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[PATCH 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm

Started byMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
First post2017-09-06 07:30 +0200
Last post2017-09-07 01:10 +0200
Articles 7 — 3 participants

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  [PATCH 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com> - 2017-09-06 07:30 +0200
    [PATCH v2 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com> - 2017-09-07 00:50 +0200
      [PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read() Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com> - 2017-09-07 00:50 +0200
        Re: [PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for  __up_read() Ingo Molnar <mingo@kernel.org> - 2017-09-07 09:20 +0200
      [PATCH v2 3/3] locking/rwsem/x86: Add stack frame dependency for __downgrade_write() Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com> - 2017-09-07 00:50 +0200
      [PATCH v2 2/3] locking/rwsem/x86: Add stack frame dependency for __up_write() Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com> - 2017-09-07 00:50 +0200
      Re: [PATCH v2 0/3] locking/rwsem/x86: Add stack frame dependency for  some inline asm Josh Poimboeuf <jpoimboe@redhat.com> - 2017-09-07 01:10 +0200

#1727163 — [PATCH 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm

FromMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Date2017-09-06 07:30 +0200
Subject[PATCH 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm
Message-ID<umB4t-5b7-3@gated-at.bofh.it>
Some warning were showed by objtool using gcc 7.2.0

kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup
kernel/locking/rwsem.o: warning: objtool: up_write()+0x17: call without frame pointer save/setup
kernel/locking/rwsem.o: warning: objtool: downgrade_write()+0x22: call without frame pointer save/setup

which means gcc placed an inline asm function and its call instruction before
the frame pointer setup.
 
This series forces a stack frame to be created before the call instruction
by listing the stack pointer as an output operand in the inline asm statement.

Miguel Bernal Marin (3):
  locking/rwsem/x86: Add stack frame dependency for __up_read()
  locking/rwsem/x86: Add stack frame dependency for __up_write()
  locking/rwsem/x86: Add stack frame dependency for __downgrade_write()

 arch/x86/include/asm/rwsem.h | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

-- 
2.14.1

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#1727802 — [PATCH v2 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm

FromMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Date2017-09-07 00:50 +0200
Subject[PATCH v2 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm
Message-ID<umRiV-85i-1@gated-at.bofh.it>
In reply to#1727163
Some warning were showed by objtool using gcc 7.2.0

kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup
kernel/locking/rwsem.o: warning: objtool: up_write()+0x17: call without frame pointer save/setup
kernel/locking/rwsem.o: warning: objtool: downgrade_write()+0x22: call without frame pointer save/setup

which means gcc placed an inline asm function and its call instruction before
the frame pointer setup.
 
This series forces a stack frame to be created before the call instruction
by listing the stack pointer as an output operand in the inline asm statement.

Changes in v2:
  - Update first parameter from _ASM_ADD to '%3' at __downgrade_write()

Miguel Bernal Marin (3):
  locking/rwsem/x86: Add stack frame dependency for __up_read()
  locking/rwsem/x86: Add stack frame dependency for __up_write()
  locking/rwsem/x86: Add stack frame dependency for __downgrade_write()

 arch/x86/include/asm/rwsem.h | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

-- 
2.14.1

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#1727804 — [PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read()

FromMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Date2017-09-07 00:50 +0200
Subject[PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read()
Message-ID<umRiV-85i-7@gated-at.bofh.it>
In reply to#1727802
kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup

The warning means gcc 7.2.0 placed the __up_read() inline asm (and its
call instruction) before the frame pointer setup in up_read(),
which breaks frame pointer convention and can result in incorrect
stack traces.

Force a stack frame to be created before the call instruction by listing
the stack pointer as an output operand in the inline asm statement.

