linux-hardening - [PATCH 2/4] Compiler Attributes: Add _

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Date:   Tue,  1 Feb 2022 16:30:31 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>, llvm@...ts.linux.dev,
        George Burgess IV <gbiv@...gle.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: [PATCH 2/4] Compiler Attributes: Add __overloadable

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@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: llvm@...ts.linux.dev
Signed-off-by: Kees Cook <keescook@...omium.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