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[Libguestfs] [PATCH febootstrap 8/8 v2] Add ext2 output module.



Here is a working, only lightly tested patch 8/8.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
Fedora now supports 80 OCaml packages (the OPEN alternative to F#)
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>From 24a8250b097994cc73fbd34eb824327a79c115ee Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones redhat com>
Date: Thu, 19 Aug 2010 15:55:01 +0100
Subject: [PATCH] Add ext2 output module.

---
 .gitignore              |    1 +
 Makefile.am             |    1 +
 README                  |    4 +
 configure.ac            |   23 +++
 helper/Makefile.am      |   21 ++-
 helper/elf-default-arch |   27 +++
 helper/ext2.c           |  447 ++++++++++++++++++++++++++++++++++++++++++++++-
 helper/ext2cpio.c       |  358 +++++++++++++++++++++++++++++++++++++
 helper/ext2initrd.c     |  263 ++++++++++++++++++++++++++++
 helper/ext2internal.h   |   45 +++++
 helper/init.c           |  172 ++++++++++++++++++
 11 files changed, 1354 insertions(+), 8 deletions(-)
 create mode 100755 helper/elf-default-arch
 create mode 100644 helper/ext2cpio.c
 create mode 100644 helper/ext2initrd.c
 create mode 100644 helper/ext2internal.h
 create mode 100644 helper/init.c

diff --git a/.gitignore b/.gitignore
index 310aa6e..748667f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -27,6 +27,7 @@ febootstrap-supermin-helper
 febootstrap*.8
 febootstrap*.txt
 febootstrap-*.tar.gz
+helper/init
 lib/alloca.h
 lib/arg-nonnull.h
 lib/c++defs.h
diff --git a/Makefile.am b/Makefile.am
index 9db86e9..c7bd650 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -28,6 +28,7 @@ bin_SCRIPTS = \
 	febootstrap-minimize \
 	febootstrap-to-initramfs \
 	febootstrap-to-supermin
+DISTCLEANSCRIPTS = $(bin_SCRIPTS)
 
 febootstrap: febootstrap.sh
 	rm -f $@
diff --git a/README b/README
index b8df88e..5383dcb 100644
--- a/README
+++ b/README
@@ -38,6 +38,10 @@ Requirements
   qemu
     - If you want to test-run your systems.
 
+  libext2fs
+  /sbin/mke2fs
+    - These are part of e2fsprogs.
+
 Building and installing
 -----------------------
 
diff --git a/configure.ac b/configure.ac
index 1a94700..9b9f39c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -58,6 +58,29 @@ if test "x$YUM" = "xno" ; then
   AC_MSG_FAILURE([yum program not found])
 fi
 
+AC_PATH_PROG([MKE2FS],[mke2fs],[no])
+if test "x$MKE2FS" = "xno" ; then
+  AC_MSG_FAILURE([mke2fs program not found (is /sbin in your current path?)])
+fi
+AC_DEFINE_UNQUOTED([MKE2FS],["$MKE2FS"],
+  [Full path to the mke2fs program.])
+
+old_LIBS="$LIBS"
+AC_CHECK_LIB([com_err],[error_message],[],[
+  AC_MSG_FAILURE([com_err library not found (part of e2fsprogs)])
+])
+LIBS="$old_LIBS"
+
+old_LIBS="$LIBS"
+AC_CHECK_LIB([ext2fs],[ext2fs_file_open2],[],[
+  AC_MSG_FAILURE([libext2fs library not found (part of e2fsprogs)])
+])
+LIBS="$old_LIBS"
+
+AC_CHECK_HEADER([ext2fs/ext2fs.h],[],[
+  AC_MSG_FAILURE([Header <ext2fs/ext2fs.h> not found (part of e2fsprogs)])
+])
+
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_FILES([Makefile lib/Makefile helper/Makefile examples/Makefile])
 AC_OUTPUT
diff --git a/helper/Makefile.am b/helper/Makefile.am
index 5c5966c..c8edf7f 100644
--- a/helper/Makefile.am
+++ b/helper/Makefile.am
@@ -19,18 +19,35 @@
 
 bin_PROGRAMS = \
 	febootstrap-supermin-helper
-DISTCLEANFILES = $(bin_SCRIPTS)
 
 febootstrap_supermin_helper_SOURCES = \
 	helper.h \
 	appliance.c \
 	cpio.c \
 	ext2.c \
+	ext2cpio.c \
+	ext2initrd.c \
+	ext2internal.h \
 	kernel.c \
 	main.c \
 	utils.c
 febootstrap_supermin_helper_CFLAGS = -Wall -I../lib
-febootstrap_supermin_helper_LDADD = $(LTLIBINTL) -L../lib -lgnu
+febootstrap_supermin_helper_LDADD = \
+	ext2init.o -lext2fs -lcom_err $(LTLIBINTL) -L../lib -lgnu
+
+# init "script" used by ext2 initrd.
+noinst_PROGRAMS = init
+init_SOURCES = init.c
+init_CFLAGS = -static
+init_LDFLAGS = -all-static
+
+# http://www.doof.me.uk/2010/05/07/cute-objcopy-hack/
+ELF_DEFAULT_ARCH = $(shell $(srcdir)/elf-default-arch)
+ext2init.o: init
+	strip --strip-all $<
+	@file $< | grep -isq static || \
+	  (echo "*** error: init is not staticly linked"; exit 1)
+	objcopy -I binary -B i386 -O $(ELF_DEFAULT_ARCH) $< $@
 
 man_MANS = \
 	febootstrap-supermin-helper.8
diff --git a/helper/elf-default-arch b/helper/elf-default-arch
new file mode 100755
index 0000000..0adc351
--- /dev/null
+++ b/helper/elf-default-arch
@@ -0,0 +1,27 @@
+#!/bin/sh -
+# Copyright (C) 2010 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+# Calculate the default ELF object architecture for this format.
+# There doesn't seem to be an easy way to derive this from binutils,
+# so instead we hard code it.
+
+case $(uname -m) in
+    i[3456]86) echo elf32-i386 ;;
+    x86_64) echo elf64-x86-64 ;;
+    *)
+        echo "This architecture is not recognized.  Please update helper/elf-default-arch."
+esac
diff --git a/helper/ext2.c b/helper/ext2.c
index 2900221..9d60da9 100644
--- a/helper/ext2.c
+++ b/helper/ext2.c
@@ -21,26 +21,461 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
 #include <sys/stat.h>
 #include <assert.h>
 
