diff options
Diffstat (limited to 'common')
| -rw-r--r-- | common/cmd_tpm.c | 703 | 
1 files changed, 596 insertions, 107 deletions
| diff --git a/common/cmd_tpm.c b/common/cmd_tpm.c index 0970a6fc1..46fae1877 100644 --- a/common/cmd_tpm.c +++ b/common/cmd_tpm.c @@ -1,5 +1,5 @@  /* - * Copyright (c) 2011 The Chromium OS Authors. + * Copyright (c) 2013 The Chromium OS Authors.   *   * See file CREDITS for list of people who contributed to this   * project. @@ -22,163 +22,652 @@  #include <common.h>  #include <command.h> +#include <malloc.h>  #include <tpm.h> +#include <asm/unaligned.h> +#include <linux/string.h> -#define MAX_TRANSACTION_SIZE 30 - -/* - * tpm_write() expects a variable number of parameters: the internal address - * followed by data to write, byte by byte. +/** + * Print a byte string in hexdecimal format, 16-bytes per line.   * - * Returns 0 on success or -1 on errors (wrong arguments or TPM failure). + * @param data		byte string to be printed + * @param count		number of bytes to be printed   */ -static int tpm_process(int argc, char * const argv[], cmd_tbl_t *cmdtp) +static void print_byte_string(uint8_t *data, size_t count)  { -	u8 tpm_buffer[MAX_TRANSACTION_SIZE]; -	u32 write_size, read_size; -	char *p; -	int rv = -1; +	int i, print_newline = 0; -	for (write_size = 0; write_size < argc; write_size++) { -		u32 datum = simple_strtoul(argv[write_size], &p, 0); -		if (*p || (datum > 0xff)) { -			printf("\n%s: bad data value\n\n", argv[write_size]); -			cmd_usage(cmdtp); -			return rv; -		} -		tpm_buffer[write_size] = (u8)datum; +	for (i = 0; i < count; i++) { +		printf(" %02x", data[i]); +		print_newline = (i % 16 == 15); +		if (print_newline) +			putc('\n');  	} +	/* Avoid duplicated newline at the end */ +	if (!print_newline) +		putc('\n'); +} -	read_size = sizeof(tpm_buffer); -	if (!tis_sendrecv(tpm_buffer, write_size, tpm_buffer, &read_size)) { -		int i; -		puts("Got TPM response:\n"); -		for (i = 0; i < read_size; i++) -			printf(" %2.2x", tpm_buffer[i]); -		puts("\n"); -		rv = 0; -	} else { -		puts("tpm command failed\n"); +/** + * Convert a text string of hexdecimal values into a byte string. + * + * @param bytes		text string of hexdecimal values with no space + *			between them + * @param data		output buffer for byte string.  The caller has to make + *			sure it is large enough for storing the output.  If + *			NULL is passed, a large enough buffer will be allocated, + *			and the caller must free it. + * @param count_ptr	output variable for the length of byte string + * @return pointer to output buffer + */ +static void *parse_byte_string(char *bytes, uint8_t *data, size_t *count_ptr) +{ +	char byte[3]; +	size_t count, length; +	int i; + +	length = strlen(bytes); +	count = length / 2; + +	if (!data) +		data = malloc(count); +	if (!data) +		return NULL; + +	byte[2] = '\0'; +	for (i = 0; i < length; i += 2) { +		byte[0] = bytes[i]; +		byte[1] = bytes[i + 1]; +		data[i / 2] = (uint8_t)simple_strtoul(byte, NULL, 16);  	} -	return rv; + +	if (count_ptr) +		*count_ptr = count; + +	return data;  } -#define CHECK(exp) do {							\ -		int _rv = exp;						\ -		if (_rv) {						\ -			printf("CHECK: %s %d %x\n", #exp, __LINE__, _rv);\ -		}							\ -	} while (0) +/** + * Convert TPM command return code to U-Boot command error codes. + * + * @param return_code	TPM command return code + * @return value of enum command_ret_t + */ +static int convert_return_code(uint32_t return_code) +{ +	if (return_code) +		return CMD_RET_FAILURE; +	