[PATCH 20/35] arm64: mte: Add in-kernel MTE helpers
Andrey Konovalov
andreyknvl at google.com
Fri Aug 14 13:27:02 EDT 2020
From: Vincenzo Frascino <vincenzo.frascino at arm.com>
Provide helper functions to manipulate allocation and pointer tags for
kernel addresses.
Low-level helper functions (mte_assign_*, written in assembly) operate
tag values from the [0x0, 0xF] range. High-level helper functions
(mte_get/set_*) use the [0xF0, 0xFF] range to preserve compatibility
with normal kernel pointers that have 0xFF in their top byte.
MTE_GRANULE_SIZE definition is moved to mte_asm.h header that doesn't
have any dependencies and is safe to include into any low-level header.
Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
Co-developed-by: Andrey Konovalov <andreyknvl at google.com>
Signed-off-by: Andrey Konovalov <andreyknvl at google.com>
---
arch/arm64/include/asm/esr.h | 1 +
arch/arm64/include/asm/mte.h | 46 +++++++++++++++++++++++++++++---
arch/arm64/include/asm/mte_asm.h | 10 +++++++
arch/arm64/kernel/mte.c | 43 +++++++++++++++++++++++++++++
arch/arm64/lib/mte.S | 41 ++++++++++++++++++++++++++++
5 files changed, 138 insertions(+), 3 deletions(-)
create mode 100644 arch/arm64/include/asm/mte_asm.h
diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 035003acfa87..bc0dc66a6a27 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -103,6 +103,7 @@
#define ESR_ELx_FSC (0x3F)
#define ESR_ELx_FSC_TYPE (0x3C)
#define ESR_ELx_FSC_EXTABT (0x10)
+#define ESR_ELx_FSC_MTE (0x11)
#define ESR_ELx_FSC_SERROR (0x11)
#define ESR_ELx_FSC_ACCESS (0x08)
#define ESR_ELx_FSC_FAULT (0x04)
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index 1c99fcadb58c..733be1cb5c95 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -5,14 +5,19 @@
#ifndef __ASM_MTE_H
#define __ASM_MTE_H
-#define MTE_GRANULE_SIZE UL(16)
+#include <asm/mte_asm.h>
+
#define MTE_GRANULE_MASK (~(MTE_GRANULE_SIZE - 1))
#define MTE_TAG_SHIFT 56
#define MTE_TAG_SIZE 4
+#define MTE_TAG_MASK GENMASK((MTE_TAG_SHIFT + (MTE_TAG_SIZE - 1)), MTE_TAG_SHIFT)
+#define MTE_TAG_MAX (MTE_TAG_MASK >> MTE_TAG_SHIFT)
#ifndef __ASSEMBLY__
+#include <linux/bitfield.h>
#include <linux/page-flags.h>
+#include <linux/types.h>
#include <asm/pgtable-types.h>
@@ -45,7 +50,16 @@ long get_mte_ctrl(struct task_struct *task);
int mte_ptrace_copy_tags(struct task_struct *child, long request,
unsigned long addr, unsigned long data);
-#else
+void *mte_assign_valid_ptr_tag(void *ptr);
+void *mte_assign_random_ptr_tag(void *ptr);
+void mte_assign_mem_tag_range(void *addr, size_t size);
+
+#define mte_get_ptr_tag(ptr) ((u8)(((u64)(ptr)) >> MTE_TAG_SHIFT))
+u8 mte_get_mem_tag(void *addr);
+u8 mte_get_random_tag(void);
+void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag);
+
+#else /* CONFIG_ARM64_MTE */
/* unused if !CONFIG_ARM64_MTE, silence the compiler */
#define PG_mte_tagged 0
@@ -80,7 +94,33 @@ static inline int mte_ptrace_copy_tags(struct task_struct *child,
return -EIO;
}
-#endif
+static inline void *mte_assign_valid_ptr_tag(void *ptr)
+{
+ return ptr;
+}
+static inline void *mte_assign_random_ptr_tag(void *ptr)
+{
+ return ptr;
+}
+static inline void mte_assign_mem_tag_range(void *addr, size_t size)
+{
+}
+
+#define mte_get_ptr_tag(ptr) 0xFF
+static inline u8 mte_get_mem_tag(void *addr)
