util/cbfstool/cbfs_image.c

/*
 * CBFS Image Manipulation
 *
 * Copyright (C) 2013 The Chromium OS Authors. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA, 02110-1301 USA
 */

#include <inttypes.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "common.h"
#include "elf.h"
#include "cbfs_image.h"

/* The file name align is not defined in CBFS spec -- only a preference by
 * (old) cbfstool. */
#define CBFS_FILENAME_ALIGN	(16)

/* To make CBFS more friendly to ROM, fill -1 (0xFF) instead of zero. */
#define CBFS_CONTENT_DEFAULT_VALUE	(-1)

/* Type and format */

struct typedesc_t {
	uint32_t type;
	const char *name;
};

static const struct typedesc_t types_cbfs_entry[] = {
	{CBFS_COMPONENT_STAGE, "stage"},
	{CBFS_COMPONENT_PAYLOAD, "payload"},
	{CBFS_COMPONENT_OPTIONROM, "optionrom"},
	{CBFS_COMPONENT_BOOTSPLASH, "bootsplash"},
	{CBFS_COMPONENT_RAW, "raw"},
	{CBFS_COMPONENT_VSA, "vsa"},
	{CBFS_COMPONENT_MBI, "mbi"},
	{CBFS_COMPONENT_MICROCODE, "microcode"},
	{CBFS_COMPONENT_CMOS_DEFAULT, "cmos_default"},
	{CBFS_COMPONENT_CMOS_LAYOUT, "cmos_layout"},
	{CBFS_COMPONENT_DELETED, "deleted"},
	{CBFS_COMPONENT_NULL, "null"},
	{0, NULL},
};

static const struct typedesc_t types_cbfs_compression[] = {
	{CBFS_COMPRESS_NONE, "none"},
	{CBFS_COMPRESS_LZMA, "LZMA"},
	{0, NULL},
};

static uint32_t align_up(uint32_t value, uint32_t align)
{
	if (value % align)
		value += align - (value % align);
	return value;
}

static uint32_t lookup_type_by_name(const struct typedesc_t *desc, const char *name,
			     uint32_t default_value)
{
	int i;
	for (i = 0; desc[i].name; i++)
		if (strcmp(desc[i].name, name) == 0)
			return desc[i].type;
	return default_value;
}

static const char *lookup_name_by_type(const struct typedesc_t *desc, uint32_t type,
				const char *default_value)
{
	int i;
	for (i = 0; desc[i].name; i++)
		if (desc[i].type == type)
			return desc[i].name;
	return default_value;
}

uint32_t get_cbfs_entry_type(const char *name, uint32_t default_value)
{
	return lookup_type_by_name(types_cbfs_entry, name, default_value);
}

const char *get_cbfs_entry_type_name(uint32_t type)
{
	return lookup_name_by_type(types_cbfs_entry, type, "(unknown)");
}

uint32_t get_cbfs_compression(const char *name, uint32_t unknown)
{
	return lookup_type_by_name(types_cbfs_compression, name, unknown);
}

/* CBFS image */

static int cbfs_calculate_file_header_size(const char *name)
{
	return (sizeof(struct cbfs_file) +
		align_up(strlen(name) + 1, CBFS_FILENAME_ALIGN));
}

static int cbfs_fix_legacy_size(struct cbfs_image *image)
{
	// A bug in old cbfstool may produce extra few bytes (by alignment) and
	// cause cbfstool to overwrite things after free space -- which is
	// usually CBFS header on x86. We need to workaround that.

	struct cbfs_file *entry, *first = NULL, *last = NULL;
	for (first = entry = cbfs_find_first_entry(image);
	     entry && cbfs_is_valid_entry(image, entry);
	     entry = cbfs_find_next_entry(image, entry)) {
		last = entry;
	}
	if ((char *)first < (char *)image->header &&
	    (char *)entry > (char *)image->header) {
		WARN("CBFS image was created with old cbfstool with size bug. "
		     "Fixing size in last entry...\n");
		last->len = htonl(ntohl(last->len) -
				  ntohl(image->header->align));
		DEBUG("Last entry has been changed from 0x%x to 0x%x.\n",
		      cbfs_get_entry_addr(image, entry),
		      cbfs_get_entry_addr(image,
					  cbfs_find_next_entry(image, last)));
	}
	return 0;
}

