Initial commit

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

16 files changed, 2169 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
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+.deps
+.dirstamp
+.gdb_history
+Makefile
+Makefile.in
+aclocal.m4
+autom4te.cache
+compile
+config.h.in
+config.log
+config.status
+configure
+depcomp
+install-sh
+missing
+stamp-h1
+config.h
+*.o
+*.a
+*~
+mksquashfs
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..f288702
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
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+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    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 3 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, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
diff --git a/Makefile.am b/Makefile.am
new file mode 100644
index 0000000..1b8284b
--- /dev/null
+++ b/Makefile.am
@@ -0,0 +1,12 @@
+ACLOCAL_AMFLAGS = -I m4
+
+AM_CPPFLAGS = -I$(top_srcdir)/include -D_GNU_SOURCE
+AM_CFLAGS = $(WARN_CFLAGS)
+
+noinst_LIBRARIES =
+bin_PROGRAMS =
+
+EXTRA_DIST = autogen.sh LICENSE
+
+include lib/Makemodule.am
+include mkfs/Makemodule.am
diff --git a/autogen.sh b/autogen.sh
new file mode 100755
index 0000000..c08fadf
--- /dev/null
+++ b/autogen.sh
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+autoreconf --force --install --symlink
diff --git a/configure.ac b/configure.ac
new file mode 100644
index 0000000..18a4a81
--- /dev/null
+++ b/configure.ac
@@ -0,0 +1,57 @@
+AC_PREREQ([2.60])
+AC_INIT([squashfs-tools-ng], [0.1], [goliath@sigma-star.at], squashfs-tools-ng)
+AC_CONFIG_MACRO_DIR([m4])
+AM_INIT_AUTOMAKE([foreign dist-xz subdir-objects])
+AM_SILENT_RULES([yes])
+AC_PROG_CC
+AC_PROG_CC_C99
+AC_PROG_RANLIB
+AC_PROG_INSTALL
+
+m4_ifndef([PKG_PROG_PKG_CONFIG],
+  [m4_fatal([Could not locate the pkg-config autoconf
+    macros. These are usually located in /usr/share/aclocal/pkg.m4.
+    If your macros are in a different location, try setting the
+    environment variable AL_OPTS="-I/other/macro/dir" before running
+    ./autogen.sh or autoreconf again. Make sure pkg-config is installed.])])
+PKG_PROG_PKG_CONFIG
+
+UL_WARN_ADD([-Wall])
+UL_WARN_ADD([-Wextra])
+UL_WARN_ADD([-Wunused])
+UL_WARN_ADD([-Wmissing-prototypes])
+UL_WARN_ADD([-Wmissing-declarations])
+UL_WARN_ADD([-Wwrite-strings])
+UL_WARN_ADD([-Wjump-misses-init])
+UL_WARN_ADD([-Wuninitialized])
+UL_WARN_ADD([-Winit-self])
+UL_WARN_ADD([-Wlogical-op])
+UL_WARN_ADD([-Wunused-but-set-parameter])
+UL_WARN_ADD([-Wunused-but-set-variable])
+UL_WARN_ADD([-Wunused-parameter])
+UL_WARN_ADD([-Wunused-result])
+UL_WARN_ADD([-Wunused-variable])
+UL_WARN_ADD([-Wduplicated-cond])
+UL_WARN_ADD([-Wduplicated-branches])
+UL_WARN_ADD([-Wrestrict])
+UL_WARN_ADD([-Wnull-dereference])
+UL_WARN_ADD([-pedantic])
+
+AC_SUBST([WARN_CFLAGS])
+
+##### search for dependencies #####
+
+have_zlib="no"
+have_lzma="no"
+
+PKG_CHECK_MODULES(ZLIB, [zlib], [have_zlib="yes"], [])
+PKG_CHECK_MODULES(XZ, [liblzma >= 5.0.0], [have_lzma="yes"], [])
+
+AM_CONDITIONAL([WITH_ZLIB], [test "x$have_zlib" == "xyes"])
+AM_CONDITIONAL([WITH_LZMA], [test "x$have_lzma" == "xyes"])
+
+##### generate output #####
+
+AC_CONFIG_HEADERS([config.h])
+
+AC_OUTPUT([Makefile])
diff --git a/include/fstree.h b/include/fstree.h
new file mode 100644
index 0000000..68bbc7d
--- /dev/null
+++ b/include/fstree.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef FSTREE_H
