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    Subject[PATCH] x86: fix pte_flags() to only return flags, fix lguest (updated)
    Date
    (Jeremy said:
    rusty: use PTE_MASK
    rusty: use PTE_MASK
    rusty: use PTE_MASK
    When I asked:
    jsgf: does that include the NX flag?
    He responded eloquently:
    rusty: use PTE_MASK
    rusty: use PTE_MASK
    yes, it's the official constant of masking flags out of ptes
    )

    Change a15af1c9ea2750a9ff01e51615c45950bad8221b 'x86/paravirt: add
    pte_flags to just get pte flags' removed lguest's private pte_flags()
    in favor of a generic one.

    Unfortunately, the generic one doesn't filter out the non-flags bits:
    this results in lguest creating corrupt shadow page tables and blowing
    up host memory.

    Since noone is supposed to use the pfn part of pte_flags(), it seems
    safest to always do the filtering.

    Cc: Jeremy Fitzhardinge <jeremy@goop.org>
    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

    diff -r ee1a6adad3d2 arch/x86/kernel/paravirt.c
    --- a/arch/x86/kernel/paravirt.c Mon Jul 21 12:49:25 2008 +1000
    +++ b/arch/x86/kernel/paravirt.c Tue Jul 22 15:31:04 2008 +1000
    @@ -428,7 +428,7 @@ struct pv_mmu_ops pv_mmu_ops = {
    #endif /* PAGETABLE_LEVELS >= 3 */

    .pte_val = native_pte_val,
    - .pte_flags = native_pte_val,
    + .pte_flags = native_pte_flags,
    .pgd_val = native_pgd_val,

    .make_pte = native_make_pte,
    diff -r ee1a6adad3d2 include/asm-x86/page.h
    --- a/include/asm-x86/page.h Mon Jul 21 12:49:25 2008 +1000
    +++ b/include/asm-x86/page.h Tue Jul 22 15:31:04 2008 +1000
    @@ -144,6 +144,11 @@ static inline pteval_t native_pte_val(pt
    return pte.pte;
    }

    +static inline pteval_t native_pte_flags(pte_t pte)
    +{
    + return native_pte_val(pte) & ~PTE_MASK;
    +}
    +
    #define pgprot_val(x) ((x).pgprot)
    #define __pgprot(x) ((pgprot_t) { (x) } )

    @@ -165,7 +170,7 @@ static inline pteval_t native_pte_val(pt
    #endif

    #define pte_val(x) native_pte_val(x)
    -#define pte_flags(x) native_pte_val(x)
    +#define pte_flags(x) native_pte_flags(x)
    #define __pte(x) native_make_pte(x)

    #endif /* CONFIG_PARAVIRT */
    diff -r ee1a6adad3d2 include/asm-x86/paravirt.h
    --- a/include/asm-x86/paravirt.h Mon Jul 21 12:49:25 2008 +1000
    +++ b/include/asm-x86/paravirt.h Tue Jul 22 15:31:04 2008 +1000
    @@ -1083,6 +1083,9 @@ static inline pteval_t pte_flags(pte_t p
    ret = PVOP_CALL1(pteval_t, pv_mmu_ops.pte_flags,
    pte.pte);

    +#ifdef CONFIG_PARAVIRT_DEBUG
    + BUG_ON(ret & PTE_MASK);
    +#endif
    return ret;
    }


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