[PATCH linux-next] power:pkeys: fix bugon.cocci warnings

[PATCH linux-next] power:pkeys: fix bugon.cocci warnings

[CGEL]

From: Jing Yangyang <jing.yangyang@zte.com.cn>

Use BUG_ON instead of a if condition followed by BUG.

./arch/powerpc/include/asm/book3s/64/pkeys.h:21:2-5:WARNING
Use BUG_ON instead of if condition followed by BUG.
./arch/powerpc/include/asm/book3s/64/pkeys.h:14:2-5:WARNING
Use BUG_ON instead of if condition followed by BUG.

Generated by: scripts/coccinelle/misc/bugon.cocci

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
---
 arch/powerpc/include/asm/book3s/64/pkeys.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h
index 5b17813..5f74f0c 100644
--- a/arch/powerpc/include/asm/book3s/64/pkeys.h
+++ b/arch/powerpc/include/asm/book3s/64/pkeys.h
@@ -10,15 +10,13 @@ static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
 	if (!mmu_has_feature(MMU_FTR_PKEY))
 		return 0x0UL;
 
-	if (radix_enabled())
-		BUG();
+	BUG_ON(radix_enabled());
 	return hash__vmflag_to_pte_pkey_bits(vm_flags);
 }
 
 static inline u16 pte_to_pkey_bits(u64 pteflags)
 {
-	if (radix_enabled())
-		BUG();
+	BUG_ON(radix_enabled());
 	return hash__pte_to_pkey_bits(pteflags);
 }
 
-- 
1.8.3.1

Re: [PATCH linux-next] power:pkeys: fix bugon.cocci warnings

[Daniel Axtens]

Hi Jing,

Thanks for your patch.

The patch looks good, but looking at the output of `make coccicheck
M=arch/powerpc MODE=report`, it looks like there might be a few other
things that we might want to fix. Would it be worth trying to make the
arch/powerpc directory free from coccinelle warnings in one big patch
series, and then we could add coccicheck to our automatic patch testing?
(see
e.g. https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20210825064228.70487-1-deng.changcheng@zte.com.cn/ )

For this patch, I think we should try to fix all of arch/powerpc at the
same time. The check points out the following other possible uses of
BUG_ON:

arch/powerpc/include/asm/book3s/64/pgtable-64k.h:68:2-5: WARNING: Use BUG_ON instead of if condition followed by BUG.
Please make sure the condition has no side effects (see conditional BUG_ON definition in include/asm-generic/bug.h)
arch/powerpc/platforms/cell/spufs/sched.c:908:2-5: WARNING: Use BUG_ON instead of if condition followed by BUG.
Please make sure the condition has no side effects (see conditional BUG_ON definition in include/asm-generic/bug.h)
arch/powerpc/platforms/powernv/idle.c:968:3-6: WARNING: Use BUG_ON instead of if condition followed by BUG.
Please make sure the condition has no side effects (see conditional BUG_ON definition in include/asm-generic/bug.h)
arch/powerpc/platforms/powernv/idle.c:456:2-5: WARNING: Use BUG_ON instead of if condition followed by BUG.
Please make sure the condition has no side effects (see conditional BUG_ON definition in include/asm-generic/bug.h)

Kind regards,
Daniel


> Use BUG_ON instead of a if condition followed by BUG.
>
> ./arch/powerpc/include/asm/book3s/64/pkeys.h:21:2-5:WARNING
> Use BUG_ON instead of if condition followed by BUG.
> ./arch/powerpc/include/asm/book3s/64/pkeys.h:14:2-5:WARNING
> Use BUG_ON instead of if condition followed by BUG.
>
> Generated by: scripts/coccinelle/misc/bugon.cocci
>
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
> ---
>  arch/powerpc/include/asm/book3s/64/pkeys.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h
> index 5b17813..5f74f0c 100644
> --- a/arch/powerpc/include/asm/book3s/64/pkeys.h
> +++ b/arch/powerpc/include/asm/book3s/64/pkeys.h
> @@ -10,15 +10,13 @@ static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
>  	if (!mmu_has_feature(MMU_FTR_PKEY))
>  		return 0x0UL;
>  
> -	if (radix_enabled())
> -		BUG();
> +	BUG_ON(radix_enabled());
>  	return hash__vmflag_to_pte_pkey_bits(vm_flags);
>  }
>  
>  static inline u16 pte_to_pkey_bits(u64 pteflags)
>  {
> -	if (radix_enabled())
> -		BUG();
> +	BUG_ON(radix_enabled());
>  	return hash__pte_to_pkey_bits(pteflags);
>  }
>  
> -- 
> 1.8.3.1