+#define FSTREE_H
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stddef.h>
+
+typedef struct tree_node_t tree_node_t;
+typedef struct file_info_t file_info_t;
+typedef struct dir_info_t dir_info_t;
+typedef struct fstree_t fstree_t;
+
+struct file_info_t {
+	char *input_file;
+	file_info_t *frag_next;
+	uint64_t size;
+	uint64_t startblock;
+	uint32_t fragment;
+	uint32_t fragment_offset;
+	uint32_t blocksizes[];
+};
+
+struct dir_info_t {
+	tree_node_t *children;
+	uint64_t size;
+	uint64_t start_block;
+	uint32_t block_offset;
+	bool created_implicitly;
+};
+
+struct tree_node_t {
+	tree_node_t *next;
+	char *name;
+	uint32_t uid;
+	uint32_t gid;
+	uint16_t mode;
+
+	union {
+		dir_info_t *dir;
+		file_info_t *file;
+		char *slink_target;
+		uint64_t devno;
+	} data;
+
+	uint8_t payload[];
+};
+
+struct fstree_t {
+	uint32_t default_uid;
+	uint32_t default_gid;
+	uint32_t default_mode;
+	uint32_t default_mtime;
+	size_t block_size;
+
+	tree_node_t *root;
+};
+
+int fstree_init(fstree_t *fs, size_t block_size, uint32_t mtime,
+		uint16_t default_mode, uint32_t default_uid,
+		uint32_t default_gid);
+
+void fstree_cleanup(fstree_t *fs);
+
+tree_node_t *fstree_add(fstree_t *fs, const char *path, uint16_t mode,
+			uint32_t uid, uint32_t gid, size_t extra_len);
+
+tree_node_t *fstree_add_file(fstree_t *fs, const char *path, uint16_t mode,
+			     uint32_t uid, uint32_t gid, uint64_t filesz,
+			     const char *input);
+
+int fstree_from_file(fstree_t *fs, const char *filename);
+
+void fstree_sort(fstree_t *fs);
+
+#endif /* FSTREE_H */
diff --git a/include/squashfs.h b/include/squashfs.h
new file mode 100644
index 0000000..68f9fce
--- /dev/null
+++ b/include/squashfs.h
@@ -0,0 +1,177 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef SQUASHFS_H
+#define SQUASHFS_H
+
+#include <stdint.h>
+
+#define SQFS_MAGIC 0x73717368
+#define SQFS_VERSION_MAJOR 4
+#define SQFS_VERSION_MINOR 0
+#define SQFS_META_BLOCK_SIZE 8192
+#define SQFS_DEFAULT_BLOCK_SIZE 131072
+#define SQFS_DEVBLK_SIZE 4096
+#define SQFS_MAX_DIR_ENT 256
+
+typedef struct {
+	uint32_t magic;
+	uint32_t inode_count;
+	uint32_t modification_time;
+	uint32_t block_size;
+	uint32_t fragment_entry_count;
+	uint16_t compression_id;
+	uint16_t block_log;
+	uint16_t flags;
+	uint16_t id_count;
+	uint16_t version_major;
+	uint16_t version_minor;
+	uint64_t root_inode_ref;
+	uint64_t bytes_used;
+	uint64_t id_table_start;
+	uint64_t xattr_id_table_start;
+	uint64_t inode_table_start;
+	uint64_t directory_table_start;
+	uint64_t fragment_table_start;
+	uint64_t export_table_start;
+} __attribute__((packed)) sqfs_super_t;
+
+typedef struct {
+	uint64_t start_offset;
+	uint32_t size;
+	uint32_t pad0;
+} sqfs_fragment_t;
+
+typedef struct {
+	uint16_t type;
+	uint16_t mode;
+	uint16_t uid_idx;
+	uint16_t gid_idx;
+	uint32_t mod_time;
+	uint32_t inode_number;
+} sqfs_inode_t;
+
+typedef struct {
+	uint32_t nlink;
+	uint32_t devno;
+} sqfs_inode_dev_t;
+
+typedef struct {
+	uint32_t nlink;
+	uint32_t devno;
+	uint32_t xattr_idx;
+} sqfs_inode_dev_ext_t;
+
+typedef struct {
+	uint32_t nlink;
+	uint32_t target_size;
+	uint8_t target[];
+} sqfs_inode_slink_t;
+
+typedef struct {
+	uint32_t blocks_start;
+	uint32_t fragment_index;
+	uint32_t fragment_offset;
+	uint32_t file_size;
+	uint32_t block_sizes[];
+} sqfs_inode_file_t;
+
+typedef struct {
+	uint64_t blocks_start;
+	uint64_t file_size;
+	uint64_t sparse;
+	uint32_t nlink;
