The MIPS frame save code was just saving a few registers, enough to
do a backtrace if every function set up a frame.  However, this is
not working if you are using DWARF unwinding, because most of the
registers are wrong.  This was causing kdump backtraces to be short
or bogus.

So save all the registers.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16989/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

The unwind_stack_by_address variant supports unwinding based
on any kernel code address.
This symbol is also exported so it can be called from modules.
Signed-off-by: NDaniel Kalmar <kalmard@homejinni.com>
Signed-off-by: NGergely Kis <gergely@homejinni.com>
Signed-off-by: NRobert Richter <robert.richter@amd.com>

Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

And gcc 3.4 doesn't even warn out this, grrr.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

  CC      arch/mips/kernel/traps.o
arch/mips/kernel/traps.c: In function 'show_backtrace':
arch/mips/kernel/traps.c:110: warning: unused variable 'ra'
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

If the PC was ret_from_irq or ret_from_exception, there will be no
more normal stackframe.  Instead of stopping the unwinding, use PC and
RA saved by an exception handler to continue unwinding into the
interrupted context.  This also simplifies the CONFIG_STACKTRACE code.
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

Implement stacktrace interface by using unwind_stack() and enable lockdep
support in Kconfig.
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>