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

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

[Jiri Slaby (SUSE)]

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

[PATCH 45/46] kasan, lto: remove extra BUILD_BUG() in memory_is_poisoned

[Jiri Slaby (SUSE)]

From: Martin Liska <mliska@suse.cz>

The function memory_is_poisoned() can handle any size which can be
propagated by LTO later on. So we can end up with a constant that is not
handled in the switch. Thus just break and call memory_is_poisoned_n()
which handles arbitrary size to avoid build errors with gcc LTO.

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/generic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index d8b5590f9484..d261f83c6687 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -152,7 +152,7 @@ static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 		case 16:
 			return memory_is_poisoned_16(addr);
 		default:
-			BUILD_BUG();
+			break;
 		}
 	}
 
-- 
2.38.1

Re: [PATCH 45/46] kasan, lto: remove extra BUILD_BUG() in memory_is_poisoned

[Andrey Konovalov]

On Mon, Nov 14, 2022 at 12:45 PM Jiri Slaby (SUSE) <jirislaby@kernel.org> wrote:
>
> From: Martin Liska <mliska@suse.cz>
>
> The function memory_is_poisoned() can handle any size which can be
> propagated by LTO later on. So we can end up with a constant that is not
> handled in the switch. Thus just break and call memory_is_poisoned_n()
> which handles arbitrary size to avoid build errors with gcc LTO.
>
> 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/generic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index d8b5590f9484..d261f83c6687 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -152,7 +152,7 @@ static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
>                 case 16:
>                         return memory_is_poisoned_16(addr);
>                 default:
> -                       BUILD_BUG();
> +                       break;
>                 }
>         }
>
> --
> 2.38.1
>

Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>