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