The only way the debugger can handle a trap in inside rcu_lock,
notify_die, or atomic_notifier_call_chain without a triple fault is
to have a low level "first opportunity handler" in the int3 exception
handler.

Generally this will be something the vast majority of folks will not
need, but for those who need it, it is added as a kernel .config
option called KGDB_LOW_LEVEL_TRAP.

CC: Ingo Molnar <mingo@elte.hu>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: H. Peter Anvin <hpa@zytor.com>
CC: x86@kernel.org
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:

a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

On x86_64 the gdb serial register structure defines the PS (also known
as eflags), CS and SS registers as 4 bytes entities.

This patch splits the x86_64 regnames enum into a 32 and 64 version to
account for the 32 bit entities in the gdb serial packets.

Also the program counter is properly filled in for the sleeping
threads.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

The BX and DX registers in the gdb serial register packet need to be
flipped for gdb to receive the correct data.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

This patch is the result of an automatic script that consolidates the
format of all the headers in include/asm-x86/.

The format:

1. No leading underscore. Names with leading underscores are reserved.
2. Pathname components are separated by two underscores. So we can
   distinguish between mm_types.h and mm/types.h.
3. Everything except letters and numbers are turned into single
   underscores.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

simplified and streamlined kgdb support on x86, both 32-bit and 64-bit,
based on patch from:

  Subject: kgdb: core-lite
  From: Jason Wessel <jason.wessel@windriver.com>

[ and countless other authors - see the patch for details. ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Signed-off-by: NJan Kiszka <jan.kiszka@web.de>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>