switch_root: improve behavior on error; improve help text

*: make "can't execute '%s'" message uniform

10 files changed, 49 insertions, 42 deletions

diff --git a/archival/libunarchive/open_transformer.c b/archival/libunarchive/open_transformer.c
index fae589ee0..47c13e6f4 100644
--- a/archival/libunarchive/open_transformer.c
+++ b/archival/libunarchive/open_transformer.c
@@ -52,7 +52,7 @@ void FAST_FUNC open_transformer(int fd,
                         argv[2] = (char*)"-";
                         argv[3] = NULL;
                         BB_EXECVP(transform_prog, argv);
-                        bb_perror_msg_and_die("can't exec %s", transform_prog);
+                        bb_perror_msg_and_die("can't execute '%s'", transform_prog);
                 }
 #endif
                 /* notreached */
diff --git a/archival/tar.c b/archival/tar.c
index 379028bd9..9b7a42a18 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -577,7 +577,7 @@ static void NOINLINE vfork_compressor(int tar_fd, int gzip)
 #endif
         if (vfork_exec_errno) {
                 errno = vfork_exec_errno;
-                bb_perror_msg_and_die("cannot exec %s", zip_exec);
+                bb_perror_msg_and_die("can't execute '%s'", zip_exec);
         }
 }
 #endif /* ENABLE_FEATURE_SEAMLESS_GZ || ENABLE_FEATURE_SEAMLESS_BZ2 */
diff --git a/coreutils/chroot.c b/coreutils/chroot.c
index 1198a415a..9b3d70044 100644
--- a/coreutils/chroot.c
+++ b/coreutils/chroot.c
@@ -33,5 +33,5 @@ int chroot_main(int argc, char **argv)
         }
 
         BB_EXECVP(*argv, argv);
-        bb_perror_msg_and_die("cannot execute %s", *argv);
+        bb_perror_msg_and_die("can't execute '%s'", *argv);
 }
diff --git a/debianutils/run_parts.c b/debianutils/run_parts.c
index 77fdcccb0..ea019c27c 100644
--- a/debianutils/run_parts.c
+++ b/debianutils/run_parts.c
@@ -164,7 +164,7 @@ int run_parts_main(int argc UNUSED_PARAM, char **argv)
                         continue;
                 n = 1;
                 if (ret < 0)
-                        bb_perror_msg("can't exec %s", name);
+                        bb_perror_msg("can't execute '%s'", name);
                 else /* ret > 0 */
                         bb_error_msg("%s exited with code %d", name, ret);
         }
diff --git a/include/usage.h b/include/usage.h
index bfb07a4cf..84da445f2 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -4125,12 +4125,13 @@
         ) \
 
 #define switch_root_trivial_usage \
-       "[-c /dev/console] NEW_ROOT NEW_INIT [ARGUMENTS_TO_INIT]"
+       "[-c /dev/console] NEW_ROOT NEW_INIT [ARG...]"
 #define switch_root_full_usage "\n\n" \
-       "Use from PID 1 under initramfs to free initramfs, chroot to NEW_ROOT,\n" \
-       "and exec NEW_INIT\n" \
+       "Free initramfs and switch to another root fs:\n" \
+       "chroot to NEW_ROOT, delete all in /, move NEW_ROOT to /,\n" \
+       "execute NEW_INIT. PID must be 1. NEW_ROOT must be a mountpoint.\n" \
      "\nOptions:" \
-     "\n        -c      Redirect console to device on new root" \
+     "\n        -c DEV  Reopen stdio to DEV after switch" \
 
 #define sync_trivial_usage \
        ""
@@ -4142,7 +4143,7 @@
 #define sysctl_full_usage "\n\n" \
        "Configure kernel parameters at runtime\n" \
      "\nOptions:" \
-     "\n        -n      Disable printing of key names" \
+     "\n        -n      Don't print key names" \
      "\n        -e      Don't warn about unknown keys" \
      "\n        -w      Change sysctl setting" \
      "\n        -p FILE Load sysctl settings from FILE (default /etc/sysctl.conf)" \
diff --git a/loginutils/adduser.c b/loginutils/adduser.c
index 8a5d902e6..df4fad694 100644
--- a/loginutils/adduser.c
+++ b/loginutils/adduser.c
@@ -60,7 +60,7 @@ static void passwd_wrapper(const char *login)
         static const char prog[] ALIGN1 = "passwd";
 
         BB_EXECLP(prog, prog, login, NULL);
-        bb_error_msg_and_die("cannot execute %s, you must set password manually", prog);
+        bb_error_msg_and_die("can't execute %s, you must set password manually", prog);
 }
 
 #if ENABLE_FEATURE_ADDUSER_LONG_OPTIONS
diff --git a/selinux/runcon.c b/selinux/runcon.c
index e94ff1454..6ecd7899d 100644
--- a/selinux/runcon.c
+++ b/selinux/runcon.c
@@ -129,10 +129,10 @@ int runcon_main(int argc UNUSED_PARAM, char **argv)
                                      context_str(con));
 
         if (setexeccon(context_str(con)))
-                bb_error_msg_and_die("cannot set up security context '%s'",
+                bb_error_msg_and_die("can't set up security context '%s'",
                                      context_str(con));
 
         execvp(argv[0], argv);
 
