1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Copyright (C) 2016 Linaro Ltd; <ard.biesheuvel@linaro.org>
4*4882a593Smuzhiyun */
5*4882a593Smuzhiyun
6*4882a593Smuzhiyun #include <linux/efi.h>
7*4882a593Smuzhiyun #include <asm/efi.h>
8*4882a593Smuzhiyun
9*4882a593Smuzhiyun #include "efistub.h"
10*4882a593Smuzhiyun
11*4882a593Smuzhiyun typedef union efi_rng_protocol efi_rng_protocol_t;
12*4882a593Smuzhiyun
13*4882a593Smuzhiyun union efi_rng_protocol {
14*4882a593Smuzhiyun struct {
15*4882a593Smuzhiyun efi_status_t (__efiapi *get_info)(efi_rng_protocol_t *,
16*4882a593Smuzhiyun unsigned long *,
17*4882a593Smuzhiyun efi_guid_t *);
18*4882a593Smuzhiyun efi_status_t (__efiapi *get_rng)(efi_rng_protocol_t *,
19*4882a593Smuzhiyun efi_guid_t *, unsigned long,
20*4882a593Smuzhiyun u8 *out);
21*4882a593Smuzhiyun };
22*4882a593Smuzhiyun struct {
23*4882a593Smuzhiyun u32 get_info;
24*4882a593Smuzhiyun u32 get_rng;
25*4882a593Smuzhiyun } mixed_mode;
26*4882a593Smuzhiyun };
27*4882a593Smuzhiyun
28*4882a593Smuzhiyun /**
29*4882a593Smuzhiyun * efi_get_random_bytes() - fill a buffer with random bytes
30*4882a593Smuzhiyun * @size: size of the buffer
31*4882a593Smuzhiyun * @out: caller allocated buffer to receive the random bytes
32*4882a593Smuzhiyun *
33*4882a593Smuzhiyun * The call will fail if either the firmware does not implement the
34*4882a593Smuzhiyun * EFI_RNG_PROTOCOL or there are not enough random bytes available to fill
35*4882a593Smuzhiyun * the buffer.
36*4882a593Smuzhiyun *
37*4882a593Smuzhiyun * Return: status code
38*4882a593Smuzhiyun */
efi_get_random_bytes(unsigned long size,u8 * out)39*4882a593Smuzhiyun efi_status_t efi_get_random_bytes(unsigned long size, u8 *out)
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
42*4882a593Smuzhiyun efi_status_t status;
43*4882a593Smuzhiyun efi_rng_protocol_t *rng = NULL;
44*4882a593Smuzhiyun
45*4882a593Smuzhiyun status = efi_bs_call(locate_protocol, &rng_proto, NULL, (void **)&rng);
46*4882a593Smuzhiyun if (status != EFI_SUCCESS)
47*4882a593Smuzhiyun return status;
48*4882a593Smuzhiyun
49*4882a593Smuzhiyun return efi_call_proto(rng, get_rng, NULL, size, out);
50*4882a593Smuzhiyun }
51*4882a593Smuzhiyun
52*4882a593Smuzhiyun /**
53*4882a593Smuzhiyun * efi_random_get_seed() - provide random seed as configuration table
54*4882a593Smuzhiyun *
55*4882a593Smuzhiyun * The EFI_RNG_PROTOCOL is used to read random bytes. These random bytes are
56*4882a593Smuzhiyun * saved as a configuration table which can be used as entropy by the kernel
57*4882a593Smuzhiyun * for the initialization of its pseudo random number generator.
58*4882a593Smuzhiyun *
59*4882a593Smuzhiyun * If the EFI_RNG_PROTOCOL is not available or there are not enough random bytes
60*4882a593Smuzhiyun * available, the configuration table will not be installed and an error code
61*4882a593Smuzhiyun * will be returned.
62*4882a593Smuzhiyun *
63*4882a593Smuzhiyun * Return: status code
64*4882a593Smuzhiyun */
efi_random_get_seed(void)65*4882a593Smuzhiyun efi_status_t efi_random_get_seed(void)
66*4882a593Smuzhiyun {
67*4882a593Smuzhiyun efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
68*4882a593Smuzhiyun efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW;
69*4882a593Smuzhiyun efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID;
70*4882a593Smuzhiyun efi_rng_protocol_t *rng = NULL;
71*4882a593Smuzhiyun struct linux_efi_random_seed *seed = NULL;
72*4882a593Smuzhiyun efi_status_t status;
73*4882a593Smuzhiyun
74*4882a593Smuzhiyun status = efi_bs_call(locate_protocol, &rng_proto, NULL, (void **)&rng);
75*4882a593Smuzhiyun if (status != EFI_SUCCESS)
76*4882a593Smuzhiyun return status;
77*4882a593Smuzhiyun
78*4882a593Smuzhiyun /*
79*4882a593Smuzhiyun * Use EFI_ACPI_RECLAIM_MEMORY here so that it is guaranteed that the
80*4882a593Smuzhiyun * allocation will survive a kexec reboot (although we refresh the seed
81*4882a593Smuzhiyun * beforehand)
82*4882a593Smuzhiyun */
83*4882a593Smuzhiyun status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
84*4882a593Smuzhiyun sizeof(*seed) + EFI_RANDOM_SEED_SIZE,
85*4882a593Smuzhiyun (void **)&seed);
86*4882a593Smuzhiyun if (status != EFI_SUCCESS)
87*4882a593Smuzhiyun return status;
88*4882a593Smuzhiyun
89*4882a593Smuzhiyun status = efi_call_proto(rng, get_rng, &rng_algo_raw,
90*4882a593Smuzhiyun EFI_RANDOM_SEED_SIZE, seed->bits);
91*4882a593Smuzhiyun
92*4882a593Smuzhiyun if (status == EFI_UNSUPPORTED)
93*4882a593Smuzhiyun /*
94*4882a593Smuzhiyun * Use whatever algorithm we have available if the raw algorithm
95*4882a593Smuzhiyun * is not implemented.
96*4882a593Smuzhiyun */
97*4882a593Smuzhiyun status = efi_call_proto(rng, get_rng, NULL,
98*4882a593Smuzhiyun EFI_RANDOM_SEED_SIZE, seed->bits);
99*4882a593Smuzhiyun
100*4882a593Smuzhiyun if (status != EFI_SUCCESS)
101*4882a593Smuzhiyun goto err_freepool;
102*4882a593Smuzhiyun
103*4882a593Smuzhiyun seed->size = EFI_RANDOM_SEED_SIZE;
104*4882a593Smuzhiyun status = efi_bs_call(install_configuration_table, &rng_table_guid, seed);
105*4882a593Smuzhiyun if (status != EFI_SUCCESS)
106*4882a593Smuzhiyun goto err_freepool;
107*4882a593Smuzhiyun
108*4882a593Smuzhiyun return EFI_SUCCESS;
109*4882a593Smuzhiyun
110*4882a593Smuzhiyun err_freepool:
111*4882a593Smuzhiyun efi_bs_call(free_pool, seed);
112*4882a593Smuzhiyun return status;
113*4882a593Smuzhiyun }
114