[PATCH 2/2] lib/ubsan: remove returns-nonnull-attribute checks.

[Andrey Ryabinin]

Similarly to type mismatch checks, new GCC 8.x and Clang also
changed for ABI for returns_nonnull checks. While we can update our
code to conform the new ABI it's more reasonable to just remove it.
Because it's just dead code, we don't have any single user of
returns_nonnull attribute in the whole kernel.

And AFAIU the advantage that this attribute could bring would be mitigated
by -fno-delete-null-pointer-checks cflag that we use to build the kernel.
So it's unlikely we will have a lot of returns_nonnull attribute in future.

So let's just remove the code, it has no use.

Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
---
 lib/ubsan.c            | 19 -------------------
 lib/ubsan.h            |  5 -----
 scripts/Makefile.ubsan |  1 -
 3 files changed, 25 deletions(-)

diff --git a/lib/ubsan.c b/lib/ubsan.c
index 50d1d5c25deb..adada1dbbe94 100644
--- a/lib/ubsan.c
+++ b/lib/ubsan.c
@@ -356,25 +356,6 @@ void __ubsan_handle_type_mismatch_v1(struct type_mismatch_data_v1 *data,
 }
 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 
-void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
-{
-	unsigned long flags;
-
-	if (suppress_report(&data->location))
-		return;
-
-	ubsan_prologue(&data->location, &flags);
-
-	pr_err("null pointer returned from function declared to never return null\n");
-
-	if (location_is_valid(&data->attr_location))
-		print_source_location("returns_nonnull attribute specified in",
-				&data->attr_location);
-
-	ubsan_epilogue(&flags);
-}
-EXPORT_SYMBOL(__ubsan_handle_nonnull_return);
-
 void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
 					unsigned long bound)
 {
diff --git a/lib/ubsan.h b/lib/ubsan.h
index 7e30b26497e0..f4d8d0bd4016 100644
--- a/lib/ubsan.h
+++ b/lib/ubsan.h
@@ -57,11 +57,6 @@ struct nonnull_arg_data {
 	int arg_index;
 };
 
-struct nonnull_return_data {
-	struct source_location location;
-	struct source_location attr_location;
-};
-
 struct vla_bound_data {
 	struct source_location location;
 	struct type_descriptor *type;
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 8fd4d44fbcd1..b593b36ccff8 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -7,7 +7,6 @@ ifdef CONFIG_UBSAN
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size)
-      CFLAGS_UBSAN += $(call cc-option, -fsanitize=returns-nonnull-attribute)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool)
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum)
 
-- 
2.13.6