kbuild: [PATCH] eliminate warnings in generated module files

From Richard Henderson:

> The compiler.h fragment should describe the problem well enough.

(I tested egcs 2.91.66, even there no problem)

Makefile

@@ -377,7 +377,7 @@ cmd_kallsyms = $(NM) -n $< | scripts/kallsyms > $@
 	$(call cmd,kallsyms)
 
 .tmp_vmlinux1: $(vmlinux-objs) arch/$(ARCH)/vmlinux.lds.s FORCE
-	$(call if_changed_rule,vmlinux__)
+	+$(call if_changed_rule,vmlinux__)
 
 .tmp_vmlinux2: $(vmlinux-objs) .tmp_kallsyms1.o arch/$(ARCH)/vmlinux.lds.s FORCE
 	$(call if_changed_rule,vmlinux__)

include/linux/compiler.h

@@ -25,6 +25,23 @@
 #define __deprecated
 #endif
 
+/*
+ * Allow us to avoid 'defined but not used' warnings on functions and data,
+ * as well as force them to be emitted to the assembly file.
+ *
+ * As of gcc 3.3, static functions that are not marked with attribute((used))
+ * may be elided from the assembly file.  As of gcc 3.3, static data not so
+ * marked will not be elided, but this may change in a future gcc version.
+ *
+ * In prior versions of gcc, such functions and data would be emitted, but
+ * would be warned about except with attribute((unused)).
+ */
+#if __GNUC__ == 3 && __GNUC_MINOR__ >= 3 || __GNUC__ > 3
+#define __attribute_used__	__attribute__((__used__))
+#else
+#define __attribute_used__	__attribute__((__unused__))
+#endif
+
 /* This macro obfuscates arithmetic on a variable address so that gcc
    shouldn't recognize the original var, and make assumptions about it */
 #define RELOC_HIDE(ptr, off)					\

scripts/modpost.c

@@ -393,6 +393,7 @@ add_header(struct buffer *b)
 {
 	buf_printf(b, "#include <linux/module.h>\n");
 	buf_printf(b, "#include <linux/vermagic.h>\n");
+	buf_printf(b, "#include <linux/compiler.h>\n");
 	buf_printf(b, "\n");
 	buf_printf(b, "const char vermagic[]\n");
 	buf_printf(b, "__attribute__((section(\"__vermagic\"))) =\n");
@@ -458,6 +459,7 @@ add_depends(struct buffer *b, struct module *mod, struct module *modules)
 
 	buf_printf(b, "\n");
 	buf_printf(b, "static const char __module_depends[]\n");
+	buf_printf(b, "__attribute_used__\n");
 	buf_printf(b, "__attribute__((section(\".modinfo\"))) =\n");
 	buf_printf(b, "\"depends=");
 	for (s = mod->unres; s; s = s->next) {