kbuild: add "Section mismatch" warning whitelist for powerpc

This patch fixes the following class of "Section mismatch" warnings when
building powerpc platforms.

WARNING: arch/powerpc/kernel/built-in.o - Section mismatch: reference to .init.data:.got2 from prom_entry (offset 0x0)
WARNING: arch/powerpc/platforms/built-in.o - Section mismatch: reference to .init.text:mpc8313_rdb_probe from .machine.desc after 'mach_mpc8313_rdb' (at offset 0x4)
....
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/mod/modpost.c

@@ -650,9 +650,10 @@ static int strrcmp(const char *s, const char *sub)
  *  tosec    = .init.text
  *
  * Pattern 10:
- *  ia64 has machvec table for each platform. It is mixture of function
- *  pointer of .init.text and .text.
- *  fromsec  = .machvec
+ *  ia64 has machvec table for each platform and
+ *  powerpc has a machine desc table for each platform.
+ *  It is mixture of function pointers of .init.text and .text.
+ *  fromsec  = .machvec | .machine.desc
  **/
 static int secref_whitelist(const char *modname, const char *tosec,
 			    const char *fromsec, const char *atsym,
@@ -751,7 +752,8 @@ static int secref_whitelist(const char *modname, const char *tosec,
 				return 1;
 
 	/* Check for pattern 10 */
-	if (strcmp(fromsec, ".machvec") == 0)
+	if ((strcmp(fromsec, ".machvec") == 0) ||
+	    (strcmp(fromsec, ".machine.desc") == 0))
 		return 1;
 
 	return 0;
@@ -887,6 +889,11 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec,
 			     elf->strtab + before->st_name, refsymname))
 		return;
 
+	/* fromsec whitelist - without a valid 'before'
+	 * powerpc has a GOT table in .got2 section */
+	if (strcmp(fromsec, ".got2") == 0)
+		return;
+
 	if (before && after) {
 		warn("%s(%s+0x%llx): Section mismatch: reference to %s:%s "
 		     "(between '%s' and '%s')\n",