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         bool                     checked;
  94         long                     magic;
  95 };
  96
  97 enum {
  98         FS__SYSFS   = 0,
  99         FS__PROCFS  = 1,
 100         FS__DEBUGFS = 2,
 101         FS__TRACEFS = 3,
 102         FS__HUGETLBFS = 4,
 103         FS__BPF_FS = 5,
 104 };
 105
 106 #ifndef TRACEFS_MAGIC
 107 #define TRACEFS_MAGIC 0x74726163
 108 #endif
 109
 110 static struct fs fs__entries[] = {
 111         [FS__SYSFS] = {
 112                 .name   = "sysfs",
 113                 .mounts = sysfs__fs_known_mountpoints,
 114                 .magic  = SYSFS_MAGIC,
 115                 .checked = false,
 116         },
 117         [FS__PROCFS] = {
 118                 .name   = "proc",
 119                 .mounts = procfs__known_mountpoints,
 120                 .magic  = PROC_SUPER_MAGIC,
 121                 .checked = false,
 122         },
 123         [FS__DEBUGFS] = {
 124                 .name   = "debugfs",
 125                 .mounts = debugfs__known_mountpoints,
 126                 .magic  = DEBUGFS_MAGIC,
 127                 .checked = false,
 128         },
 129         [FS__TRACEFS] = {
 130                 .name   = "tracefs",
 131                 .mounts = tracefs__known_mountpoints,
 132                 .magic  = TRACEFS_MAGIC,
 133                 .checked = false,
 134         },
 135         [FS__HUGETLBFS] = {
 136                 .name   = "hugetlbfs",
 137                 .mounts = hugetlbfs__known_mountpoints,
 138                 .magic  = HUGETLBFS_MAGIC,
 139                 .checked = false,
 140         },
 141         [FS__BPF_FS] = {
 142                 .name   = "bpf",
 143                 .mounts = bpf_fs__known_mountpoints,
 144                 .magic  = BPF_FS_MAGIC,
 145                 .checked = false,
 146         },
 147 };
 148
 149 static bool fs__read_mounts(struct fs *fs)
 150 {
 151         bool found = false;
 152         char type[100];
 153         FILE *fp;
 154
 155         fp = fopen("/proc/mounts", "r");
 156         if (fp == NULL)
 157                 return NULL;
 158
 159         while (!found &&
 160                fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
 161                       fs->path, type) == 2) {
 162
 163                 if (strcmp(type, fs->name) == 0)
 164                         found = true;
 165         }
 166
 167         fclose(fp);
 168         fs->checked = true;
 169         return fs->found = found;
 170 }
 171
 172 static int fs__valid_mount(const char *fs, long magic)
 173 {
 174         struct statfs st_fs;
 175
 176         if (statfs(fs, &st_fs) < 0)
 177                 return -ENOENT;
 178         else if ((long)st_fs.f_type != magic)
 179                 return -ENOENT;
 180
 181         return 0;
 182 }
 183
 184 static bool fs__check_mounts(struct fs *fs)
 185 {
 186         const char * const *ptr;
 187
 188         ptr = fs->mounts;
 189         while (*ptr) {
 190                 if (fs__valid_mount(*ptr, fs->magic) == 0) {
 191                         fs->found = true;
 192                         strcpy(fs->path, *ptr);
 193                         return true;
 194                 }
 195                 ptr++;
 196         }
 197
 198         return false;
 199 }
 200
 201 static void mem_toupper(char *f, size_t len)
 202 {
 203         while (len) {
 204                 *f = toupper(*f);
 205                 f++;
 206                 len--;
 207         }
 208 }
 209
 210 /*
 211  * Check for "NAME_PATH" environment variable to override fs location (for
 212  * testing). This matches the recommendation in Documentation/sysfs-rules.txt
 213  * for SYSFS_PATH.
