drivers/io/io_fip.c - filogic/atf - Gitiles

 /*
  * Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * Redistributions of source code must retain the above copyright notice, this
  * list of conditions and the following disclaimer.
  *
  * Redistributions in binary form must reproduce the above copyright notice,
  * this list of conditions and the following disclaimer in the documentation
  * and/or other materials provided with the distribution.
  *
  * Neither the name of ARM nor the names of its contributors may be used
  * to endorse or promote products derived from this software without specific
  * prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */

 #include <stdint.h>
 #include <uuid.h>
 #include <errno.h>
 #include <string.h>
 #include <assert.h>
 #include "platform.h"
 #include "firmware_image_package.h"
 #include "io_storage.h"
 #include "io_driver.h"
 #include "io_fip.h"
 #include "debug.h"

 /* Useful for printing UUIDs when debugging.*/
 #define PRINT_UUID2(x)								\
 	"%08x-%04hx-%04hx-%02hhx%02hhx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx",	\
 		x.time_low, x.time_mid, x.time_hi_and_version,			\
 		x.clock_seq_hi_and_reserved, x.clock_seq_low,			\
 		x.node[0], x.node[1], x.node[2], x.node[3],			\
 		x.node[4], x.node[5]

 typedef struct {
 	const char	*name;
 	const uuid_t	 uuid;
 } plat_fip_name_uuid;

 typedef struct {
 	/* Put file_pos above the struct to allow {0} on static init.
 	 * It is a workaround for a known bug in GCC
 	 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
 	 */
 	unsigned int file_pos;
 	fip_toc_entry entry;
 } file_state;

 static plat_fip_name_uuid name_uuid[] = {
 	{BL2_IMAGE_NAME, UUID_TRUSTED_BOOT_FIRMWARE_BL2},
 	{BL31_IMAGE_NAME, UUID_EL3_RUNTIME_FIRMWARE_BL31},
 	{BL32_IMAGE_NAME, UUID_SECURE_PAYLOAD_BL32},
 	{BL33_IMAGE_NAME, UUID_NON_TRUSTED_FIRMWARE_BL33},
 	{NULL, {0} }
 };

 static const uuid_t uuid_null = {0};
 static file_state current_file = {0};
 static io_dev_handle backend_dev_handle;
 static void *backend_image_spec;


 /* Firmware Image Package driver functions */
 static int fip_dev_open(void *spec, struct io_dev_info **dev_info);
 static int fip_file_open(struct io_dev_info *dev_info, const void *spec,
 			  struct io_entity *entity);
 static int fip_file_len(struct io_entity *entity, size_t *length);
 static int fip_file_read(struct io_entity *entity, void *buffer, size_t length,
 			  size_t *length_read);
 static int fip_file_close(struct io_entity *entity);
 static int fip_dev_init(struct io_dev_info *dev_info, const void *init_params);
 static int fip_dev_close(struct io_dev_info *dev_info);


 static inline int copy_uuid(uuid_t *dst, const uuid_t *src)
 {
 	memcpy(dst, src, sizeof(uuid_t));
 	return 0;
 }


 /* Return 0 for equal uuids. */
 static inline int compare_uuids(const uuid_t *uuid1, const uuid_t *uuid2)
 {
 	return memcmp(uuid1, uuid2, sizeof(uuid_t));
 }


 /* TODO: We could check version numbers or do a package checksum? */
 static inline int is_valid_header(fip_toc_header *header)
 {
 	if ((header->name == TOC_HEADER_NAME) && (header->serial_number != 0)) {
 		return 1;
 	} else {
 		return 0;
 	}
 }


 static int file_to_uuid(const char *filename, uuid_t *uuid)
 {
 	int i;
 	int status = -EINVAL;

 	for (i = 0; i < (sizeof(name_uuid)/sizeof(plat_fip_name_uuid)); i++) {
 		if (strcmp(filename, name_uuid[i].name) == 0) {
 			copy_uuid(uuid, &name_uuid[i].uuid);
 			status = 0;
 			break;
 		}
 	}
 	return status;
 }