 #include "error.h"
 #include "fts_.h"
+#include "xvasprintf.h"
 
 #include "helper.h"
+#include "ext2internal.h"
+
+ext2_filsys fs;
+
+/* The ext2 image that we build always has a fixed size, and we 'hope'
+ * that the files fit in (otherwise we'll get an error).  Note that
+ * the file is sparsely allocated.
+ *
+ * The downside of allocating a very large initial disk is that the
+ * fixed overhead of ext2 is larger (since ext2 calculates it based on
+ * the size of the disk).  For a 1GB disk the overhead is
+ * approximately 16MB.
+ *
+ * In future, make this configurable, or determine it from the input
+ * files (XXX).
+ */
+#define APPLIANCE_SIZE (1024*1024*1024)
 
 static void
 ext2_start (const char *appliance,
             const char *modpath, const char *initrd)
 {
-  abort ();
+  initialize_ext2_error_table ();
+
+  /* Make the initrd. */
+  ext2_make_initrd (modpath, initrd);
+
+  /* Make the appliance sparse image. */
+  int fd = open (appliance, O_WRONLY | O_CREAT | O_TRUNC | O_NOCTTY, 0644);
+  if (fd == -1)
+    error (EXIT_FAILURE, errno, "open: %s", appliance);
+
+  if (lseek (fd, APPLIANCE_SIZE - 1, SEEK_SET) == -1)
+    error (EXIT_FAILURE, errno, "lseek");
+
+  char c = 0;
+  if (write (fd, &c, 1) != 1)
+    error (EXIT_FAILURE, errno, "write");
+
+  if (close (fd) == -1)
+    error (EXIT_FAILURE, errno, "close");
+
+  /* Run mke2fs on the file.
+   * XXX Quoting, but this string doesn't come from an untrusted source.
+   */
+  char *cmd = xasprintf ("%s -t ext2 -F%s '%s'",
+                         MKE2FS,
+                         verbose >= 2 ? "" : "q",
+                         appliance);
+  int r = system (cmd);
+  if (r == -1 || WEXITSTATUS (r) != 0)
+    error (EXIT_FAILURE, 0, "%s: failed", cmd);
+  free (cmd);
+
+  if (verbose)
+    print_timestamped_message ("finished mke2fs");
+
+  /* Open the filesystem. */
+  errcode_t err =
+    ext2fs_open (appliance, EXT2_FLAG_RW, 0, 0, unix_io_manager, &fs);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_open: %s", error_message (err));
+
+  /* Bitmaps are not loaded by default, so load them.  ext2fs_close will
+   * write out any changes.
+   */
+  err = ext2fs_read_bitmaps (fs);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_read_bitmaps: %s", error_message (err));
+}
+
+static void
+ext2_end (void)
+{
+  /* Write out changes and close. */
+  errcode_t err = ext2fs_close (fs);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_close: %s", error_message (err));
+}
+
+void
+ext2_mkdir (ext2_ino_t dir_ino, const char *dirname, const char *basename,
+            mode_t mode, uid_t uid, gid_t gid,
+            time_t ctime, time_t atime, time_t mtime)
+{
+  errcode_t err;
+
+  mode = LINUX_S_IFDIR | (mode & 0777);
+
+  /* Does the directory exist?  This is legitimate: we just skip
+   * this case.
+   */
+  ext2_ino_t ino;
+  err = ext2fs_namei (fs, EXT2_ROOT_INO, dir_ino, basename, &ino);
+  if (err == 0)
+    return; /* skip */
+
+  /* Otherwise, create it. */
+  err = ext2fs_new_inode (fs, dir_ino, mode, 0, &ino);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_new_inode: %s", error_message (err));
+
+  err = ext2fs_mkdir (fs, dir_ino, ino, basename);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_mkdir: %s/%s: %s",
+           dirname, basename, error_message (err));
+
+  /* Copy the final permissions, UID etc. to the inode. */
+  struct ext2_inode inode;
+  err = ext2fs_read_inode (fs, ino, &inode);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_read_inode: %s", error_message (err));
+  inode.i_mode = mode;
+  inode.i_uid = uid;
+  inode.i_gid = gid;
+  inode.i_ctime = ctime;
+  inode.i_atime = atime;
+  inode.i_mtime = mtime;
+  err = ext2fs_write_inode (fs, ino, &inode);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_write_inode: %s", error_message (err));
+}
+
+void
+ext2_empty_inode (ext2_ino_t dir_ino, const char *dirname, const char *basename,
+                  mode_t mode, uid_t uid, gid_t gid,
+                  time_t ctime, time_t atime, time_t mtime,
+                  int major, int minor, int dir_ft, ext2_ino_t *ino_ret)
+{
+  errcode_t err;
+  struct ext2_inode inode;
+  ext2_ino_t ino;
+
+  err = ext2fs_new_inode (fs, dir_ino, mode, 0, &ino);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_new_inode: %s", error_message (err));
+
+  memset (&inode, 0, sizeof inode);
+  inode.i_mode = mode;
+  inode.i_uid = uid;
+  inode.i_gid = gid;
+  inode.i_blocks = 0;
+  inode.i_links_count = 1;
+  inode.i_ctime = ctime;
+  inode.i_atime = atime;
+  inode.i_mtime = mtime;
+  inode.i_size = 0;
