tools/perf/util/debugfs.c

   1 #include "util.h"
   2 #include "debugfs.h"
   3 #include "cache.h"
   4
   5 #include <linux/kernel.h>
   6 #include <sys/mount.h>
   7
   8 static int debugfs_premounted;
   9 char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
  10 char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
  11
  12 static const char *debugfs_known_mountpoints[] = {
  13         "/sys/kernel/debug/",
  14         "/debug/",
  15         0,
  16 };
  17
  18 /* use this to force a umount */
  19 void debugfs_force_cleanup(void)
  20 {
  21         debugfs_find_mountpoint();
  22         debugfs_premounted = 0;
  23         debugfs_umount();
  24 }
  25
  26 /* construct a full path to a debugfs element */
  27 int debugfs_make_path(const char *element, char *buffer, int size)
  28 {
  29         int len;
  30
  31         if (strlen(debugfs_mountpoint) == 0) {
  32                 buffer[0] = '\0';
  33                 return -1;
  34         }
  35
  36         len = strlen(debugfs_mountpoint) + strlen(element) + 1;
  37         if (len >= size)
  38                 return len+1;
  39
  40         snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
  41         return 0;
  42 }
  43
  44 static int debugfs_found;
  45
  46 /* find the path to the mounted debugfs */
  47 const char *debugfs_find_mountpoint(void)
  48 {
  49         const char **ptr;
  50         char type[100];
  51         FILE *fp;
  52
  53         if (debugfs_found)
  54                 return (const char *) debugfs_mountpoint;
  55
  56         ptr = debugfs_known_mountpoints;
  57         while (*ptr) {
  58                 if (debugfs_valid_mountpoint(*ptr) == 0) {
  59                         debugfs_found = 1;
  60                         strcpy(debugfs_mountpoint, *ptr);
  61                         return debugfs_mountpoint;
  62                 }
  63                 ptr++;
  64         }
  65
  66         /* give up and parse /proc/mounts */
  67         fp = fopen("/proc/mounts", "r");
  68         if (fp == NULL)
  69                 return NULL;
  70
  71         while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
  72                       debugfs_mountpoint, type) == 2) {
  73                 if (strcmp(type, "debugfs") == 0)
  74                         break;
  75         }
  76         fclose(fp);
  77
  78         if (strcmp(type, "debugfs") != 0)
  79                 return NULL;
  80
  81         debugfs_found = 1;
  82
  83         return debugfs_mountpoint;
  84 }
  85
  86 /* verify that a mountpoint is actually a debugfs instance */
  87
  88 int debugfs_valid_mountpoint(const char *debugfs)
  89 {
  90         struct statfs st_fs;
  91
  92         if (statfs(debugfs, &st_fs) < 0)
  93                 return -ENOENT;
  94         else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
  95                 return -ENOENT;
  96
  97         return 0;
  98 }
  99
 100
 101 int debugfs_valid_entry(const char *path)
 102 {
 103         struct stat st;
 104
 105         if (stat(path, &st))
 106                 return -errno;
 107
 108         return 0;
 109 }
 110
 111 static void debugfs_set_tracing_events_path(const char *mountpoint)
 112 {
 113         snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
 114                  mountpoint, "tracing/events");
 115 }
 116
 117 /* mount the debugfs somewhere if it's not mounted */
 118
 119 char *debugfs_mount(const char *mountpoint)
 120 {
 121         /* see if it's already mounted */
 122         if (debugfs_find_mountpoint()) {
 123                 debugfs_premounted = 1;
 124                 goto out;
 125         }
 126
 127         /* if not mounted and no argument */
 128         if (mountpoint == NULL) {
 129                 /* see if environment variable set */
 130                 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
 131                 /* if no environment variable, use default */
 132                 if (mountpoint == NULL)
 133                         mountpoint = "/sys/kernel/debug";
 134         }
 135
 136         if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
 137                 return NULL;
 138
 139         /* save the mountpoint */
 140         debugfs_found = 1;
 141         strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 142 out:
 143         debugfs_set_tracing_events_path(debugfs_mountpoint);
 144         return debugfs_mountpoint;
 145 }
 146
 147 void debugfs_set_path(const char *mountpoint)
 148 {
 149         snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
 150         debugfs_set_tracing_events_path(mountpoint);
 151 }
 152
 153 /* umount the debugfs */
 154
 155 int debugfs_umount(void)
 156 {
 157         char umountcmd[128];
 158         int ret;
 159
 160         /* if it was already mounted, leave it */
 161         if (debugfs_premounted)
 162                 return 0;
 163
 164         /* make sure it's a valid mount point */
 165         ret = debugfs_valid_mountpoint(debugfs_mountpoint);
 166         if (ret)
 167                 return ret;
 168
 169         snprintf(umountcmd, sizeof(umountcmd),
 170                  "/bin/umount %s", debugfs_mountpoint);
 171         return system(umountcmd);
 172 }
 173
 174 int debugfs_write(const char *entry, const char *value)
 175 {
 176         char path[PATH_MAX + 1];
 177         int ret, count;
 178         int fd;
 179
 180         /* construct the path */
 181         snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
 182
 183         /* verify that it exists */
 184         ret = debugfs_valid_entry(path);
 185         if (ret)
 186                 return ret;
 187
 188         /* get how many chars we're going to write */
 189         count = strlen(value);
 190
 191         /* open the debugfs entry */
 192         fd = open(path, O_RDWR);
 193         if (fd < 0)
 194                 return -errno;
 195
 196         while (count > 0) {
 197                 /* write it */
 198                 ret = write(fd, value, count);
 199                 if (ret <= 0) {
 200                         if (ret == EAGAIN)
 201                                 continue;
 202                         close(fd);
 203                         return -errno;
 204                 }
 205                 count -= ret;
 206         }
 207
 208         /* close it */
 209         close(fd);
 210
 211         /* return success */
 212         return 0;
 213 }
 214
 215 /*
 216  * read a debugfs entry
 217  * returns the number of chars read or a negative errno
 218  */
 219 int debugfs_read(const char *entry, char *buffer, size_t size)
 220 {
 221         char path[PATH_MAX + 1];
 222         int ret;
 223         int fd;
 224
 225         /* construct the path */
 226         snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
 227
 228         /* verify that it exists */
 229         ret = debugfs_valid_entry(path);
 230         if (ret)
 231                 return ret;
 232
 233         /* open the debugfs entry */
 234         fd = open(path, O_RDONLY);
 235         if (fd < 0)
 236                 return -errno;
 237
 238         do {
 239                 /* read it */
 240                 ret = read(fd, buffer, size);
 241                 if (ret == 0) {
 242                         close(fd);
 243                         return EOF;
 244                 }
 245         } while (ret < 0 && errno == EAGAIN);
 246
 247         /* close it */
 248         close(fd);
 249
 250         /* make *sure* there's a null character at the end */
 251         buffer[ret] = '\0';
 252
 253         /* return the number of chars read */
 254         return ret;
 255 }