diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index a0bf310da74b426c62333293b537bdb0611823a5..1716b3d02489072c2974dba61ee3b9a8d63d4eea 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -7,12 +7,28 @@
#ifndef __ASSEMBLY__
+#include <linux/page-flags.h>
+
+#include <asm/pgtable-types.h>
+
+void mte_clear_page_tags(void *addr);
+
#ifdef CONFIG_ARM64_MTE
+/* track which pages have valid allocation tags */
+#define PG_mte_tagged PG_arch_2
+
+void mte_sync_tags(pte_t *ptep, pte_t pte);
void flush_mte_state(void);
#else
+/* unused if !CONFIG_ARM64_MTE, silence the compiler */
+#define PG_mte_tagged 0
+
+static inline void mte_sync_tags(pte_t *ptep, pte_t pte)
+{
+}
static inline void flush_mte_state(void)
{
}
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index d5d3fbe739534f7523a8f5e28bb9afb7364520fd..0a205a8e91b2e2df53b223e0783d967eb10bad99 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -9,6 +9,7 @@
#include <asm/proc-fns.h>
#include <asm/memory.h>
+#include <asm/mte.h>
#include <asm/pgtable-hwdef.h>
#include <asm/pgtable-prot.h>
#include <asm/tlbflush.h>
@@ -90,6 +91,8 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
#define pte_user_exec(pte) (!(pte_val(pte) & PTE_UXN))
#define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT))
#define pte_devmap(pte) (!!(pte_val(pte) & PTE_DEVMAP))
+#define pte_tagged(pte) ((pte_val(pte) & PTE_ATTRINDX_MASK) == \
+ PTE_ATTRINDX(MT_NORMAL_TAGGED))
#define pte_cont_addr_end(addr, end) \
({ unsigned long __boundary = ((addr) + CONT_PTE_SIZE) & CONT_PTE_MASK; \
@@ -284,6 +287,10 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
__sync_icache_dcache(pte);
+ if (system_supports_mte() &&
+ pte_present(pte) && pte_tagged(pte) && !pte_special(pte))
+ mte_sync_tags(ptep, pte);
+
__check_racy_pte_update(mm, ptep, pte);
set_pte(ptep, pte);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index fabc8a237223600414e97f0c473416baf68c1729..add9da5d8ea34075b8023ac40ff508c9f6b73dd4 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -75,6 +75,7 @@
#include <asm/cpu_ops.h>
#include <asm/fpsimd.h>
#include <asm/mmu_context.h>
+#include <asm/mte.h>
#include <asm/processor.h>
#include <asm/sysreg.h>
#include <asm/traps.h>
@@ -1704,6 +1705,22 @@ static void bti_enable(const struct arm64_cpu_capabilities *__unused)
}
#endif /* CONFIG_ARM64_BTI */
+#ifdef CONFIG_ARM64_MTE
+static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap)
+{
+ static bool cleared_zero_page = false;
+
+ /*
+ * Clear the tags in the zero page. This needs to be done via the
+ * linear map which has the Tagged attribute.
+ */
+ if (!cleared_zero_page) {
+ cleared_zero_page = true;
+ mte_clear_page_tags(lm_alias(empty_zero_page));
+ }
+}
+#endif /* CONFIG_ARM64_MTE */
+
/* Internal helper functions to match cpu capability type */
static bool
cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap)
@@ -2133,6 +2150,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.field_pos = ID_AA64PFR1_MTE_SHIFT,
.min_field_value = ID_AA64PFR1_MTE,
.sign = FTR_UNSIGNED,
+ .cpu_enable = cpu_enable_mte,
},
#endif /* CONFIG_ARM64_MTE */
{},
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 032016823957baa152693a3a1941865e998e69fa..5bf9bbed5a252e9d93fa520c62bb00b52415fa3a 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -3,12 +3,26 @@
* Copyright (C) 2020 ARM Ltd.
*/
+#include <linux/bitops.h>
+#include <linux/mm.h>
#include <linux/thread_info.h>
#include <asm/cpufeature.h>
#include <asm/mte.h>
#include <asm/sysreg.h>
+void mte_sync_tags(pte_t *ptep, pte_t pte)
+{
+ struct page *page = pte_page(pte);
+ long i, nr_pages = compound_nr(page);
+
+ /* if PG_mte_tagged is set, tags have already been initialised */
+ for (i = 0; i < nr_pages; i++, page++) {
+ if (!test_and_set_bit(PG_mte_tagged, &page->flags))
+ mte_clear_page_tags(page_address(page));
+ }
+}
+
void flush_mte_state(void)
{
if (!system_supports_mte())
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 2fc253466dbf8a657796bd1f8fa71a8508ddc23c..d31e1169d9b8e94a98f8034fc3bd32720f90898f 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 0000000000000000000000000000000000000000..a367056400862ae3c2e6a7420ee8f2732e50e7c2
--- /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)