tools/lib/api/fs/fs.c

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