[PATCH 2/4] Compiler Attributes: Add __overloadable

[Kees Cook]

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 at kernel.org>
Cc: Nick Desaulniers <ndesaulniers at google.com>
Cc: Nathan Chancellor <nathan at kernel.org>
Cc: llvm at lists.linux.dev
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 include/linux/compiler_attributes.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index cc751e0770f5..51e063347fd6 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -257,6 +257,15 @@
  */
 #define __noreturn                      __attribute__((__noreturn__))
 
+/*
+ * 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