1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Helpers for early access to EFI configuration table.
4 *
5 * Originally derived from arch/x86/boot/compressed/acpi.c
6 */
7
8#include "misc.h"
9
10#include <asm/bootparam.h>
11
12/**
13 * efi_get_type - Given a pointer to boot_params, determine the type of EFI environment.
14 *
15 * @bp: pointer to boot_params
16 *
17 * Return: EFI_TYPE_{32,64} for valid EFI environments, EFI_TYPE_NONE otherwise.
18 */
19enum efi_type efi_get_type(struct boot_params *bp)
20{
21 struct efi_info *ei;
22 enum efi_type et;
23 const char *sig;
24
25 ei = &bp->efi_info;
26 sig = (char *)&ei->efi_loader_signature;
27
28 if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
29 et = EFI_TYPE_64;
30 } else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
31 et = EFI_TYPE_32;
32 } else {
33 debug_putstr("No EFI environment detected.\n");
34 et = EFI_TYPE_NONE;
35 }
36
37#ifndef CONFIG_X86_64
38 /*
39 * Existing callers like acpi.c treat this case as an indicator to
40 * fall-through to non-EFI, rather than an error, so maintain that
41 * functionality here as well.
42 */
43 if (ei->efi_systab_hi || ei->efi_memmap_hi) {
44 debug_putstr("EFI system table is located above 4GB and cannot be accessed.\n");
45 et = EFI_TYPE_NONE;
46 }
47#endif
48
49 return et;
50}
51
52/**
53 * efi_get_system_table - Given a pointer to boot_params, retrieve the physical address
54 * of the EFI system table.
55 *
56 * @bp: pointer to boot_params
57 *
58 * Return: EFI system table address on success. On error, return 0.
59 */
60unsigned long efi_get_system_table(struct boot_params *bp)
61{
62 unsigned long sys_tbl_pa;
63 struct efi_info *ei;
64 enum efi_type et;
65
66 /* Get systab from boot params. */
67 ei = &bp->efi_info;
68#ifdef CONFIG_X86_64
69 sys_tbl_pa = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
70#else
71 sys_tbl_pa = ei->efi_systab;
72#endif
73 if (!sys_tbl_pa) {
74 debug_putstr("EFI system table not found.");
75 return 0;
76 }
77
78 return sys_tbl_pa;
79}
80
81/*
82 * EFI config table address changes to virtual address after boot, which may
83 * not be accessible for the kexec'd kernel. To address this, kexec provides
84 * the initial physical address via a struct setup_data entry, which is
85 * checked for here, along with some sanity checks.
86 */
87static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
88 enum efi_type et)
89{
90#ifdef CONFIG_X86_64
91 struct efi_setup_data *esd = NULL;
92 struct setup_data *data;
93 u64 pa_data;
94
95 pa_data = bp->hdr.setup_data;
96 while (pa_data) {
97 data = (struct setup_data *)pa_data;
98 if (data->type == SETUP_EFI) {
99 esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
100 break;
101 }
102
103 pa_data = data->next;
104 }
105
106 /*
107 * Original ACPI code falls back to attempting normal EFI boot in these
108 * cases, so maintain existing behavior by indicating non-kexec
109 * environment to the caller, but print them for debugging.
110 */
111 if (esd && !esd->tables) {
112 debug_putstr("kexec EFI environment missing valid configuration table.\n");
113 return NULL;
114 }
115
116 return esd;
117#endif
118 return NULL;
119}
120
121/**
122 * efi_get_conf_table - Given a pointer to boot_params, locate and return the physical
123 * address of EFI configuration table.
124 *
125 * @bp: pointer to boot_params
126 * @cfg_tbl_pa: location to store physical address of config table
127 * @cfg_tbl_len: location to store number of config table entries
128 *
129 * Return: 0 on success. On error, return params are left unchanged.
