Messages in this thread | | | Date | Tue, 16 Nov 2010 15:18:03 +0000 | Subject | Re: [PATCH v2 05/20] ARM: LPAE: Introduce L_PTE_NOEXEC and L_PTE_NOWRITE | From | Catalin Marinas <> |
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On 15 November 2010 18:30, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > On Fri, Nov 12, 2010 at 06:00:25PM +0000, Catalin Marinas wrote: >> The LPAE page table format needs to explicitly disable execution or >> write permissions on a page by setting the corresponding bits (similar >> to the classic page table format with Access Flag enabled). This patch >> introduces null definitions for the 2-level format and the actual noexec >> and nowrite bits for the LPAE format. It also changes several PTE >> maintenance macros and masks. >> >> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> >> --- >> arch/arm/include/asm/pgtable-2level.h | 2 + >> arch/arm/include/asm/pgtable.h | 44 +++++++++++++++++++++------------ >> arch/arm/mm/mmu.c | 6 ++-- >> 3 files changed, 33 insertions(+), 19 deletions(-) >> >> diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h >> index 36bdef7..4e21166 100644 >> --- a/arch/arm/include/asm/pgtable-2level.h >> +++ b/arch/arm/include/asm/pgtable-2level.h >> @@ -128,6 +128,8 @@ >> #define L_PTE_USER (1 << 8) >> #define L_PTE_EXEC (1 << 9) >> #define L_PTE_SHARED (1 << 10) /* shared(v6), coherent(xsc3) */ >> +#define L_PTE_NOEXEC (0) >> +#define L_PTE_NOWRITE (0) > > Let's not make this more complicated than it has to be. If we need the > inverse of WRITE and EXEC, then that's what we should change everyone to, > not invent a new system to work along side the old system.
This adds an additional instruction in set_pte_ext, unless you can write the bit checking in a better way:
tst r1, #L_PTE_NOWRITE orrne r3, r3, #PTE_EXT_APX tsteq r1, #L_PTE_DIRTY orreq r3, r3, #PTE_EXT_APX
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