+{
+ return 0xFF;
+}
+static inline u8 mte_get_random_tag(void)
+{
+ return 0xFF;
+}
+static inline void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
+{
+ return addr;
+}
+
+#endif /* CONFIG_ARM64_MTE */
#endif /* __ASSEMBLY__ */
#endif /* __ASM_MTE_H */
diff --git a/arch/arm64/include/asm/mte_asm.h b/arch/arm64/include/asm/mte_asm.h
new file mode 100644
index 000000000000..aa532c1851e1
--- /dev/null
+++ b/arch/arm64/include/asm/mte_asm.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_MTE_ASM_H
+#define __ASM_MTE_ASM_H
+
+#define MTE_GRANULE_SIZE UL(16)
+
+#endif /* __ASM_MTE_ASM_H */
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index eb39504e390a..e2d708b4583d 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -13,8 +13,10 @@
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/thread_info.h>
+#include <linux/types.h>
#include <linux/uio.h>
+#include <asm/barrier.h>
#include <asm/cpufeature.h>
#include <asm/mte.h>
#include <asm/ptrace.h>
@@ -72,6 +74,47 @@ int memcmp_pages(struct page *page1, struct page *page2)
return ret;
}
+u8 mte_get_mem_tag(void *addr)
+{
+ if (system_supports_mte())
+ addr = mte_assign_valid_ptr_tag(addr);
+
+ return 0xF0 | mte_get_ptr_tag(addr);
+}
+
+u8 mte_get_random_tag(void)
+{
+ u8 tag = 0xF;
+
+ if (system_supports_mte())
+ tag = mte_get_ptr_tag(mte_assign_random_ptr_tag(NULL));
+
+ return 0xF0 | tag;
+}
+
+void * __must_check mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
+{
+ void *ptr = addr;
+
+ if ((!system_supports_mte()) || (size == 0))
+ return addr;
+
+ tag = 0xF0 | (tag & 0xF);
+ ptr = (void *)__tag_set(ptr, tag);
+ size = ALIGN(size, MTE_GRANULE_SIZE);
+
+ mte_assign_mem_tag_range(ptr, size);
+
+ /*
+ * mte_assign_mem_tag_range() can be invoked in a multi-threaded
+ * context, ensure that tags are written in memory before the
+ * reference is used.
+ */
+ smp_wmb();
+
+ return ptr;
+}
+
static void update_sctlr_el1_tcf0(u64 tcf0)
{
/* ISB required for the kernel uaccess routines */
diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S
index 03ca6d8b8670..8c743540e32c 100644
--- a/arch/arm64/lib/mte.S
+++ b/arch/arm64/lib/mte.S
@@ -149,3 +149,44 @@ SYM_FUNC_START(mte_restore_page_tags)
ret
SYM_FUNC_END(mte_restore_page_tags)
+
+/*
+ * Assign pointer tag based on the allocation tag
+ * x0 - source pointer
+ * Returns:
+ * x0 - pointer with the correct tag to access memory
+ */
+SYM_FUNC_START(mte_assign_valid_ptr_tag)
+ ldg x0, [x0]
+ ret
+SYM_FUNC_END(mte_assign_valid_ptr_tag)
+
+/*
+ * Assign random pointer tag
+ * x0 - source pointer
+ * Returns:
+ * x0 - pointer with a random tag
+ */
+SYM_FUNC_START(mte_assign_random_ptr_tag)
+ irg x0, x0
+ ret
+SYM_FUNC_END(mte_assign_random_ptr_tag)
+
+/*
+ * Assign allocation tags for a region of memory based on the pointer tag
+ * x0 - source pointer
+ * x1 - size
+ *
+ * Note: size is expected to be MTE_GRANULE_SIZE aligned
+ */
+SYM_FUNC_START(mte_assign_mem_tag_range)
+ /* if (src == NULL) return; */
+ cbz x0, 2f
+ /* if (size == 0) return; */
+ cbz x1, 2f
+1: stg x0, [x0]
+ add x0, x0, #MTE_GRANULE_SIZE
+ sub x1, x1, #MTE_GRANULE_SIZE
+ cbnz x1, 1b
+2: ret
+SYM_FUNC_END(mte_assign_mem_tag_range)
--
2.28.0.220.ged08abb693-goog
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