Re: [PATCH linux-next] power:pkeys: fix bugon.cocci warnings

[Michael Ellerman]

CGEL <cgel.zte@gmail.com> writes:
> From: Jing Yangyang <jing.yangyang@zte.com.cn>
>
> Use BUG_ON instead of a if condition followed by BUG.
>
> ./arch/powerpc/include/asm/book3s/64/pkeys.h:21:2-5:WARNING
> Use BUG_ON instead of if condition followed by BUG.
> ./arch/powerpc/include/asm/book3s/64/pkeys.h:14:2-5:WARNING
> Use BUG_ON instead of if condition followed by BUG.
>
> Generated by: scripts/coccinelle/misc/bugon.cocci
>
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
> ---
>  arch/powerpc/include/asm/book3s/64/pkeys.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h
> index 5b17813..5f74f0c 100644
> --- a/arch/powerpc/include/asm/book3s/64/pkeys.h
> +++ b/arch/powerpc/include/asm/book3s/64/pkeys.h
> @@ -10,15 +10,13 @@ static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
>  	if (!mmu_has_feature(MMU_FTR_PKEY))
>  		return 0x0UL;
>  
> -	if (radix_enabled())
> -		BUG();
> +	BUG_ON(radix_enabled());
>  	return hash__vmflag_to_pte_pkey_bits(vm_flags);
>  }
>  
>  static inline u16 pte_to_pkey_bits(u64 pteflags)
>  {
> -	if (radix_enabled())
> -		BUG();
> +	BUG_ON(radix_enabled());
>  	return hash__pte_to_pkey_bits(pteflags);
>  }

Have you checked how this changes the generated code?

radix_enabled() is a jump label, via mmu_feature().

Possibly the compiler just works it all out and generates the same code,
but I'd want some evidence of that before merging this.

cheers

Re: [PATCH linux-next] power:pkeys: fix bugon.cocci warnings

[Christophe Leroy]

Le 02/05/2022 à 15:24, Michael Ellerman a écrit :
> CGEL <cgel.zte@gmail.com> writes:
>> From: Jing Yangyang <jing.yangyang@zte.com.cn>
>>
>> Use BUG_ON instead of a if condition followed by BUG.
>>
>> ./arch/powerpc/include/asm/book3s/64/pkeys.h:21:2-5:WARNING
>> Use BUG_ON instead of if condition followed by BUG.
>> ./arch/powerpc/include/asm/book3s/64/pkeys.h:14:2-5:WARNING
>> Use BUG_ON instead of if condition followed by BUG.
>>
>> Generated by: scripts/coccinelle/misc/bugon.cocci
>>
>> Reported-by: Zeal Robot <zealci@zte.com.cn>
>> Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
>> ---
>>   arch/powerpc/include/asm/book3s/64/pkeys.h | 6 ++----
>>   1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h
>> index 5b17813..5f74f0c 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pkeys.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pkeys.h
>> @@ -10,15 +10,13 @@ static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
>>   	if (!mmu_has_feature(MMU_FTR_PKEY))
>>   		return 0x0UL;
>>   
>> -	if (radix_enabled())
>> -		BUG();
>> +	BUG_ON(radix_enabled());
>>   	return hash__vmflag_to_pte_pkey_bits(vm_flags);
>>   }
>>   
>>   static inline u16 pte_to_pkey_bits(u64 pteflags)
>>   {
>> -	if (radix_enabled())
>> -		BUG();
>> +	BUG_ON(radix_enabled());
>>   	return hash__pte_to_pkey_bits(pteflags);
>>   }
> 
> Have you checked how this changes the generated code?
> 
> radix_enabled() is a jump label, via mmu_feature().
> 
> Possibly the compiler just works it all out and generates the same code,
> but I'd want some evidence of that before merging this.

