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x86: fix crash in _x86_mmu_get_flags

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Looking up the PTE flags was page faulting if the address wasn't
marked as present in the page directory, since there is no page table
for that directory entry.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2017-10-16 16:01:33 -07:00 • committed by Andrew Boie
commit 094f2cb77b
1 changed files with 5 additions and 1 deletions
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4
arch/x86/core/x86_mmu.c
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@ -36,7 +36,11 @@ void _x86_mmu_get_flags(void *addr, u32_t *pde_flags, u32_t *pte_flags)
{
*pde_flags = X86_MMU_GET_PDE(addr)->value & ~MMU_PDE_PAGE_TABLE_MASK;
if (*pde_flags & MMU_ENTRY_PRESENT) {
*pte_flags = X86_MMU_GET_PTE(addr)->value & ~MMU_PTE_PAGE_MASK;
} else {
*pte_flags = 0;
}
}