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authorMiguel Ojeda <miguel.ojeda.sandonis@gmail.com>2019-02-08 23:51:05 +0100
committerMax Krummenacher <max.krummenacher@toradex.com>2019-09-16 13:28:14 +0200
commit0ec72b7b8de3edf6ca1c7a6405e1ecf1dd2b9381 (patch)
tree2375b6febeb3c3a184edac8908b524a38c2c0457
parentf997df18c0e4c988de49e984329cefdf6e13ed86 (diff)
Compiler Attributes: add support for __copy (gcc >= 9)
[ Upstream commit c0d9782f5b6d7157635ae2fd782a4b27d55a6013 From the GCC manual: copy copy(function) The copy attribute applies the set of attributes with which function has been declared to the declaration of the function to which the attribute is applied. The attribute is designed for libraries that define aliases or function resolvers that are expected to specify the same set of attributes as their targets. The copy attribute can be used with functions, variables, or types. However, the kind of symbol to which the attribute is applied (either function or variable) must match the kind of symbol to which the argument refers. The copy attribute copies only syntactic and semantic attributes but not attributes that affect a symbol’s linkage or visibility such as alias, visibility, or weak. The deprecated attribute is also not copied. https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html The upcoming GCC 9 release extends the -Wmissing-attributes warnings (enabled by -Wall) to C and aliases: it warns when particular function attributes are missing in the aliases but not in their target, e.g.: void __cold f(void) {} void __alias("f") g(void); diagnoses: warning: 'g' specifies less restrictive attribute than its target 'f': 'cold' [-Wmissing-attributes] Using __copy(f) we can copy the __cold attribute from f to g: void __cold f(void) {} void __copy(f) __alias("f") g(void); This attribute is most useful to deal with situations where an alias is declared but we don't know the exact attributes the target has. For instance, in the kernel, the widely used module_init/exit macros define the init/cleanup_module aliases, but those cannot be marked always as __init/__exit since some modules do not have their functions marked as such. Cc: <stable@vger.kernel.org> # 4.14+ Suggested-by: Martin Sebor <msebor@gcc.gnu.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Signed-off-by: Stefan Agner <stefan@agner.ch> (cherry picked from commit c4fa716aa388078b44017d25ebc66fb661cef7c3) Conflicts: include/linux/compiler.h
-rw-r--r--include/linux/compiler-gcc.h4
-rw-r--r--include/linux/compiler.h4
2 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index abbac368aa1c..28d01f79636e 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -206,6 +206,10 @@
#endif
#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
+#if GCC_VERSION >= 90100
+#define __copy(symbol) __attribute__((__copy__(symbol)))
+#endif
+
#endif /* gcc version >= 40000 specific checks */
#if !defined(__noclone)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index fe7a686dfd8d..25dca0de114e 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -275,6 +275,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
# define __attribute_const__ /* unimplemented */
#endif
+#ifndef __copy
+# define __copy(symbol)
+#endif
+
/*
* Tell gcc if a function is cold. The compiler will assume any path
* directly leading to the call is unlikely.