objtool: add UACCESS exceptions for __tsan_volatile_read/write

[ Upstream commit d5d469247264e56960705dc5ae7e1d014861fe40 ]

A lot of the tsan helpers are already excempt from the UACCESS warnings,
but some more functions were added that need the same thing:

kernel/kcsan/core.o: warning: objtool: __tsan_volatile_read16+0x0: call to __tsan_unaligned_read16() with UACCESS enabled
kernel/kcsan/core.o: warning: objtool: __tsan_volatile_write16+0x0: call to __tsan_unaligned_write16() with UACCESS enabled
vmlinux.o: warning: objtool: __tsan_unaligned_volatile_read16+0x4: call to __tsan_unaligned_read16() with UACCESS enabled
vmlinux.o: warning: objtool: __tsan_unaligned_volatile_write16+0x4: call to __tsan_unaligned_write16() with UACCESS enabled

As Marco points out, these functions don't even call each other
explicitly but instead gcc (but not clang) notices the functions
being identical and turns one symbol into a direct branch to the
other.

Link: https://lkml.kernel.org/r/20230215130058.3836177-4-arnd@kernel.org
Fixes: 75d75b7a4d54 ("kcsan: Support distinguishing volatile accesses")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 51494c3..0c1b6ac 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1059,6 +1059,8 @@ static const char *uaccess_safe_builtin[] = {
        "__tsan_atomic64_compare_exchange_val",
        "__tsan_atomic_thread_fence",
        "__tsan_atomic_signal_fence",
+       "__tsan_unaligned_read16",
+       "__tsan_unaligned_write16",
        /* KCOV */
        "write_comp_data",
        "check_kcov_mode",