130 */
131int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
132 unsigned int *cfg_tbl_len)
133{
134 unsigned long sys_tbl_pa;
135 enum efi_type et;
136 int ret;
137
138 if (!cfg_tbl_pa || !cfg_tbl_len)
139 return -EINVAL;
140
141 sys_tbl_pa = efi_get_system_table(bp);
142 if (!sys_tbl_pa)
143 return -EINVAL;
144
145 /* Handle EFI bitness properly */
146 et = efi_get_type(bp);
147 if (et == EFI_TYPE_64) {
148 efi_system_table_64_t *stbl = (efi_system_table_64_t *)sys_tbl_pa;
149 struct efi_setup_data *esd;
150
151 /* kexec provides an alternative EFI conf table, check for it. */
152 esd = get_kexec_setup_data(bp, et);
153
154 *cfg_tbl_pa = esd ? esd->tables : stbl->tables;
155 *cfg_tbl_len = stbl->nr_tables;
156 } else if (et == EFI_TYPE_32) {
157 efi_system_table_32_t *stbl = (efi_system_table_32_t *)sys_tbl_pa;
158
159 *cfg_tbl_pa = stbl->tables;
160 *cfg_tbl_len = stbl->nr_tables;
161 } else {
162 return -EINVAL;
163 }
164
165 return 0;
166}
167
168/* Get vendor table address/guid from EFI config table at the given index */
169static int get_vendor_table(void *cfg_tbl, unsigned int idx,
170 unsigned long *vendor_tbl_pa,
171 efi_guid_t *vendor_tbl_guid,
172 enum efi_type et)
173{
174 if (et == EFI_TYPE_64) {
175 efi_config_table_64_t *tbl_entry = (efi_config_table_64_t *)cfg_tbl + idx;
176
177 if (!IS_ENABLED(CONFIG_X86_64) && tbl_entry->table >> 32) {
178 debug_putstr("Error: EFI config table entry located above 4GB.\n");
179 return -EINVAL;
180 }
181
182 *vendor_tbl_pa = tbl_entry->table;
183 *vendor_tbl_guid = tbl_entry->guid;
184
185 } else if (et == EFI_TYPE_32) {
186 efi_config_table_32_t *tbl_entry = (efi_config_table_32_t *)cfg_tbl + idx;
187
188 *vendor_tbl_pa = tbl_entry->table;
189 *vendor_tbl_guid = tbl_entry->guid;
190 } else {
191 return -EINVAL;
192 }
193
194 return 0;
195}
196
197/**
198 * efi_find_vendor_table - Given EFI config table, search it for the physical
199 * address of the vendor table associated with GUID.
200 *
201 * @bp: pointer to boot_params
202 * @cfg_tbl_pa: pointer to EFI configuration table
203 * @cfg_tbl_len: number of entries in EFI configuration table
204 * @guid: GUID of vendor table
205 *
206 * Return: vendor table address on success. On error, return 0.
207 */
208unsigned long efi_find_vendor_table(struct boot_params *bp,
209 unsigned long cfg_tbl_pa,
210 unsigned int cfg_tbl_len,
211 efi_guid_t guid)
212{
213 enum efi_type et;
214 unsigned int i;
215
216 et = efi_get_type(bp);
217 if (et == EFI_TYPE_NONE)
218 return 0;
219
220 for (i = 0; i < cfg_tbl_len; i++) {
221 unsigned long vendor_tbl_pa;
222 efi_guid_t vendor_tbl_guid;
223 int ret;
224
225 ret = get_vendor_table(cfg_tbl: (void *)cfg_tbl_pa, idx: i,
226 vendor_tbl_pa: &vendor_tbl_pa,
227 vendor_tbl_guid: &vendor_tbl_guid, et);
228 if (ret)
229 return 0;
230
231 if (!efi_guidcmp(left: guid, right: vendor_tbl_guid))
232 return vendor_tbl_pa;
233 }
234
235 return 0;
236}
237

source code of linux/arch/x86/boot/compressed/efi.c