Subject: mm/kasan: add API to check memory regions

From: Andrey Ryabinin <[email-masked]>
Date: Fri, 20 May 2016 16:59:28 -0700

commit 64f8ebaf115bcddc4aaa902f981c57ba6506bc42 upstream.

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/[email-masked]
Signed-off-by: Andrey Ryabinin <[email-masked]>
Acked-by: Alexander Potapenko <[email-masked]>
Cc: Dmitry Vyukov <[email-masked]>
Cc: Ingo Molnar <[email-masked]>
Cc: "H. Peter Anvin" <[email-masked]>
Cc: Thomas Gleixner <[email-masked]>
Signed-off-by: Andrew Morton <[email-masked]>
Signed-off-by: Linus Torvalds <[email-masked]>
[bwh: Backported to 4.4: drop change in MAINTAINERS]
Signed-off-by: Ben Hutchings <[email-masked]>
---
 include/linux/kasan-checks.h | 12 ++++++++++++
 mm/kasan/kasan.c             | 12 ++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 include/linux/kasan-checks.h

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 b80d86d905c2..410b0fcb0c73 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -278,6 +278,18 @@ 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)
 {