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
  17 #define _STR(x) #x
  18 #define STR(x) _STR(x)
  19
  20 #ifndef SYSFS_MAGIC
  21 #define SYSFS_MAGIC            0x62656572
  22 #endif
  23
  24 #ifndef PROC_SUPER_MAGIC
  25 #define PROC_SUPER_MAGIC       0x9fa0
  26 #endif
  27
  28 #ifndef DEBUGFS_MAGIC
  29 #define DEBUGFS_MAGIC          0x64626720
  30 #endif
  31
  32 #ifndef TRACEFS_MAGIC
  33 #define TRACEFS_MAGIC          0x74726163
  34 #endif
  35
  36 static const char * const sysfs__fs_known_mountpoints[] = {
  37         "/sys",
  38         0,
  39 };
  40
  41 static const char * const procfs__known_mountpoints[] = {
  42         "/proc",
  43         0,
  44 };
  45
  46 #ifndef DEBUGFS_DEFAULT_PATH
  47 #define DEBUGFS_DEFAULT_PATH "/sys/kernel/debug"
  48 #endif
  49
  50 static const char * const debugfs__known_mountpoints[] = {
  51         DEBUGFS_DEFAULT_PATH,
  52         "/debug",
  53         0,
  54 };
  55
  56
  57 #ifndef TRACEFS_DEFAULT_PATH
  58 #define TRACEFS_DEFAULT_PATH "/sys/kernel/tracing"
  59 #endif
  60
  61 static const char * const tracefs__known_mountpoints[] = {
  62         TRACEFS_DEFAULT_PATH,
  63         "/sys/kernel/debug/tracing",
  64         "/tracing",
  65         "/trace",
  66         0,
  67 };
  68
  69 struct fs {
  70         const char              *name;
  71         const char * const      *mounts;
  72         char                     path[PATH_MAX];
  73         bool                     found;
  74         long                     magic;
  75 };
  76
  77 enum {
  78         FS__SYSFS   = 0,
  79         FS__PROCFS  = 1,
  80         FS__DEBUGFS = 2,
  81         FS__TRACEFS = 3,
  82 };
  83
  84 #ifndef TRACEFS_MAGIC
  85 #define TRACEFS_MAGIC 0x74726163
  86 #endif
  87
  88 static struct fs fs__entries[] = {
  89         [FS__SYSFS] = {
  90                 .name   = "sysfs",
  91                 .mounts = sysfs__fs_known_mountpoints,
  92                 .magic  = SYSFS_MAGIC,
  93         },
  94         [FS__PROCFS] = {
  95                 .name   = "proc",
  96                 .mounts = procfs__known_mountpoints,
  97                 .magic  = PROC_SUPER_MAGIC,
  98         },
  99         [FS__DEBUGFS] = {
 100                 .name   = "debugfs",
 101                 .mounts = debugfs__known_mountpoints,
 102                 .magic  = DEBUGFS_MAGIC,
 103         },
 104         [FS__TRACEFS] = {
 105                 .name   = "tracefs",
 106                 .mounts = tracefs__known_mountpoints,
 107                 .magic  = TRACEFS_MAGIC,
 108         },
 109 };
 110
 111 static bool fs__read_mounts(struct fs *fs)
 112 {
 113         bool found = false;
 114         char type[100];
 115         FILE *fp;
 116
 117         fp = fopen("/proc/mounts", "r");
 118         if (fp == NULL)
 119                 return NULL;
 120
 121         while (!found &&
 122                fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
 123                       fs->path, type) == 2) {
 124
 125                 if (strcmp(type, fs->name) == 0)
 126                         found = true;
 127         }
 128
 129         fclose(fp);
 130         return fs->found = found;
 131 }
 132
 133 static int fs__valid_mount(const char *fs, long magic)
 134 {
 135         struct statfs st_fs;
 136
 137         if (statfs(fs, &st_fs) < 0)
 138                 return -ENOENT;
 139         else if ((long)st_fs.f_type != magic)
 140                 return -ENOENT;
 141
 142         return 0;
 143 }
 144
 145 static bool fs__check_mounts(struct fs *fs)
 146 {
 147         const char * const *ptr;
 148
 149         ptr = fs->mounts;
 150         while (*ptr) {
 151                 if (fs__valid_mount(*ptr, fs->magic) == 0) {
 152                         fs->found = true;
 153                         strcpy(fs->path, *ptr);
 154                         return true;
 155                 }
 156                 ptr++;
 157         }
 158
 159         return false;
 160 }
 161
 162 static void mem_toupper(char *f, size_t len)
 163 {
 164         while (len) {
 165                 *f = toupper(*f);
 166                 f++;
 167                 len--;
 168         }
 169 }
 170
 171 /*
 172  * Check for "NAME_PATH" environment variable to override fs location (for
 173  * testing). This matches the recommendation in Documentation/sysfs-rules.txt
 174  * for SYSFS_PATH.