void cbfs_put_header(void *dest, const struct cbfs_header *header)
{
	struct buffer outheader;

	outheader.data = dest;
	outheader.size = 0;

	xdr_be.put32(&outheader, header->magic);
	xdr_be.put32(&outheader, header->version);
	xdr_be.put32(&outheader, header->romsize);
	xdr_be.put32(&outheader, header->bootblocksize);
	xdr_be.put32(&outheader, header->align);
	xdr_be.put32(&outheader, header->offset);
	xdr_be.put32(&outheader, header->architecture);
}
int cbfs_image_create(struct cbfs_image *image,
		      uint32_t myarch,
		      size_t size,
		      uint32_t align,
		      struct buffer *bootblock,
		      int32_t bootblock_offset,
		      int32_t header_offset,
		      int32_t entries_offset)
{
	struct cbfs_header header;
	struct cbfs_file *entry;
	uint32_t cbfs_len;
	size_t entry_header_len;

	DEBUG("cbfs_image_create: bootblock=0x%x+0x%zx, "
	      "header=0x%x+0x%zx, entries_offset=0x%x\n",
	      bootblock_offset, bootblock->size,
	      header_offset, sizeof(header), entries_offset);

	if (buffer_create(&image->buffer, size, "(new)") != 0)
		return -1;
	image->header = NULL;
	memset(image->buffer.data, CBFS_CONTENT_DEFAULT_VALUE, size);

	// Adjust legcay top-aligned address to ROM offset.
	if (IS_TOP_ALIGNED_ADDRESS(entries_offset))
		entries_offset += (int32_t)size;
	if (IS_TOP_ALIGNED_ADDRESS(bootblock_offset))
		bootblock_offset += (int32_t)size;
	if (IS_TOP_ALIGNED_ADDRESS(header_offset))
		header_offset += (int32_t) size;

	DEBUG("cbfs_create_image: (real offset) bootblock=0x%x, "
	      "header=0x%x, entries_offset=0x%x\n",
	      bootblock_offset, header_offset, entries_offset);

	if (align == 0)
		align = 64;  // default align size.

	// Prepare bootblock
	if (bootblock_offset + bootblock->size > size) {
		ERROR("Bootblock (0x%x+0x%zx) exceed ROM size (0x%zx)\n",
		      bootblock_offset, bootblock->size, size);
		return -1;
	}
	if (entries_offset > bootblock_offset &&
	    entries_offset < bootblock->size) {
		ERROR("Bootblock (0x%x+0x%zx) overlap CBFS data (0x%x)\n",
		      bootblock_offset, bootblock->size, entries_offset);
		return -1;
	}
	memcpy(image->buffer.data + bootblock_offset, bootblock->data,
	       bootblock->size);

	// Prepare header
	if (header_offset + sizeof(header) > size) {
		ERROR("Header (0x%x+0x%zx) exceed ROM size (0x%zx)\n",
		      header_offset, sizeof(header), size);
		return -1;
	}
	image->header = (struct cbfs_header *)(image->buffer.data + header_offset);
	header.magic = CBFS_HEADER_MAGIC;
	header.version = CBFS_HEADER_VERSION;
	header.romsize = size;
	header.bootblocksize = bootblock->size;
	header.align = align;
	header.offset = entries_offset;
	header.architecture = myarch;
	cbfs_put_header(image->header, &header);

	// Prepare entries
	if (align_up(entries_offset, align) != entries_offset) {
		ERROR("Offset (0x%x) must be aligned to 0x%x.\n",
		      entries_offset, align);
		return -1;
	}
	entry_header_len = cbfs_calculate_file_header_size("");
	if (entries_offset + entry_header_len > size) {
		ERROR("Offset (0x%x+0x%zx) exceed ROM size(0x%zx)\n",
		      entries_offset, entry_header_len, size);
		return -1;
	}
	entry = (struct cbfs_file *)(image->buffer.data + entries_offset);
	// To calculate available length, find
	//   e = min(bootblock, header, size) where e > entries_offset.
	cbfs_len = size;
	if (bootblock_offset > entries_offset && bootblock_offset < cbfs_len)
		cbfs_len = bootblock_offset;
	if (header_offset > entries_offset && header_offset < cbfs_len)
		cbfs_len = header_offset;
	cbfs_len -= entries_offset + align + entry_header_len;
	cbfs_create_empty_entry(image, entry, cbfs_len, "");
	LOG("Created CBFS image (capacity = %d bytes)\n", cbfs_len);
	return 0;
}