+  inode.i_block[0] = (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12);
+
+  err = ext2fs_write_new_inode (fs, ino, &inode);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_write_inode: %s", error_message (err));
+
+  ext2_link (dir_ino, basename, ino, dir_ft);
+
+  ext2fs_inode_alloc_stats2 (fs, ino, 1, 0);
+
+  if (ino_ret)
+    *ino_ret = ino;
+}
+
+/* You must create the file first with ext2_empty_inode. */
+void
+ext2_write_file (ext2_ino_t ino, const char *buf, size_t size)
+{
+  errcode_t err;
+  ext2_file_t file;
+  err = ext2fs_file_open2 (fs, ino, NULL, EXT2_FILE_WRITE, &file);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_file_open2: %s", error_message (err));
+
+  /* ext2fs_file_write cannot deal with partial writes.  You have
+   * to write the entire file in a single call.
+   */
+  unsigned int written;
+  err = ext2fs_file_write (file, buf, size, &written);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_file_write: %s", error_message (err));
+  if ((size_t) written != size)
+    error (EXIT_FAILURE, 0,
+           "ext2fs_file_write: size = %zu != written = %u\n",
+           size, written);
+
+  err = ext2fs_file_flush (file);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_file_flush: %s", error_message (err));
+  err = ext2fs_file_close (file);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_file_close: %s", error_message (err));
+
+  /* Update the true size in the inode. */
+  struct ext2_inode inode;
+  err = ext2fs_read_inode (fs, ino, &inode);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_read_inode: %s", error_message (err));
+  inode.i_size = size;
+  err = ext2fs_write_inode (fs, ino, &inode);
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_write_inode: %s", error_message (err));
+}
+
+/* This is just a wrapper around ext2fs_link which calls
+ * ext2fs_expand_dir as necessary if the directory fills up.  See
+ * definition of expand_dir in the sources of debugfs.
+ */
+void
+ext2_link (ext2_ino_t dir_ino, const char *basename, ext2_ino_t ino, int dir_ft)
+{
+  errcode_t err;
+
+ again:
+  err = ext2fs_link (fs, dir_ino, basename, ino, dir_ft);
+
+  if (err == EXT2_ET_DIR_NO_SPACE) {
+    err = ext2fs_expand_dir (fs, dir_ino);
+    if (err != 0)
+      error (EXIT_FAILURE, 0, "ext2_link: ext2fs_expand_dir: %s: %s",
+             basename, error_message (err));
+    goto again;
+  }
+
+  if (err != 0)
+    error (EXIT_FAILURE, 0, "ext2fs_link: %s: %s",
+             basename, error_message (err));
+}
+
+static int
+release_block (ext2_filsys fs, blk_t *blocknr,
+                int blockcnt, void *private)
+{
+  blk_t block;
+
+  block = *blocknr;
+  ext2fs_block_alloc_stats (fs, block, -1);
+  return 0;
+}
+
+/* unlink or rmdir path, if it exists. */
+void
+ext2_clean_path (ext2_ino_t dir_ino,
+                 const char *dirname, const char *basename,
+                 int isdir)
+{
+  errcode_t err;
+
+  ext2_ino_t ino;
+  err = ext2fs_lookup (fs, dir_ino, basename, strlen (basename),
+                       NULL, &ino);
+  if (err == EXT2_ET_FILE_NOT_FOUND)
+    return;
+
+  if (!isdir) {
+    struct ext2_inode inode;
+    err = ext2fs_read_inode (fs, ino, &inode);
+    if (err != 0)
+      error (EXIT_FAILURE, 0, "ext2fs_read_inode: %s", error_message (err));
+    inode.i_links_count--;
+    err = ext2fs_write_inode (fs, ino, &inode);
+    if (err != 0)
+      error (EXIT_FAILURE, 0, "ext2fs_write_inode: %s", error_message (err));
+
+    err = ext2fs_unlink (fs, dir_ino, basename, 0, 0);
+    if (err != 0)
+      error (EXIT_FAILURE, 0, "ext2fs_unlink_inode: %s", error_message (err));
+
+    if (inode.i_links_count == 0) {
+      inode.i_dtime = time (NULL);
+      err = ext2fs_write_inode (fs, ino, &inode);
+      if (err != 0)
+        error (EXIT_FAILURE, 0, "ext2fs_write_inode: %s", error_message (err));
+
+      if (ext2fs_inode_has_valid_blocks (&inode))
+        ext2fs_block_iterate (fs, ino, BLOCK_FLAG_READ_ONLY, NULL,
+                              release_block, NULL);
+
+      ext2fs_inode_alloc_stats2 (fs, ino, -1, isdir);
+    }
+  }
+  /* else it's a directory, what to do? XXX */
+}
+
+/* Read in the whole file into memory.  Check the size is still 'size'. */
+static char *
+read_whole_file (const char *filename, size_t size)
+{
+  char *buf = malloc (size);
+  if (buf == NULL)
+    error (EXIT_FAILURE, errno, "malloc");
+
+  int fd = open (filename, O_RDONLY);
+  if (fd == -1)
+    error (EXIT_FAILURE, errno, "open: %s", filename);
+
+  size_t n = 0;
+  char *p = buf;
+
+  while (n < size) {
+    ssize_t r = read (fd, p, size - n);