 214  */
 215 static bool fs__env_override(struct fs *fs)
 216 {
 217         char *override_path;
 218         size_t name_len = strlen(fs->name);
 219         /* name + "_PATH" + '\0' */
 220         char upper_name[name_len + 5 + 1];
 221
 222         memcpy(upper_name, fs->name, name_len);
 223         mem_toupper(upper_name, name_len);
 224         strcpy(&upper_name[name_len], "_PATH");
 225
 226         override_path = getenv(upper_name);
 227         if (!override_path)
 228                 return false;
 229
 230         fs->found = true;
 231         fs->checked = true;
 232         strncpy(fs->path, override_path, sizeof(fs->path) - 1);
 233         fs->path[sizeof(fs->path) - 1] = '\0';
 234         return true;
 235 }
 236
 237 static const char *fs__get_mountpoint(struct fs *fs)
 238 {
 239         if (fs__env_override(fs))
 240                 return fs->path;
 241
 242         if (fs__check_mounts(fs))
 243                 return fs->path;
 244
 245         if (fs__read_mounts(fs))
 246                 return fs->path;
 247
 248         return NULL;
 249 }
 250
 251 static const char *fs__mountpoint(int idx)
 252 {
 253         struct fs *fs = &fs__entries[idx];
 254
 255         if (fs->found)
 256                 return (const char *)fs->path;
 257
 258         /* the mount point was already checked for the mount point
 259          * but and did not exist, so return NULL to avoid scanning again.
 260          * This makes the found and not found paths cost equivalent
 261          * in case of multiple calls.
 262          */
 263         if (fs->checked)
 264                 return NULL;
 265
 266         return fs__get_mountpoint(fs);
 267 }
 268
 269 static const char *mount_overload(struct fs *fs)
 270 {
 271         size_t name_len = strlen(fs->name);
 272         /* "PERF_" + name + "_ENVIRONMENT" + '\0' */
 273         char upper_name[5 + name_len + 12 + 1];
 274
 275         snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
 276         mem_toupper(upper_name, name_len);
 277
 278         return getenv(upper_name) ?: *fs->mounts;
 279 }
 280
 281 static const char *fs__mount(int idx)
 282 {
 283         struct fs *fs = &fs__entries[idx];
 284         const char *mountpoint;
 285
 286         if (fs__mountpoint(idx))
 287                 return (const char *)fs->path;
 288
 289         mountpoint = mount_overload(fs);
 290
 291         if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
 292                 return NULL;
 293
 294         return fs__check_mounts(fs) ? fs->path : NULL;
 295 }
 296
 297 #define FS(name, idx)                           \
 298 const char *name##__mountpoint(void)            \
 299 {                                               \
 300         return fs__mountpoint(idx);             \
 301 }                                               \
 302                                                 \
 303 const char *name##__mount(void)                 \
 304 {                                               \
 305         return fs__mount(idx);                  \
 306 }                                               \
 307                                                 \
 308 bool name##__configured(void)                   \
 309 {                                               \
 310         return name##__mountpoint() != NULL;    \
 311 }
 312
 313 FS(sysfs,   FS__SYSFS);
 314 FS(procfs,  FS__PROCFS);
 315 FS(debugfs, FS__DEBUGFS);
 316 FS(tracefs, FS__TRACEFS);
 317 FS(hugetlbfs, FS__HUGETLBFS);
 318 FS(bpf_fs, FS__BPF_FS);
 319
 320 int filename__read_int(const char *filename, int *value)
 321 {
 322         char line[64];
 323         int fd = open(filename, O_RDONLY), err = -1;
 324
 325         if (fd < 0)
 326                 return -1;
 327
 328         if (read(fd, line, sizeof(line)) > 0) {
 329                 *value = atoi(line);
 330                 err = 0;
 331         }
 332
 333         close(fd);
 334         return err;
 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         char line[64];
 345         int fd = open(filename, O_RDONLY), err = -1;
 346
 347         if (fd < 0)
 348                 return -1;
 349
 350         if (read(fd, line, sizeof(line)) > 0) {
 351                 *value = strtoull(line, NULL, 0);
 352                 if (*value != ULLONG_MAX)
 353                         err = 0;
 354         }
 355
 356         close(fd);
 357         return err;
 358 }
 359
 360 #define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
 361
 362 int filename__read_str(const char *filename, char **buf, size_t *sizep)
 363 {
 364         size_t size = 0, alloc_size = 0;
 365         void *bf = NULL, *nbf;
 366         int fd, n, err = 0;
