tools/lib/api/fs/fs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <ctype.h>
   3 #include <errno.h>
   4 #include <limits.h>
   5 #include <stdbool.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <sys/vfs.h>
  10 #include <sys/types.h>
  11 #include <sys/stat.h>
  12 #include <fcntl.h>
  13 #include <unistd.h>
  14 #include <sys/mount.h>
  15
  16 #include "fs.h"
  17 #include "debug-internal.h"
  18
  19 #define _STR(x) #x
  20 #define STR(x) _STR(x)
  21
  22 #ifndef SYSFS_MAGIC
  23 #define SYSFS_MAGIC            0x62656572
  24 #endif
  25
  26 #ifndef PROC_SUPER_MAGIC
  27 #define PROC_SUPER_MAGIC       0x9fa0
  28 #endif
  29
  30 #ifndef DEBUGFS_MAGIC
  31 #define DEBUGFS_MAGIC          0x64626720
  32 #endif
  33
  34 #ifndef TRACEFS_MAGIC
  35 #define TRACEFS_MAGIC          0x74726163
  36 #endif
  37
  38 #ifndef HUGETLBFS_MAGIC
  39 #define HUGETLBFS_MAGIC        0x958458f6
  40 #endif
  41
  42 #ifndef BPF_FS_MAGIC
  43 #define BPF_FS_MAGIC           0xcafe4a11
  44 #endif
  45
  46 static const char * const sysfs__fs_known_mountpoints[] = {
  47         "/sys",
  48         0,
  49 };
  50
  51 static const char * const procfs__known_mountpoints[] = {
  52         "/proc",
  53         0,
  54 };
  55
  56 #ifndef DEBUGFS_DEFAULT_PATH
  57 #define DEBUGFS_DEFAULT_PATH "/sys/kernel/debug"
  58 #endif
  59
  60 static const char * const debugfs__known_mountpoints[] = {
  61         DEBUGFS_DEFAULT_PATH,
  62         "/debug",
  63         0,
  64 };
  65
  66
  67 #ifndef TRACEFS_DEFAULT_PATH
  68 #define TRACEFS_DEFAULT_PATH "/sys/kernel/tracing"
  69 #endif
  70
  71 static const char * const tracefs__known_mountpoints[] = {
  72         TRACEFS_DEFAULT_PATH,
  73         "/sys/kernel/debug/tracing",
  74         "/tracing",
  75         "/trace",
  76         0,
  77 };
  78
  79 static const char * const hugetlbfs__known_mountpoints[] = {
  80         0,
  81 };
  82
  83 static const char * const bpf_fs__known_mountpoints[] = {
  84         "/sys/fs/bpf",
  85         0,
  86 };
  87
  88 struct fs {
  89         const char              *name;
  90         const char * const      *mounts;
  91         char                     path[PATH_MAX];
  92         bool                     found;
  93         long                     magic;
  94 };
  95
  96 enum {
  97         FS__SYSFS   = 0,
  98         FS__PROCFS  = 1,
  99         FS__DEBUGFS = 2,
 100         FS__TRACEFS = 3,
 101         FS__HUGETLBFS = 4,
 102         FS__BPF_FS = 5,
 103 };
 104
 105 #ifndef TRACEFS_MAGIC
 106 #define TRACEFS_MAGIC 0x74726163
 107 #endif
 108
 109 static struct fs fs__entries[] = {
 110         [FS__SYSFS] = {
 111                 .name   = "sysfs",
 112                 .mounts = sysfs__fs_known_mountpoints,
 113                 .magic  = SYSFS_MAGIC,
 114         },
 115         [FS__PROCFS] = {
 116                 .name   = "proc",
 117                 .mounts = procfs__known_mountpoints,
 118                 .magic  = PROC_SUPER_MAGIC,
 119         },
 120         [FS__DEBUGFS] = {
 121                 .name   = "debugfs",
 122                 .mounts = debugfs__known_mountpoints,
 123                 .magic  = DEBUGFS_MAGIC,
 124         },
 125         [FS__TRACEFS] = {
 126                 .name   = "tracefs",
 127                 .mounts = tracefs__known_mountpoints,
 128                 .magic  = TRACEFS_MAGIC,
 129         },
 130         [FS__HUGETLBFS] = {
 131                 .name   = "hugetlbfs",
 132                 .mounts = hugetlbfs__known_mountpoints,
 133                 .magic  = HUGETLBFS_MAGIC,
 134         },
 135         [FS__BPF_FS] = {
 136                 .name   = "bpf",
 137                 .mounts = bpf_fs__known_mountpoints,
 138                 .magic  = BPF_FS_MAGIC,
 139         },
 140 };
 141
 142 static bool fs__read_mounts(struct fs *fs)
 143 {
 144         bool found = false;
 145         char type[100];
 146         FILE *fp;
 147
 148         fp = fopen("/proc/mounts", "r");
 149         if (fp == NULL)
 150                 return NULL;
 151
 152         while (!found &&
 153                fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
 154                       fs->path, type) == 2) {
 155
 156                 if (strcmp(type, fs->name) == 0)
 157                         found = true;
 158         }
 159
 160         fclose(fp);
 161         return fs->found = found;
 162 }
 163
 164 static int fs__valid_mount(const char *fs, long magic)
 165 {
 166         struct statfs st_fs;
 167
 168         if (statfs(fs, &st_fs) < 0)
 169                 return -ENOENT;
 170         else if ((long)st_fs.f_type != magic)
 171                 return -ENOENT;
 172
 173         return 0;
 174 }
 175
 176 static bool fs__check_mounts(struct fs *fs)
 177 {
 178         const char * const *ptr;
 179
 180         ptr = fs->mounts;
 181         while (*ptr) {
 182                 if (fs__valid_mount(*ptr, fs->magic) == 0) {
 183                         fs->found = true;
 184                         strcpy(fs->path, *ptr);
 185                         return true;
 186                 }
 187                 ptr++;
 188         }
 189
 190         return false;
 191 }
 192
 193 static void mem_toupper(char *f, size_t len)
 194 {
 195         while (len) {
 196                 *f = toupper(*f);
 197                 f++;
 198                 len--;
 199         }
 200 }
 201
 202 /*
 203  * Check for "NAME_PATH" environment variable to override fs location (for
 204  * testing). This matches the recommendation in Documentation/sysfs-rules.txt
 205  * for SYSFS_PATH.
 206  */
 207 static bool fs__env_override(struct fs *fs)
 208 {
 209         char *override_path;
 210         size_t name_len = strlen(fs->name);
 211         /* name + "_PATH" + '\0' */
 212         char upper_name[name_len + 5 + 1];
 213         memcpy(upper_name, fs->name, name_len);
 214         mem_toupper(upper_name, name_len);
 215         strcpy(&upper_name[name_len], "_PATH");
 216
 217         override_path = getenv(upper_name);
 218         if (!override_path)
 219                 return false;
 220
 221         fs->found = true;
 222         strncpy(fs->path, override_path, sizeof(fs->path));
 223         return true;
 224 }
 225
 226 static const char *fs__get_mountpoint(struct fs *fs)
 227 {
 228         if (fs__env_override(fs))
 229                 return fs->path;
 230
 231         if (fs__check_mounts(fs))
 232                 return fs->path;
 233
 234         if (fs__read_mounts(fs))
 235                 return fs->path;
 236
 237         return NULL;
 238 }
 239
 240 static const char *fs__mountpoint(int idx)
 241 {
 242         struct fs *fs = &fs__entries[idx];
 243
 244         if (fs->found)
 245                 return (const char *)fs->path;
 246
 247         return fs__get_mountpoint(fs);
 248 }
 249
 250 static const char *mount_overload(struct fs *fs)
 251 {
 252         size_t name_len = strlen(fs->name);
 253         /* "PERF_" + name + "_ENVIRONMENT" + '\0' */
 254         char upper_name[5 + name_len + 12 + 1];
 255
 256         snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
 257         mem_toupper(upper_name, name_len);
 258
 259         return getenv(upper_name) ?: *fs->mounts;
 260 }
 261
 262 static const char *fs__mount(int idx)
 263 {
 264         struct fs *fs = &fs__entries[idx];
 265         const char *mountpoint;
 266
 267         if (fs__mountpoint(idx))
 268                 return (const char *)fs->path;
 269
 270         mountpoint = mount_overload(fs);
 271
 272         if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
 273                 return NULL;
 274
 275         return fs__check_mounts(fs) ? fs->path : NULL;
 276 }
 277
 278 #define FS(name, idx)                           \
 279 const char *name##__mountpoint(void)            \
 280 {                                               \
 281         return fs__mountpoint(idx);             \
 282 }                                               \
 283                                                 \
 284 const char *name##__mount(void)                 \
 285 {                                               \
 286         return fs__mount(idx);                  \
 287 }                                               \
 288                                                 \
 289 bool name##__configured(void)                   \
 290 {                                               \
 291         return name##__mountpoint() != NULL;    \
 292 }
 293
 294 FS(sysfs,   FS__SYSFS);
 295 FS(procfs,  FS__PROCFS);
 296 FS(debugfs, FS__DEBUGFS);
 297 FS(tracefs, FS__TRACEFS);
 298 FS(hugetlbfs, FS__HUGETLBFS);
 299 FS(bpf_fs, FS__BPF_FS);
 300
 301 int filename__read_int(const char *filename, int *value)
 302 {
 303         char line[64];
 304         int fd = open(filename, O_RDONLY), err = -1;
 305
 306         if (fd < 0)
 307                 return -1;
 308
 309         if (read(fd, line, sizeof(line)) > 0) {
 310                 *value = atoi(line);
 311                 err = 0;
 312         }
 313
 314         close(fd);
 315         return err;
 316 }
 317
 318 /*
 319  * Parses @value out of @filename with strtoull.
 320  * By using 0 for base, the strtoull detects the
 321  * base automatically (see man strtoull).
 322  */
 323 int filename__read_ull(const char *filename, unsigned long long *value)
 324 {
 325         char line[64];
 326         int fd = open(filename, O_RDONLY), err = -1;
 327
 328         if (fd < 0)
 329                 return -1;
 330
 331         if (read(fd, line, sizeof(line)) > 0) {
 332                 *value = strtoull(line, NULL, 0);
 333                 if (*value != ULLONG_MAX)
 334                         err = 0;
 335         }
 336
 337         close(fd);
 338         return err;
 339 }
 340
 341 #define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
 342
 343 int filename__read_str(const char *filename, char **buf, size_t *sizep)
 344 {
 345         size_t size = 0, alloc_size = 0;
 346         void *bf = NULL, *nbf;
 347         int fd, n, err = 0;
 348         char sbuf[STRERR_BUFSIZE];
 349
 350         fd = open(filename, O_RDONLY);
 351         if (fd < 0)
 352                 return -errno;
 353
 354         do {
 355                 if (size == alloc_size) {
 356                         alloc_size += BUFSIZ;
 357                         nbf = realloc(bf, alloc_size);
 358                         if (!nbf) {
 359                                 err = -ENOMEM;
 360                                 break;
 361                         }
 362
 363                         bf = nbf;
 364                 }
 365
 366                 n = read(fd, bf + size, alloc_size - size);
 367                 if (n < 0) {
 368                         if (size) {
 369                                 pr_warning("read failed %d: %s\n", errno,
 370                                          strerror_r(errno, sbuf, sizeof(sbuf)));
 371                                 err = 0;
 372                         } else
 373                                 err = -errno;
 374
 375                         break;
 376                 }
 377
 378                 size += n;
 379         } while (n > 0);
 380
 381         if (!err) {
 382                 *sizep = size;
 383                 *buf   = bf;
 384         } else
 385                 free(bf);
 386
 387         close(fd);
 388         return err;
 389 }
 390
 391 int filename__write_int(const char *filename, int value)
 392 {
 393         int fd = open(filename, O_WRONLY), err = -1;
 394         char buf[64];
 395
 396         if (fd < 0)
 397                 return err;
 398
 399         sprintf(buf, "%d", value);
 400         if (write(fd, buf, sizeof(buf)) == sizeof(buf))
 401                 err = 0;
 402
 403         close(fd);
 404         return err;
 405 }
 406
 407 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
 408 {
 409         char path[PATH_MAX];
 410         const char *procfs = procfs__mountpoint();
 411
 412         if (!procfs)
 413                 return -1;
 414
 415         snprintf(path, sizeof(path), "%s/%s", procfs, entry);
 416
 417         return filename__read_str(path, buf, sizep);
 418 }
 419
 420 int sysfs__read_ull(const char *entry, unsigned long long *value)
 421 {
 422         char path[PATH_MAX];
 423         const char *sysfs = sysfs__mountpoint();
 424
 425         if (!sysfs)
 426                 return -1;
 427
 428         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 429
 430         return filename__read_ull(path, value);
 431 }
 432
 433 int sysfs__read_int(const char *entry, int *value)
 434 {
 435         char path[PATH_MAX];
 436         const char *sysfs = sysfs__mountpoint();
 437
 438         if (!sysfs)
 439                 return -1;
 440
 441         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 442
 443         return filename__read_int(path, value);
 444 }
 445
 446 int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
 447 {
 448         char path[PATH_MAX];
 449         const char *sysfs = sysfs__mountpoint();
 450
 451         if (!sysfs)
 452                 return -1;
 453
 454         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 455
 456         return filename__read_str(path, buf, sizep);
 457 }
 458
 459 int sysfs__read_bool(const char *entry, bool *value)
 460 {
 461         char *buf;
 462         size_t size;
 463         int ret;
 464
 465         ret = sysfs__read_str(entry, &buf, &size);
 466         if (ret < 0)
 467                 return ret;
 468
 469         switch (buf[0]) {
 470         case '1':
 471         case 'y':
 472         case 'Y':
 473                 *value = true;
 474                 break;
 475         case '0':
 476         case 'n':
 477         case 'N':
 478                 *value = false;
 479                 break;
 480         default:
 481                 ret = -1;
 482         }
 483
 484         free(buf);
 485
 486         return ret;
 487 }
 488 int sysctl__read_int(const char *sysctl, int *value)
 489 {
 490         char path[PATH_MAX];
 491         const char *procfs = procfs__mountpoint();
 492
 493         if (!procfs)
 494                 return -1;
 495
 496         snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
 497
 498         return filename__read_int(path, value);
 499 }
 500
 501 int sysfs__write_int(const char *entry, int value)
 502 {
 503         char path[PATH_MAX];
 504         const char *sysfs = sysfs__mountpoint();
 505
 506         if (!sysfs)
 507                 return -1;
 508
 509         if (snprintf(path, sizeof(path), "%s/%s", sysfs, entry) >= PATH_MAX)
 510                 return -1;
 511
 512         return filename__write_int(path, value);
 513 }