* [PATCH] x86: use register variable to get stack pointer value
@ 2017-09-29 14:15 Andrey Ryabinin
2017-09-29 15:38 ` Josh Poimboeuf
2017-09-29 20:15 ` [tip:x86/urgent] x86/asm: Use " tip-bot for Andrey Ryabinin
0 siblings, 2 replies; 5+ messages in thread
From: Andrey Ryabinin @ 2017-09-29 14:15 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, x86
Cc: Josh Poimboeuf, Peter Zijlstra, Andy Lutomirski, Linus Torvalds,
linux-kernel, Andrey Ryabinin
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 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 removed function.
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
arch/x86/include/asm/asm.h | 4 ++--
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, 7 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 30c3c9ac784a..b0dc91f4bedc 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -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 */
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 5161da1a0fa0..89e7eeb5cec1 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -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.
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index 1f38d9a4d9de..d4eb450144fd 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -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);
}
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 34ea3651362e..67db4f43309e 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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();
}
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 93fe97cce581..49d9778376d7 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -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)))
--
2.13.6
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] x86: use register variable to get stack pointer value
2017-09-29 14:15 [PATCH] x86: use register variable to get stack pointer value Andrey Ryabinin
@ 2017-09-29 15:38 ` Josh Poimboeuf
2017-09-29 18:37 ` Andy Lutomirski
2017-09-29 20:15 ` [tip:x86/urgent] x86/asm: Use " tip-bot for Andrey Ryabinin
1 sibling, 1 reply; 5+ messages in thread
From: Josh Poimboeuf @ 2017-09-29 15:38 UTC (permalink / raw)
To: Andrey Ryabinin
Cc: Thomas Gleixner, Ingo Molnar, H. Peter Anvin, x86,
Peter Zijlstra, Andy Lutomirski, Linus Torvalds, linux-kernel
On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
> 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 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 removed function.
>
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
--
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86: use register variable to get stack pointer value
2017-09-29 15:38 ` Josh Poimboeuf
@ 2017-09-29 18:37 ` Andy Lutomirski
2017-09-29 19:16 ` Josh Poimboeuf
0 siblings, 1 reply; 5+ messages in thread
From: Andy Lutomirski @ 2017-09-29 18:37 UTC (permalink / raw)
To: Josh Poimboeuf
Cc: Andrey Ryabinin, Thomas Gleixner, Ingo Molnar, H. Peter Anvin,
X86 ML, Peter Zijlstra, Andy Lutomirski, Linus Torvalds,
linux-kernel
On Fri, Sep 29, 2017 at 8:38 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
>> 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 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 removed function.
>>
>> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>
> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Ok with me. As an alternative, you could leave it as
current_stack_pointer(), but either way is fine.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86: use register variable to get stack pointer value
2017-09-29 18:37 ` Andy Lutomirski
@ 2017-09-29 19:16 ` Josh Poimboeuf
0 siblings, 0 replies; 5+ messages in thread
From: Josh Poimboeuf @ 2017-09-29 19:16 UTC (permalink / raw)
To: Andy Lutomirski
Cc: Andrey Ryabinin, Thomas Gleixner, Ingo Molnar, H. Peter Anvin,
X86 ML, Peter Zijlstra, Linus Torvalds, linux-kernel
On Fri, Sep 29, 2017 at 11:37:52AM -0700, Andy Lutomirski wrote:
> On Fri, Sep 29, 2017 at 8:38 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
> >> 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 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 removed function.
> >>
> >> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> >
> > Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
>
>
> Ok with me. As an alternative, you could leave it as
> current_stack_pointer(), but either way is fine.
Good point, I think changing current_stack_pointer() to return the
global variable would be cleaner.
--
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread
* [tip:x86/urgent] x86/asm: Use register variable to get stack pointer value
2017-09-29 14:15 [PATCH] x86: use register variable to get stack pointer value Andrey Ryabinin
2017-09-29 15:38 ` Josh Poimboeuf
@ 2017-09-29 20:15 ` tip-bot for Andrey Ryabinin
1 sibling, 0 replies; 5+ messages in thread
From: tip-bot for Andrey Ryabinin @ 2017-09-29 20:15 UTC (permalink / raw)
To: linux-tip-commits
Cc: torvalds, linux-kernel, luto, aryabinin, tglx, hpa, mingo,
jpoimboe, peterz
Commit-ID: 196bd485ee4f03ce4c690bfcf38138abfcd0a4bc
Gitweb: https://git.kernel.org/tip/196bd485ee4f03ce4c690bfcf38138abfcd0a4bc
Author: Andrey Ryabinin <aryabinin@virtuozzo.com>
AuthorDate: Fri, 29 Sep 2017 17:15:36 +0300
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 29 Sep 2017 19:39:44 +0200
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:
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>
---
arch/x86/include/asm/asm.h | 4 ++--
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, 7 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 30c3c9a..b0dc91f 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -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 */
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 5161da1a..89e7eeb 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -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.
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index 1f38d9a..d4eb450 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -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);
}
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 34ea365..67db4f4 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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();
}
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 93fe97c..49d9778 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -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)))
^ permalink raw reply related [flat|nested] 5+ messages in thread
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2017-09-29 14:15 [PATCH] x86: use register variable to get stack pointer value Andrey Ryabinin
2017-09-29 15:38 ` Josh Poimboeuf
2017-09-29 18:37 ` Andy Lutomirski
2017-09-29 19:16 ` Josh Poimboeuf
2017-09-29 20:15 ` [tip:x86/urgent] x86/asm: Use " tip-bot for Andrey Ryabinin
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