[PATCH 4.9 39/42] Backport minimal compiler_attributes.h to support GCC 9

[Greg Kroah-Hartman]

From: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>

This adds support for __copy to v4.9.y so that we can use it in
init/exit_module to avoid -Werror=missing-attributes errors on GCC 9.

Link: https://lore.kernel.org/lkml/259986242.BvXPX32bHu@devpool35/
Cc: <stable@xxxxxxxxxxxxxxx>
Suggested-by: Rolf Eike Beer <eb@xxxxxxxxx>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/linux/compiler.h |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -54,6 +54,22 @@ extern void __chk_io_ptr(const volatile
 
 #ifdef __KERNEL__
 
+/*
+ * Minimal backport of compiler_attributes.h to add support for __copy
+ * to v4.9.y so that we can use it in init/exit_module to avoid
+ * -Werror=missing-attributes errors on GCC 9.
+ */
+#ifndef __has_attribute
+# define __has_attribute(x) __GCC4_has_attribute_##x
+# define __GCC4_has_attribute___copy__                0
+#endif
+
+#if __has_attribute(__copy__)
+# define __copy(symbol)                 __attribute__((__copy__(symbol)))
+#else
+# define __copy(symbol)
+#endif
+
 #ifdef __GNUC__
 #include <linux/compiler-gcc.h>
 #endif