mm/kasan: add API to check memory regions

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.

Link: http://lkml.kernel.org/r/1462538722-1574-3-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 25 insertions, 1 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 374ffa2d81b7..8b92445561b6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6242,7 +6242,7 @@ 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 000000000000..b7f8aced7870
--- /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 e5beb40d97b1..18b6a2b8d183 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)
 {