Messages in this thread | | | Date | Tue, 20 May 2008 08:31:31 +0100 | From | Jeremy Fitzhardinge <> | Subject | Re: [Bug 10732] REGRESSION: 2.6.26-rc2-git4: X server failed start onX61s laptop |
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Linus Torvalds wrote: > 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? >
That's pretty close to the core of my patches (just reposted), which have been cooking in x86.git for a week or so.
One thing I'd take from your patch is something like your __PHYSICAL_LOW_BITS definition, since its a bit clearer than what I did. (I haven't updated my patch before posting just because I wanted to post exactly as tested.)
> 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) > >
J
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