[tip: sched/core] ubsan: Fix objtool UACCESS warns

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     f18b0d7ee815abb33eb1cc540fdde64fbb922d1a
Gitweb:        https://git.kernel.org/tip/f18b0d7ee815abb33eb1cc540fdde64fbb922d1a
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Thu, 12 Jan 2023 20:43:56 +01:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 13 Jan 2023 11:48:17 +01:00

ubsan: Fix objtool UACCESS warns

clang-14 allyesconfig gives:

  vmlinux.o: warning: objtool: emulator_cmpxchg_emulated+0x705: call to __ubsan_handle_load_invalid_value() with UACCESS enabled
  vmlinux.o: warning: objtool: paging64_update_accessed_dirty_bits+0x39e: call to __ubsan_handle_load_invalid_value() with UACCESS enabled
  vmlinux.o: warning: objtool: paging32_update_accessed_dirty_bits+0x390: call to __ubsan_handle_load_invalid_value() with UACCESS enabled
  vmlinux.o: warning: objtool: ept_update_accessed_dirty_bits+0x43f: call to __ubsan_handle_load_invalid_value() with UACCESS enabled

Add the required eflags save/restore and whitelist the thing.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Tested-by: Tony Lindgren <tony@xxxxxxxxxxx>
Tested-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Acked-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230112195541.906007455@xxxxxxxxxxxxx
---
 lib/ubsan.c           | 5 ++++-
 tools/objtool/check.c | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 60c7099..4d39e0b 100644
--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -339,9 +339,10 @@ void __ubsan_handle_load_invalid_value(void *_data, void *val)
 {
 	struct invalid_value_data *data = _data;
 	char val_str[VALUE_LENGTH];
+	unsigned long ua_flags = user_access_save();
 
 	if (suppress_report(&data->location))
-		return;
+		goto out;
 
 	ubsan_prologue(&data->location, "invalid-load");
 
@@ -351,6 +352,8 @@ void __ubsan_handle_load_invalid_value(void *_data, void *val)
 		val_str, data->type->type_name);
 
 	ubsan_epilogue();
+out:
+	user_access_restore(ua_flags);
 }
 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
 
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 64954aa..9767bab 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1216,6 +1216,7 @@ static const char *uaccess_safe_builtin[] = {
 	"__ubsan_handle_type_mismatch",
 	"__ubsan_handle_type_mismatch_v1",
 	"__ubsan_handle_shift_out_of_bounds",
+	"__ubsan_handle_load_invalid_value",
 	/* misc */
 	"csum_partial_copy_generic",
 	"copy_mc_fragile",