On 01/15/2018 03:35 PM, Greg Kroah-Hartman wrote:
4.9-stable review patch. If anyone has any objections, please let me know.
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]
If we want ASM_CALL_CONSTRAINT it would be more correct to backport f5caf621ee35 ("x86/asm: Fix inline asm call constraints for Clang") and some fixes for it: 520a13c530ae ("x86/asm: Fix inline asm call constraints for GCC 4.4") ca26cffa4e4a ("x86/asm: Allow again using asm.h when building for the 'bpf' clang target")
Because ASM_CALL_CONSTRAINT added in f5caf621ee35, not in this patch.
The end result looks fine though. So it's ok to keep it that way.
Signed-off-by: David Woodhouse dwmw@amazon.co.ku Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
arch/x86/include/asm/asm.h | 11 +++++++++++ arch/x86/include/asm/thread_info.h | 11 ----------- arch/x86/kernel/irq_32.c | 6 +++--- arch/x86/kernel/traps.c | 2 +- arch/x86/mm/tlb.c | 2 +- 5 files changed, 16 insertions(+), 16 deletions(-)
--- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -125,4 +125,15 @@ /* For C file, we already have NOKPROBE_SYMBOL macro */ #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 */