int cbfs_image_from_file(struct cbfs_image *image, const char *filename)
{
	if (buffer_from_file(&image->buffer, filename) != 0)
		return -1;
	DEBUG("read_cbfs_image: %s (%zd bytes)\n", image->buffer.name,
	      image->buffer.size);
	image->header = cbfs_find_header(image->buffer.data,
					 image->buffer.size);
	if (!image->header) {
		ERROR("%s does not have CBFS master header.\n", filename);
		cbfs_image_delete(image);
		return -1;
	}
	cbfs_fix_legacy_size(image);

	return 0;
}

int cbfs_image_write_file(struct cbfs_image *image, const char *filename)
{
	assert(image && image->buffer.data);
	return buffer_write_file(&image->buffer, filename);
}

int cbfs_image_delete(struct cbfs_image *image)
{
	buffer_delete(&image->buffer);
	image->header = NULL;
	return 0;
}

/* Tries to add an entry with its data (CBFS_SUBHEADER) at given offset. */
static int cbfs_add_entry_at(struct cbfs_image *image,
			     struct cbfs_file *entry,
			     uint32_t size,
			     const char *name,
			     uint32_t type,
			     const void *data,
			     uint32_t content_offset)
{
	struct cbfs_file *next = cbfs_find_next_entry(image, entry);
	uint32_t addr = cbfs_get_entry_addr(image, entry),
		 addr_next = cbfs_get_entry_addr(image, next);
	uint32_t header_size = cbfs_calculate_file_header_size(name),
		 min_entry_size = cbfs_calculate_file_header_size("");
	uint32_t len, target;
	uint32_t align = ntohl(image->header->align);

	target = content_offset - header_size;
	if (target % align)
		target -= target % align;
	if (target < addr) {
		ERROR("No space to hold cbfs_file header.");
		return -1;
	}

	// Process buffer BEFORE content_offset.
	if (target - addr > min_entry_size) {
		DEBUG("|min|...|header|content|... <create new entry>\n");
		len = target - addr - min_entry_size;
		cbfs_create_empty_entry(image, entry, len, "");
		if (verbose > 1) cbfs_print_entry_info(image, entry, stderr);
		entry = cbfs_find_next_entry(image, entry);
		addr = cbfs_get_entry_addr(image, entry);
	}

	len = size + (content_offset - addr - header_size);
	cbfs_create_empty_entry(image, entry, len, name);
	if (len != size) {
		DEBUG("|..|header|content|... <use offset to create entry>\n");
		DEBUG("before: offset=0x%x, len=0x%x\n",
		      ntohl(entry->offset), ntohl(entry->len));
		// TODO reset expanded name buffer to 0xFF.
		entry->offset = htonl(ntohl(entry->offset) + (len - size));
		entry->len = htonl(size);
		DEBUG("after: offset=0x%x, len=0x%x\n",
		      ntohl(entry->offset), ntohl(entry->len));
	}

	// Ready to fill data into entry.
	assert(ntohl(entry->len) == size);
	entry->type = htonl(type);
	DEBUG("content_offset: 0x%x, entry location: %x\n",
	      content_offset, (int)((char*)CBFS_SUBHEADER(entry) -
				    image->buffer.data));
	assert((char*)CBFS_SUBHEADER(entry) - image->buffer.data ==
	       content_offset);
	memcpy(CBFS_SUBHEADER(entry), data, size);
	if (verbose > 1) cbfs_print_entry_info(image, entry, stderr);

	// Process buffer AFTER entry.
	entry = cbfs_find_next_entry(image, entry);
	addr = cbfs_get_entry_addr(image, entry);
	assert(addr < addr_next);

	if (addr_next - addr < min_entry_size) {
		DEBUG("No space after content to keep CBFS structure.\n");
		return -1;
	}

	len = addr_next - addr - min_entry_size;
	cbfs_create_empty_entry(image, entry, len, "");
	if (verbose > 1) cbfs_print_entry_info(image, entry, stderr);
	return 0;
}

