[PATCH v3 42/51] ubsan: Fix objtool UACCESS warns

Peter Zijlstra
2023-01-12T20:03:13Z

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@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
---
lib/ubsan.c | 5 ++++-
tools/objtool/check.c | 1 +
2 files changed, 5 insertions(+), 1 deletion(-)

--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -340,9 +340,10 @@ void __ubsan_handle_load_invalid_value(v
{
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");

@@ -352,6 +353,8 @@ void __ubsan_handle_load_invalid_value(v
val_str, data->type->type_name);

ubsan_epilogue();
+out:
+ user_access_restore(ua_flags);
}
EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1068,6 +1068,7 @@ 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",