else +		return CMD_RET_SUCCESS; +} -static int tpm_process_stress(int repeat_count) +/** + * Return number of values defined by a type string. + * + * @param type_str	type string + * @return number of values of type string + */ +static int type_string_get_num_values(const char *type_str)  { -	int i; -	int rv = 0; -	u8 request[] = {0x0, 0xc1, -			0x0, 0x0, 0x0, 0x16, -			0x0, 0x0, 0x0, 0x65, -			0x0, 0x0, 0x0, 0x4, -			0x0, 0x0, 0x0, 0x4, -			0x0, 0x0, 0x1, 0x9}; -	u8 response[MAX_TRANSACTION_SIZE]; -	u32 rlength = MAX_TRANSACTION_SIZE; +	return strlen(type_str); +} -	CHECK(tis_init()); +/** + * Return total size of values defined by a type string. + * + * @param type_str	type string + * @return total size of values of type string, or 0 if type string + *  contains illegal type character. + */ +static size_t type_string_get_space_size(const char *type_str) +{ +	size_t size; -	for (i = 0; i < repeat_count; i++) { -		CHECK(tis_open()); -		rv = tis_sendrecv(request, sizeof(request), response, &rlength); -		if (rv) { -			printf("tpm test failed at step %d with 0x%x\n", i, rv); -			CHECK(tis_close()); +	for (size = 0; *type_str; type_str++) { +		switch (*type_str) { +		case 'b': +			size += 1; +			break; +		case 'w': +			size += 2;  			break; +		case 'd': +			size += 4; +			break; +		default: +			return 0;  		} -		CHECK(tis_close()); -		if ((response[6] || response[7] || response[8] || response[9]) -		    && response[9] != 0x26) { -			/* Ignore postinit errors */ -			printf("tpm command failed at step %d\n" -			       "tpm error code: %02x%02x%02x%02x\n", i, -			       response[6], response[7], -			       response[8], response[9]); -			rv = -1; +	} + +	return size; +} + +/** + * Allocate a buffer large enough to hold values defined by a type + * string.  The caller has to free the buffer. + * + * @param type_str	type string + * @param count		pointer for storing size of buffer + * @return pointer to buffer or NULL on error + */ +static void *type_string_alloc(const char *type_str, uint32_t *count) +{ +	void *data; +	size_t size; + +	size = type_string_get_space_size(type_str); +	if (!size) +		return NULL; +	data = malloc(size); +	if (data) +		*count = size; + +	return data; +} + +/** + * Pack values defined by a type string into a buffer.  The buffer must have + * large enough space. + * + * @param type_str	type string + * @param values	text strings of values to be packed + * @param data		output buffer of values + * @return 0 on success, non-0 on error + */ +static int type_string_pack(const char *type_str, char * const values[], +		uint8_t *data) +{ +	size_t offset; +	uint32_t value; + +	for (offset = 0; *type_str; type_str++, values++) { +		value = simple_strtoul(values[0], NULL, 0); +		switch (*type_str) { +		case 'b': +			data[offset] = value; +			offset += 1; +			break; +		case 'w': +			put_unaligned_be16(value, data + offset); +			offset += 2;  			break; +		case 'd': +			put_unaligned_be32(value, data + offset); +			offset += 4; +			break; +		default: +			return -1;  		}  	} -	return rv; + +	return 0;  } +/** + * Read values defined by a type string from a buffer, and write these values + * to environment variables. + * + * @param type_str	type string + * @param data		input buffer of values + * @param vars		names of environment variables + * @return 0 on success, non-0 on error + */ +static int type_string_write_vars(const char *type_str, uint8_t *data, +		char * const vars[]) +{ +	size_t offset; +	uint32_t value; + +	for (offset = 