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* [PATCH 1/2] x86/mm: consolidate bad_area handling to the end
@ 2019-09-19  2:08 Wei Yang
  2019-09-19  2:08 ` [PATCH 2/2] x86/mm: replace a goto by merging two if clause Wei Yang
  0 siblings, 1 reply; 5+ messages in thread
From: Wei Yang @ 2019-09-19  2:08 UTC (permalink / raw)
  To: dave.hansen, luto, peterz; +Cc: x86, linux-kernel, Wei Yang

There are totally 7 bad_area[_nosemaphore] error branch in
do_user_addr_fault().

Consolidate all these handling to the end to make the code a little
neat.

BTW, after doing so, function bad_area is not used any more. Remove it.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 arch/x86/mm/fault.c | 44 ++++++++++++++++----------------------------
 1 file changed, 16 insertions(+), 28 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9ceacd1156db..9d18b73b5f77 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -933,12 +933,6 @@ __bad_area(struct pt_regs *regs, unsigned long error_code,
 	__bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
 }
 
-static noinline void
-bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
-{
-	__bad_area(regs, error_code, address, 0, SEGV_MAPERR);
-}
-
 static inline bool bad_area_access_from_pkeys(unsigned long error_code,
 		struct vm_area_struct *vma)
 {
@@ -1313,19 +1307,14 @@ void do_user_addr_fault(struct pt_regs *regs,
 	if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) &&
 		     !(hw_error_code & X86_PF_USER) &&
 		     !(regs->flags & X86_EFLAGS_AC)))
-	{
-		bad_area_nosemaphore(regs, hw_error_code, address);
-		return;
-	}
+		goto bad_area_nosem;
 
 	/*
 	 * If we're in an interrupt, have no user context or are running
 	 * in a region with pagefaults disabled then we must not take the fault
 	 */
-	if (unlikely(faulthandler_disabled() || !mm)) {
-		bad_area_nosemaphore(regs, hw_error_code, address);
-		return;
-	}
+	if (unlikely(faulthandler_disabled() || !mm))
+		goto bad_area_nosem;
 
 	/*
 	 * It's safe to allow irq's after cr2 has been saved and the
@@ -1385,8 +1374,7 @@ void do_user_addr_fault(struct pt_regs *regs,
 			 * Fault from code in kernel from
 			 * which we do not expect faults.
 			 */
-			bad_area_nosemaphore(regs, hw_error_code, address);
-			return;
+			goto bad_area_nosem;
 		}
 retry:
 		down_read(&mm->mmap_sem);
@@ -1400,20 +1388,14 @@ void do_user_addr_fault(struct pt_regs *regs,
 	}
 
 	vma = find_vma(mm, address);
-	if (unlikely(!vma)) {
-		bad_area(regs, hw_error_code, address);
-		return;
-	}
+	if (unlikely(!vma))
+		goto bad_area;
 	if (likely(vma->vm_start <= address))
 		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
-		bad_area(regs, hw_error_code, address);
-		return;
-	}
-	if (unlikely(expand_stack(vma, address))) {
-		bad_area(regs, hw_error_code, address);
-		return;
-	}
+	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
+		goto bad_area;
+	if (unlikely(expand_stack(vma, address)))
+		goto bad_area;
 
 	/*
 	 * Ok, we have a good vm_area for this memory access, so
@@ -1483,6 +1465,12 @@ void do_user_addr_fault(struct pt_regs *regs,
 	}
 
 	check_v8086_mode(regs, address, tsk);
+	return;
+
+bad_area:
+	up_read(&mm->mmap_sem);
+bad_area_nosem:
+	bad_area_nosemaphore(regs, hw_error_code, address);
 }
 NOKPROBE_SYMBOL(do_user_addr_fault);
 
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH 2/2] x86/mm: replace a goto by merging two if clause
  2019-09-19  2:08 [PATCH 1/2] x86/mm: consolidate bad_area handling to the end Wei Yang
@ 2019-09-19  2:08 ` Wei Yang
  2019-09-23  9:22   ` Peter Zijlstra
  0 siblings, 1 reply; 5+ messages in thread
From: Wei Yang @ 2019-09-19  2:08 UTC (permalink / raw)
  To: dave.hansen, luto, peterz; +Cc: x86, linux-kernel, Wei Yang

