tools/lib/api/fs/fs.c

   1 /* TODO merge/factor in debugfs.c here */
   2
   3 #include <ctype.h>
   4 #include <errno.h>
   5 #include <stdbool.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <sys/vfs.h>
  10 #include <sys/types.h>
  11 #include <sys/stat.h>
  12 #include <fcntl.h>
  13 #include <unistd.h>
  14
  15 #include "debugfs.h"
  16 #include "fs.h"
  17
  18 static const char * const sysfs__fs_known_mountpoints[] = {
  19         "/sys",
  20         0,
  21 };
  22
  23 static const char * const procfs__known_mountpoints[] = {
  24         "/proc",
  25         0,
  26 };
  27
  28 struct fs {
  29         const char              *name;
  30         const char * const      *mounts;
  31         char                     path[PATH_MAX + 1];
  32         bool                     found;
  33         long                     magic;
  34 };
  35
  36 enum {
  37         FS__SYSFS  = 0,
  38         FS__PROCFS = 1,
  39 };
  40
  41 static struct fs fs__entries[] = {
  42         [FS__SYSFS] = {
  43                 .name   = "sysfs",
  44                 .mounts = sysfs__fs_known_mountpoints,
  45                 .magic  = SYSFS_MAGIC,
  46         },
  47         [FS__PROCFS] = {
  48                 .name   = "proc",
  49                 .mounts = procfs__known_mountpoints,
  50                 .magic  = PROC_SUPER_MAGIC,
  51         },
  52 };
  53
  54 static bool fs__read_mounts(struct fs *fs)
  55 {
  56         bool found = false;
  57         char type[100];
  58         FILE *fp;
  59
  60         fp = fopen("/proc/mounts", "r");
  61         if (fp == NULL)
  62                 return NULL;
  63
  64         while (!found &&
  65                fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
  66                       fs->path, type) == 2) {
  67
  68                 if (strcmp(type, fs->name) == 0)
  69                         found = true;
  70         }
  71
  72         fclose(fp);
  73         return fs->found = found;
  74 }
  75
  76 static int fs__valid_mount(const char *fs, long magic)
  77 {
  78         struct statfs st_fs;
  79
  80         if (statfs(fs, &st_fs) < 0)
  81                 return -ENOENT;
  82         else if ((long)st_fs.f_type != magic)
  83                 return -ENOENT;
  84
  85         return 0;
  86 }
  87
  88 static bool fs__check_mounts(struct fs *fs)
  89 {
  90         const char * const *ptr;
  91
  92         ptr = fs->mounts;
  93         while (*ptr) {
  94                 if (fs__valid_mount(*ptr, fs->magic) == 0) {
  95                         fs->found = true;
  96                         strcpy(fs->path, *ptr);
  97                         return true;
  98                 }
  99                 ptr++;
 100         }
 101
 102         return false;
 103 }
 104
 105 static void mem_toupper(char *f, size_t len)
 106 {
 107         while (len) {
 108                 *f = toupper(*f);
 109                 f++;
 110                 len--;
 111         }
 112 }
 113
 114 /*
 115  * Check for "NAME_PATH" environment variable to override fs location (for
 116  * testing). This matches the recommendation in Documentation/sysfs-rules.txt
 117  * for SYSFS_PATH.
 118  */
 119 static bool fs__env_override(struct fs *fs)
 120 {
 121         char *override_path;
 122         size_t name_len = strlen(fs->name);
 123         /* name + "_PATH" + '\0' */
 124         char upper_name[name_len + 5 + 1];
 125         memcpy(upper_name, fs->name, name_len);
 126         mem_toupper(upper_name, name_len);
 127         strcpy(&upper_name[name_len], "_PATH");
 128
 129         override_path = getenv(upper_name);
 130         if (!override_path)
 131                 return false;
 132
 133         fs->found = true;
 134         strncpy(fs->path, override_path, sizeof(fs->path));
 135         return true;
 136 }
 137
 138 static const char *fs__get_mountpoint(struct fs *fs)
 139 {
 140         if (fs__env_override(fs))
 141                 return fs->path;
 142
 143         if (fs__check_mounts(fs))
 144                 return fs->path;
 145
 146         if (fs__read_mounts(fs))
 147                 return fs->path;
 148
 149         return NULL;
 150 }
 151
 152 static const char *fs__mountpoint(int idx)
 153 {
 154         struct fs *fs = &fs__entries[idx];
 155
 156         if (fs->found)
 157                 return (const char *)fs->path;
 158
 159         return fs__get_mountpoint(fs);
 160 }
 161
 162 #define FS__MOUNTPOINT(name, idx)       \
 163 const char *name##__mountpoint(void)    \
 164 {                                       \
 165         return fs__mountpoint(idx);     \
 166 }
 167
 168 FS__MOUNTPOINT(sysfs,  FS__SYSFS);
 169 FS__MOUNTPOINT(procfs, FS__PROCFS);
 170
 171 int filename__read_int(const char *filename, int *value)
 172 {
 173         char line[64];
 174         int fd = open(filename, O_RDONLY), err = -1;
 175
 176         if (fd < 0)
 177                 return -1;
 178
 179         if (read(fd, line, sizeof(line)) > 0) {
 180                 *value = atoi(line);
 181                 err = 0;
 182         }
 183
 184         close(fd);
 185         return err;
 186 }
 187
 188 int sysctl__read_int(const char *sysctl, int *value)
 189 {
 190         char path[PATH_MAX];
 191         const char *procfs = procfs__mountpoint();
 192
 193         if (!procfs)
 194                 return -1;
 195
 196         snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
 197
 198         return filename__read_int(path, value);
 199 }