Messages in this thread | | | Date | Tue, 24 Jul 2012 06:52:14 -0400 | From | Cyril Chemparathy <> | Subject | Re: [RFC 02/23] ARM: LPAE: use signed arithmetic for mask definitions |
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On 7/24/2012 6:05 AM, Catalin Marinas wrote: > On Tue, Jul 24, 2012 at 02:09:04AM +0100, Cyril Chemparathy wrote: >> This patch applies to PAGE_MASK, PMD_MASK, and PGDIR_MASK, where forcing >> unsigned long math truncates the mask at the 32-bits. This clearly does bad >> things on PAE systems. >> >> This patch fixes this problem by defining these masks as signed quantities. >> We then rely on sign extension to do the right thing. >> >> Signed-off-by: Cyril Chemparathy <cyril@ti.com> >> Signed-off-by: Vitaly Andrianov <vitalya@ti.com> >> --- >> arch/arm/include/asm/page.h | 7 ++++++- >> arch/arm/include/asm/pgtable-3level.h | 6 +++--- >> 2 files changed, 9 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h >> index ecf9019..1c810d2 100644 >> --- a/arch/arm/include/asm/page.h >> +++ b/arch/arm/include/asm/page.h >> @@ -13,7 +13,12 @@ >> /* PAGE_SHIFT determines the page size */ >> #define PAGE_SHIFT 12 >> #define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT) >> -#define PAGE_MASK (~(PAGE_SIZE-1)) >> + >> +/* >> + * We do not use PAGE_SIZE in the following because we rely on sign >> + * extension to appropriately extend upper bits for PAE systems >> + */ >> +#define PAGE_MASK (~((1 << PAGE_SHIFT) - 1)) > > Would it work if we use a 1ULL here and avoid the sign trick? I'm > worried about some context where this would lose the sign. We could have > an #ifdef here while the PGDIR/PMD masks are in a separate file already. >
Sure, I will modify accordingly in the next version.
-- Thanks - Cyril
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