tools/lib/api/fs/fs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <assert.h>
   3 #include <ctype.h>
   4 #include <errno.h>
   5 #include <limits.h>
   6 #include <stdbool.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <sys/vfs.h>
  11 #include <sys/types.h>
  12 #include <sys/stat.h>
  13 #include <fcntl.h>
  14 #include <pthread.h>
  15 #include <unistd.h>
  16 #include <sys/mount.h>
  17
  18 #include "fs.h"
  19 #include "debug-internal.h"
  20
  21 #define _STR(x) #x
  22 #define STR(x) _STR(x)
  23
  24 #ifndef SYSFS_MAGIC
  25 #define SYSFS_MAGIC            0x62656572
  26 #endif
  27
  28 #ifndef PROC_SUPER_MAGIC
  29 #define PROC_SUPER_MAGIC       0x9fa0
  30 #endif
  31
  32 #ifndef DEBUGFS_MAGIC
  33 #define DEBUGFS_MAGIC          0x64626720
  34 #endif
  35
  36 #ifndef TRACEFS_MAGIC
  37 #define TRACEFS_MAGIC          0x74726163
  38 #endif
  39
  40 #ifndef HUGETLBFS_MAGIC
  41 #define HUGETLBFS_MAGIC        0x958458f6
  42 #endif
  43
  44 #ifndef BPF_FS_MAGIC
  45 #define BPF_FS_MAGIC           0xcafe4a11
  46 #endif
  47
  48 static const char * const sysfs__known_mountpoints[] = {
  49         "/sys",
  50         0,
  51 };
  52
  53 static const char * const procfs__known_mountpoints[] = {
  54         "/proc",
  55         0,
  56 };
  57
  58 #ifndef DEBUGFS_DEFAULT_PATH
  59 #define DEBUGFS_DEFAULT_PATH "/sys/kernel/debug"
  60 #endif
  61
  62 static const char * const debugfs__known_mountpoints[] = {
  63         DEBUGFS_DEFAULT_PATH,
  64         "/debug",
  65         0,
  66 };
  67
  68
  69 #ifndef TRACEFS_DEFAULT_PATH
  70 #define TRACEFS_DEFAULT_PATH "/sys/kernel/tracing"
  71 #endif
  72
  73 static const char * const tracefs__known_mountpoints[] = {
  74         TRACEFS_DEFAULT_PATH,
  75         "/sys/kernel/debug/tracing",
  76         "/tracing",
  77         "/trace",
  78         0,
  79 };
  80
  81 static const char * const hugetlbfs__known_mountpoints[] = {
  82         0,
  83 };
  84
  85 static const char * const bpf_fs__known_mountpoints[] = {
  86         "/sys/fs/bpf",
  87         0,
  88 };
  89
  90 struct fs {
  91         const char *             const name;
  92         const char * const *     const mounts;
  93         char                    *path;
  94         pthread_mutex_t          mount_mutex;
  95         const long               magic;
  96 };
  97
  98 #ifndef TRACEFS_MAGIC
  99 #define TRACEFS_MAGIC 0x74726163
 100 #endif
 101
 102 static void fs__init_once(struct fs *fs);
 103 static const char *fs__mountpoint(const struct fs *fs);
 104 static const char *fs__mount(struct fs *fs);
 105
 106 #define FS(lower_name, fs_name, upper_name)             \
 107 static struct fs fs__##lower_name = {                   \
 108         .name = #fs_name,                               \
 109         .mounts = lower_name##__known_mountpoints,      \
 110         .magic = upper_name##_MAGIC,                    \
 111         .mount_mutex = PTHREAD_MUTEX_INITIALIZER,       \
 112 };                                                      \
 113                                                         \
 114 static void lower_name##_init_once(void)                \
 115 {                                                       \
 116         struct fs *fs = &fs__##lower_name;              \
 117                                                         \
 118         fs__init_once(fs);                              \
 119 }                                                       \
 120                                                         \
 121 const char *lower_name##__mountpoint(void)              \
 122 {                                                       \
 123         static pthread_once_t init_once = PTHREAD_ONCE_INIT;    \
 124         struct fs *fs = &fs__##lower_name;              \
 125                                                         \
 126         pthread_once(&init_once, lower_name##_init_once);       \
 127         return fs__mountpoint(fs);                      \
 128 }                                                       \
 129                                                         \
 130 const char *lower_name##__mount(void)                   \
 131 {                                                       \
 132         const char *mountpoint = lower_name##__mountpoint();    \
 133         struct fs *fs = &fs__##lower_name;              \
 134                                                         \
 135         if (mountpoint)                                 \
 136                 return mountpoint;                      \
 137                                                         \
 138         return fs__mount(fs);                           \
 139 }                                                       \
 140                                                         \
 141 bool lower_name##__configured(void)                     \
 142 {                                                       \
 143         return lower_name##__mountpoint() != NULL;      \
 144 }
 145
 146 FS(sysfs, sysfs, SYSFS);
 147 FS(procfs, procfs, PROC_SUPER);
 148 FS(debugfs, debugfs, DEBUGFS);
 149 FS(tracefs, tracefs, TRACEFS);
 150 FS(hugetlbfs, hugetlbfs, HUGETLBFS);
 151 FS(bpf_fs, bpf, BPF_FS);
 152
 153 static bool fs__read_mounts(struct fs *fs)
 154 {
 155         char type[100];
 156         FILE *fp;
 157         char path[PATH_MAX + 1];
 158
 159         fp = fopen("/proc/mounts", "r");
 160         if (fp == NULL)
 161                 return false;
 162
 163         while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
 164                       path, type) == 2) {
 165
 166                 if (strcmp(type, fs->name) == 0) {
 167                         fs->path = strdup(path);
 168                         fclose(fp);
 169                         return fs->path != NULL;
 170                 }
 171         }
 172         fclose(fp);
 173         return false;
 174 }
 175
 176 static int fs__valid_mount(const char *fs, long magic)
 177 {
 178         struct statfs st_fs;
 179
 180         if (statfs(fs, &st_fs) < 0)
 181                 return -ENOENT;
 182         else if ((long)st_fs.f_type != magic)
 183                 return -ENOENT;
 184
 185         return 0;
 186 }
 187
 188 static bool fs__check_mounts(struct fs *fs)
 189 {
 190         const char * const *ptr;
 191
 192         ptr = fs->mounts;
 193         while (*ptr) {
 194                 if (fs__valid_mount(*ptr, fs->magic) == 0) {
 195                         fs->path = strdup(*ptr);
 196                         if (!fs->path)
 197                                 return false;
 198                         return true;
 199                 }
 200                 ptr++;
 201         }
 202
 203         return false;
 204 }
 205
 206 static void mem_toupper(char *f, size_t len)
 207 {
 208         while (len) {
 209                 *f = toupper(*f);
 210                 f++;
 211                 len--;
 212         }
 213 }
 214
 215 /*
 216  * Check for "NAME_PATH" environment variable to override fs location (for
 217  * testing). This matches the recommendation in Documentation/admin-guide/sysfs-rules.rst
 218  * for SYSFS_PATH.
 219  */
 220 static bool fs__env_override(struct fs *fs)
 221 {
 222         char *override_path;
 223         size_t name_len = strlen(fs->name);
 224         /* name + "_PATH" + '\0' */
 225         char upper_name[name_len + 5 + 1];
 226
 227         memcpy(upper_name, fs->name, name_len);
 228         mem_toupper(upper_name, name_len);
 229         strcpy(&upper_name[name_len], "_PATH");
 230
 231         override_path = getenv(upper_name);
 232         if (!override_path)
 233                 return false;
 234
 235         fs->path = strdup(override_path);
 236         if (!fs->path)
 237                 return false;
 238         return true;
 239 }
 240
 241 static void fs__init_once(struct fs *fs)
 242 {
 243         if (!fs__env_override(fs) &&
 244             !fs__check_mounts(fs) &&
 245             !fs__read_mounts(fs)) {
 246                 assert(!fs->path);
 247         } else {
 248                 assert(fs->path);
 249         }
 250 }
 251
 252 static const char *fs__mountpoint(const struct fs *fs)
 253 {
 254         return fs->path;
 255 }
 256
 257 static const char *mount_overload(struct fs *fs)
 258 {
 259         size_t name_len = strlen(fs->name);
 260         /* "PERF_" + name + "_ENVIRONMENT" + '\0' */
 261         char upper_name[5 + name_len + 12 + 1];
 262
 263         snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
 264         mem_toupper(upper_name, name_len);
 265
 266         return getenv(upper_name) ?: *fs->mounts;
 267 }
 268
 269 static const char *fs__mount(struct fs *fs)
 270 {
 271         const char *mountpoint;
 272
 273         pthread_mutex_lock(&fs->mount_mutex);
 274
 275         /* Check if path found inside the mutex to avoid races with other callers of mount. */
 276         mountpoint = fs__mountpoint(fs);
 277         if (mountpoint)
 278                 goto out;
 279
 280         mountpoint = mount_overload(fs);
 281
 282         if (mount(NULL, mountpoint, fs->name, 0, NULL) == 0 &&
 283             fs__valid_mount(mountpoint, fs->magic) == 0) {
 284                 fs->path = strdup(mountpoint);
 285                 mountpoint = fs->path;
 286         }
 287 out:
 288         pthread_mutex_unlock(&fs->mount_mutex);
 289         return mountpoint;
 290 }
 291
 292 int filename__read_int(const char *filename, int *value)
 293 {
 294         char line[64];
 295         int fd = open(filename, O_RDONLY), err = -1;
 296
 297         if (fd < 0)
 298                 return -1;
 299
 300         if (read(fd, line, sizeof(line)) > 0) {
 301                 *value = atoi(line);
 302                 err = 0;
 303         }
 304
 305         close(fd);
 306         return err;
 307 }
 308
 309 static int filename__read_ull_base(const char *filename,
 310                                    unsigned long long *value, int base)
 311 {
 312         char line[64];
 313         int fd = open(filename, O_RDONLY), err = -1;
 314
 315         if (fd < 0)
 316                 return -1;
 317
 318         if (read(fd, line, sizeof(line)) > 0) {
 319                 *value = strtoull(line, NULL, base);
 320                 if (*value != ULLONG_MAX)
 321                         err = 0;
 322         }
 323
 324         close(fd);
 325         return err;
 326 }
 327
 328 /*
 329  * Parses @value out of @filename with strtoull.
 330  * By using 16 for base to treat the number as hex.
 331  */
 332 int filename__read_xll(const char *filename, unsigned long long *value)
 333 {
 334         return filename__read_ull_base(filename, value, 16);
 335 }
 336
 337 /*
 338  * Parses @value out of @filename with strtoull.
 339  * By using 0 for base, the strtoull detects the
 340  * base automatically (see man strtoull).
