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switch_root: shrink

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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
This commit is contained in:
Denis Vlasenko 2008-07-11 23:44:50 +00:00
parent e7067e38ea
commit 39acf45335
1 changed files with 11 additions and 21 deletions
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32
util-linux/switch_root.c
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@ -9,9 +9,7 @@
#include "libbb.h" #include "libbb.h"
#include <sys/vfs.h> #include <sys/vfs.h>
// Make up for header deficiencies. // Make up for header deficiencies.
#ifndef RAMFS_MAGIC #ifndef RAMFS_MAGIC
#define RAMFS_MAGIC ((unsigned)0x858458f6) #define RAMFS_MAGIC ((unsigned)0x858458f6)
#endif #endif
@ -24,18 +22,16 @@
#define MS_MOVE 8192 #define MS_MOVE 8192
#endif #endif
static dev_t rootdev;
// Recursively delete contents of rootfs. // Recursively delete contents of rootfs.
static void delete_contents(const char *directory, dev_t rootdev)
static void delete_contents(const char *directory)
{ {
DIR *dir; DIR *dir;
struct dirent *d; struct dirent *d;
struct stat st; struct stat st;
// Don't descend into other filesystems // 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. // Recursively delete the contents of directories.
if (S_ISDIR(st.st_mode)) { if (S_ISDIR(st.st_mode)) {
@ -45,13 +41,13 @@ static void delete_contents(const char *directory)
char *newdir = d->d_name; char *newdir = d->d_name;
// Skip . and .. // Skip . and ..
if (*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2]))) if (DOT_OR_DOTDOT(newdir))
continue; continue;
// Recurse to delete contents // Recurse to delete contents
newdir = alloca(strlen(directory) + strlen(d->d_name) + 2); newdir = concat_path_file(directory, newdir);
sprintf(newdir, "%s/%s", directory, d->d_name); delete_contents(newdir, rootdev);
delete_contents(newdir); free(newdir);
} }
closedir(dir); closedir(dir);
@ -60,7 +56,6 @@ static void delete_contents(const char *directory)
} }
// It wasn't a directory. Zap it. // It wasn't a directory. Zap it.
} else unlink(directory); } else unlink(directory);
} }
@ -70,15 +65,14 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
char *newroot, *console = NULL; char *newroot, *console = NULL;
struct stat st1, st2; struct stat st1, st2;
struct statfs stfs; struct statfs stfs;
dev_t rootdev;
// Parse args (-c console) // Parse args (-c console)
opt_complementary = "-2"; // minimum 2 params opt_complementary = "-2"; // minimum 2 params
getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option
argv += optind; argv += optind;
// Change to new root directory and verify it's a different fs. // Change to new root directory and verify it's a different fs.
newroot = *argv++; newroot = *argv++;
xchdir(newroot); 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 // 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 // we mean it. (I could make this a CONFIG option, but I would get email
// from all the people who WILL eat their filesystems.) // from all the people who WILL eat their filesystems.)
if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs)
|| (((unsigned)stfs.f_type != RAMFS_MAGIC) && ((unsigned)stfs.f_type != TMPFS_MAGIC)) || (((unsigned)stfs.f_type != RAMFS_MAGIC) && ((unsigned)stfs.f_type != TMPFS_MAGIC))
|| (getpid() != 1) || (getpid() != 1)
@ -99,24 +92,21 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
} }
// Zap everything out of rootdev // Zap everything out of rootdev
delete_contents("/", rootdev);
delete_contents("/");
// Overmount / with newdir and chroot into it. The chdir is needed to // Overmount / with newdir and chroot into it. The chdir is needed to
// recalculate "." and ".." links. // recalculate "." and ".." links.
if (mount(".", "/", NULL, MS_MOVE, NULL)) if (mount(".", "/", NULL, MS_MOVE, NULL))
bb_error_msg_and_die("error moving root"); bb_error_msg_and_die("error moving root");
xchroot("."); xchroot(".");
xchdir("/"); xchdir("/");
// If a new console specified, redirect stdin/stdout/stderr to that. // If a new console specified, redirect stdin/stdout/stderr to that.
if (console) { if (console) {
close(0); close(0);
xopen(console, O_RDWR); xopen(console, O_RDWR);
dup2(0, 1); xdup2(0, 1);
dup2(0, 2); xdup2(0, 2);
} }
// Exec real init. (This is why we must be pid 1.) // Exec real init. (This is why we must be pid 1.)