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| author | Catalin Marinas <catalin.marinas@arm.com> | 2019-11-27 09:51:13 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-09-03 17:26:31 +0100 |
| commit | 0178dc7613684561ff3bb1625cd5504f1e7fbe3d (patch) | |
| tree | e2ecb07f1cab6a6d46e5f7d5c6cfeca88b22b38e /arch/arm64/mm/mmu.c | |
| parent | c058b1c4a5ea7b88cce4c961c1000acf482ea64b (diff) | |
| download | lwn-0178dc7613684561ff3bb1625cd5504f1e7fbe3d.tar.gz lwn-0178dc7613684561ff3bb1625cd5504f1e7fbe3d.zip | |
arm64: mte: Use Normal Tagged attributes for the linear map
Once user space is given access to tagged memory, the kernel must be
able to clear/save/restore tags visible to the user. This is done via
the linear mapping, therefore map it as such. The new MT_NORMAL_TAGGED
index for MAIR_EL1 is initially mapped as Normal memory and later
changed to Normal Tagged via the cpufeature infrastructure. From a
mismatched attribute aliases perspective, the Tagged memory is
considered a permission and it won't lead to undefined behaviour.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Diffstat (limited to 'arch/arm64/mm/mmu.c')
| -rw-r--r-- | arch/arm64/mm/mmu.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 75df62fea1b6..936c4762dadf 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -122,7 +122,7 @@ static bool pgattr_change_is_safe(u64 old, u64 new) * The following mapping attributes may be updated in live * kernel mappings without the need for break-before-make. */ - static const pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE | PTE_NG; + pteval_t mask = PTE_PXN | PTE_RDONLY | PTE_WRITE | PTE_NG; /* creating or taking down mappings is always safe */ if (old == 0 || new == 0) @@ -136,6 +136,17 @@ static bool pgattr_change_is_safe(u64 old, u64 new) if (old & ~new & PTE_NG) return false; + /* + * Changing the memory type between Normal and Normal-Tagged is safe + * since Tagged is considered a permission attribute from the + * mismatched attribute aliases perspective. + */ + if (((old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) || + (old & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED)) && + ((new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL) || + (new & PTE_ATTRINDX_MASK) == PTE_ATTRINDX(MT_NORMAL_TAGGED))) + mask |= PTE_ATTRINDX_MASK; + return ((old ^ new) & ~mask) == 0; } @@ -491,7 +502,12 @@ static void __init map_mem(pgd_t *pgdp) if (memblock_is_nomap(reg)) continue; - __map_memblock(pgdp, start, end, PAGE_KERNEL, flags); + /* + * The linear map must allow allocation tags reading/writing + * if MTE is present. Otherwise, it has the same attributes as + * PAGE_KERNEL. + */ + __map_memblock(pgdp, start, end, PAGE_KERNEL_TAGGED, flags); } /* |