linux-next: 1ea0704e (ptep_modify_prot transaction abstraction) breaks no-mmu

linux-next: 1ea0704e (ptep_modify_prot transaction abstraction) breaks no-mmu

[Mike Frysinger]

the functions added to asm-generic/pgtable.h are only used by
mm/mprotect.c (a MMU-only file), but they were not added inside of the
CONFIG_MMU ifdef block.  since the functions rely on things inside of
CONFIG_MMU (the lines just above in pgtable.h), we get build failure
on all no-mmu setups:
  CC      init/main.o
In file included from include/asm/pgtable.h:94,
                 from include/linux/mm.h:39,
                 from include/asm/dma.h:39,
                 from include/linux/bootmem.h:8,
                 from init/main.c:27:
include/asm-generic/pgtable.h: In function '__ptep_modify_prot_start':
include/asm-generic/pgtable.h:210: error: implicit declaration of
function 'ptep_get_and_clear'
include/asm-generic/pgtable.h:210: error: incompatible types in return
make[1]: *** [init/main.o] Error 1
make: *** [init/main.o] Error 2
-mike

Re: linux-next: 1ea0704e (ptep_modify_prot transaction abstraction) breaks no-mmu

[Jeremy Fitzhardinge]

Mike Frysinger wrote:
> the functions added to asm-generic/pgtable.h are only used by
> mm/mprotect.c (a MMU-only file), but they were not added inside of the
> CONFIG_MMU ifdef block.  since the functions rely on things inside of
> CONFIG_MMU (the lines just above in pgtable.h), we get build failure
> on all no-mmu setups:
>   CC      init/main.o
> In file included from include/asm/pgtable.h:94,
>                  from include/linux/mm.h:39,
>                  from include/asm/dma.h:39,
>                  from include/linux/bootmem.h:8,
>                  from init/main.c:27:
> include/asm-generic/pgtable.h: In function '__ptep_modify_prot_start':
> include/asm-generic/pgtable.h:210: error: implicit declaration of
> function 'ptep_get_and_clear'
> include/asm-generic/pgtable.h:210: error: incompatible types in return
> make[1]: *** [init/main.o] Error 1
> make: *** [init/main.o] Error 2
> -mike
>   

Uh, OK.  What does mprotect do on a nommu system?  Would it be 
sufficient to move the definitions of __ptep_modify_prot_start/commit 
out of a CONFIG_MMU block, or provide separate no-op versions?

    J

Re: linux-next: 1ea0704e (ptep_modify_prot transaction abstraction) breaks no-mmu

[Adrian Bunk]

On Thu, Jul 03, 2008 at 08:53:52AM -0700, Jeremy Fitzhardinge wrote:
> Mike Frysinger wrote:
>> the functions added to asm-generic/pgtable.h are only used by
>> mm/mprotect.c (a MMU-only file), but they were not added inside of the
>> CONFIG_MMU ifdef block.  since the functions rely on things inside of
>> CONFIG_MMU (the lines just above in pgtable.h), we get build failure
>> on all no-mmu setups:
>>   CC      init/main.o
>> In file included from include/asm/pgtable.h:94,
>>                  from include/linux/mm.h:39,
>>                  from include/asm/dma.h:39,
>>                  from include/linux/bootmem.h:8,
>>                  from init/main.c:27:
>> include/asm-generic/pgtable.h: In function '__ptep_modify_prot_start':
>> include/asm-generic/pgtable.h:210: error: implicit declaration of
>> function 'ptep_get_and_clear'
>> include/asm-generic/pgtable.h:210: error: incompatible types in return
>> make[1]: *** [init/main.o] Error 1
>> make: *** [init/main.o] Error 2
>> -mike
>>   
>
> Uh, OK.  What does mprotect do on a nommu system?  Would it be  
> sufficient to move the definitions of __ptep_modify_prot_start/commit  
> out of a CONFIG_MMU block, or provide separate no-op versions?

FYI:
The compile error now moved into Linus' tree, and broke at least the 
blackfin and m68knommu ports.

