Remove all files on the initramfs before switching root

The code from pjones's tree did not include the recursive remove code,
so I readded it from the nash source code.

diff --git a/switch_root.c b/switch_root.c
index be5720ed7de98886251e0c1ae3b8f2ac178ea4b6..1db062d86622d2bf9a1ba0bf9251e8aac8e89136 100644 (file)
--- a/switch_root.c
+++ b/switch_root.c
@@ -34,6 +34,7 @@
 #include <string.h>
 #include <errno.h>
 #include <ctype.h>
+#include <dirent.h>
 
 #ifndef MS_MOVE
 #define MS_MOVE 8192
@@ -49,6 +50,73 @@ enum {
        err_usage,
 };
 
+/* remove all files/directories below dirName -- don't cross mountpoints */
+static int
+recursiveRemove(char * dirName)
+ {
+    struct stat sb,rb;
+    DIR * dir;
+    struct dirent * d;
+    char * strBuf = alloca(strlen(dirName) + 1024);
+
+    if (!(dir = opendir(dirName))) {
+        printf("error opening %s: %m\n", dirName);
+        return 0;
+    }
+
+    if (fstat(dirfd(dir),&rb)) {
+        printf("unable to stat %s: %m\n", dirName);
+        closedir(dir);
+        return 0;
+    }
+
+    errno = 0;
+    while ((d = readdir(dir))) {
+        errno = 0;
+
+        if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, "..")) {
+            errno = 0;
+            continue;
+        }
+
+        strcpy(strBuf, dirName);
+        strcat(strBuf, "/");
+        strcat(strBuf, d->d_name);
+
+        if (lstat(strBuf, &sb)) {
+            printf("failed to stat %s: %m\n", strBuf);
+            errno = 0;
+            continue;
+        }
+
+        /* only descend into subdirectories if device is same as dir */
+        if (S_ISDIR(sb.st_mode)) {
+            if (sb.st_dev == rb.st_dev) {
+               recursiveRemove(strBuf);
+                if (rmdir(strBuf))
+                    printf("failed to rmdir %s: %m\n", strBuf);
+            }
+            errno = 0;
+            continue;
+        }
+        if (unlink(strBuf)) {
+            printf("failed to remove %s: %m\n", strBuf);
+            errno = 0;
+            continue;
+        }
+    }
+
+    if (errno) {
+        closedir(dir);
+        printf("error reading from %s: %m\n", dirName);
+        return 1;
+    }
+
+    closedir(dir);
+
+    return 0;
+ }
+
 static int switchroot(const char *newroot)
 {
        /*  Don't try to unmount the old "/", there's no way to do it. */
@@ -74,7 +142,7 @@ static int switchroot(const char *newroot)
          errno=errnum;
          return -1;
        }
-
+       recursiveRemove("/");
        if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
                errnum = errno;
                fprintf(stderr, "switchroot: mount failed: %m\n");