 /* Identify the device type as a virtual driver */
 io_type device_type_fip(void)
 {
 	return IO_TYPE_FIRMWARE_IMAGE_PACKAGE;
 }


 static struct io_dev_connector fip_dev_connector = {
 	.dev_open = fip_dev_open
 };


 static struct io_dev_funcs fip_dev_funcs = {
 	.type = device_type_fip,
 	.open = fip_file_open,
 	.seek = NULL,
 	.size = fip_file_len,
 	.read = fip_file_read,
 	.write = NULL,
 	.close = fip_file_close,
 	.dev_init = fip_dev_init,
 	.dev_close = fip_dev_close,
 };


 static struct io_dev_info fip_dev_info = {
 	.funcs = &fip_dev_funcs,
 	.info = (uintptr_t)NULL
 };


 /* Open a connection to the FIP device */
 static int fip_dev_open(void *spec __attribute__((unused)),
 			 struct io_dev_info **dev_info)
 {
 	assert(dev_info != NULL);
 	*dev_info = &fip_dev_info;

 	return IO_SUCCESS;
 }


 /* Do some basic package checks. */
 static int fip_dev_init(struct io_dev_info *dev_info, const void *init_params)
 {
 	int result = IO_FAIL;
 	char *image_name = (char *)init_params;
 	io_handle backend_handle;
 	fip_toc_header header;
 	size_t bytes_read;

 	/* Obtain a reference to the image by querying the platform layer */
 	result = plat_get_image_source(image_name, &backend_dev_handle,
 				       &backend_image_spec);
 	if (result != IO_SUCCESS) {
 		WARN("Failed to obtain reference to image '%s' (%i)\n",
 			image_name, result);
 		result = IO_FAIL;
 		goto fip_dev_init_exit;
 	}

 	/* Attempt to access the FIP image */
 	result = io_open(backend_dev_handle, backend_image_spec,
 			 &backend_handle);
 	if (result != IO_SUCCESS) {
 		WARN("Failed to access image '%s' (%i)\n", image_name, result);
 		result = IO_FAIL;
 		goto fip_dev_init_exit;
 	}

 	result = io_read(backend_handle, &header, sizeof(header), &bytes_read);
 	if (result == IO_SUCCESS) {
 		if (!is_valid_header(&header)) {
 			WARN("Firmware Image Package header check failed.\n");
 			result = IO_FAIL;
 		} else {
 			INFO("FIP header looks OK.\n");
 		}
 	}

 	io_close(backend_handle);

  fip_dev_init_exit:
 	return result;
 }

 /* Close a connection to the FIP device */
 static int fip_dev_close(struct io_dev_info *dev_info)
 {
 	/* TODO: Consider tracking open files and cleaning them up here */

 	/* Clear the backend. */
 	backend_dev_handle = NULL;
 	backend_image_spec = NULL;

 	return IO_SUCCESS;
 }


 /* Open a file for access from package. */
 static int fip_file_open(struct io_dev_info *dev_info, const void *spec,
 			 struct io_entity *entity)
 {
 	int result = IO_FAIL;
 	io_handle backend_handle;
 	uuid_t file_uuid;
 	const io_file_spec *file_spec = (io_file_spec *)spec;
 	size_t bytes_read;
 	int found_file = 0;

 	assert(file_spec != NULL);
 	assert(entity != NULL);

 	/* Can only have one file open at a time for the moment. We need to
 	 * track state like file cursor position. We know the header lives at
 	 * offset zero, so this entry should never be zero for an active file.
 	 * When the system supports dynamic memory allocation we can allow more
 	 * than one open file at a time if needed.
 	 */
 	if (current_file.entry.offset_address != 0) {
 		WARN("fip_file_open : Only one open file at a time.\n");
 		return IO_RESOURCES_EXHAUSTED;
 	}

 	/* Attempt to access the FIP image */
 	result = io_open(backend_dev_handle, backend_image_spec,
 			 &backend_handle);
 	if (result != IO_SUCCESS) {
 		WARN("Failed to open Firmware Image Package (%i)\n", result);
 		result = IO_FAIL;
 		goto fip_file_open_exit;
 	}

