tools/perf/util/debugfs.c

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