int cbfs_add_entry(struct cbfs_image *image, struct buffer *buffer,
		   const char *name, uint32_t type, uint32_t content_offset)
{
	uint32_t entry_type;
	uint32_t addr, addr_next;
	struct cbfs_file *entry, *next;
	uint32_t header_size, need_size, new_size;

	header_size = cbfs_calculate_file_header_size(name);

	need_size = header_size + buffer->size;
	DEBUG("cbfs_add_entry('%s'@0x%x) => need_size = %u+%zu=%u\n",
	      name, content_offset, header_size, buffer->size, need_size);

	if (IS_TOP_ALIGNED_ADDRESS(content_offset)) {
		// legacy cbfstool takes top-aligned address.
		uint32_t theromsize = ntohl(image->header->romsize);
		INFO("Converting top-aligned address 0x%x to offset: 0x%x\n",
		     content_offset, content_offset + theromsize);
		content_offset += theromsize;
	}

	// Merge empty entries.
	DEBUG("(trying to merge empty entries...)\n");
	cbfs_walk(image, cbfs_merge_empty_entry, NULL);

	for (entry = cbfs_find_first_entry(image);
	     entry && cbfs_is_valid_entry(image, entry);
	     entry = cbfs_find_next_entry(image, entry)) {

		entry_type = ntohl(entry->type);
		if (entry_type != CBFS_COMPONENT_NULL)
			continue;

		addr = cbfs_get_entry_addr(image, entry);
		next = cbfs_find_next_entry(image, entry);
		addr_next = cbfs_get_entry_addr(image, next);

		DEBUG("cbfs_add_entry: space at 0x%x+0x%x(%d) bytes\n",
		      addr, addr_next - addr, addr_next - addr);

		/* Will the file fit? Don't yet worry if we have space for a new
		 * "empty" entry. We take care of that later.
		 */
		if (addr + need_size > addr_next)
			continue;

		// Can we simply put object here?
		if (!content_offset || content_offset == addr + header_size) {
			DEBUG("Filling new entry data (%zd bytes).\n",
			      buffer->size);
			cbfs_create_empty_entry(image, entry, buffer->size,
						name);
			entry->type = htonl(type);
			memcpy(CBFS_SUBHEADER(entry), buffer->data, buffer->size);
			if (verbose)
				cbfs_print_entry_info(image, entry, stderr);

			// setup new entry
			DEBUG("Setting new empty entry.\n");
			entry = cbfs_find_next_entry(image, entry);
			new_size = (cbfs_get_entry_addr(image, next) -
				    cbfs_get_entry_addr(image, entry));

			/* Entry was added and no space for new "empty" entry */
			if (new_size < cbfs_calculate_file_header_size("")) {
				DEBUG("No need for new \"empty\" entry\n");
				/* No need to increase the size of the just
				 * stored file to extend to next file. Alignment
				 * of next file takes care of this.
				 */
				return 0;
			}
			new_size -= cbfs_calculate_file_header_size("");
			DEBUG("new size: %d\n", new_size);
			cbfs_create_empty_entry(image, entry, new_size, "");
			if (verbose)
				cbfs_print_entry_info(image, entry, stderr);
			return 0;
		}

		// We need to put content here, and the case is really
		// complicated...
		assert(content_offset);
		if (addr_next < content_offset) {
			DEBUG("Not for specified offset yet");
			continue;
		} else if (addr > content_offset) {
			DEBUG("Exceed specified content_offset.");
			break;
		} else if (addr + header_size > content_offset) {
			ERROR("Not enough space for header.\n");
			break;
		} else if (content_offset + buffer->size > addr_next) {
			ERROR("Not enough space for content.\n");
			break;
		}

		// TODO there are more few tricky cases that we may
		// want to fit by altering offset.
		DEBUG("section 0x%x+0x%x for content_offset 0x%x.\n",
		      addr, addr_next - addr, content_offset);

		if (cbfs_add_entry_at(image, entry, buffer->size, name, type,
				      buffer->data, content_offset) == 0) {
			return 0;
		}
		break;
	}

