[v2,5/5] asm-generic: fix build error in fix_to_virt with CONFIG_DEBUG_EXPERIENCE

Commit Message

Du, Changbin May 3, 2018, 1:25 p.m. UTC

On Wed, May 02, 2018 at 10:19:30AM -0400, Steven Rostedt wrote:
> On Wed,  2 May 2018 21:45:00 +0800
> [e-mail] wrote:
> 
> > From: Changbin Du <[e-mail]>
> > 
> > With '-Og' optimization level, GCC would not optimize a count for a loop
> > as a constant value. But BUILD_BUG_ON() only accept compile-time constant
> > values.
> > 
> > arch/arm/mm/mmu.o: In function `fix_to_virt':
> > /home/changbin/work/linux/./include/asm-generic/fixmap.h:31: undefined reference to `__compiletime_assert_31'
> > Makefile:1051: recipe for target 'vmlinux' failed
> > make: *** [vmlinux] Error 1
> > 
> > Signed-off-by: Changbin Du <[e-mail]>
> > ---
> >  include/asm-generic/fixmap.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
> > index 827e4d3..a6576d4 100644
> > --- a/include/asm-generic/fixmap.h
> > +++ b/include/asm-generic/fixmap.h
> > @@ -28,7 +28,8 @@
> >   */
> >  static __always_inline unsigned long fix_to_virt(const unsigned int idx)
> >  {
> > -	BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
> > +	BUILD_BUG_ON(__builtin_constant_p(idx) &&
> > +		     idx >= __end_of_fixed_addresses);
> 
> Hmm, this changes the check slightly. Perhaps we should only do this
> when your config is active:
> 
> {
> 	BUILD_BUG_ON(
> /* CONFIG_DEBUG_OPTIMIZE may cause idx not to be constant */
> #ifdef CONFIG_DEBUG_OPTIMIZE
> 		__builtin_constant_p(idx) &&
> #endif
> 		idx >= __end_of_fixed_addresses);
> 
> }
I think fix_to_virt() is designed for constant idx only. So I think we should
fix it at the caller side by replacing it with __fix_to_virt().

> -- Steve
> 
> >  	return __fix_to_virt(idx);
> >  }
> >  
>

Comments

Steven Rostedt May 3, 2018, 2:19 p.m. UTC | #1

On Thu, 3 May 2018 21:25:08 +0800
"Du, Changbin" <[e-mail]> wrote:

> I think fix_to_virt() is designed for constant idx only. So I think we should
> fix it at the caller side by replacing it with __fix_to_virt().
> 
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -1599,7 +1599,7 @@ static void __init early_fixmap_shutdown(void)
>                 pte_t *pte;
>                 struct map_desc map;
> 
> -               map.virtual = fix_to_virt(i);
> +               map.virtual = __fix_to_virt(i);
>                 pte = pte_offset_early_fixmap(pmd_off_k(map.virtual), map.virtual);

That's a better solution than the current patch.

-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

weylin May 3, 2018, 4:39 p.m. UTC | #2

Dear kernel devs,

After configuring for 2 hours settings, faced below on making :

cc1: error: 
/usr/src/linux-next-master/arch/x86/crypto/serpent-sse2-x86_64-asm_64.S: 
Input/output error

Thank you for your attantion to config matter last days, It is really 
physically  hard every time sort sort out menu again. If it would 
ppossible to have standard -- Conservative Unix style secure / paranoid 
choice alongwith -- allyesconfig .


Thank you !


On 05/03/2018 02:19 PM, Steven Rostedt wrote:
> On Thu, 3 May 2018 21:25:08 +0800
> "Du, Changbin" <[e-mail]> wrote:
>
>> I think fix_to_virt() is designed for constant idx only. So I think we should
>> fix it at the caller side by replacing it with __fix_to_virt().
>>
>> --- a/arch/arm/mm/mmu.c
>> +++ b/arch/arm/mm/mmu.c
>> @@ -1599,7 +1599,7 @@ static void __init early_fixmap_shutdown(void)
>>                  pte_t *pte;
>>                  struct map_desc map;
>>
>> -               map.virtual = fix_to_virt(i);
>> +               map.virtual = __fix_to_virt(i);
>>                  pte = pte_offset_early_fixmap(pmd_off_k(map.virtual), map.virtual);
> That's a better solution than the current patch.
>
> -- Steve
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in
> the body of a message to [e-mail]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

--
To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in
the body of a message to [e-mail]
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1599,7 +1599,7 @@  static void __init early_fixmap_shutdown(void)
                pte_t *pte;
                struct map_desc map;

-               map.virtual = fix_to_virt(i);
+               map.virtual = __fix_to_virt(i);
                pte = pte_offset_early_fixmap(pmd_off_k(map.virtual), map.virtual);

>