diff mbox

arm: cacheflush: get rid of restarting block

Message ID 1416928737-29723-1-git-send-email-vladimir.murzin@arm.com
State New, archived
Headers show

Commit Message

Vladimir Murzin Nov. 25, 2014, 3:18 p.m. UTC
We cannot restart cacheflush safely if a process provides user-defined
signal handler and signal is pending. In this case -EINTR is returned
and it is expected that process re-invokes syscall. However, there are
a few problems with that:
 * looks like nobody bothers checking return value from cacheflush
 * but if it did, we don't provide the restart address for that, so the
   process has to use the same range again
 * ...and again, what might lead to looping forever

So, remove cacheflush restarting code and terminate cache flushing
as early as fatal signal is pending.

Cc: stable@vger.kernel.org # 3.12+
Reported-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
---
Hi,

There is my proposal for the problem reported in [1]. Since that
thread has not been progressing much, I'm addressing the problem in
separate patch.

Comments?

[1] https://lkml.org/lkml/2014/11/13/29

 arch/arm/include/asm/thread_info.h |   11 -----------
 arch/arm/kernel/traps.c            |   31 ++-----------------------------
 2 files changed, 2 insertions(+), 40 deletions(-)

Comments

Chanho Min Nov. 27, 2014, 4:02 a.m. UTC | #1
> -----Original Message-----
> From: Vladimir Murzin [mailto:vladimir.murzin@arm.com]
> Sent: Wednesday, November 26, 2014 12:19 AM
> To: linux-arm-kernel@lists.infradead.org; linux@arm.linux.org.uk
> Cc: chanho.min@lge.com; will.deacon@arm.com; stable@vger.kernel.org
> Subject: [PATCH] arm: cacheflush: get rid of restarting block
> 
> We cannot restart cacheflush safely if a process provides user-defined
> signal handler and signal is pending. In this case -EINTR is returned
> and it is expected that process re-invokes syscall. However, there are
> a few problems with that:
>  * looks like nobody bothers checking return value from cacheflush
>  * but if it did, we don't provide the restart address for that, so the
>    process has to use the same range again
>  * ...and again, what might lead to looping forever
> 
> So, remove cacheflush restarting code and terminate cache flushing
> as early as fatal signal is pending.
> 
> Cc: stable@vger.kernel.org # 3.12+
> Reported-by: Chanho Min <chanho.min@lge.com>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> Acked-by: Will Deacon <will.deacon@arm.com>
> ---
> Hi,
> 
> There is my proposal for the problem reported in [1]. Since that
> thread has not been progressing much, I'm addressing the problem in
> separate patch.
> 
> Comments?
Thanks, We hope this to be applied.

