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((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}