+    if (r == -1)
+      error (EXIT_FAILURE, errno, "read: %s", filename);
+    if (r == 0)
+      error (EXIT_FAILURE, 0,
+             "error: file has changed size unexpectedly: %s", filename);
+    n += r;
+    p += r;
+  }
+
+  if (close (fd) == -1)
+    error (EXIT_FAILURE, errno, "close: %s", filename);
+
+  return buf;
+}
+
+/* Add a file (or directory etc) from the host. */
+static void
+ext2_file_stat (const char *orig_filename, const struct stat *statbuf)
+{
+  errcode_t err;
+
+  if (verbose >= 2)
+    fprintf (stderr, "ext2_file_stat %s 0%o\n",
+             orig_filename, statbuf->st_mode);
+
+  /* Sanity check the path.  These rules are always true for the paths
+   * passed to us here from the appliance layer.  The assertions just
+   * verify that the rules haven't changed.
+   */
+  size_t n = strlen (orig_filename);
+  assert (n <= PATH_MAX);
+  assert (n > 0);
+  assert (orig_filename[0] == '/'); /* always absolute path */
+  assert (n == 1 || orig_filename[n-1] != '/'); /* no trailing slash */
+
+  /* Don't make the root directory, it always exists.  This simplifies
+   * the code that follows.
+   */
+  if (n == 1) return;
+
+  const char *dirname, *basename;
+  const char *p = strrchr (orig_filename, '/');
+  ext2_ino_t dir_ino;
+  if (orig_filename == p) {     /* "/foo" */
+    dirname = "/";
+    basename = orig_filename+1;
+    dir_ino = EXT2_ROOT_INO;
+  } else {                      /* "/foo/bar" */
+    dirname = strndup (orig_filename, p-orig_filename);
+    basename = p+1;
+
+    /* Look up the parent directory. */
+    err = ext2fs_namei (fs, EXT2_ROOT_INO, EXT2_ROOT_INO, dirname, &dir_ino);
+    if (err != 0)
+      error (EXIT_FAILURE, 0, "ext2: parent directory not found: %s: %s",
+             dirname, error_message (err));
+  }
+
+  ext2_clean_path (dir_ino, dirname, basename, S_ISDIR (statbuf->st_mode));
+
+  int dir_ft;
+
+  /* Create regular file. */
+  if (S_ISREG (statbuf->st_mode)) {
+    /* XXX Hard links get duplicated here. */
+    ext2_ino_t ino;
+    ext2_empty_inode (dir_ino, dirname, basename,
+                      statbuf->st_mode, statbuf->st_uid, statbuf->st_gid,
+                      statbuf->st_ctime, statbuf->st_atime, statbuf->st_mtime,
+                      0, 0, EXT2_FT_REG_FILE, &ino);
+
+    if (statbuf->st_size > 0) {
+      char *buf = read_whole_file (orig_filename, statbuf->st_size);
+      ext2_write_file (ino, buf, statbuf->st_size);
+      free (buf);
+    }
+  }
+  /* Create a symlink. */
+  else if (S_ISLNK (statbuf->st_mode)) {
+    ext2_ino_t ino;
+    ext2_empty_inode (dir_ino, dirname, basename,
+                      statbuf->st_mode, statbuf->st_uid, statbuf->st_gid,
+                      statbuf->st_ctime, statbuf->st_atime, statbuf->st_mtime,
+                      0, 0, EXT2_FT_SYMLINK, &ino);
+
+    char buf[PATH_MAX+1];
+    ssize_t r = readlink (orig_filename, buf, sizeof buf);
+    if (r == -1)
+      error (EXIT_FAILURE, errno, "readlink: %s", orig_filename);
+    ext2_write_file (ino, buf, r);
+  }
+  /* Create directory. */
+  else if (S_ISDIR (statbuf->st_mode))
+    ext2_mkdir (dir_ino, dirname, basename,
+                statbuf->st_mode, statbuf->st_uid, statbuf->st_gid,
+                statbuf->st_ctime, statbuf->st_atime, statbuf->st_mtime);
+  /* Create a special file. */
+  else if (S_ISBLK (statbuf->st_mode)) {
+    dir_ft = EXT2_FT_BLKDEV;
+    goto make_special;
+  }
+  else if (S_ISCHR (statbuf->st_mode)) {
+    dir_ft = EXT2_FT_CHRDEV;
+    goto make_special;
+  } else if (S_ISFIFO (statbuf->st_mode)) {
+    dir_ft = EXT2_FT_FIFO;
+    goto make_special;
+  } else if (S_ISSOCK (statbuf->st_mode)) {
+    dir_ft = EXT2_FT_SOCK;
+  make_special:
+    ext2_empty_inode (dir_ino, dirname, basename,
+                      statbuf->st_mode, statbuf->st_uid, statbuf->st_gid,
+                      statbuf->st_ctime, statbuf->st_atime, statbuf->st_mtime,
+                      major (statbuf->st_rdev), minor (statbuf->st_rdev),
+                      dir_ft, NULL);
+  }
+}
+
+static void
+ext2_file (const char *filename)
+{
+  struct stat statbuf;
+
+  if (lstat (filename, &statbuf) == -1)
+    error (EXIT_FAILURE, errno, "lstat: %s", filename);
+  ext2_file_stat (filename, &statbuf);
+}
+
+/* In theory this could be optimized to avoid a namei lookup, but
+ * it probably wouldn't make much difference.
+ */
+static void
+ext2_fts_entry (FTSENT *entry)
+{
+  if (entry->fts_info & FTS_NS || entry->fts_info & FTS_NSOK)
+    ext2_file (entry->fts_path);
+  else
+    ext2_file_stat (entry->fts_path, entry->fts_statp);
 }
 