> 
> [1] https://lkml.org/lkml/2014/11/13/29
> 
>  arch/arm/include/asm/thread_info.h |   11 -----------
>  arch/arm/kernel/traps.c            |   31 ++-----------------------------
>  2 files changed, 2 insertions(+), 40 deletions(-)
> 
> diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
> index fc44d37..ce73ab6 100644
> --- a/arch/arm/include/asm/thread_info.h
> +++ b/arch/arm/include/asm/thread_info.h
> @@ -44,16 +44,6 @@ struct cpu_context_save {
>  	__u32	extra[2];		/* Xscale 'acc' register, etc */
>  };
> 
> -struct arm_restart_block {
> -	union {
> -		/* For user cache flushing */
> -		struct {
> -			unsigned long start;
> -			unsigned long end;
> -		} cache;
> -	};
> -};
> -
>  /*
>   * low level task data that entry.S needs immediate access to.
>   * __switch_to() assumes cpu_context follows immediately after cpu_domain.
> @@ -79,7 +69,6 @@ struct thread_info {
>  	unsigned long		thumbee_state;	/* ThumbEE Handler Base register */
>  #endif
>  	struct restart_block	restart_block;
> -	struct arm_restart_block	arm_restart_block;
>  };
> 
>  #define INIT_THREAD_INFO(tsk)						\
> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> index 0c8b108..8dd03ee 100644
> --- a/arch/arm/kernel/traps.c
> +++ b/arch/arm/kernel/traps.c
> @@ -533,8 +533,6 @@ static int bad_syscall(int n, struct pt_regs *regs)
>  	return regs->ARM_r0;
>  }
> 
> -static long do_cache_op_restart(struct restart_block *);
> -
>  static inline int
>  __do_cache_op(unsigned long start, unsigned long end)
>  {
> @@ -543,24 +541,8 @@ __do_cache_op(unsigned long start, unsigned long end)
>  	do {
>  		unsigned long chunk = min(PAGE_SIZE, end - start);
> 
> -		if (signal_pending(current)) {
> -			struct thread_info *ti = current_thread_info();
> -
> -			ti->restart_block = (struct restart_block) {
> -				.fn	= do_cache_op_restart,
> -			};
> -
> -			ti->arm_restart_block = (struct arm_restart_block) {
> -				{
> -					.cache = {
> -						.start	= start,
> -						.end	= end,
> -					},
> -				},
> -			};
> -
> -			return -ERESTART_RESTARTBLOCK;
> -		}
> +		if (fatal_signal_pending(current))
> +			return 0;
> 
>  		ret = flush_cache_user_range(start, start + chunk);
>  		if (ret)
> @@ -573,15 +555,6 @@ __do_cache_op(unsigned long start, unsigned long end)
>  	return 0;
>  }
> 
> -static long do_cache_op_restart(struct restart_block *unused)
> -{
> -	struct arm_restart_block *restart_block;
> -
> -	restart_block = &current_thread_info()->arm_restart_block;
> -	return __do_cache_op(restart_block->cache.start,
> -			     restart_block->cache.end);
> -}
> -
>  static inline int
>  do_cache_op(unsigned long start, unsigned long end, int flags)
>  {
> --
> 1.7.9.5
Chanho
Will Deacon Nov. 27, 2014, 10:03 a.m. UTC | #2
On Thu, Nov 27, 2014 at 04:02:24AM +0000, Chanho Min wrote:
> > -----Original Message-----
> > From: Vladimir Murzin [mailto:vladimir.murzin@arm.com]
> > Sent: Wednesday, November 26, 2014 12:19 AM
> > To: linux-arm-kernel@lists.infradead.org; linux@arm.linux.org.uk
> > Cc: chanho.min@lge.com; will.deacon@arm.com; stable@vger.kernel.org
> > Subject: [PATCH] arm: cacheflush: get rid of restarting block
> > 
> > We cannot restart cacheflush safely if a process provides user-defined
> > signal handler and signal is pending. In this case -EINTR is returned
> > and it is expected that process re-invokes syscall. However, there are
> > a few problems with that:
> >  * looks like nobody bothers checking return value from cacheflush
> >  * but if it did, we don't provide the restart address for that, so the
> >    process has to use the same range again
> >  * ...and again, what might lead to looping forever
> > 
> > So, remove cacheflush restarting code and terminate cache flushing
> > as early as fatal signal is pending.
> > 
> > Cc: stable@vger.kernel.org # 3.12+
> > Reported-by: Chanho Min <chanho.min@lge.com>
> > Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> > Acked-by: Will Deacon <will.deacon@arm.com>
> > ---
> > Hi,
> > 
> > There is my proposal for the problem reported in [1]. Since that
> > thread has not been progressing much, I'm addressing the problem in
> > separate patch.
> > 
> > Comments?
> Thanks, We hope this to be applied.

Ok, good. In which case, can you put it into the patch system please,
Vladimir?

Will
Vladimir Murzin Nov. 27, 2014, 10:43 a.m. UTC | #3
On 27/11/14 10:03, Will Deacon wrote:
> On Thu, Nov 27, 2014 at 04:02:24AM +0000, Chanho Min wrote:
>>> -----Original Message-----
>>> From: Vladimir Murzin [mailto:vladimir.murzin@arm.com]
>>> Sent: Wednesday, November 26, 2014 12:19 AM
>>> To: linux-arm-kernel@lists.infradead.org; linux@arm.linux.org.uk
>>> Cc: chanho.min@lge.com; will.deacon@arm.com; stable@vger.kernel.org
>>> Subject: [PATCH] arm: cacheflush: get rid of restarting block
>>>
>>> We cannot restart cacheflush safely if a process provides user-defined
>>> signal handler and signal is pending. In this case -EINTR is returned
>>> and it is expected that process re-invokes syscall. However, there are
>>> a few problems with that:
>>>  * looks like nobody bothers checking return value from cacheflush
>>>  * but if it did, we don't provide the restart address for that, so the
>>>    process has to use the same range again
>>>  * ...and again, what might lead to looping forever
>>>
>>> So, remove cacheflush restarting code and terminate cache flushing
>>> as early as fatal signal is pending.
>>>
>>> Cc: stable@vger.kernel.org # 3.12+
>>> Reported-by: Chanho Min <chanho.min@lge.com>
>>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>>> Acked-by: Will Deacon <will.deacon@arm.com>
>>> ---
>>> Hi,
>>>
>>> There is my proposal for the problem reported in [1]. Since that
>>> thread has not been progressing much, I'm addressing the problem in
>>> separate patch.
>>>
>>> Comments?
>> Thanks, We hope this to be applied.
>
> Ok, good. In which case, can you put it into the patch system please,
> Vladimir?

Already in patch system as 8226/1.

