switch_root: shrink

function                                             old     new   delta
switch_root_main                                     402     401      -1
rootdev                                                8       -      -8
delete_contents                                      226     179     -47
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 0/2 up/down: 0/-56)             Total: -56 bytes

1 files changed, 11 insertions, 21 deletions

diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c
index 1f6ec2dc7..21cc99229 100644
--- a/util-linux/switch_root.c
+++ b/util-linux/switch_root.c
@@ -9,9 +9,7 @@
 #include "libbb.h"
 #include <sys/vfs.h>
 
-
 // Make up for header deficiencies.
-
 #ifndef RAMFS_MAGIC
 #define RAMFS_MAGIC ((unsigned)0x858458f6)
 #endif
@@ -24,18 +22,16 @@
 #define MS_MOVE     8192
 #endif
 
-static dev_t rootdev;
-
 // Recursively delete contents of rootfs.
-
-static void delete_contents(const char *directory)
+static void delete_contents(const char *directory, dev_t rootdev)
 {
         DIR *dir;
         struct dirent *d;
         struct stat st;
 
         // Don't descend into other filesystems
-        if (lstat(directory, &st) || st.st_dev != rootdev) return;
+        if (lstat(directory, &st) || st.st_dev != rootdev)
+                return;
 
         // Recursively delete the contents of directories.
         if (S_ISDIR(st.st_mode)) {
@@ -45,13 +41,13 @@ static void delete_contents(const char *directory)
                                 char *newdir = d->d_name;
 
                                 // Skip . and ..
-                                if (*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2])))
+                                if (DOT_OR_DOTDOT(newdir))
                                         continue;
 
                                 // Recurse to delete contents
-                                newdir = alloca(strlen(directory) + strlen(d->d_name) + 2);
-                                sprintf(newdir, "%s/%s", directory, d->d_name);
-                                delete_contents(newdir);
+                                newdir = concat_path_file(directory, newdir);
+                                delete_contents(newdir, rootdev);
+                                free(newdir);
                         }
                         closedir(dir);
 
@@ -60,7 +56,6 @@ static void delete_contents(const char *directory)
                 }
 
         // It wasn't a directory.  Zap it.
-
         } else unlink(directory);
 }
 
@@ -70,15 +65,14 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
         char *newroot, *console = NULL;
         struct stat st1, st2;
         struct statfs stfs;
+        dev_t rootdev;
 
         // Parse args (-c console)
-
         opt_complementary = "-2"; // minimum 2 params
         getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option
         argv += optind;
 
         // Change to new root directory and verify it's a different fs.
-
         newroot = *argv++;
 
         xchdir(newroot);
@@ -90,7 +84,6 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
         // Additional sanity checks: we're about to rm -rf /,  so be REALLY SURE
         // we mean it.  (I could make this a CONFIG option, but I would get email
         // from all the people who WILL eat their filesystems.)
-
         if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs)
          || (((unsigned)stfs.f_type != RAMFS_MAGIC) && ((unsigned)stfs.f_type != TMPFS_MAGIC))
          || (getpid() != 1)
@@ -99,24 +92,21 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
         }
 
         // Zap everything out of rootdev
-
-        delete_contents("/");
+        delete_contents("/", rootdev);
 
         // Overmount / with newdir and chroot into it.  The chdir is needed to
         // recalculate "." and ".." links.
-
         if (mount(".", "/", NULL, MS_MOVE, NULL))
                 bb_error_msg_and_die("error moving root");
         xchroot(".");
         xchdir("/");
 
         // If a new console specified, redirect stdin/stdout/stderr to that.
-
         if (console) {
                 close(0);
                 xopen(console, O_RDWR);
-                dup2(0, 1);
-                dup2(0, 2);
+                xdup2(0, 1);
+                xdup2(0, 2);
         }
 
         // Exec real init.  (This is why we must be pid 1.)