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arm64: mte: Use Normal Tagged attributes for the linear map

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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>
This commit is contained in:
Catalin Marinas 2019-11-27 09:51:13 +00:00
parent c058b1c4a5
commit 0178dc7613
5 changed files with 31 additions and 4 deletions
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1
arch/arm64/include/asm/memory.h
View File

@ -133,6 +133,7 @@
#define MT_NORMAL_NC 3
#define MT_NORMAL 4
#define MT_NORMAL_WT 5
#define MT_NORMAL_TAGGED 6
/*
* Memory types for Stage-2 translation

2
arch/arm64/include/asm/pgtable-prot.h
View File

@ -50,6 +50,7 @@ extern bool arm64_use_ng_mappings;
#define PROT_NORMAL_NC (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_NC))
#define PROT_NORMAL_WT (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_WT))
#define PROT_NORMAL (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL))
#define PROT_NORMAL_TAGGED (PROT_DEFAULT | PTE_PXN | PTE_UXN | PTE_WRITE | PTE_ATTRINDX(MT_NORMAL_TAGGED))
#define PROT_SECT_DEVICE_nGnRE (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
#define PROT_SECT_NORMAL (PROT_SECT_DEFAULT | PMD_SECT_PXN | PMD_SECT_UXN | PMD_ATTRINDX(MT_NORMAL))
@ -59,6 +60,7 @@ extern bool arm64_use_ng_mappings;
#define _HYP_PAGE_DEFAULT _PAGE_DEFAULT
#define PAGE_KERNEL __pgprot(PROT_NORMAL)
#define PAGE_KERNEL_TAGGED __pgprot(PROT_NORMAL_TAGGED)
#define PAGE_KERNEL_RO __pgprot((PROT_NORMAL & ~PTE_WRITE) | PTE_RDONLY)
#define PAGE_KERNEL_ROX __pgprot((PROT_NORMAL & ~(PTE_WRITE | PTE_PXN)) | PTE_RDONLY)
#define PAGE_KERNEL_EXEC __pgprot(PROT_NORMAL & ~PTE_PXN)

4
arch/arm64/mm/dump.c
View File

@ -169,6 +169,10 @@ static const struct prot_bits pte_bits[] = {
.mask = PTE_ATTRINDX_MASK,
.val = PTE_ATTRINDX(MT_NORMAL),
.set = "MEM/NORMAL",
}, {
.mask = PTE_ATTRINDX_MASK,
.val = PTE_ATTRINDX(MT_NORMAL_TAGGED),
.set = "MEM/NORMAL-TAGGED",
}
};

20
arch/arm64/mm/mmu.c
View File

@ -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);
}
/*

8
arch/arm64/mm/proc.S
View File

@ -44,14 +44,18 @@
#define TCR_KASAN_FLAGS 0
#endif
/* Default MAIR_EL1 */
/*
* Default MAIR_EL1. MT_NORMAL_TAGGED is initially mapped as Normal memory and
* changed during __cpu_setup to Normal Tagged if the system supports MTE.
*/
#define MAIR_EL1_SET \
(MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRnE, MT_DEVICE_nGnRnE) | \
MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRE, MT_DEVICE_nGnRE) | \
MAIR_ATTRIDX(MAIR_ATTR_DEVICE_GRE, MT_DEVICE_GRE) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL_NC, MT_NORMAL_NC) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL_WT, MT_NORMAL_WT))
MAIR_ATTRIDX(MAIR_ATTR_NORMAL_WT, MT_NORMAL_WT) | \
MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL_TAGGED))
#ifdef CONFIG_CPU_PM
/**