[PATCH 42/46] mm/kasan, lto: Mark kasan mem{cpy,move,set} as __used

["Jiri Slaby (SUSE)" <jirislaby@kernel.org>]

From: Martin Liska <mliska@suse.cz>

gcc doesn't always recognize that memcpy/set/move called through
__builtins are referenced because the reference happens too late in the
RTL expansion phase. This can make LTO to drop them, leading to
undefined symbols. Mark them as __used to avoid that.

Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Signed-off-by: Martin Liska <mliska@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 mm/kasan/shadow.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 0e3648b603a6..94c98feea9c8 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -39,7 +39,7 @@ bool __kasan_check_write(const volatile void *p, unsigned int size)
 EXPORT_SYMBOL(__kasan_check_write);
 
 #undef memset
-void *memset(void *addr, int c, size_t len)
+__used void *memset(void *addr, int c, size_t len)
 {
 	if (!kasan_check_range((unsigned long)addr, len, true, _RET_IP_))
 		return NULL;
@@ -49,7 +49,7 @@ void *memset(void *addr, int c, size_t len)
 
 #ifdef __HAVE_ARCH_MEMMOVE
 #undef memmove
-void *memmove(void *dest, const void *src, size_t len)
+__used void *memmove(void *dest, const void *src, size_t len)
 {
 	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
 	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
@@ -60,7 +60,7 @@ void *memmove(void *dest, const void *src, size_t len)
 #endif
 
 #undef memcpy
-void *memcpy(void *dest, const void *src, size_t len)
+__used void *memcpy(void *dest, const void *src, size_t len)
 {
 	if (!kasan_check_range((unsigned long)src, len, false, _RET_IP_) ||
 	    !kasan_check_range((unsigned long)dest, len, true, _RET_IP_))
-- 
2.38.1