objtool: kmsan: list KMSAN API functions as uaccess-safe

KMSAN inserts API function calls in a lot of places (function entries and
exits, local variables, memory accesses), so they may get called from the
uaccess regions as well.

KMSAN API functions are used to update the metadata (shadow/origin pages)
for kernel memory accesses.  The metadata pages for kernel pointers are
also located in the kernel memory, so touching them is not a problem.  For
userspace pointers, no metadata is allocated.

If an API function is supposed to read or modify the metadata, it does so
for kernel pointers and ignores userspace pointers.  If an API function is
supposed to return a pair of metadata pointers for the instrumentation to
use (like all __msan_metadata_ptr_for_TYPE_SIZE() functions do), it
returns the allocated metadata for kernel pointers and special dummy
buffers residing in the kernel memory for userspace pointers.

As a result, none of KMSAN API functions perform userspace accesses, but
since they might be called from UACCESS regions they use
user_access_save/restore().

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexander Potapenko <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Ilya Leoshkevich <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Stephen Rothwell <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Vegard Nossum <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 20 insertions, 0 deletions

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e55fdf952a3a..7c048c11ce7d 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1062,6 +1062,26 @@ static const char *uaccess_safe_builtin[] = {
 	"__sanitizer_cov_trace_cmp4",
 	"__sanitizer_cov_trace_cmp8",
 	"__sanitizer_cov_trace_switch",
+	/* KMSAN */
+	"kmsan_copy_to_user",
+	"kmsan_report",
+	"kmsan_unpoison_entry_regs",
+	"kmsan_unpoison_memory",
+	"__msan_chain_origin",
+	"__msan_get_context_state",
+	"__msan_instrument_asm_store",
+	"__msan_metadata_ptr_for_load_1",
+	"__msan_metadata_ptr_for_load_2",
+	"__msan_metadata_ptr_for_load_4",
+	"__msan_metadata_ptr_for_load_8",
+	"__msan_metadata_ptr_for_load_n",
+	"__msan_metadata_ptr_for_store_1",
+	"__msan_metadata_ptr_for_store_2",
+	"__msan_metadata_ptr_for_store_4",
+	"__msan_metadata_ptr_for_store_8",
+	"__msan_metadata_ptr_for_store_n",
+	"__msan_poison_alloca",
+	"__msan_warning",
 	/* UBSAN */
 	"ubsan_type_mismatch_common",
 	"__ubsan_handle_type_mismatch",