 	/* Seek past the FIP header into the Table of Contents */
 	result = io_seek(backend_handle, IO_SEEK_SET, sizeof(fip_toc_header));
 	if (result != IO_SUCCESS) {
 		WARN("fip_file_open: failed to seek\n");
 		result = IO_FAIL;
 		goto fip_file_open_close;
 	}

 	file_to_uuid(file_spec->path, &file_uuid);

 	found_file = 0;
 	do {
 		result = io_read(backend_handle, &current_file.entry,
 				 sizeof(current_file.entry),
 				 &bytes_read);
 		if (result == IO_SUCCESS) {
 			if (compare_uuids(&current_file.entry.uuid,
 					  &file_uuid) == 0) {
 				found_file = 1;
 				break;
 			}
 		} else {
 			WARN("Failed to read FIP (%i)\n", result);
 			goto fip_file_open_close;
 		}
 	} while (compare_uuids(&current_file.entry.uuid, &uuid_null) != 0);

 	if (found_file == 1) {
 		/* All fine. Update entity info with file state and return. Set
 		 * the file position to 0. The 'current_file.entry' holds the
 		 * base and size of the file.
 		 */
 		current_file.file_pos = 0;
 		entity->info = (uintptr_t)&current_file;
 	} else {
 		/* Did not find the file in the FIP. */
 		current_file.entry.offset_address = 0;
 		result = IO_FAIL;
 	}

  fip_file_open_close:
 	io_close(backend_handle);

  fip_file_open_exit:
 	return result;
 }


 /* Return the size of a file in package */
 static int fip_file_len(struct io_entity *entity, size_t *length)
 {
 	assert(entity != NULL);
 	assert(length != NULL);

 	*length =  ((file_state *)entity->info)->entry.size;

 	return IO_SUCCESS;
 }


 /* Read data from a file in package */
 static int fip_file_read(struct io_entity *entity, void *buffer, size_t length,
 			  size_t *length_read)
 {
 	int result = IO_FAIL;
 	file_state *fp;
 	size_t file_offset;
 	size_t bytes_read;
 	io_handle backend_handle;

 	assert(entity != NULL);
 	assert(buffer != NULL);
 	assert(length_read != NULL);
 	assert((void *)entity->info != NULL);

 	/* Open the backend, attempt to access the blob image */
 	result = io_open(backend_dev_handle, backend_image_spec,
 			 &backend_handle);
 	if (result != IO_SUCCESS) {
 		WARN("Failed to open FIP (%i)\n", result);
 		result = IO_FAIL;
 		goto fip_file_read_exit;
 	}

 	fp = (file_state *)entity->info;

 	/* Seek to the position in the FIP where the payload lives */
 	file_offset = fp->entry.offset_address + fp->file_pos;
 	result = io_seek(backend_handle, IO_SEEK_SET, file_offset);
 	if (result != IO_SUCCESS) {
 		WARN("fip_file_read: failed to seek\n");
 		result = IO_FAIL;
 		goto fip_file_read_close;
 	}

 	result = io_read(backend_handle, buffer, length, &bytes_read);
 	if (result != IO_SUCCESS) {
 		/* We cannot read our data. Fail. */
 		WARN("Failed to read payload (%i)\n", result);
 		result = IO_FAIL;
 		goto fip_file_read_close;
 	} else {
 		/* Set caller length and new file position. */
 		*length_read = bytes_read;
 		fp->file_pos += bytes_read;
 	}

 /* Close the backend. */
  fip_file_read_close:
 	io_close(backend_handle);

  fip_file_read_exit:
 	return result;
 }


 /* Close a file in package */
 static int fip_file_close(struct io_entity *entity)
 {
 	/* Clear our current file pointer.
 	 * If we had malloc() we would free() here.
 	 */
 	if (current_file.entry.offset_address != 0) {
 		memset(&current_file, 0, sizeof(current_file));
 	}