	ERROR("Could not add [%s, %zd bytes (%zd KB)@0x%x]; too big?\n",
	      buffer->name, buffer->size, buffer->size / 1024, content_offset);
	return -1;
}

struct cbfs_file *cbfs_get_entry(struct cbfs_image *image, const char *name)
{
	struct cbfs_file *entry;
	for (entry = cbfs_find_first_entry(image);
	     entry && cbfs_is_valid_entry(image, entry);
	     entry = cbfs_find_next_entry(image, entry)) {
		if (strcasecmp(CBFS_NAME(entry), name) == 0) {
			DEBUG("cbfs_get_entry: found %s\n", name);
			return entry;
		}
	}
	return NULL;
}

int cbfs_export_entry(struct cbfs_image *image, const char *entry_name,
		      const char *filename)
{
	struct cbfs_file *entry = cbfs_get_entry(image, entry_name);
	struct buffer buffer;
	if (!entry) {
		ERROR("File not found: %s\n", entry_name);
		return -1;
	}
	LOG("Found file %.30s at 0x%x, type %.12s, size %d\n",
	    entry_name, cbfs_get_entry_addr(image, entry),
	    get_cbfs_entry_type_name(ntohl(entry->type)), ntohl(entry->len));

	if (ntohl(entry->type) != CBFS_COMPONENT_RAW) {
		WARN("Only 'raw' files are safe to extract.\n");
	}

	buffer.data = CBFS_SUBHEADER(entry);
	buffer.size = ntohl(entry->len);
	buffer.name = (char *)"(cbfs_export_entry)";
	if (buffer_write_file(&buffer, filename) != 0) {
		ERROR("Failed to write %s into %s.\n",
		      entry_name, filename);
		return -1;
	}
	INFO("Successfully dumped the file to: %s\n", filename);
	return 0;
}

int cbfs_remove_entry(struct cbfs_image *image, const char *name)
{
	struct cbfs_file *entry, *next;
	size_t len;
	entry = cbfs_get_entry(image, name);
	if (!entry) {
		ERROR("CBFS file %s not found.\n", name);
		return -1;
	}
	next = cbfs_find_next_entry(image, entry);
	assert(next);
	DEBUG("cbfs_remove_entry: Removed %s @ 0x%x\n",
	      CBFS_NAME(entry), cbfs_get_entry_addr(image, entry));
	entry->type = htonl(CBFS_COMPONENT_DELETED);
	len = (cbfs_get_entry_addr(image, next) -
	       cbfs_get_entry_addr(image, entry));
	entry->offset = htonl(cbfs_calculate_file_header_size(""));
	entry->len = htonl(len - ntohl(entry->offset));
	memset(CBFS_NAME(entry), 0, ntohl(entry->offset) - sizeof(*entry));
	memset(CBFS_SUBHEADER(entry), CBFS_CONTENT_DEFAULT_VALUE,
	       ntohl(entry->len));
	return 0;
}

int cbfs_print_header_info(struct cbfs_image *image)
{
	char *name = strdup(image->buffer.name);
	assert(image && image->header);
	printf("%s: %zd kB, bootblocksize %d, romsize %d, offset 0x%x\n"
	       "alignment: %d bytes\n\n",
	       basename(name),
	       image->buffer.size / 1024,
	       ntohl(image->header->bootblocksize),
	       ntohl(image->header->romsize),
	       ntohl(image->header->offset),
	       ntohl(image->header->align));
	free(name);
	return 0;
}

static int cbfs_print_stage_info(struct cbfs_stage *stage, FILE* fp)
{
	fprintf(fp,
		"    %s compression, entry: 0x%" PRIx64 ", load: 0x%" PRIx64 ", "
		"length: %d/%d\n",
		lookup_name_by_type(types_cbfs_compression,
				    stage->compression, "(unknown)"),
		stage->entry,
		stage->load,
		stage->len,
		stage->memlen);
	return 0;
}

static int cbfs_print_payload_segment_info(struct cbfs_payload_segment *payload,
					   FILE *fp)
{
	switch(payload->type) {
		case PAYLOAD_SEGMENT_CODE:
		case PAYLOAD_SEGMENT_DATA:
			fprintf(fp, "    %s (%s compression, offset: 0x%x, "
				"load: 0x%" PRIx64 ", length: %d/%d)\n",
				(payload->type == PAYLOAD_SEGMENT_CODE ?
				 "code " : "data"),
				lookup_name_by_type(types_cbfs_compression,
						    ntohl(payload->compression),
						    "(unknown)"),
				ntohl(payload->offset),
				ntohll(payload->load_addr),
				ntohl(payload->len), ntohl(payload->mem_len));
			break;