0; *type_str; type_str++, vars++) { +		switch (*type_str) { +		case 'b': +			value = data[offset]; +			offset += 1; +			break; +		case 'w': +			value = get_unaligned_be16(data + offset); +			offset += 2; +			break; +		case 'd': +			value = get_unaligned_be32(data + offset); +			offset += 4; +			break; +		default: +			return -1; +		} +		if (setenv_ulong(*vars, value)) +			return -1; +	} -static int do_tpm_many(cmd_tbl_t *cmdtp, int flag, -		       int argc, char * const argv[], int repeat_count) +	return 0; +} +static int do_tpm_startup(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[])  { -	int rv = 0; +	enum tpm_startup_type mode; -	if (argc < 7 && repeat_count == 0) { -		puts("command should be at least six bytes in size\n"); -		return -1; +	if (argc != 2) +		return CMD_RET_USAGE; +	if (!strcasecmp("TPM_ST_CLEAR", argv[1])) { +		mode = TPM_ST_CLEAR; +	} else if (!strcasecmp("TPM_ST_STATE", argv[1])) { +		mode = TPM_ST_STATE; +	} else if (!strcasecmp("TPM_ST_DEACTIVATED", argv[1])) { +		mode = TPM_ST_DEACTIVATED; +	} else { +		printf("Couldn't recognize mode string: %s\n", argv[1]); +		return CMD_RET_FAILURE;  	} -	if (repeat_count > 0) { -		rv = tpm_process_stress(repeat_count); -		return rv; +	return convert_return_code(tpm_startup(mode)); +} + +static int do_tpm_nv_define_space(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, perm, size; + +	if (argc != 4) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[1], NULL, 0); +	perm = simple_strtoul(argv[2], NULL, 0); +	size = simple_strtoul(argv[3], NULL, 0); + +	return convert_return_code(tpm_nv_define_space(index, perm, size)); +} + +static int do_tpm_nv_read_value(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, count, rc; +	void *data; + +	if (argc != 4) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[1], NULL, 0); +	data = (void *)simple_strtoul(argv[2], NULL, 0); +	count = simple_strtoul(argv[3], NULL, 0); + +	rc = tpm_nv_read_value(index, data, count); +	if (!rc) { +		puts("area content:\n"); +		print_byte_string(data, count);  	} -	if (tis_init()) { -		puts("tis_init() failed!\n"); -		return -1; +	return convert_return_code(rc); +} + +static int do_tpm_nv_write_value(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, rc; +	size_t count; +	void *data; + +	if (argc != 3) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[1], NULL, 0); +	data = parse_byte_string(argv[2], NULL, &count); +	if (!data) { +		printf("Couldn't parse byte string %s\n", argv[2]); +		return CMD_RET_FAILURE;  	} -	if (tis_open()) { -		puts("tis_open() failed!\n"); -		return -1; +	rc = tpm_nv_write_value(index, data, count); +	free(data); + +	return convert_return_code(rc); +} + +static int do_tpm_extend(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, rc; +	uint8_t in_digest[20], out_digest[20]; + +	if (argc != 3) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[1], NULL, 0); +	if (!parse_byte_string(argv[2], in_digest, NULL)) { +		printf("Couldn't parse byte string %s\n", argv[2]); +		return CMD_RET_FAILURE;  	} -	rv = tpm_process(argc - 1, argv + 1, cmdtp); +	rc = tpm_extend(index, in_digest, out_digest); +	if (!rc) { +		puts("PCR value after execution of the command:\n"); +		print_byte_string(out_digest, sizeof(out_digest)); +	} -	if (tis_close()) { -		puts("tis_close() failed!