From: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
[ 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@xxxxxxxxxxxxxxx> # 4.14+
Suggested-by: Martin Sebor <msebor@xxxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
---
include/linux/compiler-gcc.h | 4 ++++
include/linux/compiler_types.h | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index a8ff0ca0c321..3ebee1ce6f98 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -201,6 +201,10 @@
#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
#endif
+#if GCC_VERSION >= 90100
+#define __copy(symbol) __attribute__((__copy__(symbol)))
+#endif
+
#if !defined(__noclone)
#define __noclone /* not needed */
#endif
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index c2ded31a4cec..2b8ed70c4c77 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -180,6 +180,10 @@ struct ftrace_likely_data {
#define __diag_GCC(version, severity, string)
#endif
+#ifndef __copy
+# define __copy(symbol)
+#endif
+
#define __diag_push() __diag(push)
#define __diag_pop() __diag(pop)
--
2.21.0