		case PAYLOAD_SEGMENT_ENTRY:
			fprintf(fp, "    entry (0x%" PRIx64 ")\n",
				ntohll(payload->load_addr));
			break;

		case PAYLOAD_SEGMENT_BSS:
			fprintf(fp, "    BSS (address 0x%016" PRIx64 ", "
				"length 0x%x)\n",
				ntohll(payload->load_addr),
				ntohl(payload->len));
			break;

		case PAYLOAD_SEGMENT_PARAMS:
			fprintf(fp, "    parameters\n");
			break;

		default:
			fprintf(fp, "   0x%x (%s compression, offset: 0x%x, "
				"load: 0x%" PRIx64 ", length: %d/%d\n",
				payload->type,
				lookup_name_by_type(types_cbfs_compression,
						    payload->compression,
						    "(unknown)"),
				ntohl(payload->offset),
				ntohll(payload->load_addr),
				ntohl(payload->len),
				ntohl(payload->mem_len));
			break;
	}
	return 0;
}

int cbfs_print_entry_info(struct cbfs_image *image, struct cbfs_file *entry,
			  void *arg)
{
	const char *name = CBFS_NAME(entry);
	struct cbfs_payload_segment *payload;
	FILE *fp = (FILE *)arg;

	if (!cbfs_is_valid_entry(image, entry)) {
		ERROR("cbfs_print_entry_info: Invalid entry at 0x%x\n",
		      cbfs_get_entry_addr(image, entry));
		return -1;
	}
	if (!fp)
		fp = stdout;

	fprintf(fp, "%-30s 0x%-8x %-12s %d\n",
		*name ? name : "(empty)",
		cbfs_get_entry_addr(image, entry),
		get_cbfs_entry_type_name(ntohl(entry->type)),
		ntohl(entry->len));

	if (!verbose)
		return 0;

	DEBUG(" cbfs_file=0x%x, offset=0x%x, content_address=0x%x+0x%x\n",
	      cbfs_get_entry_addr(image, entry), ntohl(entry->offset),
	      cbfs_get_entry_addr(image, entry) + ntohl(entry->offset),
	      ntohl(entry->len));

	/* note the components of the subheader may be in host order ... */
	switch (ntohl(entry->type)) {
		case CBFS_COMPONENT_STAGE:
			cbfs_print_stage_info((struct cbfs_stage *)
					      CBFS_SUBHEADER(entry), fp);
			break;

		case CBFS_COMPONENT_PAYLOAD:
			payload  = (struct cbfs_payload_segment *)
					CBFS_SUBHEADER(entry);
			while (payload) {
				cbfs_print_payload_segment_info(payload, fp);
				if (payload->type == PAYLOAD_SEGMENT_ENTRY)
					break;
				else
					payload ++;
			}
			break;
		default:
			break;
	}
	return 0;
}

int cbfs_print_directory(struct cbfs_image *image)
{
	cbfs_print_header_info(image);
	printf("%-30s %-10s %-12s Size\n", "Name", "Offset", "Type");
	cbfs_walk(image, cbfs_print_entry_info, NULL);
	return 0;
}

int cbfs_merge_empty_entry(struct cbfs_image *image, struct cbfs_file *entry,
			   void *arg)
{
	struct cbfs_file *next;
	uint32_t type, addr, last_addr;

	type = ntohl(entry->type);
	if (type == CBFS_COMPONENT_DELETED) {
		// Ready to be recycled.
		type = CBFS_COMPONENT_NULL;
		entry->type = htonl(type);
	}
	if (type != CBFS_COMPONENT_NULL)
		return 0;

	next = cbfs_find_next_entry(image, entry);

	while (next && cbfs_is_valid_entry(image, next)) {
		type = ntohl(next->type);
		if (type == CBFS_COMPONENT_DELETED) {
			type = CBFS_COMPONENT_NULL;
			next->type = htonl(type);
		}
		if (type != CBFS_COMPONENT_NULL)
			return 0;

		addr = cbfs_get_entry_addr(image, entry);
		last_addr = cbfs_get_entry_addr(
				image, cbfs_find_next_entry(image, next));

