[PATCH 3/4] mm/kasan: add API to check memory regions

[Andrey Ryabinin]

Memory access coded in an assembly won't be seen by KASAN as a compiler
can instrument only C code. Add kasan_check_[read,write]() API
which is going to be used to check a certain memory range.

Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
---
 MAINTAINERS                  |  2 +-
 include/linux/kasan-checks.h | 12 ++++++++++++
 mm/kasan/kasan.c             | 12 ++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/kasan-checks.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 43b85c1..3a9471c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6363,7 +6363,7 @@ S:	Maintained
 F:	arch/*/include/asm/kasan.h
 F:	arch/*/mm/kasan_init*
 F:	Documentation/kasan.txt
-F:	include/linux/kasan.h
+F:	include/linux/kasan*.h
 F:	lib/test_kasan.c
 F:	mm/kasan/
 F:	scripts/Makefile.kasan
diff --git a/include/linux/kasan-checks.h b/include/linux/kasan-checks.h
new file mode 100644
index 0000000..b7f8ace
--- /dev/null
+++ b/include/linux/kasan-checks.h
@@ -0,0 +1,12 @@
+#ifndef _LINUX_KASAN_CHECKS_H
+#define _LINUX_KASAN_CHECKS_H
+
+#ifdef CONFIG_KASAN
+void kasan_check_read(const void *p, unsigned int size);
+void kasan_check_write(const void *p, unsigned int size);
+#else
+static inline void kasan_check_read(const void *p, unsigned int size) { }
+static inline void kasan_check_write(const void *p, unsigned int size) { }
+#endif
+
+#endif
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 6e4072c..54f0ea7 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -299,6 +299,18 @@ static void check_memory_region(unsigned long addr,
 	check_memory_region_inline(addr, size, write, ret_ip);
 }
 
+void kasan_check_read(const void *p, unsigned int size)
+{
+	check_memory_region((unsigned long)p, size, false, _RET_IP_);
+}
+EXPORT_SYMBOL(kasan_check_read);
+
+void kasan_check_write(const void *p, unsigned int size)
+{
+	check_memory_region((unsigned long)p, size, true, _RET_IP_);
+}
+EXPORT_SYMBOL(kasan_check_write);
+
 #undef memset
 void *memset(void *addr, int c, size_t len)
 {
-- 
2.7.3