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MIPS: Clear ISA bit correctly in get_frame_info()

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get_frame_info() can be called in microMIPS kernels with the ISA bit
already clear. For example this happens when unwind_stack_by_address()
is called because we begin with a PC that has the ISA bit set & subtract
the (odd) offset from the preceding symbol (which does not have the ISA
bit set). Since get_frame_info() unconditionally subtracts 1 from the PC
in microMIPS kernels it incorrectly misaligns the address it then
attempts to access code at, leading to an address error exception.

Fix this by using msk_isa16_mode() to clear the ISA bit, which allows
get_frame_info() to function regardless of whether it is provided with a
PC that has the ISA bit set or not.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 34c2f668d0 ("MIPS: microMIPS: Add unaligned access support.")
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # v3.10+
Patchwork: https://patchwork.linux-mips.org/patch/14528/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2016-11-07 15:07:02 +00:00 committed by Ralf Baechle
parent ca0c40c38c
commit ccaf7caf2c
1 changed files with 2 additions and 5 deletions
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7
arch/mips/kernel/process.c
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@ -304,17 +304,14 @@ static inline int is_sp_move_ins(union mips_instruction *ip)
static int get_frame_info(struct mips_frame_info *info)
{
#ifdef CONFIG_CPU_MICROMIPS
union mips_instruction *ip = (void *) (((char *) info->func) - 1);
#else
union mips_instruction *ip = info->func;
#endif
union mips_instruction *ip;
unsigned max_insns = info->func_size / sizeof(union mips_instruction);
unsigned i;
info->pc_offset = -1;
info->frame_size = 0;
ip = (void *)msk_isa16_mode((ulong)info->func);
if (!ip)
goto err;