 struct writer ext2_writer = {
   .wr_start = ext2_start,
-  /* .wr_end = ,
-  .wr_file = ,
-  .wr_file_stat = ,
-  .wr_fts_entry = ,
-  .wr_cpio_file = , */
+  .wr_end = ext2_end,
+  .wr_file = ext2_file,
+  .wr_file_stat = ext2_file_stat,
+  .wr_fts_entry = ext2_fts_entry,
+  .wr_cpio_file = ext2_cpio_file,
 };
diff --git a/helper/ext2cpio.c b/helper/ext2cpio.c
new file mode 100644
index 0000000..7690553
--- /dev/null
+++ b/helper/ext2cpio.c
@@ -0,0 +1,358 @@
+/* febootstrap-supermin-helper reimplementation in C.
+ * Copyright (C) 2009-2010 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <assert.h>
+
+#include "error.h"
+
+#include "helper.h"
+#include "ext2internal.h"
+
+/* This function must unpack the cpio file and add the files it
+ * contains to the ext2 filesystem.  Essentially this is doing the
+ * same thing as the kernel init/initramfs.c code.  Note that we
+ * assume that the cpio is uncompressed newc format and can't/won't
+ * deal with anything else.  All this cpio parsing code is copied to
+ * some extent from init/initramfs.c in the kernel.
+ */
+#define N_ALIGN(len) ((((len) + 1) & ~3) + 2)
+
+static unsigned long cpio_ino, nlink;
+static mode_t mode;
+static unsigned long body_len, name_len;
+static uid_t uid;
+static gid_t gid;
+static time_t mtime;
+static int dev_major, dev_minor, rdev_major, rdev_minor;
+static loff_t curr, next_header;
+static FILE *fp;
+
+static void parse_header (char *s);
+static int parse_next_entry (void);
+static void skip_to_next_header (void);
+static void read_file (void);
+static char *read_whole_body (void);
+static ext2_ino_t maybe_link (void);
+static void add_link (ext2_ino_t real_ino);
+static void clear_links (void);
+
+void
+ext2_cpio_file (const char *cpio_file)
+{
+  fp = fopen (cpio_file, "r");
+  if (fp == NULL)
+    error (EXIT_FAILURE, errno, "open: %s", cpio_file);
+
+  curr = 0;
+  while (parse_next_entry ())
+    ;
+
+  fclose (fp);
+}
+
+static int
+parse_next_entry (void)
+{
+  clearerr (fp);
+
+  char header[110];
+
+  /* Skip padding and synchronize with the next header. */
+ again:
+  if (fread (&header[0], 4, 1, fp) != 1) {
+    if (feof (fp))
+      return 0;
+    error (EXIT_FAILURE, errno, "read failure reading cpio file");
+  }
+  curr += 4;
+  if (memcmp (header, "\0\0\0\0", 4) == 0)
+    goto again;
+
+  /* Read the rest of the header field. */
+  if (fread (&header[4], sizeof header - 4, 1, fp) != 1)
+    error (EXIT_FAILURE, errno, "read failure reading cpio file");
+  curr += sizeof header - 4;
+
+  if (verbose >= 2)
+    fprintf (stderr, "cpio header %s\n", header);
+
+  if (memcmp (header, "070707", 6) == 0)
+    error (EXIT_FAILURE, 0, "incorrect cpio method: use -H newc option");
+  if (memcmp (header, "070701", 6) != 0)
+    error (EXIT_FAILURE, 0, "input is not a cpio file");
+
+  parse_header (header);
+
+  next_header = curr + N_ALIGN(name_len) + body_len;
+  next_header = (next_header + 3) & ~3;
+  if (name_len <= 0 || name_len > PATH_MAX)
+    skip_to_next_header ();
+  else if (S_ISLNK (mode)) {
+    if (body_len <= 0 || body_len > PATH_MAX)
+      skip_to_next_header ();
+    else
+      read_file ();
+  }
+  else if (!S_ISREG (mode) && body_len > 0)
+    skip_to_next_header (); /* only regular files have bodies */
+  else
+    read_file (); /* could be file, directory, block special, ... */
+
+  return 1;
+}
+
+static void
+parse_header (char *s)
+{
+  unsigned long parsed[12];
+  char buf[9];
+  int i;
+
+  buf[8] = '\0';
+  for (i = 0, s += 6; i < 12; i++, s += 8) {
+    memcpy (buf, s, 8);
+    parsed[i] = strtoul (buf, NULL, 16);
+  }
+  cpio_ino = parsed[0]; /* fake inode number from cpio file */
+  mode = parsed[1];
+  uid = parsed[2];
+  gid = parsed[3];
+  nlink = parsed[4];
+  mtime = parsed[5];
+  body_len = parsed[6];
+  dev_major = parsed[7];
+  dev_minor = parsed[8];
+  rdev_major = parsed[9];
+  rdev_minor = parsed[10];
+  name_len = parsed[11];
+}
+
+static void
+skip_to_next_header (void)
+{
+  char buf[65536];
+
+  while (curr < next_header) {
+    size_t bytes = (size_t) (next_header - curr);
+    if (bytes > sizeof buf)
+      bytes = sizeof buf;
+    size_t r = fread (buf, 1, bytes, fp);
+    if (r == 0)
+      error (EXIT_FAILURE, errno, "error or unexpected end of cpio file");
+    curr += r;
+  }
+}
+
+/* Read any sort of file.  The body will only be present for
+ * regular files and symlinks.
+ */
+static void
+read_file (void)
+{
+  errcode_t err;
+  int dir_ft;
+  char name[N_ALIGN(name_len)+1]; /* asserted above this is <= PATH_MAX */
+
+  if (fread (name, N_ALIGN(name_len), 1, fp) != 1)
+    error (EXIT_FAILURE, errno, "read failure reading name field in cpio file");
+  curr += N_ALIGN(name_len);
+
+  name[name_len] = '\0';
+
+  if (verbose >= 2)
+    fprintf (stderr, "ext2 read_file %s %o\n", name, mode);
+
+  if (strcmp (name, "TRAILER!!!") == 0) {
+    clear_links ();
+    goto skip;
+  }
+
+  /* The name will be something like "bin/ls" or "./bin/ls".  It won't
+   * (ever?) be an absolute path.  Skip leading parts, and if it refers
+   * to the root directory just skip it entirely.
+   */
+  char *dirname = name, *basename;
+  if (*dirname == '.')
+    dirname++;
+  if (*dirname == '/')
+    dirname++;
+  if (*dirname == '\0')
+    goto skip;
+
+  ext2_ino_t dir_ino;
+  basename = strrchr (dirname, '/');
+  if (basename == NULL) {
+    basename = dirname;
+    dir_ino = EXT2_ROOT_INO;
