xref: /linux/arch/x86/boot/compressed/efi.c (revision 103bf75f)
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  */
efi_get_type(struct boot_params * bp)19 enum 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  */
efi_get_system_table(struct boot_params * bp)60 unsigned 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  */
get_kexec_setup_data(struct boot_params * bp,enum efi_type et)87 static 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  */
efi_get_conf_table(struct boot_params * bp,unsigned long * cfg_tbl_pa,unsigned int * cfg_tbl_len)131 int 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 */
get_vendor_table(void * cfg_tbl,unsigned int idx,unsigned long * vendor_tbl_pa,efi_guid_t * vendor_tbl_guid,enum efi_type et)169 static 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  */
efi_find_vendor_table(struct boot_params * bp,unsigned long cfg_tbl_pa,unsigned int cfg_tbl_len,efi_guid_t guid)208 unsigned 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((void *)cfg_tbl_pa, i,
226 				       &vendor_tbl_pa,
227 				       &vendor_tbl_guid, et);
228 		if (ret)
229 			return 0;
230 
231 		if (!efi_guidcmp(guid, vendor_tbl_guid))
232 			return vendor_tbl_pa;
233 	}
234 
235 	return 0;
236 }
237