introduce and use bb_basename()

[oweals/busybox.git] / libbb / find_root_device.c

diff --git a/libbb/find_root_device.c b/libbb/find_root_device.c
index 71b79b8d09178950dca2aafb26067740531c552e..9779f7e82d190d064782fdd38aba50522ca74e66 100644 (file)
--- a/libbb/find_root_device.c
+++ b/libbb/find_root_device.c
@@ -9,25 +9,66 @@
 
 #include "libbb.h"
 
-char *find_block_device(char *path)
+/* Find block device /dev/XXX which contains specified file
+ * We handle /dev/dir/dir/dir too, at a cost of ~80 more bytes code */
+
+/* Do not reallocate all this stuff on each recursion */
+enum { DEVNAME_MAX = 256 };
+struct arena {
+       struct stat st;
+       dev_t dev;
+       /* Was PATH_MAX, but we recurse _/dev_. We can assume
+        * people are not crazy enough to have mega-deep tree there */
+       char devpath[DEVNAME_MAX];
+};
+
+static char *find_block_device_in_dir(struct arena *ap)
 {
        DIR *dir;
        struct dirent *entry;
-       struct stat st;
-       dev_t dev;
-       char *retpath=NULL;
-
-       if(stat(path, &st) || !(dir = opendir("/dev"))) return NULL;
-       dev = (st.st_mode & S_IFMT) == S_IFBLK ? st.st_rdev : st.st_dev;
-       while((entry = readdir(dir)) != NULL) {
-               char devpath[PATH_MAX];
-               sprintf(devpath,"/dev/%s", entry->d_name);
-               if(!stat(devpath, &st) && S_ISBLK(st.st_mode) && st.st_rdev == dev) {
-                       retpath = xstrdup(devpath);
+       char *retpath = NULL;
+       int len, rem;
+
+       dir = opendir(ap->devpath);
+       if (!dir)
+               return NULL;
+
+       len = strlen(ap->devpath);
+       rem = DEVNAME_MAX-2 - len;
+       if (rem <= 0)
+               return NULL;
+       ap->devpath[len++] = '/';
+
+       while ((entry = readdir(dir)) != NULL) {
+               safe_strncpy(ap->devpath + len, entry->d_name, rem);
+               /* lstat: do not follow links */
+               if (lstat(ap->devpath, &ap->st) != 0)
+                       continue;
+               if (S_ISBLK(ap->st.st_mode) && ap->st.st_rdev == ap->dev) {
+                       retpath = xstrdup(ap->devpath);
                        break;
                }
+               if (S_ISDIR(ap->st.st_mode)) {
+                       /* Do not recurse for '.' and '..' */
+                       if (DOT_OR_DOTDOT(entry->d_name))
+                               continue;
+                       retpath = find_block_device_in_dir(ap);
+                       if (retpath)
+                               break;
+               }
        }
        closedir(dir);
 
        return retpath;
 }
+
+char *find_block_device(const char *path)
+{
+       struct arena a;
+
+       if (stat(path, &a.st) != 0)
+               return NULL;
+       a.dev = S_ISBLK(a.st.st_mode) ? a.st.st_rdev : a.st.st_dev;
+       strcpy(a.devpath, "/dev");
+       return find_block_device_in_dir(&a);
+}