		// Now, we find two deleted/empty entries; try to merge now.
		DEBUG("join_empty_entry: combine 0x%x+0x%x and 0x%x+0x%x.\n",
		      cbfs_get_entry_addr(image, entry), ntohl(entry->len),
		      cbfs_get_entry_addr(image, next), ntohl(next->len));
		cbfs_create_empty_entry(image, entry,
					(last_addr - addr -
					 cbfs_calculate_file_header_size("")),
					"");
		DEBUG("new empty entry: length=0x%x\n", ntohl(entry->len));
		next = cbfs_find_next_entry(image, entry);
	}
	return 0;
}

int cbfs_walk(struct cbfs_image *image, cbfs_entry_callback callback,
	      void *arg)
{
	int count = 0;
	struct cbfs_file *entry;
	for (entry = cbfs_find_first_entry(image);
	     entry && cbfs_is_valid_entry(image, entry);
	     entry = cbfs_find_next_entry(image, entry)) {
		count ++;
		if (callback(image, entry, arg) != 0)
			break;
	}
	return count;
}

struct cbfs_header *cbfs_find_header(char *data, size_t size)
{
	size_t offset;
	int found = 0;
	uint32_t x86sig;
	struct cbfs_header *header, *result = NULL;

	// Try x86 style (check signature in bottom) header first.
	x86sig = *(uint32_t *)(data + size - sizeof(uint32_t));
	offset = (x86sig + (uint32_t)size);
	DEBUG("x86sig: 0x%x, offset: 0x%zx\n", x86sig, offset);
	if (offset >= size - sizeof(*header) ||
	    ntohl(((struct cbfs_header *)(data + offset))->magic) !=
	    CBFS_HEADER_MAGIC)
		offset = 0;

	for (; offset + sizeof(*header) < size; offset++) {
		header = (struct cbfs_header *)(data + offset);
		if (ntohl(header->magic) !=(CBFS_HEADER_MAGIC))
		    continue;
		if (ntohl(header->version) != CBFS_HEADER_VERSION1 &&
		    ntohl(header->version) != CBFS_HEADER_VERSION2) {
			// Probably not a real CBFS header?
			continue;
		}
		found++;
		result = header;
	}
	if (found > 1) {
		ERROR("multiple (%d) CBFS headers found!\n",
		       found);
		result = NULL;
	}
	return result;
}


struct cbfs_file *cbfs_find_first_entry(struct cbfs_image *image)
{
	assert(image && image->header);
	return (struct cbfs_file *)(image->buffer.data +
				   ntohl(image->header->offset));
}

struct cbfs_file *cbfs_find_next_entry(struct cbfs_image *image,
				       struct cbfs_file *entry)
{
	uint32_t addr = cbfs_get_entry_addr(image, entry);
	int align = ntohl(image->header->align);
	assert(entry && cbfs_is_valid_entry(image, entry));
	addr += ntohl(entry->offset) + ntohl(entry->len);
	addr = align_up(addr, align);
	return (struct cbfs_file *)(image->buffer.data + addr);
}

uint32_t cbfs_get_entry_addr(struct cbfs_image *image, struct cbfs_file *entry)
{
	assert(image && image->buffer.data && entry);
	return (int32_t)((char *)entry - image->buffer.data);
}

int cbfs_is_valid_entry(struct cbfs_image *image, struct cbfs_file *entry)
{
	return (entry &&
		(char *)entry >= image->buffer.data &&
		(char *)entry + sizeof(entry->magic) <
			image->buffer.data + image->buffer.size &&
		memcmp(entry->magic, CBFS_FILE_MAGIC,
		       sizeof(entry->magic)) == 0);
}

int cbfs_create_empty_entry(struct cbfs_image *image, struct cbfs_file *entry,
		      size_t len, const char *name)
{
	memset(entry, CBFS_CONTENT_DEFAULT_VALUE, sizeof(*entry));
	memcpy(entry->magic, CBFS_FILE_MAGIC, sizeof(entry->magic));
	entry->type = htonl(CBFS_COMPONENT_NULL);
	entry->len = htonl(len);
	entry->checksum = 0;  // TODO Build a checksum algorithm.
	entry->offset = htonl(cbfs_calculate_file_header_size(name));
	memset(CBFS_NAME(entry), 0, ntohl(entry->offset) - sizeof(*entry));
	strcpy(CBFS_NAME(entry), name);
	memset(CBFS_SUBHEADER(entry), CBFS_CONTENT_DEFAULT_VALUE, len);
	return 0;
}

