cbfstool: Catch failing parse_elf_to_payload()

Otherwise cbfstool will segfault if you try to add an x86
payload to an ARM image.

Change-Id: Ie468005ce9325a4f17c4f206c59f48e39d9338df
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/2028
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
diff --git a/util/cbfstool/cbfstool.c b/util/cbfstool/cbfstool.c
index 10b29de..6b52062 100644
--- a/util/cbfstool/cbfstool.c
+++ b/util/cbfstool/cbfstool.c
@@ -106,7 +106,7 @@
 
 static int cbfs_add_payload(void)
 {
-	uint32_t filesize = 0;
+	int32_t filesize = 0;
 	void *rom, *filedata, *cbfsfile;
 	unsigned char *payload;
 
@@ -136,6 +136,12 @@
 	}
 
 	filesize = parse_elf_to_payload(filedata, &payload, rom_algo);
+	if (filesize <= 0) {
+		fprintf(stderr, "E: Adding payload '%s' failed.\n",
+			rom_filename);
+		free(rom);
+		return 1;
+	}
 
 	cbfsfile = create_cbfs_file(rom_name, payload, &filesize,
 				CBFS_COMPONENT_PAYLOAD, &rom_baseaddress);