Messages in this thread Patch in this message | | | Date | Mon, 19 May 2008 16:10:02 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [Bug 10732] REGRESSION: 2.6.26-rc2-git4: X server failed start onX61s laptop |
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On Mon, 19 May 2008, Hugh Dickins wrote: > > This comes from an assumption in 1c12c4cf9411eb130b245fa8d0fbbaf989477c7b > mprotect: prevent alteration of the PAT bits, that PTE_MASK is what it's > supposed to be: whereas it's been wrong forever with PAE, staying 32-bit > where 64-bit is needed.
Can we *please* just fix PTE_MASK?
And can we agree to never EVER use that PAGE_MASK thing (which was only ever meant to work on *addresses*) for any pte operations (including the definition of PTE_MASK)? Because PAGE_MASK is very much the word-size, and in 32-bit PAE, the page table entry is bigger.
IOE, PTE_MASK should be a "pteval_t". And it should have absolutely *nothing* to do with PAGE_MASK. EVER.
IOW, maybe something like this?
And no, I haven't tested this at all. But it should make PTE_MASK have (a) the right type ("pteval_t", not "long" - the latter is pure and utter crap) (b) the right value (proper mask, not a sign-extended long - again, the latter is pure and utter crap)
but for all I know there might be some broken code that depends on the current incorrect and totally broken #defines, so this needs testing and thinking about.
It also causes these warnings on 32-bit PAE:
AS arch/x86/kernel/head_32.o arch/x86/kernel/head_32.S: Assembler messages: arch/x86/kernel/head_32.S:225: Warning: left operand is a bignum; integer 0 assumed arch/x86/kernel/head_32.S:609: Warning: left operand is a bignum; integer 0 assumed
and I do not see why (the end result seems to be identical).
Ingo, comments?
Oh, and those #define's should be moved from <asm/page.h> to <asm/pgtable.h>, I think. They have nothing to do with pages (despite the name of "physical_page_mask", and really are meaningful only in the context of some kind of page table entry.
Linus
--- include/asm-x86/page.h | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/asm-x86/page.h b/include/asm-x86/page.h index b381f4a..34b4845 100644 --- a/include/asm-x86/page.h +++ b/include/asm-x86/page.h @@ -10,8 +10,8 @@ #ifdef __KERNEL__ -#define PHYSICAL_PAGE_MASK (PAGE_MASK & __PHYSICAL_MASK) -#define PTE_MASK (_AT(long, PHYSICAL_PAGE_MASK)) +#define PHYSICAL_PAGE_MASK (__PHYSICAL_MASK & ~__PHYSICAL_LOW_BITS) +#define PTE_MASK (_AT(pteval_t, PHYSICAL_PAGE_MASK)) #define PMD_PAGE_SIZE (_AC(1, UL) << PMD_SHIFT) #define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1)) @@ -24,6 +24,7 @@ /* to align the pointer to the (next) page boundary */ #define PAGE_ALIGN(addr) (((addr)+PAGE_SIZE-1)&PAGE_MASK) +#define __PHYSICAL_LOW_BITS _AT(phys_addr_t, (PAGE_SIZE-1)) #define __PHYSICAL_MASK _AT(phys_addr_t, (_AC(1,ULL) << __PHYSICAL_MASK_SHIFT) - 1) #define __VIRTUAL_MASK ((_AC(1,UL) << __VIRTUAL_MASK_SHIFT) - 1)
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