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Commit 196bd485 authored by Andrey Ryabinin's avatar Andrey Ryabinin Committed by Ingo Molnar
Browse files

x86/asm: Use register variable to get stack pointer value 



Currently we use current_stack_pointer() function to get the value
of the stack pointer register. Since commit:

  f5caf621 ("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: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: default avatarJosh 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: default avatarIngo Molnar <mingo@kernel.org>
parent bc829ee3

arch/x86/include/asm/asm.h

+2 −2
Original line number Diff line number Diff line
@@ -141,8 +141,8 @@ 
 * 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 __asm_call_sp asm(_ASM_SP);

#define ASM_CALL_CONSTRAINT "+r" (__asm_call_sp)

register unsigned long current_stack_pointer asm(_ASM_SP);

#define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer)

#endif



#endif /* _ASM_X86_ASM_H */

arch/x86/include/asm/thread_info.h

+0 −11
Original line number Diff line number Diff line
@@ -158,17 +158,6 @@ struct thread_info { 
 */

#ifndef __ASSEMBLY__



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;

}



/*

 * Walks up the stack frames to make sure that the specified object is

 * entirely contained by a single stack frame.

arch/x86/kernel/irq_32.c

+3 −3
Original line number Diff line number Diff line
@@ -64,7 +64,7 @@ static void call_on_stack(void *func, void *stack) 


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)
@@ -88,7 +88,7 @@ static inline int execute_on_irq_stack(int overflow, struct irq_desc *desc) 


	/* 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);
@@ -139,7 +139,7 @@ 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);

}

arch/x86/kernel/traps.c

+1 −1
Original line number Diff line number Diff line
@@ -142,7 +142,7 @@ void ist_begin_non_atomic(struct pt_regs *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();

}

arch/x86/mm/tlb.c

+1 −1
Original line number Diff line number Diff line
@@ -191,7 +191,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, 
			 * mapped in the new pgd, we'll double-fault.  Forcibly

			 * map it.

			 */

			unsigned int index = pgd_index(current_stack_pointer());

			unsigned int index = pgd_index(current_stack_pointer);

			pgd_t *pgd = next->pgd + index;



			if (unlikely(pgd_none(*pgd)))