1 // SPDX-License-Identifier: GPL-2.0+
2
3 #include <linux/efi.h>
4 #include <linux/module.h>
5 #include <linux/pstore.h>
6 #include <linux/slab.h>
7 #include <linux/ucs2_string.h>
8
9 MODULE_IMPORT_NS(EFIVAR);
10
11 #define DUMP_NAME_LEN 66
12
13 static unsigned int record_size = 1024;
14 module_param(record_size, uint, 0444);
15 MODULE_PARM_DESC(record_size, "size of each pstore UEFI var (in bytes, min/default=1024)");
16
17 #define PSTORE_EFI_ATTRIBUTES \
18 (EFI_VARIABLE_NON_VOLATILE | \
19 EFI_VARIABLE_BOOTSERVICE_ACCESS | \
20 EFI_VARIABLE_RUNTIME_ACCESS)
21
22 static bool pstore_disable = IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);
23
24 static int efivars_pstore_init(void);
25 static void efivars_pstore_exit(void);
26
efi_pstore_disable_set(const char * val,const struct kernel_param * kp)27 static int efi_pstore_disable_set(const char *val, const struct kernel_param *kp)
28 {
29 int err;
30 bool old_pstore_disable = pstore_disable;
31
32 err = param_set_bool(val, kp);
33 if (err)
34 return err;
35
36 if (old_pstore_disable != pstore_disable) {
37 if (pstore_disable)
38 efivars_pstore_exit();
39 else
40 efivars_pstore_init();
41 }
42
43 return 0;
44 }
45
46 static const struct kernel_param_ops pstore_disable_ops = {
47 .set = efi_pstore_disable_set,
48 .get = param_get_bool,
49 };
50
51 module_param_cb(pstore_disable, &pstore_disable_ops, &pstore_disable, 0644);
52 __MODULE_PARM_TYPE(pstore_disable, "bool");
53
efi_pstore_open(struct pstore_info * psi)54 static int efi_pstore_open(struct pstore_info *psi)
55 {
56 int err;
57
58 err = efivar_lock();
59 if (err)
60 return err;
61
62 psi->data = kzalloc(record_size, GFP_KERNEL);
63 if (!psi->data)
64 return -ENOMEM;
65
66 return 0;
67 }
68
efi_pstore_close(struct pstore_info * psi)69 static int efi_pstore_close(struct pstore_info *psi)
70 {
71 efivar_unlock();
72 kfree(psi->data);
73 return 0;
74 }
75
generic_id(u64 timestamp,unsigned int part,int count)76 static inline u64 generic_id(u64 timestamp, unsigned int part, int count)
77 {
78 return (timestamp * 100 + part) * 1000 + count;
79 }
80
efi_pstore_read_func(struct pstore_record * record,efi_char16_t * varname)81 static int efi_pstore_read_func(struct pstore_record *record,
82 efi_char16_t *varname)
83 {
84 unsigned long wlen, size = record_size;
85 char name[DUMP_NAME_LEN], data_type;
86 efi_status_t status;
87 int cnt;
88 unsigned int part;
89 u64 time;
90
91 ucs2_as_utf8(name, varname, DUMP_NAME_LEN);
92
93 if (sscanf(name, "dump-type%u-%u-%d-%llu-%c",
94 &record->type, &part, &cnt, &time, &data_type) == 5) {
95 record->id = generic_id(time, part, cnt);
96 record->part = part;
97 record->count = cnt;
98 record->time.tv_sec = time;
99 record->time.tv_nsec = 0;
100 if (data_type == 'C')
101 record->compressed = true;
102 else
103 record->compressed = false;
104 record->ecc_notice_size = 0;
105 } else if (sscanf(name, "dump-type%u-%u-%d-%llu",
106 &record->type, &part, &cnt, &time) == 4) {
107 record->id = generic_id(time, part, cnt);
108 record->part = part;
109 record->count = cnt;
110 record->time.tv_sec = time;
111 record->time.tv_nsec = 0;
112 record->compressed = false;
113 record->ecc_notice_size = 0;
114 } else if (sscanf(name, "dump-type%u-%u-%llu",
115 &record->type, &part, &time) == 3) {
116 /*
117 * Check if an old format,
118 * which doesn't support holding
119 * multiple logs, remains.
120 */
121 record->id = generic_id(time, part, 0);
122 record->part = part;
123 record->count = 0;
124 record->time.tv_sec = time;
125 record->time.tv_nsec = 0;
126 record->compressed = false;
127 record->ecc_notice_size = 0;
128 } else
129 return 0;
130
131 record->buf = kmalloc(size, GFP_KERNEL);
132 if (!record->buf)
133 return -ENOMEM;
134
135 status = efivar_get_variable(varname, &LINUX_EFI_CRASH_GUID, NULL,
136 &size, record->buf);
137 if (status != EFI_SUCCESS) {
138 kfree(record->buf);
139 return efi_status_to_err(status);
140 }
141
142 /*
143 * Store the name of the variable in the pstore_record priv field, so
144 * we can reuse it later if we need to delete the EFI variable from the
145 * variable store.
