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