 	/* Clear the Entity info. */
 	entity->info = 0;

 	return IO_SUCCESS;
 }

 /* Exported functions */

 /* Register the Firmware Image Package driver with the IO abstraction */
 int register_io_dev_fip(struct io_dev_connector **dev_con)
 {
 	int result = IO_FAIL;
 	assert(dev_con != NULL);

 	result = io_register_device(&fip_dev_info);
 	if (result == IO_SUCCESS)
 		*dev_con = &fip_dev_connector;

 	return result;
 }
	/*
	* Copyright (c) 2014, ARM Limited and Contributors. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	*
	* Redistributions of source code must retain the above copyright notice, this
	* list of conditions and the following disclaimer.
	*
	* Redistributions in binary form must reproduce the above copyright notice,
	* this list of conditions and the following disclaimer in the documentation
	* and/or other materials provided with the distribution.
	*
	* Neither the name of ARM nor the names of its contributors may be used
	* to endorse or promote products derived from this software without specific
	* prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
	* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
	* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	* POSSIBILITY OF SUCH DAMAGE.
	*/

	#include <stdint.h>
	#include <uuid.h>
	#include <errno.h>
	#include <string.h>
	#include <assert.h>
	#include "platform.h"
	#include "firmware_image_package.h"
	#include "io_storage.h"
	#include "io_driver.h"
	#include "io_fip.h"
	#include "debug.h"

	/* Useful for printing UUIDs when debugging.*/
	#define PRINT_UUID2(x) \
	"%08x-%04hx-%04hx-%02hhx%02hhx-%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx", \
	x.time_low, x.time_mid, x.time_hi_and_version, \
	x.clock_seq_hi_and_reserved, x.clock_seq_low, \
	x.node[0], x.node[1], x.node[2], x.node[3], \
	x.node[4], x.node[5]

	typedef struct {
	const char *name;
	const uuid_t uuid;
	} plat_fip_name_uuid;

	typedef struct {
	/* Put file_pos above the struct to allow {0} on static init.
	* It is a workaround for a known bug in GCC
	* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
	*/
	unsigned int file_pos;
	fip_toc_entry entry;
	} file_state;

	static plat_fip_name_uuid name_uuid[] = {
	{BL2_IMAGE_NAME, UUID_TRUSTED_BOOT_FIRMWARE_BL2},
	{BL31_IMAGE_NAME, UUID_EL3_RUNTIME_FIRMWARE_BL31},
	{BL32_IMAGE_NAME, UUID_SECURE_PAYLOAD_BL32},
	{BL33_IMAGE_NAME, UUID_NON_TRUSTED_FIRMWARE_BL33},
	{NULL, {0} }
	};

	static const uuid_t uuid_null = {0};
	static file_state current_file = {0};
	static io_dev_handle backend_dev_handle;
	static void *backend_image_spec;


	/* Firmware Image Package driver functions */
	static int fip_dev_open(void spec, struct io_dev_info *dev_info);
	static int fip_file_open(struct io_dev_info dev_info, const void spec,
	struct io_entity *entity);
	static int fip_file_len(struct io_entity entity, size_t length);
	static int fip_file_read(struct io_entity entity, void buffer, size_t length,
	size_t *length_read);
	static int fip_file_close(struct io_entity *entity);
	static int fip_dev_init(struct io_dev_info dev_info, const void init_params);
	static int fip_dev_close(struct io_dev_info *dev_info);


	static inline int copy_uuid(uuid_t dst, const uuid_t src)
	{
	memcpy(dst, src, sizeof(uuid_t));
	return 0;
	}


	/* Return 0 for equal uuids. */
	static inline int compare_uuids(const uuid_t uuid1, const uuid_t uuid2)
	{
	return memcmp(uuid1, uuid2, sizeof(uuid_t));
	}


	/* TODO: We could check version numbers or do a package checksum? */
	static inline int is_valid_header(fip_toc_header *header)
	{
	if ((header->name == TOC_HEADER_NAME) && (header->serial_number != 0)) {
	return 1;
	} else {
	return 0;
	}
	}


	static int file_to_uuid(const char filename, uuid_t uuid)
	{
	int i;
	int status = -EINVAL;

	for (i = 0; i < (sizeof(name_uuid)/sizeof(plat_fip_name_uuid)); i++) {
	if (strcmp(filename, name_uuid[i].name) == 0) {
	copy_uuid(uuid, &name_uuid[i].uuid);
	status = 0;
	break;
	}
	}
	return status;
	}


