mod/file2alias: make modpost compile on darwin again

commit e49ce14150c64b29a8dd211df785576fa19a9858 breaks cross compiling
the linux kernel on darwin hosts.
This fix introduce some minimal glue to adopt linker section handling
for darwin hosts.

Signed-off-by: Andreas Bießmann <andreas@biessmann.de>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Jochen Friedrich <jochen@scram.de>
CC: Samuel Ortiz <sameo@linux.intel.com>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Bernhard Walle <bernhard@bwalle.de>

scripts/mod/file2alias.c

@@ -46,11 +46,37 @@ struct devtable {
 	void *function;
 };
 
+#define ___cat(a,b) a ## b
+#define __cat(a,b) ___cat(a,b)
+
+/* we need some special handling for this host tool running eventually on
+ * Darwin. The Mach-O section handling is a bit different than ELF section
+ * handling. The differnces in detail are:
+ *  a) we have segments which have sections
+ *  b) we need a API call to get the respective section symbols */
+#if defined(__MACH__)
+#include <mach-o/getsect.h>
+
+#define INIT_SECTION(name)  do {					\
+		unsigned long name ## _len;				\
+		char *__cat(pstart_,name) = getsectdata("__TEXT",	\
+			#name, &__cat(name,_len));			\
+		char *__cat(pstop_,name) = __cat(pstart_,name) +	\
+			__cat(name, _len);				\
+		__cat(__start_,name) = (void *)__cat(pstart_,name);	\
+		__cat(__stop_,name) = (void *)__cat(pstop_,name);	\
+	} while (0)
+#define SECTION(name)   __attribute__((section("__TEXT, " #name)))
+
+struct devtable **__start___devtable, **__stop___devtable;
+#else
+#define INIT_SECTION(name) /* no-op for ELF */
+#define SECTION(name)   __attribute__((section(#name)))
+
 /* We construct a table of pointers in an ELF section (pointers generally
  * go unpadded by gcc).  ld creates boundary syms for us. */
 extern struct devtable *__start___devtable[], *__stop___devtable[];
-#define ___cat(a,b) a ## b
-#define __cat(a,b) ___cat(a,b)
+#endif /* __MACH__ */
 
 #if __GNUC__ == 3 && __GNUC_MINOR__ < 3
 # define __used			__attribute__((__unused__))
@@ -65,8 +91,8 @@ extern struct devtable *__start___devtable[], *__stop___devtable[];
 						(type *)NULL,		\
 						(char *)NULL)),		\
 		sizeof(type), (function) };				\
-	static struct devtable *__attribute__((section("__devtable"))) \
-		__used __cat(devtable_ptr,__LINE__) = &__cat(devtable,__LINE__)
+	static struct devtable *SECTION(__devtable) __used \
+		__cat(devtable_ptr,__LINE__) = &__cat(devtable,__LINE__)
 
 #define ADD(str, sep, cond, field)                              \
 do {                                                            \
@@ -1080,6 +1106,7 @@ void handle_moddevtable(struct module *mod, struct elf_info *info,
 		do_pnp_card_entries(symval, sym->st_size, mod);
 	else {
 		struct devtable **p;
+		INIT_SECTION(__devtable);
 
 		for (p = __start___devtable; p < __stop___devtable; p++) {
 			if (sym_is(name, namelen, (*p)->device_id)) {