Signed-off-by: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
---
 arch/x86/include/asm/rwsem.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index a34e0d4b957d..762167afaec0 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -166,14 +166,16 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem)
 static inline void __up_read(struct rw_semaphore *sem)
 {
 	long tmp;
+	register void *__sp asm(_ASM_SP);
+
 	asm volatile("# beginning __up_read\n\t"
-		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"
+		     LOCK_PREFIX "  xadd      %1,(%3)\n\t"
 		     /* subtracts 1, returns the old value */
 		     "  jns        1f\n\t"
 		     "  call call_rwsem_wake\n" /* expects old value in %edx */
 		     "1:\n"
 		     "# ending __up_read\n"
-		     : "+m" (sem->count), "=d" (tmp)
+		     : "+m" (sem->count), "=d" (tmp), "+r" (__sp)
 		     : "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)
 		     : "memory", "cc");
 }
-- 
2.14.1

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#1727967 — Re: [PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read()

FromIngo Molnar <mingo@kernel.org>
Date2017-09-07 09:20 +0200
SubjectRe: [PATCH v2 1/3] locking/rwsem/x86: Add stack frame dependency for __up_read()
Message-ID<umZgv-5bg-13@gated-at.bofh.it>
In reply to#1727804
* Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com> wrote:

> kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup
> 
> The warning means gcc 7.2.0 placed the __up_read() inline asm (and its
> call instruction) before the frame pointer setup in up_read(),
> which breaks frame pointer convention and can result in incorrect
> stack traces.
> 
> Force a stack frame to be created before the call instruction by listing
> the stack pointer as an output operand in the inline asm statement.
> 
> Signed-off-by: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
> ---
>  arch/x86/include/asm/rwsem.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
> index a34e0d4b957d..762167afaec0 100644
> --- a/arch/x86/include/asm/rwsem.h
> +++ b/arch/x86/include/asm/rwsem.h
> @@ -166,14 +166,16 @@ static inline bool __down_write_trylock(struct rw_semaphore *sem)
>  static inline void __up_read(struct rw_semaphore *sem)
>  {
>  	long tmp;
> +	register void *__sp asm(_ASM_SP);
> +
>  	asm volatile("# beginning __up_read\n\t"
> -		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"
> +		     LOCK_PREFIX "  xadd      %1,(%3)\n\t"
>  		     /* subtracts 1, returns the old value */
>  		     "  jns        1f\n\t"
>  		     "  call call_rwsem_wake\n" /* expects old value in %edx */
>  		     "1:\n"
>  		     "# ending __up_read\n"
> -		     : "+m" (sem->count), "=d" (tmp)
> +		     : "+m" (sem->count), "=d" (tmp), "+r" (__sp)
>  		     : "a" (sem), "1" (-RWSEM_ACTIVE_READ_BIAS)
>  		     : "memory", "cc");

Please also convert it to named operands (in separate patches!) - this apparently 
BASIC inspired labeling syntax of GCC is utterly confusing, counterproductive and 
somewhat embarrasing as well, considering that we write 2017.

Thanks,

	Ingo

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#1727805 — [PATCH v2 3/3] locking/rwsem/x86: Add stack frame dependency for __downgrade_write()

FromMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Date2017-09-07 00:50 +0200
Subject[PATCH v2 3/3] locking/rwsem/x86: Add stack frame dependency for __downgrade_write()
Message-ID<umRiV-85i-11@gated-at.bofh.it>
In reply to#1727802
kernel/locking/rwsem.o: warning: objtool: downgrade_write()+0x22: call without frame pointer save/setup

The warning means gcc 7.2.0 placed the __downgrade_write() inline asm (and
its call instruction) before the frame pointer setup in downgrade_write(),
which breaks frame pointer convention and can result in incorrect
stack traces.

Force a stack frame to be created before the call instruction by listing
the stack pointer as an output operand in the inline asm statement.

Signed-off-by: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
---
 arch/x86/include/asm/rwsem.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index d26b6916b935..a749dc6a3103 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -205,8 +205,10 @@ static inline void __up_write(struct rw_semaphore *sem)
  */
 static inline void __downgrade_write(struct rw_semaphore *sem)
 {
+	register void *__sp asm(_ASM_SP);
+
 	asm volatile("# beginning __downgrade_write\n\t"
-		     LOCK_PREFIX _ASM_ADD "%2,(%1)\n\t"
+		     LOCK_PREFIX _ASM_ADD "%3,(%2)\n\t"
 		     /*
 		      * transitions 0xZZZZ0001 -> 0xYYYY0001 (i386)
 		      *     0xZZZZZZZZ00000001 -> 0xYYYYYYYY00000001 (x86_64)
@@ -215,7 +217,7 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
 		     "  call call_rwsem_downgrade_wake\n"
 		     "1:\n\t"
 		     "# ending __downgrade_write\n"
-		     : "+m" (sem->count)
+		     : "+m" (sem->count), "+r" (__sp)
 		     : "a" (sem), "er" (-RWSEM_WAITING_BIAS)
 		     : "memory", "cc");
 }
-- 
2.14.1

