arm64: vdso: Don't prefix sigreturn trampoline with a BTI C instruction

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For better or worse, GDB relies on the exact instruction sequence in the
VDSO sigreturn trampoline in order to unwind from signals correctly.
Commit c91db232da ("arm64: vdso: Convert to modern assembler annotations")
unfortunately added a BTI C instruction to the start of __kernel_rt_sigreturn,
which breaks this check. Thankfully, it's also not required, since the
trampoline is called from a RET instruction when returning from the signal
handler

Remove the unnecessary BTI C instruction from __kernel_rt_sigreturn,
and do the same for the 32-bit VDSO as well for good measure.

Cc: Daniel Kiss <daniel.kiss@arm.com>
Cc: Tamas Zsoldos <tamas.zsoldos@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Fixes: c91db232da ("arm64: vdso: Convert to modern assembler annotations")
Signed-off-by: Will Deacon <will@kernel.org>

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This commit is contained in:

Will Deacon 2020-05-19 12:38:33 +01:00

parent e4e9f6dfee

commit 9a96428557

3 changed files with 20 additions and 13 deletions

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6

arch/arm64/include/asm/linkage.h

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11

arch/arm64/kernel/vdso/sigreturn.S

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16

arch/arm64/kernel/vdso32/sigreturn.S

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