diff options
| author | Andrey Ryabinin <aryabinin@virtuozzo.com> | 2017-09-29 17:15:36 +0300 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2018-03-19 18:58:31 +0000 |
| commit | 8b34723841be5ceb3af07c8bd316337f9a79f26f (patch) | |
| tree | 285f84e2df11160214893a4adb6b29d26006c4c5 | |
| parent | 691d2485e41b55e01c6e487ed5b7560ebcb20a58 (diff) | |
x86/asm: Use register variable to get stack pointer value
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>
| -rw-r--r-- | arch/x86/include/asm/asm.h | 11 | ||||
| -rw-r--r-- | arch/x86/include/asm/thread_info.h | 3 |
2 files changed, 11 insertions, 3 deletions
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index 9355ea86aa34..14b488f77030 100644 --- 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 */ diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index d7ef849714a1..829c2343796e 100644 --- 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) { |