>    J

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

Re: linux-next: 1ea0704e (ptep_modify_prot transaction abstraction) breaks no-mmu

[Mike Frysinger]

On Thu, Jul 3, 2008 at 11:53 AM, Jeremy Fitzhardinge wrote:
> Mike Frysinger wrote:
>> the functions added to asm-generic/pgtable.h are only used by
>> mm/mprotect.c (a MMU-only file), but they were not added inside of the
>> CONFIG_MMU ifdef block.  since the functions rely on things inside of
>> CONFIG_MMU (the lines just above in pgtable.h), we get build failure
>> on all no-mmu setups:
>>  CC      init/main.o
>> In file included from include/asm/pgtable.h:94,
>>                 from include/linux/mm.h:39,
>>                 from include/asm/dma.h:39,
>>                 from include/linux/bootmem.h:8,
>>                 from init/main.c:27:
>> include/asm-generic/pgtable.h: In function '__ptep_modify_prot_start':
>> include/asm-generic/pgtable.h:210: error: implicit declaration of
>> function 'ptep_get_and_clear'
>> include/asm-generic/pgtable.h:210: error: incompatible types in return
>> make[1]: *** [init/main.o] Error 1
>> make: *** [init/main.o] Error 2
>
> Uh, OK.  What does mprotect do on a nommu system?

it depends on the port.  by default, i'm pretty sure mprotect on all
nommu systems are realistically pretty much noops.  the Blackfin can
do real protection (CONFIG_MPU), but with significant performance
degradation (since the page fault handler is not in hardware nor
hardware assisted in any way).

> Would it be sufficient to
> move the definitions of __ptep_modify_prot_start/commit out of a CONFIG_MMU
> block, or provide separate no-op versions?

simply move them into CONFIG_MMU for now
-mike

[PATCH] mm: fix ptep_modify_* for no-MMU systems

[Jeremy Fitzhardinge]

Fixes build problem: 
 the functions added to asm-generic/pgtable.h are only used by
 mm/mprotect.c (a MMU-only file), but they were not added inside of the
 CONFIG_MMU ifdef block.  since the functions rely on things inside of
 CONFIG_MMU (the lines just above in pgtable.h), we get build failure
 on all no-mmu setups:
   CC      init/main.o
 In file included from include/asm/pgtable.h:94,
                  from include/linux/mm.h:39,
                  from include/asm/dma.h:39,
                  from include/linux/bootmem.h:8,
                  from init/main.c:27:
 include/asm-generic/pgtable.h: In function '__ptep_modify_prot_start':
 include/asm-generic/pgtable.h:210: error: implicit declaration of
 function 'ptep_get_and_clear'
 include/asm-generic/pgtable.h:210: error: incompatible types in return
 make[1]: *** [init/main.o] Error 1
 make: *** [init/main.o] Error 2

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Mike Frysinger <vapier.adi@gmail.com>
---
 include/asm-generic/pgtable.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

===================================================================
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -195,7 +195,6 @@
 	}
 	return 0;
 }
-#endif /* CONFIG_MMU */
 
 static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm,
 					     unsigned long addr,
@@ -253,6 +252,7 @@
 	__ptep_modify_prot_commit(mm, addr, ptep, pte);
 }
 #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
+#endif /* CONFIG_MMU */
 
 /*
  * A facility to provide lazy MMU batching.  This allows PTE updates and

Re: [PATCH] mm: fix ptep_modify_* for no-MMU systems

[Adrian Bunk]

On Tue, Jul 15, 2008 at 01:39:07PM -0700, Jeremy Fitzhardinge wrote:
> Fixes build problem: the functions added to asm-generic/pgtable.h are 
> only used by
> mm/mprotect.c (a MMU-only file), but they were not added inside of the
> CONFIG_MMU ifdef block.  since the functions rely on things inside of
> CONFIG_MMU (the lines just above in pgtable.h), we get build failure
> on all no-mmu setups:
>   CC      init/main.o
> In file included from include/asm/pgtable.h:94,
>                  from include/linux/mm.h:39,
>                  from include/asm/dma.h:39,
>                  from include/linux/bootmem.h:8,
>                  from init/main.c:27:
> include/asm-generic/pgtable.h: In function '__ptep_modify_prot_start':
> include/asm-generic/pgtable.h:210: error: implicit declaration of
> function 'ptep_get_and_clear'
> include/asm-generic/pgtable.h:210: error: incompatible types in return
> make[1]: *** [init/main.o] Error 1
> make: *** [init/main.o] Error 2
>...

Thanks, seems to work fine.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed