drivers/firmware/efi/efi-pstore.c

   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
  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
  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
  69 static int efi_pstore_close(struct pstore_info *psi)
  70 {
  71         efivar_unlock();
  72         kfree(psi->data);
  73         return 0;
  74 }
  75
  76 static inline u64 generic_id(u64 timestamp, unsigned int part, int count)
  77 {
  78         return (timestamp * 100 + part) * 1000 + count;
  79 }
  80
  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
 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
 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
 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
 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
 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");