* Jeremy Fitzhardinge <[EMAIL PROTECTED]> wrote:
> Huang, Ying wrote:
>> This patch fixes a bug of change_page_attr/change_page_attr_addr on
>> Intel i386/x86_64 CPUs. After changing page attribute to be
>> executable with these functions, the page remains un-executable on
>> Intel i386/x86_64 CPU. Because on Intel i386/x86_64 CPU, only if the
>> "NX" bits of all three level page tables are cleared (PAE is
>> enabled), the corresponding page is executable (refer to section
>> 4.13.2 of Intel 64 and IA-32 Architectures Software Developer's
>> Manual). So, the bug is fixed through clearing the "NX" bit of PMD
>> when splitting the huge PMD.
oops, nice detail!
>> Signed-off-by: Huang Ying <[EMAIL PROTECTED]>
>>
>> ---
>> arch/x86/mm/pageattr.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> --- a/arch/x86/mm/pageattr.c
>> +++ b/arch/x86/mm/pageattr.c
>> @@ -124,6 +124,7 @@ static int split_large_page(pte_t *kpte,
>> /*
>> * Install the new, split up pagetable:
>> */
>> + pgprot_val(ref_prot) &= ~_PAGE_NX;
>>
>
> I don't think its a good idea to treat pgprot_val() as an lvalue - it
> precludes it from being turned into an inline function. I know there
> are numerous other places which do, but we should avoid making it
> worse.
applied it with the following cleanup from Thomas:
static int split_large_page(pte_t *kpte, unsigned long address)
{
- pgprot_t ref_prot = pte_pgprot(pte_clrhuge(*kpte));
+ pgprot_t ref_prot;
...
+ ref_prot = pte_pgprot(pte_mkexec(pte_clrhuge(*kpte)));
i.e. it now goes through all the proper accessors.
Ingo
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