diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2020-05-04 14:42:36 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-09-04 12:46:06 +0100 |
| commit | 34bfeea4a9e9cdae713637541f240c3adfdfede3 (patch) | |
| tree | b4e13c4df48e00547764673d4d6ceec187ecf5b3 /arch/arm64/lib | |
| parent | 72e6afa08e988744822f9bf18043fc04c4df2178 (diff) | |
| download | lwn-34bfeea4a9e9cdae713637541f240c3adfdfede3.tar.gz lwn-34bfeea4a9e9cdae713637541f240c3adfdfede3.zip | |
arm64: mte: Clear the tags when a page is mapped in user-space with PROT_MTE
Pages allocated by the kernel are not guaranteed to have the tags
zeroed, especially as the kernel does not (yet) use MTE itself. To
ensure the user can still access such pages when mapped into its address
space, clear the tags via set_pte_at(). A new page flag - PG_mte_tagged
(PG_arch_2) - is used to track pages with valid allocation tags.
Since the zero page is mapped as pte_special(), it won't be covered by
the above set_pte_at() mechanism. Clear its tags during early MTE
initialisation.
Co-developed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/lib')
| -rw-r--r-- | arch/arm64/lib/Makefile | 2 | ||||
| -rw-r--r-- | arch/arm64/lib/mte.S | 34 |
2 files changed, 36 insertions, 0 deletions
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile index 2fc253466dbf..d31e1169d9b8 100644 --- a/arch/arm64/lib/Makefile +++ b/arch/arm64/lib/Makefile @@ -16,3 +16,5 @@ lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o obj-$(CONFIG_CRC32) += crc32.o obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o + +obj-$(CONFIG_ARM64_MTE) += mte.o diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S new file mode 100644 index 000000000000..a36705640086 --- /dev/null +++ b/arch/arm64/lib/mte.S @@ -0,0 +1,34 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2020 ARM Ltd. + */ +#include <linux/linkage.h> + +#include <asm/assembler.h> +#include <asm/sysreg.h> + + .arch armv8.5-a+memtag + +/* + * multitag_transfer_size - set \reg to the block size that is accessed by the + * LDGM/STGM instructions. + */ + .macro multitag_transfer_size, reg, tmp + mrs_s \reg, SYS_GMID_EL1 + ubfx \reg, \reg, #SYS_GMID_EL1_BS_SHIFT, #SYS_GMID_EL1_BS_SIZE + mov \tmp, #4 + lsl \reg, \tmp, \reg + .endm + +/* + * Clear the tags in a page + * x0 - address of the page to be cleared + */ +SYM_FUNC_START(mte_clear_page_tags) + multitag_transfer_size x1, x2 +1: stgm xzr, [x0] + add x0, x0, x1 + tst x0, #(PAGE_SIZE - 1) + b.ne 1b + ret +SYM_FUNC_END(mte_clear_page_tags) |