[PATCH 1/5] Fix spurious segmentation faults

[Bryan Wu]

Sebjan,

I heard this bug from Ogra before. And this patch touches the ARM common MM
code, I also failed to find it in upstream mainline.

I think if you or Rob can pointed out in the git log, it is better for us to review.

Ogra, do we have a bug in LP about this?

BTW, CONFIG_CPU_USE_DOMAINS=n in our ti-omap4 config

Thanks,
-Bryan

On 07/01/2010 01:02 PM, Bryan Wu wrote:
> From: Rob Clark <rob at ti.com>
> 
> This patch helps fixing some 'segmentation faults' seen on Maverick FS.
> It is an import of a part of an ARM patch.
> 
> Signed-off-by: Sebastien Jan <s-jan at ti.com>
> ---
>  arch/arm/mm/proc-macros.S |    9 ++++++++-
>  arch/arm/mm/proc-v7.S     |    3 +++
>  2 files changed, 11 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> index 7d63bea..1ccf579 100644
> --- a/arch/arm/mm/proc-macros.S
> +++ b/arch/arm/mm/proc-macros.S
> @@ -99,7 +99,11 @@
>   *  110x   0   1   0	r/w	r/o
>   *  11x0   0   1   0	r/w	r/o
>   *  1111   0   1   1	r/w	r/w
> - */
> + *
> + * If !CONFIG_CPU_USE_DOMAINS, the following permissions are changed:
> + *  110x   1   1   1	r/o	r/o
> + *  11x0   1   1   1	r/o	r/o
> +  */
>  	.macro	armv6_mt_table pfx
>  \pfx\()_mt_table:
>  	.long	0x00						@ L_PTE_MT_UNCACHED
> @@ -138,8 +142,11 @@
>  
>  	tst	r1, #L_PTE_USER
>  	orrne	r3, r3, #PTE_EXT_AP1
> +#ifdef CONFIG_CPU_USE_DOMAINS
> +	@ allow kernel read/write access to read-only user pages
>  	tstne	r3, #PTE_EXT_APX
>  	bicne	r3, r3, #PTE_EXT_APX | PTE_EXT_AP0
> +#endif
>  
>  	tst	r1, #L_PTE_EXEC
>  	orreq	r3, r3, #PTE_EXT_XN
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index df74916..c1c3fe0 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -152,8 +152,11 @@ ENTRY(cpu_v7_set_pte_ext)
>  
>  	tst	r1, #L_PTE_USER
>  	orrne	r3, r3, #PTE_EXT_AP1
> +#ifdef CONFIG_CPU_USE_DOMAINS
> +	@ allow kernel read/write access to read-only user pages
>  	tstne	r3, #PTE_EXT_APX
>  	bicne	r3, r3, #PTE_EXT_APX | PTE_EXT_AP0
> +#endif
>  
>  	tst	r1, #L_PTE_EXEC
>  	orreq	r3, r3, #PTE_EXT_XN