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 */
 17enum 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 */
 58unsigned 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 */
 85static 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 */
129int 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 */
167static 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 */
206unsigned 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}