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Date: Fri, 10 Mar 2017 11:25:22 +0000
From: Mark Rutland <mark.rutland@....com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org, keescook@...omium.org,
labbott@...oraproject.org, kernel-hardening@...ts.openwall.com,
will.deacon@....com, catalin.marinas@....com
Subject: Re: [PATCH v6 10/11] arm64/mm: remove pointless map/unmap sequences
when creating page tables
On Thu, Mar 09, 2017 at 09:52:08PM +0100, Ard Biesheuvel wrote:
> 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@...aro.org>
Reviewed-by: Mark Rutland <mark.rutland@....com>
Mark.
> ---
> 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
>
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