 341  */
 342 int filename__read_ull(const char *filename, unsigned long long *value)
 343 {
 344         return filename__read_ull_base(filename, value, 0);
 345 }
 346
 347 #define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
 348
 349 int filename__read_str(const char *filename, char **buf, size_t *sizep)
 350 {
 351         size_t size = 0, alloc_size = 0;
 352         void *bf = NULL, *nbf;
 353         int fd, n, err = 0;
 354         char sbuf[STRERR_BUFSIZE];
 355
 356         fd = open(filename, O_RDONLY);
 357         if (fd < 0)
 358                 return -errno;
 359
 360         do {
 361                 if (size == alloc_size) {
 362                         alloc_size += BUFSIZ;
 363                         nbf = realloc(bf, alloc_size);
 364                         if (!nbf) {
 365                                 err = -ENOMEM;
 366                                 break;
 367                         }
 368
 369                         bf = nbf;
 370                 }
 371
 372                 n = read(fd, bf + size, alloc_size - size);
 373                 if (n < 0) {
 374                         if (size) {
 375                                 pr_warn("read failed %d: %s\n", errno,
 376                                         strerror_r(errno, sbuf, sizeof(sbuf)));
 377                                 err = 0;
 378                         } else
 379                                 err = -errno;
 380
 381                         break;
 382                 }
 383
 384                 size += n;
 385         } while (n > 0);
 386
 387         if (!err) {
 388                 *sizep = size;
 389                 *buf   = bf;
 390         } else
 391                 free(bf);
 392
 393         close(fd);
 394         return err;
 395 }
 396
 397 int filename__write_int(const char *filename, int value)
 398 {
 399         int fd = open(filename, O_WRONLY), err = -1;
 400         char buf[64];
 401
 402         if (fd < 0)
 403                 return err;
 404
 405         sprintf(buf, "%d", value);
 406         if (write(fd, buf, sizeof(buf)) == sizeof(buf))
 407                 err = 0;
 408
 409         close(fd);
 410         return err;
 411 }
 412
 413 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
 414 {
 415         char path[PATH_MAX];
 416         const char *procfs = procfs__mountpoint();
 417
 418         if (!procfs)
 419                 return -1;
 420
 421         snprintf(path, sizeof(path), "%s/%s", procfs, entry);
 422
 423         return filename__read_str(path, buf, sizep);
 424 }
 425
 426 static int sysfs__read_ull_base(const char *entry,
 427                                 unsigned long long *value, int base)
 428 {
 429         char path[PATH_MAX];
 430         const char *sysfs = sysfs__mountpoint();
 431
 432         if (!sysfs)
 433                 return -1;
 434
 435         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 436
 437         return filename__read_ull_base(path, value, base);
 438 }
 439
 440 int sysfs__read_xll(const char *entry, unsigned long long *value)
 441 {
 442         return sysfs__read_ull_base(entry, value, 16);
 443 }
 444
 445 int sysfs__read_ull(const char *entry, unsigned long long *value)
 446 {
 447         return sysfs__read_ull_base(entry, value, 0);
 448 }
 449
 450 int sysfs__read_int(const char *entry, int *value)
 451 {
 452         char path[PATH_MAX];
 453         const char *sysfs = sysfs__mountpoint();
 454
 455         if (!sysfs)
 456                 return -1;
 457
 458         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 459
 460         return filename__read_int(path, value);
 461 }
 462
 463 int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
 464 {
 465         char path[PATH_MAX];
 466         const char *sysfs = sysfs__mountpoint();
 467
 468         if (!sysfs)
 469                 return -1;
 470
 471         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 472
 473         return filename__read_str(path, buf, sizep);
 474 }
 475
 476 int sysfs__read_bool(const char *entry, bool *value)
 477 {
 478         char *buf;
 479         size_t size;
 480         int ret;
 481
 482         ret = sysfs__read_str(entry, &buf, &size);
 483         if (ret < 0)
 484                 return ret;
 485
 486         switch (buf[0]) {
 487         case '1':
 488         case 'y':
 489         case 'Y':
 490                 *value = true;
 491                 break;
 492         case '0':
 493         case 'n':
 494         case 'N':
 495                 *value = false;
 496                 break;
 497         default:
 498                 ret = -1;
 499         }
 500
 501         free(buf);
 502
 503         return ret;
 504 }
 505 int sysctl__read_int(const char *sysctl, int *value)
 506 {
 507         char path[PATH_MAX];
 508         const char *procfs = procfs__mountpoint();
 509
 510         if (!procfs)
 511                 return -1;
 512
 513         snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
 514
 515         return filename__read_int(path, value);
 516 }
 517
 518 int sysfs__write_int(const char *entry, int value)
 519 {
 520         char path[PATH_MAX];
 521         const char *sysfs = sysfs__mountpoint();
 522
 523         if (!sysfs)
 524                 return -1;
 525
 526         if (snprintf(path, sizeof(path), "%s/%s", sysfs, entry) >= PATH_MAX)
 527                 return -1;
 528
 529         return filename__write_int(path, value);
 530 }