[RFC/PATCH -next 03/21] x86: add kasan hooks fort memcpy/memmove/memset functions

[Andrey Ryabinin]

Since functions memset, memmove, memcpy are written in assembly,
compiler can't instrument memory accesses inside them.

This patch replaces these functions with our own instrumented
functions (kasan_mem*) for CONFIG_KASAN = y

In rare circumstances you may need to use the original functions,
in such case put #undef KASAN_HOOKS before includes.

Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
---
 arch/x86/include/asm/string_32.h | 28 ++++++++++++++++++++++++++++
 arch/x86/include/asm/string_64.h | 24 ++++++++++++++++++++++++
 arch/x86/lib/Makefile            |  2 ++
 3 files changed, 54 insertions(+)

diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index 3d3e835..a86615a 100644
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -321,6 +321,32 @@ void *__constant_c_and_count_memset(void *s, unsigned long pattern,
 	 : __memset_generic((s), (c), (count)))
 
 #define __HAVE_ARCH_MEMSET
+
+#if defined(CONFIG_KASAN) && defined(KASAN_HOOKS)
+
+/*
+ * Since some of the following functions (memset, memmove, memcpy)
+ * are written in assembly, compiler can't instrument memory accesses
+ * inside them.
+ *
+ * To solve this issue we replace these functions with our own instrumented
+ * functions (kasan_mem*)
+ *
+ * In rare circumstances you may need to use the original functions,
+ * in such case put #undef KASAN_HOOKS before includes.
+ */
+
+#undef memcpy
+void *kasan_memset(void *ptr, int val, size_t len);
+void *kasan_memcpy(void *dst, const void *src, size_t len);
+void *kasan_memmove(void *dst, const void *src, size_t len);
+
+#define memcpy(dst, src, len) kasan_memcpy((dst), (src), (len))
+#define memset(ptr, val, len) kasan_memset((ptr), (val), (len))
+#define memmove(dst, src, len) kasan_memmove((dst), (src), (len))
+
+#else /* CONFIG_KASAN && KASAN_HOOKS */
+
 #if (__GNUC__ >= 4)
 #define memset(s, c, count) __builtin_memset(s, c, count)
 #else
@@ -331,6 +357,8 @@ void *__constant_c_and_count_memset(void *s, unsigned long pattern,
 	 : __memset((s), (c), (count)))
 #endif
 
+#endif /* CONFIG_KASAN && KASAN_HOOKS */
+
 /*
  * find the first occurrence of byte 'c', or 1 past the area if none
  */
diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
index 19e2c46..2af2dbe 100644
--- a/arch/x86/include/asm/string_64.h
+++ b/arch/x86/include/asm/string_64.h
@@ -63,6 +63,30 @@ char *strcpy(char *dest, const char *src);
 char *strcat(char *dest, const char *src);
 int strcmp(const char *cs, const char *ct);
 
+#if defined(CONFIG_KASAN) && defined(KASAN_HOOKS)
+
+/*
+ * Since some of the following functions (memset, memmove, memcpy)
+ * are written in assembly, compiler can't instrument memory accesses
+ * inside them.
+ *
+ * To solve this issue we replace these functions with our own instrumented
+ * functions (kasan_mem*)
+ *
+ * In rare circumstances you may need to use the original functions,
+ * in such case put #undef KASAN_HOOKS before includes.
+ */
+
+void *kasan_memset(void *ptr, int val, size_t len);
+void *kasan_memcpy(void *dst, const void *src, size_t len);
+void *kasan_memmove(void *dst, const void *src, size_t len);
+
+#define memcpy(dst, src, len) kasan_memcpy((dst), (src), (len))
+#define memset(ptr, val, len) kasan_memset((ptr), (val), (len))
+#define memmove(dst, src, len) kasan_memmove((dst), (src), (len))
+
+#endif /* CONFIG_KASAN && KASAN_HOOKS */
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_X86_STRING_64_H */
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 4d4f96a..d82bc35 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -2,6 +2,8 @@
 # Makefile for x86 specific library files.
 #
 
+KASAN_SANITIZE_memcpy_32.o := n
+
 inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk
 inat_tables_maps = $(srctree)/arch/x86/lib/x86-opcode-map.txt
 quiet_cmd_inat_tables = GEN     $@
-- 
1.8.5.5

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