 175  */
 176 static bool fs__env_override(struct fs *fs)
 177 {
 178         char *override_path;
 179         size_t name_len = strlen(fs->name);
 180         /* name + "_PATH" + '\0' */
 181         char upper_name[name_len + 5 + 1];
 182         memcpy(upper_name, fs->name, name_len);
 183         mem_toupper(upper_name, name_len);
 184         strcpy(&upper_name[name_len], "_PATH");
 185
 186         override_path = getenv(upper_name);
 187         if (!override_path)
 188                 return false;
 189
 190         fs->found = true;
 191         strncpy(fs->path, override_path, sizeof(fs->path));
 192         return true;
 193 }
 194
 195 static const char *fs__get_mountpoint(struct fs *fs)
 196 {
 197         if (fs__env_override(fs))
 198                 return fs->path;
 199
 200         if (fs__check_mounts(fs))
 201                 return fs->path;
 202
 203         if (fs__read_mounts(fs))
 204                 return fs->path;
 205
 206         return NULL;
 207 }
 208
 209 static const char *fs__mountpoint(int idx)
 210 {
 211         struct fs *fs = &fs__entries[idx];
 212
 213         if (fs->found)
 214                 return (const char *)fs->path;
 215
 216         return fs__get_mountpoint(fs);
 217 }
 218
 219 static const char *mount_overload(struct fs *fs)
 220 {
 221         size_t name_len = strlen(fs->name);
 222         /* "PERF_" + name + "_ENVIRONMENT" + '\0' */
 223         char upper_name[5 + name_len + 12 + 1];
 224
 225         snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
 226         mem_toupper(upper_name, name_len);
 227
 228         return getenv(upper_name) ?: *fs->mounts;
 229 }
 230
 231 static const char *fs__mount(int idx)
 232 {
 233         struct fs *fs = &fs__entries[idx];
 234         const char *mountpoint;
 235
 236         if (fs__mountpoint(idx))
 237                 return (const char *)fs->path;
 238
 239         mountpoint = mount_overload(fs);
 240
 241         if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
 242                 return NULL;
 243
 244         return fs__check_mounts(fs) ? fs->path : NULL;
 245 }
 246
 247 #define FS(name, idx)                           \
 248 const char *name##__mountpoint(void)            \
 249 {                                               \
 250         return fs__mountpoint(idx);             \
 251 }                                               \
 252                                                 \
 253 const char *name##__mount(void)                 \
 254 {                                               \
 255         return fs__mount(idx);                  \
 256 }                                               \
 257                                                 \
 258 bool name##__configured(void)                   \
 259 {                                               \
 260         return name##__mountpoint() != NULL;    \
 261 }
 262
 263 FS(sysfs,   FS__SYSFS);
 264 FS(procfs,  FS__PROCFS);
 265 FS(debugfs, FS__DEBUGFS);
 266 FS(tracefs, FS__TRACEFS);
 267
 268 int filename__read_int(const char *filename, int *value)
 269 {
 270         char line[64];
 271         int fd = open(filename, O_RDONLY), err = -1;
 272
 273         if (fd < 0)
 274                 return -1;
 275
 276         if (read(fd, line, sizeof(line)) > 0) {
 277                 *value = atoi(line);
 278                 err = 0;
 279         }
 280
 281         close(fd);
 282         return err;
 283 }
 284
 285 int filename__read_ull(const char *filename, unsigned long long *value)
 286 {
 287         char line[64];
 288         int fd = open(filename, O_RDONLY), err = -1;
 289
 290         if (fd < 0)
 291                 return -1;
 292
 293         if (read(fd, line, sizeof(line)) > 0) {
 294                 *value = strtoull(line, NULL, 10);
 295                 if (*value != ULLONG_MAX)
 296                         err = 0;
 297         }
 298
 299         close(fd);
 300         return err;
 301 }
 302
 303 int sysfs__read_ull(const char *entry, unsigned long long *value)
 304 {
 305         char path[PATH_MAX];
 306         const char *sysfs = sysfs__mountpoint();
 307
 308         if (!sysfs)
 309                 return -1;
 310
 311         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 312
 313         return filename__read_ull(path, value);
 314 }
 315
 316 int sysfs__read_int(const char *entry, int *value)
 317 {
 318         char path[PATH_MAX];
 319         const char *sysfs = sysfs__mountpoint();
 320
 321         if (!sysfs)
 322                 return -1;
 323
 324         snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
 325
 326         return filename__read_int(path, value);
 327 }
 328
 329 int sysctl__read_int(const char *sysctl, int *value)
 330 {
 331         char path[PATH_MAX];
 332         const char *procfs = procfs__mountpoint();
 333
 334         if (!procfs)
 335                 return -1;
 336
 337         snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
 338
 339         return filename__read_int(path, value);
 340 }