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         memcpy(upper_name, fs->name, name_len);
 198         mem_toupper(upper_name, name_len);
 199         strcpy(&upper_name[name_len], "_PATH");
 200
 201         override_path = getenv(upper_name);
 202         if (!override_path)
 203                 return false;
 204
 205         fs->found = true;
 206         strncpy(fs->path, override_path, sizeof(fs->path));
 207         return true;
 208 }
 209
 210 static const char *fs__get_mountpoint(struct fs *fs)
 211 {
 212         if (fs__env_override(fs))
 213                 return fs->path;
 214
 215         if (fs__check_mounts(fs))
 216                 return fs->path;
 217
 218         if (fs__read_mounts(fs))
 219                 return fs->path;
 220
 221         return NULL;
 222 }
 223
 224 static const char *fs__mountpoint(int idx)
 225 {
 226         struct fs *fs = &fs__entries[idx];
 227
 228         if (fs->found)
 229                 return (const char *)fs->path;
 230
 231         return fs__get_mountpoint(fs);
 232 }
 233
 234 static const char *mount_overload(struct fs *fs)
 235 {
 236         size_t name_len = strlen(fs->name);
 237         /* "PERF_" + name + "_ENVIRONMENT" + '\0' */
 238         char upper_name[5 + name_len + 12 + 1];
 239
 240         snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
 241         mem_toupper(upper_name, name_len);
 242
 243         return getenv(upper_name) ?: *fs->mounts;
 244 }
 245
 246 static const char *fs__mount(int idx)
 247 {
 248         struct fs *fs = &fs__entries[idx];
 249         const char *mountpoint;
 250
 251         if (fs__mountpoint(idx))
 252                 return (const char *)fs->path;
 253
 254         mountpoint = mount_overload(fs);
 255
 256         if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
 257                 return NULL;
 258
 259         return fs__check_mounts(fs) ? fs->path : NULL;
 260 }
 261
 262 #define FS(name, idx)                           \
 263 const char *name##__mountpoint(void)            \
 264 {                                               \
 265         return fs__mountpoint(idx);             \
 266 }                                               \
 267                                                 \
 268 const char *name##__mount(void)                 \
 269 {                                               \
 270         return fs__mount(idx);                  \
 271 }                                               \
 272                                                 \
 273 bool name##__configured(void)                   \
 274 {                                               \
 275         return name##__mountpoint() != NULL;    \
 276 }
 277
 278 FS(sysfs,   FS__SYSFS);
 279 FS(procfs,  FS__PROCFS);
 280 FS(debugfs, FS__DEBUGFS);
 281 FS(tracefs, FS__TRACEFS);
 282 FS(hugetlbfs, FS__HUGETLBFS);
 283
 284 int filename__read_int(const char *filename, int *value)
 285 {
 286         char line[64];
 287         int fd = open(filename, O_RDONLY), err = -1;
 288
 289         if (fd < 0)
 290                 return -1;
 291
 292         if (read(fd, line, sizeof(line)) > 0) {
 293                 *value = atoi(line);
 294                 err = 0;
 295         }
 296
 297         close(fd);
 298         return err;
 299 }
 300
 301 /*
 302  * Parses @value out of @filename with strtoull.
 303  * By using 0 for base, the strtoull detects the
 304  * base automatically (see man strtoull).
 305  */
 306 int filename__read_ull(const char *filename, unsigned long long *value)
 307 {
 308         char line[64];
 309         int fd = open(filename, O_RDONLY), err = -1;
 310
 311         if (fd < 0)
 312                 return -1;
 313
 314         if (read(fd, line, sizeof(line)) > 0) {
 315                 *value = strtoull(line, NULL, 0);
 316                 if (*value != ULLONG_MAX)
 317                         err = 0;
 318         }
 319
 320         close(fd);
 321         return err;
 322 }
 323
 324 #define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
 325
 326 int filename__read_str(const char *filename, char **buf, size_t *sizep)
 327 {
 328         size_t size = 0, alloc_size = 0;
 329         void *bf = NULL, *nbf;
 330         int fd, n, err = 0;
 331         char sbuf[STRERR_BUFSIZE];
 332
 333         fd = open(filename, O_RDONLY);
 334         if (fd < 0)
 335                 return -errno;
 336
 337         do {
 338                 if (size == alloc_size) {
 339                         alloc_size += BUFSIZ;
 340                         nbf = realloc(bf, alloc_size);
 341                         if (!nbf) {
 342                                 err = -ENOMEM;
 343                                 break;
 344                         }
 345
 346                         bf = nbf;
 347                 }
 348
 349                 n = read(fd, bf + size, alloc_size - size);
 350                 if (n < 0) {
 351                         if (size) {
 352                                 pr_warning("read failed %d: %s\n", errno,
 353                                          strerror_r(errno, sbuf, sizeof(sbuf)));
 354                                 err = 0;
 355                         } else
 356                                 err = -errno;
 357
 358                         break;
 359                 }
 360
 361                 size += n;
 362         } while (n > 0);
 363
 364         if (!err) {
 365                 *sizep = size;
 366                 *buf   = bf;
 367         } else
 368                 free(bf);
 369
 370         close(fd);
 371         return err;
 372 }
 373
 374 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
 375 {
 376         char path[PATH_MAX];
 377         const char *procfs = procfs__mountpoint();
 378
 379         if (!procfs)
 380                 return -1;
 381
 382         snprintf(path, sizeof(path), "%s/%s", procfs, entry);
 383
 384         return filename__read_str(path, buf, sizep);
 385 }
 386
 387 int sysfs__read_ull(const char *entry, unsigned long long *value)
 388 {
 389         char path[PATH_MAX];
 390         const char *sysfs = sysfs__mountpoint();
 391
 392         if (!sysfs)
 393                 return -1;
 394
 395         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 396
 397         return filename__read_ull(path, value);
 398 }
 399
 400 int sysfs__read_int(const char *entry, int *value)
 401 {
 402         char path[PATH_MAX];
 403         const char *sysfs = sysfs__mountpoint();
 404
 405         if (!sysfs)
 406                 return -1;
 407
 408         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 409
 410         return filename__read_int(path, value);
 411 }
 412
 413 int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
 414 {
 415         char path[PATH_MAX];
 416         const char *sysfs = sysfs__mountpoint();
 417
 418         if (!sysfs)
 419                 return -1;
 420
 421         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 422
 423         return filename__read_str(path, buf, sizep);
 424 }
 425
 426 int sysctl__read_int(const char *sysctl, int *value)
 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/sys/%s", procfs, sysctl);
 435
 436         return filename__read_int(path, value);
 437 }