-        bb_perror_msg_and_die("cannot execute '%s'", argv[0]);
+        bb_perror_msg_and_die("can't execute '%s'", argv[0]);
 }
diff --git a/shell/cttyhack.c b/shell/cttyhack.c
index 0aa4b8a2c..572a3af03 100644
--- a/shell/cttyhack.c
+++ b/shell/cttyhack.c
@@ -73,5 +73,5 @@ int cttyhack_main(int argc UNUSED_PARAM, char **argv)
         }
 
         BB_EXECVP(argv[0], argv);
-        bb_perror_msg_and_die("cannot exec '%s'", argv[0]);
+        bb_perror_msg_and_die("can't execute '%s'", argv[0]);
 }
diff --git a/shell/hush.c b/shell/hush.c
index 53b1f3f8b..56b12cebc 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -3048,7 +3048,7 @@ static void pseudo_exec_argv(nommu_save_t *nommu_save,
         debug_printf_exec("execing '%s'\n", argv[0]);
         sigprocmask(SIG_SETMASK, &G.inherited_set, NULL);
         execvp(argv[0], argv);
-        bb_perror_msg("can't exec '%s'", argv[0]);
+        bb_perror_msg("can't execute '%s'", argv[0]);
         _exit(EXIT_FAILURE);
 }
 
diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c
index 08aa72597..f9e3444d5 100644
--- a/util-linux/switch_root.c
+++ b/util-linux/switch_root.c
@@ -5,11 +5,10 @@
  *
  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
  */
-
 #include "libbb.h"
 #include <sys/vfs.h>
 
-// Make up for header deficiencies.
+// Make up for header deficiencies
 #ifndef RAMFS_MAGIC
 #define RAMFS_MAGIC ((unsigned)0x858458f6)
 #endif
@@ -22,7 +21,7 @@
 #define MS_MOVE     8192
 #endif
 
-// Recursively delete contents of rootfs.
+// Recursively delete contents of rootfs
 static void delete_contents(const char *directory, dev_t rootdev)
 {
         DIR *dir;
@@ -33,7 +32,7 @@ static void delete_contents(const char *directory, dev_t rootdev)
         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)) {
                 dir = opendir(directory);
                 if (dir) {
@@ -51,42 +50,47 @@ static void delete_contents(const char *directory, dev_t rootdev)
                         }
                         closedir(dir);
 
-                        // Directory should now be empty.  Zap it.
+                        // Directory should now be empty, zap it
                         rmdir(directory);
                 }
-
-        // It wasn't a directory.  Zap it.
-        } else unlink(directory);
+        } else {
+                // It wasn't a directory, zap it
+                unlink(directory);
+        }
 }
 
 int switch_root_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int switch_root_main(int argc UNUSED_PARAM, char **argv)
 {
         char *newroot, *console = NULL;
-        struct stat st1, st2;
+        struct stat st;
         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
+        getopt32(argv, "+c:", &console); // '+': stop at first non-option
         argv += optind;
-
-        // Change to new root directory and verify it's a different fs.
         newroot = *argv++;
 
+        // Change to new root directory and verify it's a different fs
         xchdir(newroot);
-        if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) {
-                bb_error_msg_and_die("bad newroot %s", newroot);
+        xstat("/", &st);
+        rootdev = st.st_dev;
+        xstat(".", &st);
+        if (st.st_dev == rootdev || getpid() != 1) {
+                // Show usage, it says new root must be a mountpoint
+                // and we must be PID 1
+                bb_show_usage();
         }
-        rootdev = st2.st_dev;
-
-        // 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)
+
+        // 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 destroy their filesystems.
+        statfs("/", &stfs); // this never fails
+        if (lstat("/init", &st) != 0 || !S_ISREG(st.st_mode)
+         || ((unsigned)stfs.f_type != RAMFS_MAGIC
+             && (unsigned)stfs.f_type != TMPFS_MAGIC)
         ) {
                 bb_error_msg_and_die("not rootfs");
         }
@@ -94,14 +98,16 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
         // Zap everything out of rootdev
         delete_contents("/", rootdev);
 
-        // Overmount / with newdir and chroot into it.  The chdir is needed to
-        // recalculate "." and ".." links.
-        if (mount(".", "/", NULL, MS_MOVE, NULL))
+        // Overmount / with newdir and chroot into it
+        if (mount(".", "/", NULL, MS_MOVE, NULL)) {
+                // For example, fails when newroot is not a mountpoint
                 bb_perror_msg_and_die("error moving root");
+        }
+        // The chdir is needed to recalculate "." and ".." links
         xchroot(".");
         xchdir("/");
 
-        // If a new console specified, redirect stdin/stdout/stderr to that.
+        // If a new console specified, redirect stdin/stdout/stderr to it
         if (console) {
                 close(0);
                 xopen(console, O_RDWR);
@@ -109,7 +115,7 @@ int switch_root_main(int argc UNUSED_PARAM, char **argv)
                 xdup2(0, 2);
         }
 
-        // Exec real init.  (This is why we must be pid 1.)
+        // Exec real init
         execv(argv[0], argv);
-        bb_perror_msg_and_die("bad init %s", argv[0]);
+        bb_perror_msg_and_die("can't execute '%s'", argv[0]);
 }