There is only one place to use good_area jump, which could be reduced by
merging the following two if clause.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 arch/x86/mm/fault.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9d18b73b5f77..72ce6c69e195 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1390,18 +1390,17 @@ void do_user_addr_fault(struct pt_regs *regs,
 	vma = find_vma(mm, address);
 	if (unlikely(!vma))
 		goto bad_area;
-	if (likely(vma->vm_start <= address))
-		goto good_area;
-	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
-		goto bad_area;
-	if (unlikely(expand_stack(vma, address)))
+	if (likely(vma->vm_start <= address)) {
+		/* good area, do nothing */
+	} else if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)) ||
+		   unlikely(expand_stack(vma, address))) {
 		goto bad_area;
+	}
 
 	/*
 	 * Ok, we have a good vm_area for this memory access, so
 	 * we can handle it..
 	 */
-good_area:
 	if (unlikely(access_error(hw_error_code, vma))) {
 		bad_area_access_error(regs, hw_error_code, address, vma);
 		return;
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] x86/mm: replace a goto by merging two if clause
  2019-09-19  2:08 ` [PATCH 2/2] x86/mm: replace a goto by merging two if clause Wei Yang
@ 2019-09-23  9:22   ` Peter Zijlstra
  2019-09-24  0:29     ` Wei Yang
  2019-10-01 11:47     ` Wei Yang
  0 siblings, 2 replies; 5+ messages in thread
From: Peter Zijlstra @ 2019-09-23  9:22 UTC (permalink / raw)
  To: Wei Yang; +Cc: dave.hansen, luto, x86, linux-kernel

On Thu, Sep 19, 2019 at 10:08:44AM +0800, Wei Yang wrote:
> There is only one place to use good_area jump, which could be reduced by
> merging the following two if clause.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
>  arch/x86/mm/fault.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 9d18b73b5f77..72ce6c69e195 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1390,18 +1390,17 @@ void do_user_addr_fault(struct pt_regs *regs,
>  	vma = find_vma(mm, address);
>  	if (unlikely(!vma))
>  		goto bad_area;
> -	if (likely(vma->vm_start <= address))
> -		goto good_area;
> -	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
> -		goto bad_area;
> -	if (unlikely(expand_stack(vma, address)))
> +	if (likely(vma->vm_start <= address)) {
> +		/* good area, do nothing */
> +	} else if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)) ||
> +		   unlikely(expand_stack(vma, address))) {
>  		goto bad_area;
> +	}
>  
>  	/*
>  	 * Ok, we have a good vm_area for this memory access, so
>  	 * we can handle it..
>  	 */
> -good_area:
>  	if (unlikely(access_error(hw_error_code, vma))) {
>  		bad_area_access_error(regs, hw_error_code, address, vma);
>  		return;

I find the old code far easier to read... is there any actual reason to
do this?

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] x86/mm: replace a goto by merging two if clause
  2019-09-23  9:22   ` Peter Zijlstra
@ 2019-09-24  0:29     ` Wei Yang
  2019-10-01 11:47     ` Wei Yang
  1 sibling, 0 replies; 5+ messages in thread
From: Wei Yang @ 2019-09-24  0:29 UTC (permalink / raw)
  To: Peter Zijlstra; +Cc: Wei Yang, dave.hansen, luto, x86, linux-kernel

