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| author | Peter Zijlstra <peterz@infradead.org> | 2020-04-01 16:38:19 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-04-22 10:53:50 +0200 |
| commit | e25eea89bb8853763a22fa2547199cf96b571ba1 (patch) | |
| tree | f766e439a5bb171c5c71a56943a684f0e6716723 /arch/x86/include/asm/unwind_hints.h | |
| parent | b746046238bb99b8f703c79f6d95357428fb6476 (diff) | |
| download | linux-e25eea89bb8853763a22fa2547199cf96b571ba1.tar.bz2 | |
objtool: Introduce HINT_RET_OFFSET
Normally objtool ensures a function keeps the stack layout invariant.
But there is a useful exception, it is possible to stuff the return
stack in order to 'inject' a 'call':
push $fun
ret
In this case the invariant mentioned above is violated.
Add an objtool HINT to annotate this and allow a function exit with a
modified stack frame.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200416115118.690601403@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/unwind_hints.h')
| -rw-r--r-- | arch/x86/include/asm/unwind_hints.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h index f5e2eb12cb71..aabf7ace0476 100644 --- a/arch/x86/include/asm/unwind_hints.h +++ b/arch/x86/include/asm/unwind_hints.h @@ -94,6 +94,16 @@ UNWIND_HINT type=UNWIND_HINT_TYPE_RESTORE .endm + +/* + * RET_OFFSET: Used on instructions that terminate a function; mostly RETURN + * and sibling calls. On these, sp_offset denotes the expected offset from + * initial_func_cfi. + */ +.macro UNWIND_HINT_RET_OFFSET sp_offset=8 + UNWIND_HINT type=UNWIND_HINT_TYPE_RET_OFFSET sp_offset=\sp_offset +.endm + #else /* !__ASSEMBLY__ */ #define UNWIND_HINT(sp_reg, sp_offset, type, end) \ |