\n"); -		rv = -1; +	return convert_return_code(rc); +} + +static int do_tpm_pcr_read(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, count, rc; +	void *data; + +	if (argc != 4) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[1], NULL, 0); +	data = (void *)simple_strtoul(argv[2], NULL, 0); +	count = simple_strtoul(argv[3], NULL, 0); + +	rc = tpm_pcr_read(index, data, count); +	if (!rc) { +		puts("Named PCR content:\n"); +		print_byte_string(data, count);  	} -	return rv; +	return convert_return_code(rc);  } +static int do_tpm_tsc_physical_presence(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint16_t presence; -static int do_tpm(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]) +	if (argc != 2) +		return CMD_RET_USAGE; +	presence = (uint16_t)simple_strtoul(argv[1], NULL, 0); + +	return convert_return_code(tpm_tsc_physical_presence(presence)); +} + +static int do_tpm_read_pubek(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[])  { -	return do_tpm_many(cmdtp, flag, argc, argv, 0); +	uint32_t count, rc; +	void *data; + +	if (argc != 3) +		return CMD_RET_USAGE; +	data = (void *)simple_strtoul(argv[1], NULL, 0); +	count = simple_strtoul(argv[2], NULL, 0); + +	rc = tpm_read_pubek(data, count); +	if (!rc) { +		puts("pubek value:\n"); +		print_byte_string(data, count); +	} + +	return convert_return_code(rc);  } +static int do_tpm_physical_set_deactivated(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint8_t state; -U_BOOT_CMD(tpm, MAX_TRANSACTION_SIZE, 1, do_tpm, -	   "<byte> [<byte> ...]   - write data and read response", -	   "send arbitrary data (at least 6 bytes) to the TPM " -	   "device and read the response" -); +	if (argc != 2) +		return CMD_RET_USAGE; +	state = (uint8_t)simple_strtoul(argv[1], NULL, 0); + +	return convert_return_code(tpm_physical_set_deactivated(state)); +} -static int do_tpm_stress(cmd_tbl_t *cmdtp, int flag, -			 int argc, char * const argv[]) +static int do_tpm_get_capability(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[])  { -	long unsigned int n; -	int rv; +	uint32_t cap_area, sub_cap, rc; +	void *cap; +	size_t count; -	if (argc != 2) { -		puts("usage: tpm_stress <count>\n"); -		return -1; +	if (argc != 5) +		return CMD_RET_USAGE; +	cap_area = simple_strtoul(argv[1], NULL, 0); +	sub_cap = simple_strtoul(argv[2], NULL, 0); +	cap = (void *)simple_strtoul(argv[3], NULL, 0); +	count = simple_strtoul(argv[4], NULL, 0); + +	rc = tpm_get_capability(cap_area, sub_cap, cap, count); +	if (!rc) { +		puts("capability information:\n"); +		print_byte_string(cap, count);  	} -	rv = strict_strtoul(argv[1], 10, &n); -	if (rv) { -		puts("tpm_stress: bad count"); -		return -1; +	return convert_return_code(rc); +} + +#define TPM_COMMAND_NO_ARG(cmd)				\ +static int do_##cmd(cmd_tbl_t *cmdtp, int flag,		\ +		int argc, char * const argv[])		\ +{							\ +	if (argc != 1)					\ +		return CMD_RET_USAGE;			\ +	return convert_return_code(cmd());		\ +} + +TPM_COMMAND_NO_ARG(tpm_init) +TPM_COMMAND_NO_ARG(tpm_self_test_full) +TPM_COMMAND_NO_ARG(tpm_continue_self_test) +TPM_COMMAND_NO_ARG(tpm_force_clear) +TPM_COMMAND_NO_ARG(tpm_physical_enable) +TPM_COMMAND_NO_ARG(tpm_physical_disable) + +static int do_tpm_raw_transfer(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	void *command; +	uint8_t response[1024]; +	size_t count, response_length = sizeof(response); +	uint32_t rc; + +	command = parse_byte_string(argv[1], NULL, &count); +	if (!command) { +		printf("Couldn't parse byte string %s\n", argv[1]); +		return CMD_RET_FAILURE;  	} -	return do_tpm_many(cmdtp, flag, argc, argv, n); +	rc = tis_sendrecv(command, count, response, &response_length); +	free(command); +	if (!rc) { +		puts("tpm response:\n"); +		