util/cbfstool: Add "expand" command to make CBFS span an fmap region

vboot images come with multiple regions carrying CBFS file systems. To
expedite hashing (from slow flash memory), the FW_MAIN_* regions are
truncated since they typically have pretty large unused space at the
end that is of no interest.
For test purposes it can be useful to re-engage that space, so add a
command that creates a new empty file entry covering that area (except
for the last 4 bytes for the master header pointer, as usual).

BUG=b:65853903
BRANCH=none
TEST=`cbfstool test.bin expand -r FW_MAIN_A` creates a new empty file of
the expected size on a Chrome OS firmware image.

Change-Id: I160c8529ce4bfcc28685166b6d9035ade4f6f1d1
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/21598
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/cbfstool/cbfs_image.c

@@ -442,6 +442,44 @@ int cbfs_copy_instance(struct cbfs_image *image, struct buffer *dst)
 	return 0;
 }
 
+int cbfs_expand_to_region(struct buffer *region)
+{
+	if (buffer_get(region) == NULL)
+		return 1;
+
+	struct cbfs_image image;
+	memset(&image, 0, sizeof(image));
+	if (cbfs_image_from_buffer(&image, region, 0)) {
+		ERROR("reading CBFS failed!\n");
+		return 1;
+	}
+
+	uint32_t region_sz = buffer_size(region);
+
+	struct cbfs_file *entry;
+	for (entry = buffer_get(region);
+	     cbfs_is_valid_entry(&image, entry);
+	     entry = cbfs_find_next_entry(&image, entry)) {
+	     /* just iterate through */
+	}
+
+	/* entry now points to the first aligned address after the last valid
+	 * file header. That's either outside the image or exactly the place
+	 * where we need to create a new file.
+	 */
+	int last_entry_size = region_sz - ((void *)entry - buffer_get(region))
+		- cbfs_calculate_file_header_size("") - sizeof(int32_t);
+
+	if (last_entry_size > 0) {
+		cbfs_create_empty_entry(entry, CBFS_COMPONENT_NULL,
+			last_entry_size, "");
+		/* If the last entry was an empty file, merge them. */
+		cbfs_walk(&image, cbfs_merge_empty_entry, NULL);
+	}
+
+	return 0;
+}
+
 static size_t cbfs_file_entry_metadata_size(const struct cbfs_file *f)
 {
 	return ntohl(f->offset);

util/cbfstool/cbfs_image.h

@@ -80,6 +80,10 @@ int cbfs_copy_instance(struct cbfs_image *image, struct buffer *dst);
  * beginning of the image. Returns 0 on success, otherwise non-zero.  */
 int cbfs_compact_instance(struct cbfs_image *image);
 
+/* Expand a CBFS image inside an fmap region to the entire region's space.
+   Returns 0 on success, otherwise non-zero. */
+int cbfs_expand_to_region(struct buffer *region);
+
 /* Releases the CBFS image. Returns 0 on success, otherwise non-zero. */
 int cbfs_image_delete(struct cbfs_image *image);
 

util/cbfstool/cbfstool.c

@@ -1107,6 +1107,20 @@ static int cbfs_compact(void)
 	return cbfs_compact_instance(&image);
 }
 
+static int cbfs_expand(void)
+{
+	struct buffer src_buf;
+
+	/* Obtain the source region. */
+	if (!partitioned_file_read_region(&src_buf, param.image_file,
+						param.region_name)) {
+		ERROR("Region not found in image: %s\n", param.source_region);
+		return 1;
+	}
+
+	return cbfs_expand_to_region(param.image_region);
+}
+
 static const struct command commands[] = {
 	{"add", "H:r:f:n:t:c:b:a:yvA:gh?", cbfs_add, true, true},
 	{"add-flat-binary", "H:r:f:n:l:e:c:b:vA:gh?", cbfs_add_flat_binary,
@@ -1127,6 +1141,7 @@ static const struct command commands[] = {
 	{"remove", "H:r:n:vh?", cbfs_remove, true, true},
 	{"update-fit", "H:r:n:x:vh?", cbfs_update_fit, true, true},
 	{"write", "r:f:i:Fudvh?", cbfs_write, true, true},
+	{"expand", "r:h?", cbfs_expand, true, true},
 };
 
 static struct option long_options[] = {
@@ -1276,6 +1291,8 @@ static void usage(char *name)
 			"Write file into same-size [or larger] raw region\n"
 	     " read [-r fmap-region] -f file                               "
 			"Extract raw region contents into binary file\n"
+	     " expand [-r fmap-region]                                     "
+			"Expand CBFS to span entire region\n"
 	     " update-fit [-r image,regions] -n MICROCODE_BLOB_NAME \\\n"
 	     "        -x EMTPY_FIT_ENTRIES                                 "
 			"Updates the FIT table with microcode entries\n"