[kernel-hardening] [PATCH v6 10/11] arm64/mm: remove pointless map/unmap sequences when creating page tables

Ard Biesheuvel
2017-03-09T20:52:08Z

The routines __pud_populate and __pmd_populate only create a table
entry at their respective level which refers to the next level page
by its physical address, so there is no reason to map this page and
then unmap it immediately after.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/mm/mmu.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index bc9d5eb7bfa2..85ab82f5a0bc 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -128,9 +128,7 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
phys_addr_t pte_phys;
BUG_ON(!pgtable_alloc);
pte_phys = pgtable_alloc();
- pte = pte_set_fixmap(pte_phys);
__pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
- pte_clear_fixmap();
}
BUG_ON(pmd_bad(*pmd));

@@ -168,9 +166,7 @@ static void alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end,
phys_addr_t pmd_phys;
BUG_ON(!pgtable_alloc);
pmd_phys = pgtable_alloc();
- pmd = pmd_set_fixmap(pmd_phys);
__pud_populate(pud, pmd_phys, PUD_TYPE_TABLE);
- pmd_clear_fixmap();
}
BUG_ON(pud_bad(*pud));

--
2.7.4