print_byte_string(response, response_length); +	} + +	return convert_return_code(rc); +} + +static int do_tpm_nv_define(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, perm, size; + +	if (argc != 4) +		return CMD_RET_USAGE; +	size = type_string_get_space_size(argv[1]); +	if (!size) { +		printf("Couldn't parse arguments\n"); +		return CMD_RET_USAGE; +	} +	index = simple_strtoul(argv[2], NULL, 0); +	perm = simple_strtoul(argv[3], NULL, 0); + +	return convert_return_code(tpm_nv_define_space(index, perm, size)); +} + +static int do_tpm_nv_read(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, count, err; +	void *data; + +	if (argc < 3) +		return CMD_RET_USAGE; +	if (argc != 3 + type_string_get_num_values(argv[1])) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[2], NULL, 0); +	data = type_string_alloc(argv[1], &count); +	if (!data) { +		printf("Couldn't parse arguments\n"); +		return CMD_RET_USAGE; +	} + +	err = tpm_nv_read_value(index, data, count); +	if (!err) { +		if (type_string_write_vars(argv[1], data, argv + 3)) { +			printf("Couldn't write to variables\n"); +			err = ~0; +		} +	} +	free(data); + +	return convert_return_code(err); +} + +static int do_tpm_nv_write(cmd_tbl_t *cmdtp, int flag, +		int argc, char * const argv[]) +{ +	uint32_t index, count, err; +	void *data; + +	if (argc < 3) +		return CMD_RET_USAGE; +	if (argc != 3 + type_string_get_num_values(argv[1])) +		return CMD_RET_USAGE; +	index = simple_strtoul(argv[2], NULL, 0); +	data = type_string_alloc(argv[1], &count); +	if (!data) { +		printf("Couldn't parse arguments\n"); +		return CMD_RET_USAGE; +	} +	if (type_string_pack(argv[1], argv + 3, data)) { +		printf("Couldn't parse arguments\n"); +		free(data); +		return CMD_RET_USAGE; +	} + +	err = tpm_nv_write_value(index, data, count); +	free(data); + +	return convert_return_code(err); +} + +#define MAKE_TPM_CMD_ENTRY(cmd) \ +	U_BOOT_CMD_MKENT(cmd, 0, 1, do_tpm_ ## cmd, "", "") + +static cmd_tbl_t tpm_commands[] = { +	U_BOOT_CMD_MKENT(init, 0, 1, +			do_tpm_init, "", ""), +	U_BOOT_CMD_MKENT(startup, 0, 1, +			do_tpm_startup, "", ""), +	U_BOOT_CMD_MKENT(self_test_full, 0, 1, +			do_tpm_self_test_full, "", ""), +	U_BOOT_CMD_MKENT(continue_self_test, 0, 1, +			do_tpm_continue_self_test, "", ""), +	U_BOOT_CMD_MKENT(force_clear, 0, 1, +			do_tpm_force_clear, "", ""), +	U_BOOT_CMD_MKENT(physical_enable, 0, 1, +			do_tpm_physical_enable, "", ""), +	U_BOOT_CMD_MKENT(physical_disable, 0, 1, +			do_tpm_physical_disable, "", ""), +	U_BOOT_CMD_MKENT(nv_define_space, 0, 1, +			do_tpm_nv_define_space, "", ""), +	U_BOOT_CMD_MKENT(nv_read_value, 0, 1, +			do_tpm_nv_read_value, "", ""), +	U_BOOT_CMD_MKENT(nv_write_value, 0, 1, +			do_tpm_nv_write_value, "", ""), +	U_BOOT_CMD_MKENT(extend, 0, 1, +			do_tpm_extend, "", ""), +	U_BOOT_CMD_MKENT(pcr_read, 0, 1, +			do_tpm_pcr_read, "", ""), +	U_BOOT_CMD_MKENT(tsc_physical_presence, 0, 1, +			do_tpm_tsc_physical_presence, "", ""), +	U_BOOT_CMD_MKENT(read_pubek, 0, 1, +			do_tpm_read_pubek, "", ""), +	U_BOOT_CMD_MKENT(physical_set_deactivated, 0, 1, +			do_tpm_physical_set_deactivated, "", ""), +	U_BOOT_CMD_MKENT(get_capability, 0, 1, +			do_tpm_get_capability, "", ""), +	U_BOOT_CMD_MKENT(raw_transfer, 0, 1, +			do_tpm_raw_transfer, "", ""), +	U_BOOT_CMD_MKENT(nv_define, 0, 1, +			do_tpm_nv_define, "", ""), +	U_BOOT_CMD_MKENT(nv_read, 0, 1, +			do_tpm_nv_read, "", ""), +	U_BOOT_CMD_MKENT(nv_write, 0, 1, +			do_tpm_nv_write, "", ""), +}; + +static int do_tpm(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]) +{ +	cmd_tbl_t *tpm_cmd; + +	if (argc < 2) +		return CMD_RET_USAGE; +	tpm_cmd = find_cmd_tbl(argv[1], tpm_commands, ARRAY_SIZE(tpm_commands)); +	if (!tpm_cmd) +		return CMD_RET_USAGE; + +	return tpm_cmd->cmd(cmdtp, flag, argc - 1, argv + 1);  } -U_BOOT_CMD(tpm_stress, 2, 1, do_tpm_stress, -	   "<n>   - stress-test communication with TPM", -	   "Repeat a TPM transaction (request-response) N times" +U_BOOT_CMD(tpm, CONFIG_SYS_MAXARGS, 1, do_tpm, +"Issue a TPM command", +"cmd args...