+  } else {
+    *basename++ = '\0';
+
+    /* Look up the parent directory. */
+    err = ext2fs_namei (fs, EXT2_ROOT_INO, EXT2_ROOT_INO, dirname, &dir_ino);
+    if (err != 0)
+      error (EXIT_FAILURE, 0, "ext2: parent directory not found: %s: %s",
+             dirname, error_message (err));
+  }
+
+  if (verbose >= 2)
+    fprintf (stderr, "ext2 read_file dirname %s basename %s\n",
+             dirname, basename);
+
+  ext2_clean_path (dir_ino, dirname, basename, S_ISDIR (mode));
+
+  /* Create a regular file. */
+  if (S_ISREG (mode)) {
+    ext2_ino_t ml = maybe_link ();
+    ext2_ino_t ino;
+    if (ml <= 1) {
+      ext2_empty_inode (dir_ino, dirname, basename,
+                        mode, uid, gid, mtime, mtime, mtime,
+                        0, 0, EXT2_FT_REG_FILE, &ino);
+      if (ml == 1)
+        add_link (ino);
+    }
+    else /* ml >= 2 */ {
+      /* It's a hard link back to a previous file. */
+      ino = ml;
+      ext2_link (dir_ino, basename, ino, EXT2_FT_REG_FILE);
+    }
+
+    if (body_len) {
+      char *buf = read_whole_body ();
+      ext2_write_file (ino, buf, body_len);
+      free (buf);
+    }
+  }
+  /* Create a symlink. */
+  else if (S_ISLNK (mode)) {
+    ext2_ino_t ino;
+    ext2_empty_inode (dir_ino, dirname, basename,
+                      mode, uid, gid, mtime, mtime, mtime,
+                      0, 0, EXT2_FT_SYMLINK, &ino);
+
+    char *buf = read_whole_body ();
+    ext2_write_file (ino, buf, body_len);
+    free (buf);
+  }
+  /* Create a directory. */
+  else if (S_ISDIR (mode)) {
+    ext2_mkdir (dir_ino, dirname, basename,
+                mode, uid, gid, mtime, mtime, mtime);
+  }
+  /* Create a special file. */
+  else if (S_ISBLK (mode)) {
+    dir_ft = EXT2_FT_BLKDEV;
+    goto make_special;
+  }
+  else if (S_ISCHR (mode)) {
+    dir_ft = EXT2_FT_CHRDEV;
+    goto make_special;
+  } else if (S_ISFIFO (mode)) {
+    dir_ft = EXT2_FT_FIFO;
+    goto make_special;
+  } else if (S_ISSOCK (mode)) {
+    dir_ft = EXT2_FT_SOCK;
+  make_special:
+    /* Just like the kernel, we ignore special files with nlink > 1. */
+    if (maybe_link () == 0)
+      ext2_empty_inode (dir_ino, dirname, basename,
+                        mode, uid, gid, mtime, mtime, mtime,
+                        rdev_major, rdev_minor, dir_ft, NULL);
+  }
+
+ skip:
+  skip_to_next_header ();
+}
+
+static char *
+read_whole_body (void)
+{
+  char *buf = malloc (body_len);
+  if (buf == NULL)
+    error (EXIT_FAILURE, errno, "malloc");
+
+  size_t r = fread (buf, body_len, 1, fp);
+  if (r != 1)
+    error (EXIT_FAILURE, errno, "read failure reading body in cpio file");
+  curr += body_len;
+
+  return buf;
+}
+
+struct links {
+  struct links *next;
+  unsigned long cpio_ino;       /* fake ino from cpio file */
+  int minor;
+  int major;
+  ext2_ino_t real_ino;          /* real inode number on ext2 filesystem */
+};
+static struct links *links_head = NULL;
+
+/* If it's a hard link, return the linked inode number in the real
+ * ext2 filesystem.
+ *
+ * Returns: 0 = not a hard link
+ *          1 = possible unresolved hard link
+ *          inode number = resolved hard link to this inode
+ */
+static ext2_ino_t
+maybe_link (void)
+{
+  if (nlink >= 2) {
+    struct links *p;
+    for (p = links_head; p; p = p->next) {
+      if (p->cpio_ino != cpio_ino)
+        continue;
+      if (p->minor != dev_minor)
+        continue;
+      if (p->major != dev_major)
+        continue;
+      return p->real_ino;
+    }
+    return 1;
+  }
+
+  return 0;
+}
+
+static void
+add_link (ext2_ino_t real_ino)
+{
+  struct links *p = malloc (sizeof (*p));
+  p->cpio_ino = cpio_ino;
+  p->minor = dev_minor;
+  p->major = dev_major;
+  p->real_ino = real_ino;
+}
+
+static void
+clear_links (void)
+{
+  /* Don't bother to free the linked list in this short-lived program. */
+  links_head = NULL;
+}
diff --git a/helper/ext2initrd.c b/helper/ext2initrd.c
new file mode 100644
index 0000000..c981232
--- /dev/null
+++ b/helper/ext2initrd.c
@@ -0,0 +1,263 @@
+/* febootstrap-supermin-helper reimplementation in C.
+ * Copyright (C) 2009-2010 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* ext2 requires a small initrd in order to boot.  This builds it. */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <errno.h>
+
+#include "error.h"
+#include "full-write.h"
+#include "xalloc.h"
+#include "xvasprintf.h"
+
+#include "helper.h"
+#include "ext2internal.h"
+
+static void read_module_deps (const char *modpath);
+static void free_module_deps (void);
+static const char *get_module_dep (const char *);
+
+/* The init binary. */
+extern char _binary_init_start, _binary_init_end, _binary_init_size;
+
+/* The list of modules (wildcards) we consider for inclusion in the
+ * mini initrd.  Only what is needed in order to find a device with an
+ * ext2 filesystem on it.
+ */
+static const char *kmods[] = {
+  "ext2.ko",
+  "virtio*.ko",
+  "ide*.ko",
+  "libata*.ko",
+  "piix*.ko",
+  "scsi_transport_spi.ko",
+  "scsi_mod.ko",
+  "sd_mod.ko",
+  "sym53c8xx.ko",
+  "ata_piix.ko",
+  "sr_mod.ko",
+  "mbcache.ko",
+  "crc*.ko",
+  "libcrc*.ko",
+  NULL
+};
+
+void
+ext2_make_initrd (const char *modpath, const char *initrd)
+{
+  char dir[] = "/tmp/ext2initrdXXXXXX";
+  if (mkdtemp (dir) == NULL)
+    error (EXIT_FAILURE, errno, "mkdtemp");
+
+  char *cmd;
+  int r;
+
+  /* Copy kernel modules into tmpdir. */
