[PATCH v12 5/6] arm64: introduce copy_mc_to_kernel() implementation

[Tong Tiangen]

The copy_mc_to_kernel() helper is memory copy implementation that handles
source exceptions. It can be used in memory copy scenarios that tolerate
hardware memory errors(e.g: pmem_read/dax_copy_to_iter).

Currnently, only x86 and ppc suuport this helper, after arm64 support
ARCH_HAS_COPY_MC , we introduce copy_mc_to_kernel() implementation.

Also add memcpy_mc() for memory copy that handles source exceptions.
Because there is no GPR is available for saving "bytes not copied" in
memcpy(), the mempcy_mc() is referenced to the implementation of
copy_from_user().

Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
---
 arch/arm64/include/asm/string.h  |  5 +++
 arch/arm64/include/asm/uaccess.h | 18 ++++++++
 arch/arm64/lib/Makefile          |  2 +-
 arch/arm64/lib/memcpy_mc.S       | 73 ++++++++++++++++++++++++++++++++
 mm/kasan/shadow.c                | 12 ++++++
 5 files changed, 109 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/lib/memcpy_mc.S

diff --git a/arch/arm64/include/asm/string.h b/arch/arm64/include/asm/string.h
index 3a3264ff47b9..23eca4fb24fa 100644
--- a/arch/arm64/include/asm/string.h
+++ b/arch/arm64/include/asm/string.h
@@ -35,6 +35,10 @@ extern void *memchr(const void *, int, __kernel_size_t);
 extern void *memcpy(void *, const void *, __kernel_size_t);
 extern void *__memcpy(void *, const void *, __kernel_size_t);
 
+#define __HAVE_ARCH_MEMCPY_MC
+extern int memcpy_mc(void *, const void *, __kernel_size_t);
+extern int __memcpy_mc(void *, const void *, __kernel_size_t);
+
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *, const void *, __kernel_size_t);
 extern void *__memmove(void *, const void *, __kernel_size_t);
@@ -57,6 +61,7 @@ void memcpy_flushcache(void *dst, const void *src, size_t cnt);
  */
 
 #define memcpy(dst, src, len) __memcpy(dst, src, len)
+#define memcpy_mc(dst, src, len) __memcpy_mc(dst, src, len)
 #define memmove(dst, src, len) __memmove(dst, src, len)
 #define memset(s, c, n) __memset(s, c, n)
 
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 14be5000c5a0..07c1aeaeb094 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -425,4 +425,22 @@ static inline size_t probe_subpage_writeable(const char __user *uaddr,
 
 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
 
+#ifdef CONFIG_ARCH_HAS_COPY_MC
+/**
+ * copy_mc_to_kernel - memory copy that handles source exceptions
+ *
+ * @to:		destination address
+ * @from:	source address
+ * @size:	number of bytes to copy
+ *
+ * Return 0 for success, or bytes not copied.
+ */
+static inline unsigned long __must_check
+copy_mc_to_kernel(void *to, const void *from, unsigned long size)
+{
+	return memcpy_mc(to, from, size);
+}
+#define copy_mc_to_kernel copy_mc_to_kernel
+#endif
+
 #endif /* __ASM_UACCESS_H */
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 65ec3d24d32d..0d2fc251fbae 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -13,7 +13,7 @@ endif
 
 lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o
 
-lib-$(CONFIG_ARCH_HAS_COPY_MC) += copy_mc_page.o
+lib-$(CONFIG_ARCH_HAS_COPY_MC) += copy_mc_page.o memcpy_mc.o
 
 obj-$(CONFIG_CRC32) += crc32.o
 
diff --git a/arch/arm64/lib/memcpy_mc.S b/arch/arm64/lib/memcpy_mc.S
new file mode 100644
index 000000000000..1798090eba06
--- /dev/null
+++ b/arch/arm64/lib/memcpy_mc.S
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2013 ARM Ltd.
+ * Copyright (C) 2013 Linaro.
+ *
+ * This code is based on glibc cortex strings work originally authored by Linaro
+ * be found @
+ *
+ * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
+ * files/head:/src/aarch64/
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/cache.h>
+#include <asm/asm-uaccess.h>
+
+/*
+ * Copy a buffer from src to dest (alignment handled by the hardware)
+ *
+ * Parameters:
+ *	x0 - dest
+ *	x1 - src
+ *	x2 - n
+ * Returns:
+ *	x0 - dest
+ */
+	.macro ldrb1 reg, ptr, val
+	KERNEL_ME_SAFE(9997f, ldrb  \reg, [\ptr], \val)
+	.endm
+
+	.macro strb1 reg, ptr, val
+	strb \reg, [\ptr], \val
+	.endm
+
+	.macro ldrh1 reg, ptr, val
+	KERNEL_ME_SAFE(9997f, ldrh  \reg, [\ptr], \val)
+	.endm
+
+	.macro strh1 reg, ptr, val
+	strh \reg, [\ptr], \val
+	.endm
+
+	.macro ldr1 reg, ptr, val
+	KERNEL_ME_SAFE(9997f, ldr \reg, [\ptr], \val)
+	.endm
+
+	.macro str1 reg, ptr, val
+	str \reg, [\ptr], \val
+	.endm
+
+	.macro ldp1 reg1, reg2, ptr, val
+	KERNEL_ME_SAFE(9997f, ldp \reg1, \reg2, [\ptr], \val)
+	.endm
+
+	.macro stp1 reg1, reg2, ptr, val
+	stp \reg1, \reg2, [\ptr], \val
+	.endm
+
+end	.req	x5
+SYM_FUNC_START(__memcpy_mc)
+	add	end, x0, x2
+#include "copy_template.S"
+	mov	x0, #0				// Nothing to copy
+	ret
+
+	// Exception fixups
+9997:	sub	x0, end, dst			// bytes not copied
+	ret
+SYM_FUNC_END(__memcpy_mc)
+EXPORT_SYMBOL(__memcpy_mc)
+SYM_FUNC_ALIAS_WEAK(memcpy_mc, __memcpy_mc)
+EXPORT_SYMBOL(memcpy_mc)
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index d6210ca48dda..e23632391eac 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -79,6 +79,18 @@ void *memcpy(void *dest, const void *src, size_t len)
 }
 #endif
 
+#ifdef __HAVE_ARCH_MEMCPY_MC
+#undef memcpy_mc
+int memcpy_mc(void *dest, const void *src, size_t len)
+{
+	if (!kasan_check_range(src, len, false, _RET_IP_) ||
+	    !kasan_check_range(dest, len, true, _RET_IP_))
+		return (int)len;
+
+	return __memcpy_mc(dest, src, len);
+}
+#endif
+
 void *__asan_memset(void *addr, int c, ssize_t len)
 {
 	if (!kasan_check_range(addr, len, true, _RET_IP_))
-- 
2.25.1