On Mon, Sep 23, 2019 at 11:22:31AM +0200, Peter Zijlstra wrote:
>On Thu, Sep 19, 2019 at 10:08:44AM +0800, Wei Yang wrote:
>> There is only one place to use good_area jump, which could be reduced by
>> merging the following two if clause.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> ---
>>  arch/x86/mm/fault.c | 11 +++++------
>>  1 file changed, 5 insertions(+), 6 deletions(-)
>> 
>> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
>> index 9d18b73b5f77..72ce6c69e195 100644
>> --- a/arch/x86/mm/fault.c
>> +++ b/arch/x86/mm/fault.c
>> @@ -1390,18 +1390,17 @@ void do_user_addr_fault(struct pt_regs *regs,
>>  	vma = find_vma(mm, address);
>>  	if (unlikely(!vma))
>>  		goto bad_area;
>> -	if (likely(vma->vm_start <= address))
>> -		goto good_area;
>> -	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
>> -		goto bad_area;
>> -	if (unlikely(expand_stack(vma, address)))
>> +	if (likely(vma->vm_start <= address)) {
>> +		/* good area, do nothing */
>> +	} else if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)) ||
>> +		   unlikely(expand_stack(vma, address))) {
>>  		goto bad_area;
>> +	}
>>  
>>  	/*
>>  	 * Ok, we have a good vm_area for this memory access, so
>>  	 * we can handle it..
>>  	 */
>> -good_area:
>>  	if (unlikely(access_error(hw_error_code, vma))) {
>>  		bad_area_access_error(regs, hw_error_code, address, vma);
>>  		return;
>
>I find the old code far easier to read... is there any actual reason to
>do this?

No, just want to make it easy to read.

-- 
Wei Yang
Help you, Help me

^ permalink raw reply	[flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] x86/mm: replace a goto by merging two if clause
  2019-09-23  9:22   ` Peter Zijlstra
  2019-09-24  0:29     ` Wei Yang
@ 2019-10-01 11:47     ` Wei Yang
  1 sibling, 0 replies; 5+ messages in thread
From: Wei Yang @ 2019-10-01 11:47 UTC (permalink / raw)
  To: Peter Zijlstra; +Cc: Wei Yang, dave.hansen, luto, x86, linux-kernel

On Mon, Sep 23, 2019 at 11:22:31AM +0200, Peter Zijlstra wrote:
>On Thu, Sep 19, 2019 at 10:08:44AM +0800, Wei Yang wrote:
>> There is only one place to use good_area jump, which could be reduced by
>> merging the following two if clause.
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> ---
>>  arch/x86/mm/fault.c | 11 +++++------
>>  1 file changed, 5 insertions(+), 6 deletions(-)
>> 
>> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
>> index 9d18b73b5f77..72ce6c69e195 100644
>> --- a/arch/x86/mm/fault.c
>> +++ b/arch/x86/mm/fault.c
>> @@ -1390,18 +1390,17 @@ void do_user_addr_fault(struct pt_regs *regs,
>>  	vma = find_vma(mm, address);
>>  	if (unlikely(!vma))
>>  		goto bad_area;
>> -	if (likely(vma->vm_start <= address))
>> -		goto good_area;
>> -	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
>> -		goto bad_area;
>> -	if (unlikely(expand_stack(vma, address)))
>> +	if (likely(vma->vm_start <= address)) {
>> +		/* good area, do nothing */
>> +	} else if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)) ||
>> +		   unlikely(expand_stack(vma, address))) {
>>  		goto bad_area;
>> +	}
>>  
>>  	/*
>>  	 * Ok, we have a good vm_area for this memory access, so
>>  	 * we can handle it..
>>  	 */
>> -good_area:
>>  	if (unlikely(access_error(hw_error_code, vma))) {
>>  		bad_area_access_error(regs, hw_error_code, address, vma);
>>  		return;
>
>I find the old code far easier to read... is there any actual reason to
>do this?

Hi, Peter,

Do you have some comment for the Patch 1?

-- 
Wei Yang
Help you, Help me

^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-10-01 11:47 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2019-09-19  2:08 [PATCH 1/2] x86/mm: consolidate bad_area handling to the end Wei Yang
2019-09-19  2:08 ` [PATCH 2/2] x86/mm: replace a goto by merging two if clause Wei Yang
2019-09-23  9:22   ` Peter Zijlstra
2019-09-24  0:29     ` Wei Yang
2019-10-01 11:47     ` Wei Yang

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