+  size_t n = strlen (modpath) + strlen (dir) + 64;
+  size_t i;
+  for (i = 0; kmods[i] != NULL; ++i)
+    n += strlen (kmods[i]) + 16;
+  cmd = malloc (n);
+  sprintf (cmd, "find '%s' ", modpath);
+  for (i = 0; kmods[i] != NULL; ++i) {
+    if (i > 0) strcat (cmd, "-o ");
+    strcat (cmd, "-name '");
+    strcat (cmd, kmods[i]);
+    strcat (cmd, "' ");
+  }
+  strcat (cmd, "| xargs cp -t ");
+  strcat (cmd, dir);
+  if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
+  r = system (cmd);
+  if (r == -1 || WEXITSTATUS (r) != 0)
+    error (EXIT_FAILURE, 0, "ext2_make_initrd: copy kmods failed");
+  free (cmd);
+
+  /* The above command effectively gives us the final list of modules.
+   * Calculate dependencies from modpath/modules.dep and write that
+   * into the output.
+   */
+  read_module_deps (modpath);
+
+  cmd = xasprintf ("tsort > %s/modules", dir);
+  if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
+  FILE *pp = popen (cmd, "w");
+  if (pp == NULL)
+    error (EXIT_FAILURE, errno, "tsort: failed to create modules list");
+
+  DIR *dr = opendir (dir);
+  if (dr == NULL)
+    error (EXIT_FAILURE, errno, "opendir: %s", dir);
+
+  struct dirent *d;
+  while ((errno = 0, d = readdir (dr)) != NULL) {
+    size_t n = strlen (d->d_name);
+    if (n >= 3 &&
+        d->d_name[n-3] == '.' &&
+        d->d_name[n-2] == 'k' &&
+        d->d_name[n-1] == 'o') {
+      const char *dep = get_module_dep (d->d_name);
+      if (dep)
+        /* Reversed so that tsort will print the final list in the
+         * order that it has to be loaded.
+         */
+        fprintf (pp, "%s %s\n", dep, d->d_name);
+      else
+        /* No dependencies, just make it depend on itself so that
+         * tsort prints it.
+         */
+        fprintf (pp, "%s %s\n", d->d_name, d->d_name);
+    }
+  }
+  if (errno)
+    error (EXIT_FAILURE, errno, "readdir: %s", dir);
+
+  if (closedir (dr) == -1)
+    error (EXIT_FAILURE, errno, "closedir: %s", dir);
+
+  if (pclose (pp) == -1)
+    error (EXIT_FAILURE, errno, "pclose: %s", cmd);
+
+  free (cmd);
+  free_module_deps ();
+
+  /* Copy in insmod static binary. */
+  cmd = xasprintf ("cp /sbin/insmod.static %s", dir);
+  if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
+  r = system (cmd);
+  if (r == -1 || WEXITSTATUS (r) != 0)
+    error (EXIT_FAILURE, 0,
+           "ext2_make_initrd: copy /sbin/insmod.static failed");
+  free (cmd);
+
+  /* Copy in the init program, linked into this program as a data blob. */
+  char *init = xasprintf ("%s/init", dir);
+  int fd = open (init, O_WRONLY|O_TRUNC|O_CREAT|O_NOCTTY, 0755);
+  if (fd == -1)
+    error (EXIT_FAILURE, errno, "open: %s", init);
+
+  n = (size_t) &_binary_init_size;
+  if (full_write (fd, &_binary_init_start, n) != n)
+    error (EXIT_FAILURE, errno, "write: %s", init);
+
+  if (close (fd) == -1)
+    error (EXIT_FAILURE, errno, "close: %s", init);
+
+  free (init);
+
+  /* Build the cpio file. */
+  cmd = xasprintf ("(cd %s && (echo . ; ls -1)"
+                   " | cpio --quiet -o -H newc) > '%s'",
+                   dir, initrd);
+  if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
+  r = system (cmd);
+  if (r == -1 || WEXITSTATUS (r) != 0)
+    error (EXIT_FAILURE, 0, "ext2_make_initrd: cpio failed");
+  free (cmd);
+
+  /* Construction of 'dir' above ensures this is safe. */
+  cmd = xasprintf ("rm -rf %s", dir);
+  if (verbose >= 2) fprintf (stderr, "%s\n", cmd);
+  system (cmd);
+  free (cmd);
+}
+
+/* Module dependencies. */
+struct moddep {
+  struct moddep *next;
+  char *name;
+  char *dep;
+};
+struct moddep *moddeps = NULL;
+
+static void add_module_dep (const char *name, const char *dep);
+
+static void
+free_module_deps (void)
+{
+  /* Short-lived program, don't bother to free it. */
+  moddeps = NULL;
+}
+
+/* Read modules.dep into internal structure. */
+static void
+read_module_deps (const char *modpath)
+{
+  free_module_deps ();
+
+  char *filename = xasprintf ("%s/modules.dep", modpath);
+  FILE *fp = fopen (filename, "r");
+  if (fp == NULL)
+    error (EXIT_FAILURE, errno, "open: %s", modpath);
+
+  char *line = NULL;
+  size_t llen = 0;
+  ssize_t len;
+  while ((len = getline (&line, &llen, fp)) != -1) {
+    if (len > 0 && line[len-1] == '\n')
+      line[--len] = '\0';
+
+    char *name = strtok (line, ": ");
+    if (!name) continue;
+
+    /* Only want the module basename, but keep the ".ko" extension. */
+    char *p = strrchr (name, '/');
+    if (p) name = p+1;
+
+    char *dep;
+    while ((dep = strtok (NULL, " ")) != NULL) {
+      p = strrchr (dep, '/');
+      if (p) dep = p+1;
+
+      add_module_dep (name, dep);
+    }
+  }
+
+  free (line);
+  fclose (fp);
+}
+
+/* Module 'name' requires 'dep' to be loaded first. */
+static void
+add_module_dep (const char *name, const char *dep)
+{
+  struct moddep *m = xmalloc (sizeof *m);
+  m->next = moddeps;
+  moddeps = m;
+  m->name = xstrdup (name);
+  m->dep = xstrdup (dep);
+}
+
+static const char *
+get_module_dep (const char *name)
+{
+  struct moddep *m;
+
+  for (m = moddeps; m; m = m->next)
+    if (strcmp (m->name, name) == 0)
+      return m->dep;
+
+  return NULL;
+}
diff --git a/helper/ext2internal.h b/helper/ext2internal.h
new file mode 100644
index 0000000..7efadb5
--- /dev/null
+++ b/helper/ext2internal.h
@@ -0,0 +1,45 @@
+/* febootstrap-supermin-helper reimplementation in C.
