2014-12-17 09:14:38

by Christophe Leroy

Subject: [v2 PATCH 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW

On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages
and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW

Signed-off-by: Christophe Leroy <[email protected]>

---
v2 is a complete rework compared to v1

arch/powerpc/include/asm/pte-8xx.h | 7 +++----
arch/powerpc/kernel/head_8xx.S | 3 ---
2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
index daa4616..4f5583e 100644
--- a/arch/powerpc/include/asm/pte-8xx.h
+++ b/arch/powerpc/include/asm/pte-8xx.h
@@ -46,7 +46,7 @@
* require a TLB exception handler change. It is assumed unused bits
* are always zero.
*/
-#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */
+#define _PAGE_RO 0x0400 /* lsb PP bits */
#define _PAGE_USER 0x0800 /* msb PP bits */
/* set when neither _PAGE_USER nor _PAGE_RW are set */
#define _PAGE_KNLRO 0x0200
@@ -62,9 +62,8 @@
#define PTE_ATOMIC_UPDATES 1

/* We need to add _PAGE_SHARED to kernel pages */
-#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_KNLRO)
-#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_KNLRO)
-#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
+#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO)
+#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO)

#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_PTE_8xx_H */
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 3d4b8ee..807b0db 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -441,9 +441,6 @@ DataStoreTLBMiss:
and r11, r11, r10
rlwimi r10, r11, 0, _PAGE_PRESENT
#endif
- /* invert RW */
- xori r10, r10, _PAGE_RW
-
/* The Linux PTE won't go exactly into the MMU TLB.
* Software indicator bits 22 and 28 must be clear.
* Software indicator bits 24, 25, 26, and 27 must be
--
2.1.0

2014-12-18 02:54:13

by Scott Wood

Subject: Re: [v2 PATCH 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW

On Wed, 2014-12-17 at 10:14 +0100, Christophe Leroy wrote:
> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages
> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW
>
> Signed-off-by: Christophe Leroy <[email protected]>
>
> ---
> v2 is a complete rework compared to v1
>
> arch/powerpc/include/asm/pte-8xx.h | 7 +++----
> arch/powerpc/kernel/head_8xx.S | 3 ---
> 2 files changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
> index daa4616..4f5583e 100644
> --- a/arch/powerpc/include/asm/pte-8xx.h
> +++ b/arch/powerpc/include/asm/pte-8xx.h
> @@ -46,7 +46,7 @@
> * require a TLB exception handler change. It is assumed unused bits
> * are always zero.
> */
> -#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */
> +#define _PAGE_RO 0x0400 /* lsb PP bits */

It looks like pte_update() needs to be updated to match.

> #define _PAGE_USER 0x0800 /* msb PP bits */
> /* set when neither _PAGE_USER nor _PAGE_RW are set */

Also update this comment.

> #define _PAGE_KNLRO 0x0200
> @@ -62,9 +62,8 @@
> #define PTE_ATOMIC_UPDATES 1
>
> /* We need to add _PAGE_SHARED to kernel pages */
> -#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_KNLRO)
> -#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_KNLRO)
> -#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
> +#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO)
> +#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO)
>
> #endif /* __KERNEL__ */
> #endif /* _ASM_POWERPC_PTE_8xx_H */

Where did _PAGE_KERNEL_RW go?

-Scott

2014-12-18 07:05:18

by Christophe Leroy

Subject: Re: [v2 PATCH 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW

Le 18/12/2014 03:22, Scott Wood a écrit :
> On Wed, 2014-12-17 at 10:14 +0100, Christophe Leroy wrote:
>> On powerpc 8xx, in TLB entries, 0x400 bit is set to 1 for read-only pages
>> and is set to 0 for RW pages. So we should use _PAGE_RO instead of _PAGE_RW
>>
>> Signed-off-by: Christophe Leroy <[email protected]>
>>
>> ---
>> v2 is a complete rework compared to v1
>>
>> arch/powerpc/include/asm/pte-8xx.h | 7 +++----
>> arch/powerpc/kernel/head_8xx.S | 3 ---
>> 2 files changed, 3 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
>> index daa4616..4f5583e 100644
>> --- a/arch/powerpc/include/asm/pte-8xx.h
>> +++ b/arch/powerpc/include/asm/pte-8xx.h
>> @@ -46,7 +46,7 @@
>> * require a TLB exception handler change. It is assumed unused bits
>> * are always zero.
>> */
>> -#define _PAGE_RW 0x0400 /* lsb PP bits, inverted in HW */
>> +#define _PAGE_RO 0x0400 /* lsb PP bits */
> It looks like pte_update() needs to be updated to match.
>
>> #define _PAGE_USER 0x0800 /* msb PP bits */
>> /* set when neither _PAGE_USER nor _PAGE_RW are set */
> Also update this comment.
>
>> #define _PAGE_KNLRO 0x0200
>> @@ -62,9 +62,8 @@
>> #define PTE_ATOMIC_UPDATES 1
>>
>> /* We need to add _PAGE_SHARED to kernel pages */
>> -#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_KNLRO)
>> -#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_KNLRO)
>> -#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
>> +#define _PAGE_KERNEL_RO (_PAGE_SHARED | _PAGE_RO | _PAGE_KNLRO)
>> +#define _PAGE_KERNEL_ROX (_PAGE_EXEC | _PAGE_RO | _PAGE_KNLRO)
>>
>> #endif /* __KERNEL__ */
>> #endif /* _ASM_POWERPC_PTE_8xx_H */
> Where did _PAGE_KERNEL_RW go?
>
>
It is already defined like this in pte-common.h:

#ifndef _PAGE_KERNEL_RW
#define _PAGE_KERNEL_RW (_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
#endif


Christophe