forked from Minki/linux
arm64: mm: ensure that the zero page is visible to the page table walker
In paging_init, we allocate the zero page, memset it to zero and then point TTBR0 to it in order to avoid speculative fetches through the identity mapping. In order to guarantee that the freshly zeroed page is indeed visible to the page table walker, we need to execute a dsb instruction prior to writing the TTBR. Cc: <stable@vger.kernel.org> # v3.14+, for older kernels need to drop the 'ishst' Signed-off-by: Will Deacon <will.deacon@arm.com>
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@ -464,6 +464,9 @@ void __init paging_init(void)
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empty_zero_page = virt_to_page(zero_page);
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/* Ensure the zero page is visible to the page table walker */
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dsb(ishst);
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/*
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* TTBR0 is only used for the identity mapping at this stage. Make it
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* point to zero page to avoid speculatively fetching new entries.
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