+ * Copyright (C) 2009-2010 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* This is a private interface used between the parts of the ext2 plugin. */
+
+#ifndef FEBOOTSTRAP_SUPERMIN_EXT2INTERNAL_H
+#define FEBOOTSTRAP_SUPERMIN_EXT2INTERNAL_H
+
+/* Inlining is broken in the ext2fs header file.  Disable it by
+ * defining the following:
+ */
+#define NO_INLINE_FUNCS
+#include <ext2fs/ext2fs.h>
+
+/* ext2.c */
+extern ext2_filsys fs;
+
+extern void ext2_mkdir (ext2_ino_t dir_ino, const char *dirname, const char *basename, mode_t mode, uid_t uid, gid_t gid, time_t ctime, time_t atime, time_t mtime);
+extern void ext2_empty_inode (ext2_ino_t dir_ino, const char *dirname, const char *basename, mode_t mode, uid_t uid, gid_t gid, time_t ctime, time_t atime, time_t mtime, int major, int minor, int dir_ft, ext2_ino_t *ino_ret);
+extern void ext2_write_file (ext2_ino_t ino, const char *buf, size_t size);
+extern void ext2_link (ext2_ino_t dir_ino, const char *basename, ext2_ino_t ino, int dir_ft);
+extern void ext2_clean_path (ext2_ino_t dir_ino, const char *dirname, const char *basename, int isdir);
+
+/* ext2cpio.c */
+extern void ext2_cpio_file (const char *cpio_file);
+
+/* ext2initrd.c */
+extern void ext2_make_initrd (const char *modpath, const char *initrd);
+
+#endif /* FEBOOTSTRAP_SUPERMIN_EXT2INTERNAL_H */
diff --git a/helper/init.c b/helper/init.c
new file mode 100644
index 0000000..1ea92cb
--- /dev/null
+++ b/helper/init.c
@@ -0,0 +1,172 @@
+/* febootstrap-supermin-helper reimplementation in C.
+ * Copyright (C) 2009-2010 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/* This very minimal init "script" goes in the mini-initrd used to
+ * boot the ext2-based appliance.  Note we have no shell, so we cannot
+ * use system(3) to run external commands.  In fact, we don't have
+ * very much at all, except this program, insmod.static, and some
+ * kernel modules.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+#define verbose 1
+
+static void insmod (const char *filename);
+static char line[1024];
+
+void
+main ()
+{
+  fprintf (stderr, "febootstrap: ext2 mini initrd starting up\n");
+
+  /* Create some fixed directories. */
+  mkdir ("/dev", 0755);
+  mkdir ("/root", 0755);
+  mkdir ("/sys", 0755);
+
+  /* Mount /sys. */
+  if (verbose)
+    fprintf (stderr, "febootstrap: mounting /sys\n");
+  if (mount ("sysfs", "/sys", "sysfs", 0, "") == -1) {
+    perror ("mount: /sys");
+    exit (EXIT_FAILURE);
+  }
+
+  FILE *fp = fopen ("/modules", "r");
+  if (fp == NULL) {
+    perror ("fopen: /modules");
+    exit (EXIT_FAILURE);
+  }
+  while (fgets (line, sizeof line, fp)) {
+    size_t n = strlen (line);
+    if (n > 0 && line[n-1] == '\n')
+      line[--n] = '\0';
+    insmod (line);
+  }
+  fclose (fp);
+
+  /* Look for the ext2 filesystem device.  It's always the last
+   * one that was added.
+   * XXX More than 25 devices?
+   */
+  char path[] = "/sys/block/xdx/dev";
+  char class[3] = { 'v', 's', 'h' };
+  size_t i, j;
+  fp = NULL;
+  for (i = 0; i < sizeof class; ++i) {
+    for (j = 'z'; j >= 'a'; --j) {
+      path[11] = class[i];
+      path[13] = j;
+      fp = fopen (path, "r");
+      if (fp != NULL)
+        goto found;
+    }
+  }
+  fprintf (stderr,
+           "febootstrap: no ext2 root device found\n"
+           "Please include FULL verbose output in your bug report.\n");
+  exit (EXIT_FAILURE);
+
+ found:
+  if (verbose)
+    fprintf (stderr, "febootstrap: picked %s as root device\n", path);
+
+  fgets (line, sizeof line, fp);
+  int major = atoi (line);
+  char *p = line + strcspn (line, ":") + 1;
+  int minor = atoi (p);
+
+  fclose (fp);
+  if (umount ("/sys") == -1) {
+    perror ("umount: /sys");
+    exit (EXIT_FAILURE);
+  }
+
+  if (verbose)
+    fprintf (stderr, "febootstrap: creating /dev/root as block special %d:%d\n",
+             major, minor);
+
+  if (mknod ("/dev/root", S_IFBLK|0700, makedev (major, minor)) == -1) {
+    perror ("mknod: /dev/root");
+    exit (EXIT_FAILURE);
+  }
+
+  /* Mount new root and chroot to it. */
+  if (verbose)
+    fprintf (stderr, "febootstrap: mounting new root on /root\n");
+  if (mount ("/dev/root", "/root", "ext2", MS_NOATIME, "") == -1) {
+    perror ("mount: /root");
+    exit (EXIT_FAILURE);
+  }
+
+  /* Note that pivot_root won't work.  See the note in
+   * Documentation/filesystems/ramfs-rootfs-initramfs.txt
+   * We could remove the old initramfs files, but let's not bother.
+   */
+  if (verbose)
+    fprintf (stderr, "febootstrap: chroot\n");
+
+  if (chroot ("/root") == -1) {
+    perror ("chroot: /root");
+    exit (EXIT_FAILURE);
+  }
+
+  chdir ("/");
+
+  /* Run /init from ext2 filesystem. */
+  execl ("/init", "init", NULL);
+  perror ("execl: /init");
+  exit (EXIT_FAILURE);
+}
+
+static void
+insmod (const char *filename)
+{
+  if (verbose)
+    fprintf (stderr, "febootstrap: insmod %s\n", filename);
+
+  pid_t pid = fork ();
+  if (pid == -1) {
+    perror ("insmod: fork");
+    exit (EXIT_FAILURE);
+  }
+
+  if (pid == 0) { /* Child. */
+    execl ("/insmod.static", "insmod.static", filename, NULL);
+    perror ("insmod: execl");
+    _exit (EXIT_FAILURE);
+  }
+
+  /* Parent. */
+  int status;
+  if (wait (&status) == -1 ||
+      WEXITSTATUS (status) != 0)
+    perror ("insmod: wait");
+    /* but ignore the error, some will be because the device is not found */
+}
-- 
1.7.1


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