[PATCH v6 2/4] Compiler Attributes: Add __overloadable for Clang

Kees Cook
2022-02-03T17:33:15Z

In order for FORTIFY_SOURCE to use __pass_object_size on an "inline
extern" function, as all the fortified string functions are, the functions
must be marked as being overloadable (i.e. different prototypes).
This allows the __pass_object_size versions to take precedence.

Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: llvm@lists.linux.dev
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/linux/compiler_attributes.h | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index 4ce370094e3a..dc3bf2a6e1c9 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -257,6 +257,18 @@
*/
#define __noreturn __attribute__((__noreturn__))

+/*
+ * Optional: not supported by gcc.
+ * Optional: not supported by icc.
+ *
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#overloadable
+ */
+#if __has_attribute(__overloadable__)
+# define __overloadable __attribute__((__overloadable__))
+#else
+# define __overloadable
+#endif
+
/*
* gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#index-packed-type-attribute
* clang: https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-packed-variable-attribute
--
2.30.2