Vladimir

>
> Will
>
>
>


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Vladimir Murzin Nov. 27, 2014, 10:45 a.m. UTC | #4
On 27/11/14 10:43, Vladimir Murzin wrote:
> On 27/11/14 10:03, Will Deacon wrote:
>> On Thu, Nov 27, 2014 at 04:02:24AM +0000, Chanho Min wrote:
>>>> -----Original Message-----
>>>> From: Vladimir Murzin [mailto:vladimir.murzin@arm.com]
>>>> Sent: Wednesday, November 26, 2014 12:19 AM
>>>> To: linux-arm-kernel@lists.infradead.org; linux@arm.linux.org.uk
>>>> Cc: chanho.min@lge.com; will.deacon@arm.com; stable@vger.kernel.org
>>>> Subject: [PATCH] arm: cacheflush: get rid of restarting block
>>>>
>>>> We cannot restart cacheflush safely if a process provides user-defined
>>>> signal handler and signal is pending. In this case -EINTR is returned
>>>> and it is expected that process re-invokes syscall. However, there are
>>>> a few problems with that:
>>>>  * looks like nobody bothers checking return value from cacheflush
>>>>  * but if it did, we don't provide the restart address for that, so the
>>>>    process has to use the same range again
>>>>  * ...and again, what might lead to looping forever
>>>>
>>>> So, remove cacheflush restarting code and terminate cache flushing
>>>> as early as fatal signal is pending.
>>>>
>>>> Cc: stable@vger.kernel.org # 3.12+
>>>> Reported-by: Chanho Min <chanho.min@lge.com>
>>>> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
>>>> Acked-by: Will Deacon <will.deacon@arm.com>
>>>> ---
>>>> Hi,
>>>>
>>>> There is my proposal for the problem reported in [1]. Since that
>>>> thread has not been progressing much, I'm addressing the problem in
>>>> separate patch.
>>>>
>>>> Comments?
>>> Thanks, We hope this to be applied.
>>
>> Ok, good. In which case, can you put it into the patch system please,
>> Vladimir?
> 
> Already in patch system as 8226/1.
> 
> Vladimir
> 

Sorry for banner - I should have checked that I use proper smtp server :(

Vladimir

>>
>> Will
>>
>>
>>
> 
> 
> -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium.  Thank you.
> 
> ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered in England & Wales, Company No:  2557590
> ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered in England & Wales, Company No:  2548782
> 
> --
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> the body of a message to majordomo@vger.kernel.org
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> 
> 
>
diff mbox

Patch

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index fc44d37..ce73ab6 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -44,16 +44,6 @@  struct cpu_context_save {
 	__u32	extra[2];		/* Xscale 'acc' register, etc */
 };
 
-struct arm_restart_block {
-	union {
-		/* For user cache flushing */
-		struct {
-			unsigned long start;
-			unsigned long end;
-		} cache;
-	};
-};
-
 /*
  * low level task data that entry.S needs immediate access to.
  * __switch_to() assumes cpu_context follows immediately after cpu_domain.
@@ -79,7 +69,6 @@  struct thread_info {
 	unsigned long		thumbee_state;	/* ThumbEE Handler Base register */
 #endif
 	struct restart_block	restart_block;
-	struct arm_restart_block	arm_restart_block;
 };
 
 #define INIT_THREAD_INFO(tsk)						\
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 0c8b108..8dd03ee 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -533,8 +533,6 @@  static int bad_syscall(int n, struct pt_regs *regs)
 	return regs->ARM_r0;
 }
 
-static long do_cache_op_restart(struct restart_block *);
-
 static inline int
 __do_cache_op(unsigned long start, unsigned long end)
 {
@@ -543,24 +541,8 @@  __do_cache_op(unsigned long start, unsigned long end)
 	do {
 		unsigned long chunk = min(PAGE_SIZE, end - start);
 
-		if (signal_pending(current)) {
-			struct thread_info *ti = current_thread_info();
-
-			ti->restart_block = (struct restart_block) {
-				.fn	= do_cache_op_restart,
-			};
-
-			ti->arm_restart_block = (struct arm_restart_block) {
-				{
-					.cache = {
-						.start	= start,
-						.end	= end,
-					},
-				},
-			};
-
-			return -ERESTART_RESTARTBLOCK;
-		}
+		if (fatal_signal_pending(current))
+			return 0;
 
 		ret = flush_cache_user_range(start, start + chunk);
 		if (ret)
@@ -573,15 +555,6 @@  __do_cache_op(unsigned long start, unsigned long end)
 	return 0;
 }
 
-static long do_cache_op_restart(struct restart_block *unused)
-{
-	struct arm_restart_block *restart_block;
-
-	restart_block = &current_thread_info()->arm_restart_block;
-	return __do_cache_op(restart_block->cache.start,
-			     restart_block->cache.end);
-}
-
 static inline int
 do_cache_op(unsigned long start, unsigned long end, int flags)
 {