behaviour and allows us
to share more code.

add support for copying console messages to a remote gdb

Reviewed by: kan

check return value of gdb_rx_varhex

Noticed by: Coverity Prevent analysis tool
Reviewed by: kan

/* -> /*- for copyright notices, minor format tweaks as necessary

Change gdb_cpu_setreg() to not take the value to which to set the
specified register, but a pointer to the in-memory representation of
that value. The reason for this is twofold:
1. Not all registers can be represented by a register_t. In particular
FP registers fall in that category. Passing the new register value
by reference instead of by value makes this point moot.
2. When we receive a G or P packet, both are for writing a register,
the packet will have the register value in target-byte order and
in the memory representation (modulo the fact that bytes are sent
as 2 printable hexadecimal numbers of course). We only need to
decode the packet to have a pointer to the register value.

This change fixes the bug of extracting the register value of the P
packet as a hexadecimal number instead of as a bit array. The quick
(and dirty) fix to bswap the register value in gdb_cpu_setreg() as
it has been added on i386 and amd64 can therefore be removed and has
in fact been that.

Tested on: alpha, amd64, i386, ia64, sparc64

Comment-out the debugging printf I left in in case there were some
packet related problems. No problems have been reported.

Introduce the GDB debugger backend for the new KDB framework. The
backend improves over the old GDB support in the following ways:
o Unified implementation with minimal MD code.
o A simple interface for devices to register themselves as debug
ports, ala consoles.
o Compression by using run-length encoding.
o Implements GDB threading support.