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