This is a note to let you know that I've just added the patch titled
x86/asm: Use register variable to get stack pointer value
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: x86-asm-use-register-variable-to-get-stack-pointer-value.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 196bd485ee4f03ce4c690bfcf38138abfcd0a4bc Mon Sep 17 00:00:00 2001
From: Andrey Ryabinin aryabinin@virtuozzo.com Date: Fri, 29 Sep 2017 17:15:36 +0300 Subject: x86/asm: Use register variable to get stack pointer value
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
--- 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 +- 4 files changed, 15 insertions(+), 15 deletions(-)
--- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -105,4 +105,15 @@ /* 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 */ --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -166,17 +166,6 @@ static inline struct thread_info *curren return (struct thread_info *)(current_top_of_stack() - THREAD_SIZE); }
-static inline unsigned long current_stack_pointer(void) -{ - unsigned long sp; -#ifdef CONFIG_X86_64 - asm("mov %%rsp,%0" : "=g" (sp)); -#else - asm("mov %%esp,%0" : "=g" (sp)); -#endif - return sp; -} - #else /* !__ASSEMBLY__ */
#ifdef CONFIG_X86_64 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -65,7 +65,7 @@ static void call_on_stack(void *func, vo
static inline void *current_stack(void) { - return (void *)(current_stack_pointer() & ~(THREAD_SIZE - 1)); + return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1)); }
static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc) @@ -89,7 +89,7 @@ static inline int execute_on_irq_stack(i
/* Save the next esp at the bottom of the stack */ prev_esp = (u32 *)irqstk; - *prev_esp = current_stack_pointer(); + *prev_esp = current_stack_pointer;
if (unlikely(overflow)) call_on_stack(print_stack_overflow, isp); @@ -142,7 +142,7 @@ void do_softirq_own_stack(void)
/* Push the previous esp onto the stack */ prev_esp = (u32 *)irqstk; - *prev_esp = current_stack_pointer(); + *prev_esp = current_stack_pointer;
call_on_stack(__do_softirq, isp); } --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -166,7 +166,7 @@ void ist_begin_non_atomic(struct pt_regs * from double_fault. */ BUG_ON((unsigned long)(current_top_of_stack() - - current_stack_pointer()) >= THREAD_SIZE); + current_stack_pointer) >= THREAD_SIZE);
preempt_enable_no_resched(); }
Patches currently in stable-queue which might be from aryabinin@virtuozzo.com are
queue-4.4/x86-asm-use-register-variable-to-get-stack-pointer-value.patch