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Subject[PATCH v2 22/37] arm64: mte: Add in-kernel MTE helpers
From
From: Vincenzo Frascino <vincenzo.frascino@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 and related definitions are moved to mte-def.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@arm.com>
Co-developed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
Change-Id: I1b5230254f90dc21a913447cb17f07fea7944ece
---
arch/arm64/include/asm/esr.h | 1 +
arch/arm64/include/asm/mte-helpers.h | 48 ++++++++++++++++++++++++++++
arch/arm64/include/asm/mte.h | 17 ++++++----
arch/arm64/kernel/mte.c | 48 ++++++++++++++++++++++++++++
arch/arm64/lib/mte.S | 17 ++++++++++
5 files changed, 125 insertions(+), 6 deletions(-)
create mode 100644 arch/arm64/include/asm/mte-helpers.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-helpers.h b/arch/arm64/include/asm/mte-helpers.h
new file mode 100644
index 000000000000..5dc2d443851b
--- /dev/null
+++ b/arch/arm64/include/asm/mte-helpers.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 ARM Ltd.
+ */
+#ifndef __ASM_MTE_ASM_H
+#define __ASM_MTE_ASM_H
+
+#define __MTE_PREAMBLE ".arch armv8.5-a\n.arch_extension memtag\n"
+
+#define MTE_GRANULE_SIZE UL(16)
+#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/types.h>
+
+#ifdef CONFIG_ARM64_MTE
+
+#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 */
+
+#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_ASM_H */
diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h
index 1c99fcadb58c..82cd7c89edec 100644
--- a/arch/arm64/include/asm/mte.h
+++ b/arch/arm64/include/asm/mte.h
@@ -5,14 +5,13 @@
#ifndef __ASM_MTE_H
#define __ASM_MTE_H

-#define MTE_GRANULE_SIZE UL(16)
-#define MTE_GRANULE_MASK (~(MTE_GRANULE_SIZE - 1))
-#define MTE_TAG_SHIFT 56
-#define MTE_TAG_SIZE 4
+#include <asm/mte-helpers.h>

#ifndef __ASSEMBLY__

+#include <linux/bitfield.h>
#include <linux/page-flags.h>
+#include <linux/types.h>

#include <asm/pgtable-types.h>

@@ -45,7 +44,9 @@ 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_mem_tag_range(void *addr, size_t size);
+
+#else /* CONFIG_ARM64_MTE */

/* unused if !CONFIG_ARM64_MTE, silence the compiler */
#define PG_mte_tagged 0
@@ -80,7 +81,11 @@ static inline int mte_ptrace_copy_tags(struct task_struct *child,
return -EIO;
}

-#endif
+static inline void mte_assign_mem_tag_range(void *addr, size_t size)
+{
+}
+
+#endif /* CONFIG_ARM64_MTE */

#endif /* __ASSEMBLY__ */
#endif /* __ASM_MTE_H */
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 52a0638ed967..e238ffde2679 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 +74,52 @@ int memcmp_pages(struct page *page1, struct page *page2)
return ret;
}

+u8 mte_get_mem_tag(void *addr)
+{
+ if (system_supports_mte())
+ asm volatile(ALTERNATIVE("ldr %0, [%0]",
+ __MTE_PREAMBLE "ldg %0, [%0]",
+ ARM64_MTE)
+ : "+r" (addr));
+
+ return 0xF0 | mte_get_ptr_tag(addr);
+}
+
+u8 mte_get_random_tag(void)
+{
+ u8 tag = 0xF;
+ u64 addr = 0;
+
+ if (system_supports_mte()) {
+ asm volatile(ALTERNATIVE("add %0, %0, %0",
+ __MTE_PREAMBLE "irg %0, %0",
+ ARM64_MTE)
+ : "+r" (addr));
+
+ tag = mte_get_ptr_tag(addr);
+ }
+
+ return 0xF0 | tag;
+}
+
+void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag)
+{
+ void *ptr = addr;
+
+ if ((!system_supports_mte()) || (size == 0))
+ return addr;
+
+ /* Make sure that size is aligned. */
+ WARN_ON(size & (MTE_GRANULE_SIZE - 1));
+
+ tag = 0xF0 | (tag & 0xF);
+ ptr = (void *)__tag_set(ptr, tag);
+
+ mte_assign_mem_tag_range(ptr, size);
+
+ 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..cc2c3a378c00 100644
--- a/arch/arm64/lib/mte.S
+++ b/arch/arm64/lib/mte.S
@@ -149,3 +149,20 @@ SYM_FUNC_START(mte_restore_page_tags)

ret
SYM_FUNC_END(mte_restore_page_tags)
+
+/*
+ * Assign allocation tags for a region of memory based on the pointer tag
+ * x0 - source pointer
+ * x1 - size
+ *
+ * Note: size must be non-zero and MTE_GRANULE_SIZE aligned
+ */
+SYM_FUNC_START(mte_assign_mem_tag_range)
+ /* if (src == NULL) return; */
+ cbz x0, 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)
--
2.28.0.618.gf4bc123cb7-goog
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