 367         char sbuf[STRERR_BUFSIZE];
 368
 369         fd = open(filename, O_RDONLY);
 370         if (fd < 0)
 371                 return -errno;
 372
 373         do {
 374                 if (size == alloc_size) {
 375                         alloc_size += BUFSIZ;
 376                         nbf = realloc(bf, alloc_size);
 377                         if (!nbf) {
 378                                 err = -ENOMEM;
 379                                 break;
 380                         }
 381
 382                         bf = nbf;
 383                 }
 384
 385                 n = read(fd, bf + size, alloc_size - size);
 386                 if (n < 0) {
 387                         if (size) {
 388                                 pr_warning("read failed %d: %s\n", errno,
 389                                          strerror_r(errno, sbuf, sizeof(sbuf)));
 390                                 err = 0;
 391                         } else
 392                                 err = -errno;
 393
 394                         break;
 395                 }
 396
 397                 size += n;
 398         } while (n > 0);
 399
 400         if (!err) {
 401                 *sizep = size;
 402                 *buf   = bf;
 403         } else
 404                 free(bf);
 405
 406         close(fd);
 407         return err;
 408 }
 409
 410 int filename__write_int(const char *filename, int value)
 411 {
 412         int fd = open(filename, O_WRONLY), err = -1;
 413         char buf[64];
 414
 415         if (fd < 0)
 416                 return err;
 417
 418         sprintf(buf, "%d", value);
 419         if (write(fd, buf, sizeof(buf)) == sizeof(buf))
 420                 err = 0;
 421
 422         close(fd);
 423         return err;
 424 }
 425
 426 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
 427 {
 428         char path[PATH_MAX];
 429         const char *procfs = procfs__mountpoint();
 430
 431         if (!procfs)
 432                 return -1;
 433
 434         snprintf(path, sizeof(path), "%s/%s", procfs, entry);
 435
 436         return filename__read_str(path, buf, sizep);
 437 }
 438
 439 int sysfs__read_ull(const char *entry, unsigned long long *value)
 440 {
 441         char path[PATH_MAX];
 442         const char *sysfs = sysfs__mountpoint();
 443
 444         if (!sysfs)
 445                 return -1;
 446
 447         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 448
 449         return filename__read_ull(path, value);
 450 }
 451
 452 int sysfs__read_int(const char *entry, int *value)
 453 {
 454         char path[PATH_MAX];
 455         const char *sysfs = sysfs__mountpoint();
 456
 457         if (!sysfs)
 458                 return -1;
 459
 460         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 461
 462         return filename__read_int(path, value);
 463 }
 464
 465 int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
 466 {
 467         char path[PATH_MAX];
 468         const char *sysfs = sysfs__mountpoint();
 469
 470         if (!sysfs)
 471                 return -1;
 472
 473         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 474
 475         return filename__read_str(path, buf, sizep);
 476 }
 477
 478 int sysfs__read_bool(const char *entry, bool *value)
 479 {
 480         char *buf;
 481         size_t size;
 482         int ret;
 483
 484         ret = sysfs__read_str(entry, &buf, &size);
 485         if (ret < 0)
 486                 return ret;
 487
 488         switch (buf[0]) {
 489         case '1':
 490         case 'y':
 491         case 'Y':
 492                 *value = true;
 493                 break;
 494         case '0':
 495         case 'n':
 496         case 'N':
 497                 *value = false;
 498                 break;
 499         default:
 500                 ret = -1;
 501         }
 502
 503         free(buf);
 504
 505         return ret;
 506 }
 507 int sysctl__read_int(const char *sysctl, int *value)
 508 {
 509         char path[PATH_MAX];
 510         const char *procfs = procfs__mountpoint();
 511
 512         if (!procfs)
 513                 return -1;
 514
 515         snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
 516
 517         return filename__read_int(path, value);
 518 }
 519
 520 int sysfs__write_int(const char *entry, int value)
 521 {
 522         char path[PATH_MAX];
 523         const char *sysfs = sysfs__mountpoint();
 524
 525         if (!sysfs)
 526                 return -1;
 527
 528         if (snprintf(path, sizeof(path), "%s/%s", sysfs, entry) >= PATH_MAX)
 529                 return -1;
 530
 531         return filename__write_int(path, value);
 532 }