Commit-ID: 317c2ce77d8ab73c24f4fb9c75e5bb441fbe3e30 Gitweb: http://git.kernel.org/tip/317c2ce77d8ab73c24f4fb9c75e5bb441fbe3e30 Author: Josh Poimboeuf <jpoim...@redhat.com> AuthorDate: Fri, 23 Sep 2016 16:49:39 -0500 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Sat, 24 Sep 2016 09:30:03 +0200
x86/alternatives: Add stack frame dependency to alternative_call_2() Linus reported the following objtool warning: kernel/signal.o: warning: objtool: .altinstr_replacement+0x54: call without frame pointer save/setup The warning is valid. It's caused by the fact that gcc placed the call instruction in alternative_call_2()'s inline asm before the frame pointer setup, which breaks frame pointer convention and can result in a bad stack trace. Force a stack frame to be created before the call instruction by listing the stack pointer as an output operand in the inline asm statement. Reported-and-tested-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/20160923214939.j5o7c67nhepzmh3t@treble Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/alternative.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index e77a644..1b02038 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -217,10 +217,14 @@ static inline int alternatives_text_reserved(void *start, void *end) */ #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \ output, input...) \ +{ \ + register void *__sp asm(_ASM_SP); \ asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\ "call %P[new2]", feature2) \ - : output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ - [new2] "i" (newfunc2), ## input) + : output, "+r" (__sp) \ + : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ + [new2] "i" (newfunc2), ## input); \ +} /* * use this macro(s) if you need more than one output parameter
