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linux-stable/arch/arm64/lib/mte.S

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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>
2020-05-04 13:42:36 +00:00
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2020 ARM Ltd.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
arm64: mte: Tags-aware copy_{user_,}highpage() implementations When the Memory Tagging Extension is enabled, the tags need to be preserved across page copy (e.g. for copy-on-write, page migration). Introduce MTE-aware copy_{user_,}highpage() functions to copy tags to the destination if the source page has the PG_mte_tagged flag set. copy_user_page() does not need to handle tag copying since, with this patch, it is only called by the DAX code where there is no source page structure (and no source tags). Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Co-developed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org>
2019-08-06 10:37:53 +00:00
#include <asm/page.h>
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>
2020-05-04 13:42:36 +00:00
#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)
arm64: mte: Tags-aware copy_{user_,}highpage() implementations When the Memory Tagging Extension is enabled, the tags need to be preserved across page copy (e.g. for copy-on-write, page migration). Introduce MTE-aware copy_{user_,}highpage() functions to copy tags to the destination if the source page has the PG_mte_tagged flag set. copy_user_page() does not need to handle tag copying since, with this patch, it is only called by the DAX code where there is no source page structure (and no source tags). Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Co-developed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org>
2019-08-06 10:37:53 +00:00
/*
* Copy the tags from the source page to the destination one
* x0 - address of the destination page
* x1 - address of the source page
*/
SYM_FUNC_START(mte_copy_page_tags)
mov x2, x0
mov x3, x1
multitag_transfer_size x5, x6
1: ldgm x4, [x3]
stgm x4, [x2]
add x2, x2, x5
add x3, x3, x5
tst x2, #(PAGE_SIZE - 1)
b.ne 1b
ret
SYM_FUNC_END(mte_copy_page_tags)
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