146 */
147 wlen = (ucs2_strnlen(varname, DUMP_NAME_LEN) + 1) * sizeof(efi_char16_t);
148 record->priv = kmemdup(varname, wlen, GFP_KERNEL);
149 if (!record->priv) {
150 kfree(record->buf);
151 return -ENOMEM;
152 }
153
154 return size;
155 }
156
efi_pstore_read(struct pstore_record * record)157 static ssize_t efi_pstore_read(struct pstore_record *record)
158 {
159 efi_char16_t *varname = record->psi->data;
160 efi_guid_t guid = LINUX_EFI_CRASH_GUID;
161 unsigned long varname_size;
162 efi_status_t status;
163
164 for (;;) {
165 /*
166 * A small set of old UEFI implementations reject sizes
167 * above a certain threshold, the lowest seen in the wild
168 * is 512.
169 *
170 * TODO: Commonize with the iteration implementation in
171 * fs/efivarfs to keep all the quirks in one place.
172 */
173 varname_size = 512;
174
175 /*
176 * If this is the first read() call in the pstore enumeration,
177 * varname will be the empty string, and the GetNextVariable()
178 * runtime service call will return the first EFI variable in
179 * its own enumeration order, ignoring the guid argument.
180 *
181 * Subsequent calls to GetNextVariable() must pass the name and
182 * guid values returned by the previous call, which is why we
183 * store varname in record->psi->data. Given that we only
184 * enumerate variables with the efi-pstore GUID, there is no
185 * need to record the guid return value.
186 */
187 status = efivar_get_next_variable(&varname_size, varname, &guid);
188 if (status == EFI_NOT_FOUND)
189 return 0;
190
191 if (status != EFI_SUCCESS)
192 return efi_status_to_err(status);
193
194 /* skip variables that don't concern us */
195 if (efi_guidcmp(guid, LINUX_EFI_CRASH_GUID))
196 continue;
197
198 return efi_pstore_read_func(record, varname);
199 }
200 }
201
efi_pstore_write(struct pstore_record * record)202 static int efi_pstore_write(struct pstore_record *record)
203 {
204 char name[DUMP_NAME_LEN];
205 efi_char16_t efi_name[DUMP_NAME_LEN];
206 efi_status_t status;
207 int i;
208
209 record->id = generic_id(record->time.tv_sec, record->part,
210 record->count);
211
212 /* Since we copy the entire length of name, make sure it is wiped. */
213 memset(name, 0, sizeof(name));
214
215 snprintf(name, sizeof(name), "dump-type%u-%u-%d-%lld-%c",
216 record->type, record->part, record->count,
217 (long long)record->time.tv_sec,
218 record->compressed ? 'C' : 'D');
219
220 for (i = 0; i < DUMP_NAME_LEN; i++)
221 efi_name[i] = name[i];
222
223 if (efivar_trylock())
224 return -EBUSY;
225 status = efivar_set_variable_locked(efi_name, &LINUX_EFI_CRASH_GUID,
226 PSTORE_EFI_ATTRIBUTES,
227 record->size, record->psi->buf,
228 true);
229 efivar_unlock();
230 return efi_status_to_err(status);
231 };
232
efi_pstore_erase(struct pstore_record * record)233 static int efi_pstore_erase(struct pstore_record *record)
234 {
235 efi_status_t status;
236
237 status = efivar_set_variable(record->priv, &LINUX_EFI_CRASH_GUID,
238 PSTORE_EFI_ATTRIBUTES, 0, NULL);
239
240 if (status != EFI_SUCCESS && status != EFI_NOT_FOUND)
241 return efi_status_to_err(status);
242 return 0;
243 }
244
245 static struct pstore_info efi_pstore_info = {
246 .owner = THIS_MODULE,
247 .name = KBUILD_MODNAME,
248 .flags = PSTORE_FLAGS_DMESG,
249 .open = efi_pstore_open,
250 .close = efi_pstore_close,
251 .read = efi_pstore_read,
252 .write = efi_pstore_write,
253 .erase = efi_pstore_erase,
254 };
255
efivars_pstore_init(void)256 static int efivars_pstore_init(void)
257 {
258 if (!efivar_supports_writes())
259 return 0;
260
261 if (pstore_disable)
262 return 0;
263
264 /*
265 * Notice that 1024 is the minimum here to prevent issues with
266 * decompression algorithms that were spotted during tests;
267 * even in the case of not using compression, smaller values would
268 * just pollute more the pstore FS with many small collected files.
269 */
270 if (record_size < 1024)
271 record_size = 1024;
272
273 efi_pstore_info.buf = kmalloc(record_size, GFP_KERNEL);
274 if (!efi_pstore_info.buf)
275 return -ENOMEM;
276
277 efi_pstore_info.bufsize = record_size;
278
279 if (pstore_register(&efi_pstore_info)) {
280 kfree(efi_pstore_info.buf);
281 efi_pstore_info.buf = NULL;
282 efi_pstore_info.bufsize = 0;
283 }
284
285 return 0;
286 }
287
efivars_pstore_exit(void)288 static void efivars_pstore_exit(void)
289 {
290 if (!efi_pstore_info.bufsize)
291 return;
292
293 pstore_unregister(&efi_pstore_info);
294 kfree(efi_pstore_info.buf);
295 efi_pstore_info.buf = NULL;
296 efi_pstore_info.bufsize = 0;
297 }
298
299 module_init(efivars_pstore_init);
300 module_exit(efivars_pstore_exit);
301
302 MODULE_DESCRIPTION("EFI variable backend for pstore");
303 MODULE_LICENSE("GPL");
304 MODULE_ALIAS("platform:efivars");
305