Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Mon, 12 Mar 2018 03:03:34 +0000 | Subject | [PATCH 3.2 057/104] x86/asm: Use register variable to get stack pointer value |
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3.2.101-rc1 review patch. If anyone has any objections, please let me know.
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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
commit 196bd485ee4f03ce4c690bfcf38138abfcd0a4bc upstream.
Currently we use current_stack_pointer() function to get the value of the stack pointer register. Since commit:
f5caf621ee35 ("x86/asm: Fix inline asm call constraints for Clang")
... we have a stack register variable declared. It can be used instead of current_stack_pointer() function which allows to optimize away some excessive "mov %rsp, %<dst>" instructions:
-mov %rsp,%rdx -sub %rdx,%rax -cmp $0x3fff,%rax -ja ffffffff810722fd <ist_begin_non_atomic+0x2d>
+sub %rsp,%rax +cmp $0x3fff,%rax +ja ffffffff810722fa <ist_begin_non_atomic+0x2a>
Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer and use it instead of the removed function.
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170929141537.29167-1-aryabinin@virtuozzo.com Signed-off-by: Ingo Molnar <mingo@kernel.org> [dwmw2: We want ASM_CALL_CONSTRAINT for retpoline] Signed-off-by: David Woodhouse <dwmw@amazon.co.ku> Signed-off-by: Razvan Ghitulete <rga@amazon.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: current_stack_pointer was never changed to a function, but was only defined for x86_32] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -59,4 +59,15 @@ " .previous\n" #endif +#ifndef __ASSEMBLY__ +/* + * This output constraint should be used for any inline asm which has a "call" + * instruction. Otherwise the asm may be inserted before the frame pointer + * gets set up by the containing function. If you forget to do this, objtool + * may print a "call without frame pointer save/setup" warning. + */ +register unsigned long current_stack_pointer asm(_ASM_SP); +#define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer) +#endif + #endif /* _ASM_X86_ASM_H */ --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -181,9 +181,6 @@ struct thread_info { #ifndef __ASSEMBLY__ -/* how to get the current stack pointer from C */ -register unsigned long current_stack_pointer asm("esp") __used; - /* how to get the thread information struct from C */ static inline struct thread_info *current_thread_info(void) {
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