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#1727808 — [PATCH v2 2/3] locking/rwsem/x86: Add stack frame dependency for __up_write()

FromMiguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
Date2017-09-07 00:50 +0200
Subject[PATCH v2 2/3] locking/rwsem/x86: Add stack frame dependency for __up_write()
Message-ID<umRiV-85i-17@gated-at.bofh.it>
In reply to#1727802
kernel/locking/rwsem.o: warning: objtool: up_write()+0x17: call without frame pointer save/setup

The warning means gcc 7.2.0 placed the __up_write() inline asm (and its
call instruction) before the frame pointer setup in up_write(),
which breaks frame pointer convention and can result in incorrect
stack traces.

Force a stack frame to be created before the call instruction by listing
the stack pointer as an output operand in the inline asm statement.

Signed-off-by: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
---
 arch/x86/include/asm/rwsem.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index 762167afaec0..d26b6916b935 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -186,14 +186,16 @@ static inline void __up_read(struct rw_semaphore *sem)
 static inline void __up_write(struct rw_semaphore *sem)
 {
 	long tmp;
+	register void *__sp asm(_ASM_SP);
+
 	asm volatile("# beginning __up_write\n\t"
-		     LOCK_PREFIX "  xadd      %1,(%2)\n\t"
+		     LOCK_PREFIX "  xadd      %1,(%3)\n\t"
 		     /* subtracts 0xffff0001, returns the old value */
 		     "  jns        1f\n\t"
 		     "  call call_rwsem_wake\n" /* expects old value in %edx */
 		     "1:\n\t"
 		     "# ending __up_write\n"
-		     : "+m" (sem->count), "=d" (tmp)
+		     : "+m" (sem->count), "=d" (tmp), "+r" (__sp)
 		     : "a" (sem), "1" (-RWSEM_ACTIVE_WRITE_BIAS)
 		     : "memory", "cc");
 }
-- 
2.14.1

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#1727813 — Re: [PATCH v2 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm

FromJosh Poimboeuf <jpoimboe@redhat.com>
Date2017-09-07 01:10 +0200
SubjectRe: [PATCH v2 0/3] locking/rwsem/x86: Add stack frame dependency for some inline asm
Message-ID<umRCh-8qR-3@gated-at.bofh.it>
In reply to#1727802
On Wed, Sep 06, 2017 at 05:44:58PM -0500, Miguel Bernal Marin wrote:
> Some warning were showed by objtool using gcc 7.2.0
> 
> kernel/locking/rwsem.o: warning: objtool: up_read()+0x11: call without frame pointer save/setup
> kernel/locking/rwsem.o: warning: objtool: up_write()+0x17: call without frame pointer save/setup
> kernel/locking/rwsem.o: warning: objtool: downgrade_write()+0x22: call without frame pointer save/setup
> 
> which means gcc placed an inline asm function and its call instruction before
> the frame pointer setup.
>  
> This series forces a stack frame to be created before the call instruction
> by listing the stack pointer as an output operand in the inline asm statement.
> 
> Changes in v2:
>   - Update first parameter from _ASM_ADD to '%3' at __downgrade_write()
> 
> Miguel Bernal Marin (3):
>   locking/rwsem/x86: Add stack frame dependency for __up_read()
>   locking/rwsem/x86: Add stack frame dependency for __up_write()
>   locking/rwsem/x86: Add stack frame dependency for __downgrade_write()
> 
>  arch/x86/include/asm/rwsem.h | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)

For the series:

Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

-- 
Josh

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