\n" +"    - Issue TPM command <cmd> with arguments <args...>.\n" +"Admin Startup and State Commands:\n" +"  init\n" +"    - Put TPM into a state where it waits for 'startup' command.\n" +"  startup mode\n" +"    - Issue TPM_Starup command.  <mode> is one of TPM_ST_CLEAR,\n" +"      TPM_ST_STATE, and TPM_ST_DEACTIVATED.\n" +"Admin Testing Commands:\n" +"  self_test_full\n" +"    - Test all of the TPM capabilities.\n" +"  continue_self_test\n" +"    - Inform TPM that it should complete the self-test.\n" +"Admin Opt-in Commands:\n" +"  physical_enable\n" +"    - Set the PERMANENT disable flag to FALSE using physical presence as\n" +"      authorization.\n" +"  physical_disable\n" +"    - Set the PERMANENT disable flag to TRUE using physical presence as\n" +"      authorization.\n" +"  physical_set_deactivated 0|1\n" +"    - Set deactivated flag.\n" +"Admin Ownership Commands:\n" +"  force_clear\n" +"    - Issue TPM_ForceClear command.\n" +"  tsc_physical_presence flags\n" +"    - Set TPM device's Physical Presence flags to <flags>.\n" +"The Capability Commands:\n" +"  get_capability cap_area sub_cap addr count\n" +"    - Read <count> bytes of TPM capability indexed by <cap_area> and\n" +"      <sub_cap> to memory address <addr>.\n" +"Endorsement Key Handling Commands:\n" +"  read_pubek addr count\n" +"    - Read <count> bytes of the public endorsement key to memory\n" +"      address <addr>\n" +"Integrity Collection and Reporting Commands:\n" +"  extend index digest_hex_string\n" +"    - Add a new measurement to a PCR.  Update PCR <index> with the 20-bytes\n" +"      <digest_hex_string>\n" +"  pcr_read index addr count\n" +"    - Read <count> bytes from PCR <index> to memory address <addr>.\n" +"Non-volatile Storage Commands:\n" +"  nv_define_space index permission size\n" +"    - Establish a space at index <index> with <permission> of <size> bytes.\n" +"  nv_read_value index addr count\n" +"    - Read <count> bytes from space <index> to memory address <addr>.\n" +"  nv_write_value index addr count\n" +"    - Write <count> bytes from memory address <addr> to space <index>.\n" +"Miscellaneous helper functions:\n" +"  raw_transfer byte_string\n" +"    - Send a byte string <byte_string> to TPM and print the response.\n" +" Non-volatile storage helper functions:\n" +"    These helper functions treat a non-volatile space as a non-padded\n" +"    sequence of integer values.  These integer values are defined by a type\n" +"    string, which is a text string of 'bwd' characters: 'b' means a 8-bit\n" +"    value, 'w' 16-bit value, 'd' 32-bit value.  All helper functions take\n" +"    a type string as their first argument.\n" +"  nv_define type_string index perm\n" +"    - Define a space <index> with permission <perm>.\n" +"  nv_read types_string index vars...\n" +"    - Read from space <index> to environment variables <vars...>.\n" +"  nv_write types_string index values...\n" +"    - Write to space <index> from values <values...>.\n"  ); |