Seems like the compiler is not that good, the generated code for test1() 
is much better than the one for test2(), see below.

void test1(void)
{
	if (radix_enabled())
		BUG();
}

void test2(void)
{
	BUG_ON(radix_enabled());
}

0000000000000900 <.test1>:
  900:	60 00 00 00 	nop
  904:	0f e0 00 00 	twui    r0,0
  908:	60 00 00 00 	nop
  90c:	60 00 00 00 	nop
  910:	4e 80 00 20 	blr
  914:	60 00 00 00 	nop
  918:	60 00 00 00 	nop
  91c:	60 00 00 00 	nop

0000000000000920 <.test2>:
  920:	60 00 00 00 	nop
  924:	39 20 00 01 	li      r9,1
  928:	0b 09 00 00 	tdnei   r9,0
  92c:	4e 80 00 20 	blr
  930:	39 20 00 00 	li      r9,0
  934:	0b 09 00 00 	tdnei   r9,0
  938:	4e 80 00 20 	blr


We should keep things as they are and change the coccinelle script.

Christophe

Re: [PATCH linux-next] power:pkeys: fix bugon.cocci warnings

[Arnd Bergmann]

On Sat, May 7, 2022 at 9:04 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
> Le 02/05/2022 à 15:24, Michael Ellerman a écrit :
> > CGEL <cgel.zte@gmail.com> writes:
> >> From: Jing Yangyang <jing.yangyang@zte.com.cn>
> >>
> >> Use BUG_ON instead of a if condition followed by BUG.
> >>
> >> ./arch/powerpc/include/asm/book3s/64/pkeys.h:21:2-5:WARNING
> >> Use BUG_ON instead of if condition followed by BUG.
> >> ./arch/powerpc/include/asm/book3s/64/pkeys.h:14:2-5:WARNING
> >> Use BUG_ON instead of if condition followed by BUG.
> >>
> >> Generated by: scripts/coccinelle/misc/bugon.cocci
> >>
> >> Reported-by: Zeal Robot <zealci@zte.com.cn>
> >> Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
> >> ---
> >>   arch/powerpc/include/asm/book3s/64/pkeys.h | 6 ++----
> >>   1 file changed, 2 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h
> >> index 5b17813..5f74f0c 100644
> >> --- a/arch/powerpc/include/asm/book3s/64/pkeys.h
> >> +++ b/arch/powerpc/include/asm/book3s/64/pkeys.h
> >> @@ -10,15 +10,13 @@ static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags)
> >>      if (!mmu_has_feature(MMU_FTR_PKEY))
> >>              return 0x0UL;
> >>
> >> -    if (radix_enabled())
> >> -            BUG();
> >> +    BUG_ON(radix_enabled());
> >>      return hash__vmflag_to_pte_pkey_bits(vm_flags);
> >>   }
> >>
> >>   static inline u16 pte_to_pkey_bits(u64 pteflags)
> >>   {
> >> -    if (radix_enabled())
> >> -            BUG();
> >> +    BUG_ON(radix_enabled());
> >>      return hash__pte_to_pkey_bits(pteflags);
> >>   }
> >
> > Have you checked how this changes the generated code?
> >
> > radix_enabled() is a jump label, via mmu_feature().
> >
> > Possibly the compiler just works it all out and generates the same code,
> > but I'd want some evidence of that before merging this.
>
> Seems like the compiler is not that good, the generated code for test1()
> is much better than the one for test2(), see below.
>
> void test1(void)
> {
>         if (radix_enabled())
>                 BUG();
> }
>
> void test2(void)
> {
>         BUG_ON(radix_enabled());
> }
>
> 0000000000000900 <.test1>:
>   900:  60 00 00 00     nop
>   904:  0f e0 00 00     twui    r0,0
>   908:  60 00 00 00     nop
>   90c:  60 00 00 00     nop
>   910:  4e 80 00 20     blr
>   914:  60 00 00 00     nop
>   918:  60 00 00 00     nop
>   91c:  60 00 00 00     nop
>
> 0000000000000920 <.test2>:
>   920:  60 00 00 00     nop
>   924:  39 20 00 01     li      r9,1
>   928:  0b 09 00 00     tdnei   r9,0
>   92c:  4e 80 00 20     blr
>   930:  39 20 00 00     li      r9,0
>   934:  0b 09 00 00     tdnei   r9,0
>   938:  4e 80 00 20     blr
>
>
> We should keep things as they are and change the coccinelle script.

Maybe just drop the custom ppc64 BUG_ON() then if it creates worse
code? The default BUG_ON() should be equivalent to the open-coded
version.

        Arnd