/* Finds a place to hold whole data in same memory page. */
static int is_in_same_page(uint32_t start, uint32_t size, uint32_t page)
{
	if (!page)
		return 1;
	return (start / page) == (start + size - 1) / page;
}

/* Tests if data can fit in a range by given offset:
 *  start ->| header_len | offset (+ size) |<- end
 */
static int is_in_range(uint32_t start, uint32_t end, uint32_t header_len,
		       uint32_t offset, uint32_t size)
{
	return (offset >= start + header_len && offset + size <= end);
}

int32_t cbfs_locate_entry(struct cbfs_image *image, const char *name,
			  uint32_t size, uint32_t page_size, uint32_t align)
{
	struct cbfs_file *entry;
	size_t need_len;
	uint32_t addr, addr_next, addr2, addr3, offset, header_len;

	/* Default values: allow fitting anywhere in ROM. */
	if (!page_size)
		page_size = ntohl(image->header->romsize);
	if (!align)
		align = 1;

	if (size > page_size)
		ERROR("Input file size (%d) greater than page size (%d).\n",
		      size, page_size);

	if (page_size % ntohl(image->header->align))
		WARN("%s: Page size (%#x) not aligned with CBFS image (%#x).\n",
		     __func__, page_size, ntohl(image->header->align));

	/* TODO Old cbfstool always assume input is a stage file (and adding
	 * sizeof(cbfs_stage) for header. We should fix that by adding "-t"
	 * (type) param in future. For right now, we assume cbfs_stage is the
	 * largest structure and add it into header size. */
	assert(sizeof(struct cbfs_stage) >= sizeof(struct cbfs_payload));
	header_len = (cbfs_calculate_file_header_size(name) +
		      sizeof(struct cbfs_stage));
	need_len = header_len + size;

	// Merge empty entries to build get max available space.
	cbfs_walk(image, cbfs_merge_empty_entry, NULL);

	/* Three cases of content location on memory page:
	 * case 1.
	 *          |  PAGE 1  |   PAGE 2  |
	 *          |     <header><content>| Fit. Return start of content.
	 *
	 * case 2.
	 *          |  PAGE 1  |   PAGE 2  |
	 *          | <header><content>    | Fits when we shift content to align
	 *  shift-> |  <header>|<content>  | at starting of PAGE 2.
	 *
	 * case 3. (large content filling whole page)
	 *  | PAGE 1 |  PAGE 2  | PAGE 3 |
	 *  |  <header>< content >       | Can't fit. If we shift content to
	 *  |trial-> <header>< content > | PAGE 2, header can't fit in free
	 *  |  shift->  <header><content> space, so we must use PAGE 3.
	 *
	 * The returned address can be then used as "base-address" (-b) in add-*
	 * commands (will be re-calculated and positioned by cbfs_add_entry_at).
	 * For stage targets, the address is also used to re-link stage before
	 * being added into CBFS.
	 */
	for (entry = cbfs_find_first_entry(image);
	     entry && cbfs_is_valid_entry(image, entry);
	     entry = cbfs_find_next_entry(image, entry)) {

		uint32_t type = ntohl(entry->type);
		if (type != CBFS_COMPONENT_NULL)
			continue;

		addr = cbfs_get_entry_addr(image, entry);
		addr_next = cbfs_get_entry_addr(image, cbfs_find_next_entry(
				image, entry));
		if (addr_next - addr < need_len)
			continue;

		offset = align_up(addr + header_len, align);
		if (is_in_same_page(offset, size, page_size) &&
		    is_in_range(addr, addr_next, header_len, offset, size)) {
			DEBUG("cbfs_locate_entry: FIT (PAGE1).");
			return offset;
		}

		addr2 = align_up(addr, page_size);
		offset = align_up(addr2, align);
		if (is_in_range(addr, addr_next, header_len, offset, size)) {
			DEBUG("cbfs_locate_entry: OVERLAP (PAGE2).");
			return offset;
		}

		/* Assume page_size >= header_len so adding one page will
		 * definitely provide the space for header. */
		assert(page_size >= header_len);
		addr3 = addr2 + page_size;
		offset = align_up(addr3, align);
		if (is_in_range(addr, addr_next, header_len, offset, size)) {
			DEBUG("cbfs_locate_entry: OVERLAP+ (PAGE3).");
			return offset;
		}
	}
	return -1;
}