[PATCH 2/4] kasan: added functions for unpoisoning stack variables

Greg Hackmann
2017-07-06T22:01:51Z

From: Alexander Potapenko <glider@google.com>

As a code-size optimization, LLVM builds since r279383 may
bulk-manipulate the shadow region when (un)poisoning large memory
blocks. This requires new callbacks that simply do an uninstrumented
memset().

This fixes linking the Clang-built kernel when using KASAN.

Signed-off-by: Alexander Potapenko <glider@google.com>
[ghackmann@google.com: fix memset() parameters, and tweak
commit message to describe new callbacks]
Signed-off-by: Greg Hackmann <ghackmann@google.com>
---
mm/kasan/kasan.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 892b626f564b..89911e5c69f9 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -828,6 +828,21 @@ void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
}
EXPORT_SYMBOL(__asan_allocas_unpoison);

+/* Emitted by the compiler to [un]poison local variables. */
+#define DEFINE_ASAN_SET_SHADOW(byte) \
+ void __asan_set_shadow_##byte(const void *addr, size_t size) \
+ { \
+ __memset((void *)addr, 0x##byte, size); \
+ } \
+ EXPORT_SYMBOL(__asan_set_shadow_##byte)
+
+DEFINE_ASAN_SET_SHADOW(00);
+DEFINE_ASAN_SET_SHADOW(f1);
+DEFINE_ASAN_SET_SHADOW(f2);
+DEFINE_ASAN_SET_SHADOW(f3);
+DEFINE_ASAN_SET_SHADOW(f5);
+DEFINE_ASAN_SET_SHADOW(f8);
+
#ifdef CONFIG_MEMORY_HOTPLUG
static int kasan_mem_notifier(struct notifier_block *nb,
unsigned long action, void *data)
--
2.13.2.725.g09c95d1e9-goog