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Subject[PATCH v3 2/2] powerpc/8xx: use _PAGE_RO instead of _PAGE_RW
Date
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 <christophe.leroy@c-s.fr>

---
v2 is a complete rework compared to v1
v3: fixing pte_update() and comments

arch/powerpc/include/asm/pgtable-ppc32.h | 5 +++--
arch/powerpc/include/asm/pte-8xx.h | 9 ++++-----
arch/powerpc/kernel/head_8xx.S | 3 ---
3 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable-ppc32.h b/arch/powerpc/include/asm/pgtable-ppc32.h
index caf094a..b4e0c3b 100644
--- a/arch/powerpc/include/asm/pgtable-ppc32.h
+++ b/arch/powerpc/include/asm/pgtable-ppc32.h
@@ -178,9 +178,10 @@ static inline unsigned long pte_update(pte_t *p,
andc %1,%0,%5\n\
or %1,%1,%6\n\
/* 0x200 == Extended encoding, bit 22 */ \
- /* Bit 22 has to be 1 if neither _PAGE_USER nor _PAGE_RW are set */ \
+ /* Bit 22 has to be 1 when _PAGE_USER is unset and _PAGE_RO is set */ \
rlwimi %1,%1,32-2,0x200\n /* get _PAGE_USER */ \
- rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RW */ \
+ rlwinm %3,%1,32-1,0x200\n /* get _PAGE_RO */ \
+ xori %3,%3,0x200\n \
or %1,%3,%1\n\
xori %1,%1,0x200\n"
" stwcx. %1,0,%4\n\
diff --git a/arch/powerpc/include/asm/pte-8xx.h b/arch/powerpc/include/asm/pte-8xx.h
index daa4616..eb6edb4 100644
--- a/arch/powerpc/include/asm/pte-8xx.h
+++ b/arch/powerpc/include/asm/pte-8xx.h
@@ -46,9 +46,9 @@
* 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 */
+/* set when _PAGE_USER is unset and _PAGE_RO is set */
#define _PAGE_KNLRO 0x0200

#define _PMD_PRESENT 0x0001
@@ -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


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