diff options
| author | Shaohua Li <shaohua.li@intel.com> | 2010-07-27 16:06:28 +0800 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2010-08-26 16:00:21 -0700 |
| commit | 660a293ea9be709b893d371fbc0328fcca33c33a (patch) | |
| tree | 4ef65b2eebb30e4d61ca685b23bac0678a24852f /arch/x86/mm | |
| parent | 9b861528a8012e7bc4d1f7bae07395b225331477 (diff) | |
x86, mm: Make spurious_fault check explicitly check the PRESENT bit
pte_present() returns true even present bit isn't set but _PAGE_PROTNONE
(global bit) bit is set. While with CONFIG_DEBUG_PAGEALLOC, free pages have
global bit set but present bit clear. This patch makes we could catch
free pages access with CONFIG_DEBUG_PAGEALLOC enabled.
[ hpa: added a comment in the code as a warning to janitors ]
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
LKML-Reference: <1280217988.32400.75.camel@sli10-desk.sh.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/mm')
| -rw-r--r-- | arch/x86/mm/fault.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 51f7ee71d6c..caec22906d7 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -872,8 +872,14 @@ spurious_fault(unsigned long error_code, unsigned long address) if (pmd_large(*pmd)) return spurious_fault_check(error_code, (pte_t *) pmd); + /* + * Note: don't use pte_present() here, since it returns true + * if the _PAGE_PROTNONE bit is set. However, this aliases the + * _PAGE_GLOBAL bit, which for kernel pages give false positives + * when CONFIG_DEBUG_PAGEALLOC is used. + */ pte = pte_offset_kernel(pmd, address); - if (!pte_present(*pte)) + if (!(pte_flags(*pte) & _PAGE_PRESENT)) return 0; ret = spurious_fault_check(error_code, pte); |