Compiler Attributes: Clean the new GCC 9 -Wmissing-attributes warnings

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]
 
 These patch series clean these new warnings. Most of them are caused
 by the module_init/exit macros.
 
 Link: https://lore.kernel.org/lkml/20190125104353.2791-1-labbott@redhat.com/
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Merge tag 'compiler-attributes-for-linus-v5.0-rc7' of git://github.com/ojeda/linux

Pull compiler attributes fixes from Miguel Ojeda:
 "Clean the new GCC 9 -Wmissing-attributes warnings

  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]

  These patch series clean these new warnings. Most of them are caused
  by the module_init/exit macros"

Link: https://lore.kernel.org/lkml/20190125104353.2791-1-labbott@redhat.com/

* tag 'compiler-attributes-for-linus-v5.0-rc7' of git://github.com/ojeda/linux:
  include/linux/module.h: copy __init/__exit attrs to init/cleanup_module
  Compiler Attributes: add support for __copy (gcc >= 9)
  lib/crc32.c: mark crc32_le_base/__crc32c_le_base aliases as __pure

include/linux/compiler_attributes.h

@@ -34,6 +34,7 @@
 #ifndef __has_attribute
 # define __has_attribute(x) __GCC4_has_attribute_##x
 # define __GCC4_has_attribute___assume_aligned__      (__GNUC_MINOR__ >= 9)
+# define __GCC4_has_attribute___copy__                0
 # define __GCC4_has_attribute___designated_init__     0
 # define __GCC4_has_attribute___externally_visible__  1
 # define __GCC4_has_attribute___noclone__             1
@@ -100,6 +101,19 @@
  */
 #define __attribute_const__             __attribute__((__const__))
 
+/*
+ * Optional: only supported since gcc >= 9
+ * Optional: not supported by clang
+ * Optional: not supported by icc
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-copy-function-attribute
+ */
+#if __has_attribute(__copy__)
+# define __copy(symbol)                 __attribute__((__copy__(symbol)))
+#else
+# define __copy(symbol)
+#endif
+
 /*
  * Don't. Just don't. See commit 771c035372a0 ("deprecate the '__deprecated'
  * attribute warnings entirely and for good") for more information.

include/linux/module.h

@@ -129,13 +129,13 @@ extern void cleanup_module(void);
 #define module_init(initfn)					\
 	static inline initcall_t __maybe_unused __inittest(void)		\
 	{ return initfn; }					\
-	int init_module(void) __attribute__((alias(#initfn)));
+	int init_module(void) __copy(initfn) __attribute__((alias(#initfn)));
 
 /* This is only required if you want to be unloadable. */
 #define module_exit(exitfn)					\
 	static inline exitcall_t __maybe_unused __exittest(void)		\
 	{ return exitfn; }					\
-	void cleanup_module(void) __attribute__((alias(#exitfn)));
+	void cleanup_module(void) __copy(exitfn) __attribute__((alias(#exitfn)));
 
 #endif
 

lib/crc32.c

@@ -206,8 +206,8 @@ u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len)
 EXPORT_SYMBOL(crc32_le);
 EXPORT_SYMBOL(__crc32c_le);
 
-u32 crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le);
-u32 __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le);
+u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le);
+u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le);
 
 /*
  * This multiplies the polynomials x and y modulo the given modulus.