	/* Identify the device type as a virtual driver */
	io_type device_type_fip(void)
	{
	return IO_TYPE_FIRMWARE_IMAGE_PACKAGE;
	}


	static struct io_dev_connector fip_dev_connector = {
	.dev_open = fip_dev_open
	};


	static struct io_dev_funcs fip_dev_funcs = {
	.type = device_type_fip,
	.open = fip_file_open,
	.seek = NULL,
	.size = fip_file_len,
	.read = fip_file_read,
	.write = NULL,
	.close = fip_file_close,
	.dev_init = fip_dev_init,
	.dev_close = fip_dev_close,
	};


	static struct io_dev_info fip_dev_info = {
	.funcs = &fip_dev_funcs,
	.info = (uintptr_t)NULL
	};


	/* Open a connection to the FIP device */
	static int fip_dev_open(void *spec __attribute__((unused)),
	struct io_dev_info **dev_info)
	{
	assert(dev_info != NULL);
	*dev_info = &fip_dev_info;

	return IO_SUCCESS;
	}


	/* Do some basic package checks. */
	static int fip_dev_init(struct io_dev_info dev_info, const void init_params)
	{
	int result = IO_FAIL;
	char image_name = (char )init_params;
	io_handle backend_handle;
	fip_toc_header header;
	size_t bytes_read;

	/* Obtain a reference to the image by querying the platform layer */
	result = plat_get_image_source(image_name, &backend_dev_handle,
	&backend_image_spec);
	if (result != IO_SUCCESS) {
	WARN("Failed to obtain reference to image '%s' (%i)\n",
	image_name, result);
	result = IO_FAIL;
	goto fip_dev_init_exit;
	}

	/* Attempt to access the FIP image */
	result = io_open(backend_dev_handle, backend_image_spec,
	&backend_handle);
	if (result != IO_SUCCESS) {
	WARN("Failed to access image '%s' (%i)\n", image_name, result);
	result = IO_FAIL;
	goto fip_dev_init_exit;
	}

	result = io_read(backend_handle, &header, sizeof(header), &bytes_read);
	if (result == IO_SUCCESS) {
	if (!is_valid_header(&header)) {
	WARN("Firmware Image Package header check failed.\n");
	result = IO_FAIL;
	} else {
	INFO("FIP header looks OK.\n");
	}
	}

	io_close(backend_handle);

	fip_dev_init_exit:
	return result;
	}

	/* Close a connection to the FIP device */
	static int fip_dev_close(struct io_dev_info *dev_info)
	{
	/* TODO: Consider tracking open files and cleaning them up here */

	/* Clear the backend. */
	backend_dev_handle = NULL;
	backend_image_spec = NULL;

	return IO_SUCCESS;
	}


	/* Open a file for access from package. */
	static int fip_file_open(struct io_dev_info dev_info, const void spec,
	struct io_entity *entity)
	{
	int result = IO_FAIL;
	io_handle backend_handle;
	uuid_t file_uuid;
	const io_file_spec file_spec = (io_file_spec )spec;
	size_t bytes_read;
	int found_file = 0;

	assert(file_spec != NULL);
	assert(entity != NULL);

	/* Can only have one file open at a time for the moment. We need to
	* track state like file cursor position. We know the header lives at
	* offset zero, so this entry should never be zero for an active file.
	* When the system supports dynamic memory allocation we can allow more
	* than one open file at a time if needed.
	*/
	if (current_file.entry.offset_address != 0) {
	WARN("fip_file_open : Only one open file at a time.\n");
	return IO_RESOURCES_EXHAUSTED;
	}

	/* Attempt to access the FIP image */
	result = io_open(backend_dev_handle, backend_image_spec,
	&backend_handle);
	if (result != IO_SUCCESS) {
	WARN("Failed to open Firmware Image Package (%i)\n", result);
	result = IO_FAIL;
	goto fip_file_open_exit;
	}

