1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2016 Linaro Ltd;  <ard.biesheuvel@linaro.org>
  4 */
  5
  6#include <linux/efi.h>
  7#include <asm/efi.h>
  8
  9#include "efistub.h"
 10
 11typedef union efi_rng_protocol efi_rng_protocol_t;
 12
 13union efi_rng_protocol {
 14	struct {
 15		efi_status_t (__efiapi *get_info)(efi_rng_protocol_t *,
 16						  unsigned long *,
 17						  efi_guid_t *);
 18		efi_status_t (__efiapi *get_rng)(efi_rng_protocol_t *,
 19						 efi_guid_t *, unsigned long,
 20						 u8 *out);
 21	};
 22	struct {
 23		u32 get_info;
 24		u32 get_rng;
 25	} mixed_mode;
 26};
 27
 28/**
 29 * efi_get_random_bytes() - fill a buffer with random bytes
 30 * @size:	size of the buffer
 31 * @out:	caller allocated buffer to receive the random bytes
 32 *
 33 * The call will fail if either the firmware does not implement the
 34 * EFI_RNG_PROTOCOL or there are not enough random bytes available to fill
 35 * the buffer.
 36 *
 37 * Return:	status code
 38 */
 39efi_status_t efi_get_random_bytes(unsigned long size, u8 *out)
 40{
 41	efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
 42	efi_status_t status;
 43	efi_rng_protocol_t *rng = NULL;
 44
 45	status = efi_bs_call(locate_protocol, &rng_proto, NULL, (void **)&rng);
 46	if (status != EFI_SUCCESS)
 47		return status;
 48
 49	return efi_call_proto(rng, get_rng, NULL, size, out);
 50}
 51
 52/**
 53 * efi_random_get_seed() - provide random seed as configuration table
 54 *
 55 * The EFI_RNG_PROTOCOL is used to read random bytes. These random bytes are
 56 * saved as a configuration table which can be used as entropy by the kernel
 57 * for the initialization of its pseudo random number generator.
 58 *
 59 * If the EFI_RNG_PROTOCOL is not available or there are not enough random bytes
 60 * available, the configuration table will not be installed and an error code
 61 * will be returned.
 62 *
 63 * Return:	status code
 64 */
 65efi_status_t efi_random_get_seed(void)
 66{
 67	efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
 68	efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW;
 69	efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID;
 70	efi_rng_protocol_t *rng = NULL;
 71	struct linux_efi_random_seed *seed = NULL;
 72	efi_status_t status;
 73
 74	status = efi_bs_call(locate_protocol, &rng_proto, NULL, (void **)&rng);
 75	if (status != EFI_SUCCESS)
 76		return status;
 77
 78	status = efi_bs_call(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
 79			     sizeof(*seed) + EFI_RANDOM_SEED_SIZE,
 80			     (void **)&seed);
 81	if (status != EFI_SUCCESS)
 82		return status;
 83
 84	status = efi_call_proto(rng, get_rng, &rng_algo_raw,
 85				 EFI_RANDOM_SEED_SIZE, seed->bits);
 86
 87	if (status == EFI_UNSUPPORTED)
 88		/*
 89		 * Use whatever algorithm we have available if the raw algorithm
 90		 * is not implemented.
 91		 */
 92		status = efi_call_proto(rng, get_rng, NULL,
 93					EFI_RANDOM_SEED_SIZE, seed->bits);
 94
 95	if (status != EFI_SUCCESS)
 96		goto err_freepool;
 97
 98	seed->size = EFI_RANDOM_SEED_SIZE;
 99	status = efi_bs_call(install_configuration_table, &rng_table_guid, seed);
100	if (status != EFI_SUCCESS)
101		goto err_freepool;
102
103	return EFI_SUCCESS;
104
105err_freepool:
106	efi_bs_call(free_pool, seed);
107	return status;
108}