	/* Seek past the FIP header into the Table of Contents */
	result = io_seek(backend_handle, IO_SEEK_SET, sizeof(fip_toc_header));
	if (result != IO_SUCCESS) {
	WARN("fip_file_open: failed to seek\n");
	result = IO_FAIL;
	goto fip_file_open_close;
	}

	file_to_uuid(file_spec->path, &file_uuid);

	found_file = 0;
	do {
	result = io_read(backend_handle, &current_file.entry,
	sizeof(current_file.entry),
	&bytes_read);
	if (result == IO_SUCCESS) {
	if (compare_uuids(&current_file.entry.uuid,
	&file_uuid) == 0) {
	found_file = 1;
	break;
	}
	} else {
	WARN("Failed to read FIP (%i)\n", result);
	goto fip_file_open_close;
	}
	} while (compare_uuids(&current_file.entry.uuid, &uuid_null) != 0);

	if (found_file == 1) {
	/* All fine. Update entity info with file state and return. Set
	* the file position to 0. The 'current_file.entry' holds the
	* base and size of the file.
	*/
	current_file.file_pos = 0;
	entity->info = (uintptr_t)&current_file;
	} else {
	/* Did not find the file in the FIP. */
	current_file.entry.offset_address = 0;
	result = IO_FAIL;
	}

	fip_file_open_close:
	io_close(backend_handle);

	fip_file_open_exit:
	return result;
	}


	/* Return the size of a file in package */
	static int fip_file_len(struct io_entity entity, size_t length)
	{
	assert(entity != NULL);
	assert(length != NULL);

	length = ((file_state )entity->info)->entry.size;

	return IO_SUCCESS;
	}


	/* Read data from a file in package */
	static int fip_file_read(struct io_entity entity, void buffer, size_t length,
	size_t *length_read)
	{
	int result = IO_FAIL;
	file_state *fp;
	size_t file_offset;
	size_t bytes_read;
	io_handle backend_handle;

	assert(entity != NULL);
	assert(buffer != NULL);
	assert(length_read != NULL);
	assert((void *)entity->info != NULL);

	/* Open the backend, attempt to access the blob image */
	result = io_open(backend_dev_handle, backend_image_spec,
	&backend_handle);
	if (result != IO_SUCCESS) {
	WARN("Failed to open FIP (%i)\n", result);
	result = IO_FAIL;
	goto fip_file_read_exit;
	}

	fp = (file_state *)entity->info;

	/* Seek to the position in the FIP where the payload lives */
	file_offset = fp->entry.offset_address + fp->file_pos;
	result = io_seek(backend_handle, IO_SEEK_SET, file_offset);
	if (result != IO_SUCCESS) {
	WARN("fip_file_read: failed to seek\n");
	result = IO_FAIL;
	goto fip_file_read_close;
	}

	result = io_read(backend_handle, buffer, length, &bytes_read);
	if (result != IO_SUCCESS) {
	/* We cannot read our data. Fail. */
	WARN("Failed to read payload (%i)\n", result);
	result = IO_FAIL;
	goto fip_file_read_close;
	} else {
	/* Set caller length and new file position. */
	*length_read = bytes_read;
	fp->file_pos += bytes_read;
	}

	/* Close the backend. */
	fip_file_read_close:
	io_close(backend_handle);

	fip_file_read_exit:
	return result;
	}


	/* Close a file in package */
	static int fip_file_close(struct io_entity *entity)
	{
	/* Clear our current file pointer.
	* If we had malloc() we would free() here.
	*/
	if (current_file.entry.offset_address != 0) {
	memset(&current_file, 0, sizeof(current_file));
	}

	/* Clear the Entity info. */
	entity->info = 0;

	return IO_SUCCESS;
	}

	/* Exported functions */

	/* Register the Firmware Image Package driver with the IO abstraction */
	int register_io_dev_fip(struct io_dev_connector **dev_con)
	{
	int result = IO_FAIL;
	assert(dev_con != NULL);

	result = io_register_device(&fip_dev_info);
	if (result == IO_SUCCESS)
	*dev_con = &fip_dev_connector;

	return result;
	}