+	uint32_t fragment_idx;
+	uint32_t fragment_offset;
+	uint32_t xattr_idx;
+	uint32_t block_sizes[];
+} sqfs_inode_file_ext_t;
+
+typedef struct {
+	uint32_t start_block;
+	uint32_t nlink;
+	uint16_t size;
+	uint16_t offset;
+	uint32_t parent_inode;
+} sqfs_inode_dir_t;
+
+typedef struct {
+	uint32_t nlink;
+	uint32_t size;
+	uint32_t start_block;
+	uint32_t parent_inode;
+	uint16_t inodex_count;
+	uint16_t offset;
+	uint32_t xattr_idx;
+} sqfs_inode_dir_ext_t;
+
+typedef union {
+	sqfs_inode_t inode;
+
+	union {
+		sqfs_inode_dev_t dev;
+		sqfs_inode_dev_ext_t dev_ext;
+		sqfs_inode_slink_t slink;
+		sqfs_inode_file_t file;
+		sqfs_inode_file_ext_t file_ext;
+		sqfs_inode_dir_t dir;
+		sqfs_inode_dir_ext_t dir_ext;
+	} data;
+} sqfs_inode_generic_t;
+
+typedef struct {
+	uint32_t count;
+	uint32_t start_block;
+	uint32_t inode_number;
+} sqfs_dir_header_t;
+
+typedef struct {
+	uint16_t offset;
+	uint16_t inode_number;
+	uint16_t type;
+	uint16_t size;
+	uint8_t name[];
+} sqfs_dir_entry_t;
+
+typedef enum {
+	SQFS_COMP_GZIP = 1,
+	SQFS_COMP_LZMA = 2,
+	SQFS_COMP_LZO = 3,
+	SQFS_COMP_XZ = 4,
+	SQFS_COMP_LZ4 = 5,
+	SQFS_COMP_ZSTD = 6,
+
+	SQFS_COMP_MIN = 1,
+	SQFS_COMP_MAX = 6,
+} E_SQFS_COMPRESSOR;
+
+typedef enum {
+	SQFS_FLAG_UNCOMPRESSED_INODES = 0x0001,
+	SQFS_FLAG_UNCOMPRESSED_DATA = 0x0002,
+	SQFS_FLAG_UNCOMPRESSED_FRAGMENTS = 0x0008,
+	SQFS_FLAG_NO_FRAGMENTS = 0x0010,
+	SQFS_FLAG_ALWAYS_FRAGMENTS = 0x0020,
+	SQFS_FLAG_DUPLICATES = 0x0040,
+	SQFS_FLAG_EXPORTABLE = 0x0080,
+	SQFS_FLAG_UNCOMPRESSED_XATTRS = 0x0100,
+	SQFS_FLAG_NO_XATTRS = 0x0200,
+	SQFS_FLAG_COMPRESSOR_OPTIONS = 0x0400,
+	SQFS_FLAG_UNCOMPRESSED_IDS = 0x0800,
+} E_SQFS_SUPER_FLAGS;
+
+typedef enum {
+	SQFS_INODE_DIR = 1,
+	SQFS_INODE_FILE = 2,
+	SQFS_INODE_SLINK = 3,
+	SQFS_INODE_BDEV = 4,
+	SQFS_INODE_CDEV = 5,
+	SQFS_INODE_FIFO = 6,
+	SQFS_INODE_SOCKET = 7,
+	SQFS_INODE_EXT_DIR = 8,
+	SQFS_INODE_EXT_FILE = 9,
+	SQFS_INODE_EXT_SLINK = 10,
+	SQFS_INODE_EXT_BDEV = 11,
+	SQFS_INODE_EXT_CDEV = 12,
+	SQFS_INODE_EXT_FIFO = 13,
+	SQFS_INODE_EXT_SOCKET = 14,
+} E_SQFS_INODE_TYPE;
+
+#endif /* SQUASHFS_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
new file mode 100644
index 0000000..18ec8c4
--- /dev/null
+++ b/lib/Makemodule.am
@@ -0,0 +1,5 @@
+libfstree_a_SOURCES = lib/fstree/fstree.c lib/fstree/fstree_from_file.c
+libfstree_a_SOURCES += lib/fstree/fstree_sort.c
+libfstree_a_SOURCES += include/fstree.h
+
+noinst_LIBRARIES += libfstree.a
diff --git a/lib/fstree/fstree.c b/lib/fstree/fstree.c
new file mode 100644
index 0000000..2722b4a
--- /dev/null
+++ b/lib/fstree/fstree.c
@@ -0,0 +1,200 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "fstree.h"
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+
+static tree_node_t *mknode(tree_node_t *parent, const char *name,
+			   size_t name_len, size_t extra_len,
+			   uint16_t mode, uint32_t uid, uint32_t gid)
+{
+	size_t size = sizeof(tree_node_t) + extra_len;
+	tree_node_t *n;
+
+	switch (mode & S_IFMT) {
+	case S_IFDIR:
+		size += sizeof(*n->data.dir);
+		break;
+	case S_IFREG:
+		size += sizeof(*n->data.file);
+		break;
+	}
+
+	n = calloc(1, size + name_len + 1);
+	if (n == NULL)
+		return NULL;
+
+	if (parent != NULL) {
+		n->next = parent->data.dir->children;
+		parent->data.dir->children = n;
+	}
+
+	n->uid = uid;
+	n->gid = gid;
+	n->mode = mode;
+
+	switch (mode & S_IFMT) {
+	case S_IFDIR:
+		n->data.dir = (dir_info_t *)n->payload;
+		break;
+	case S_IFREG:
+		n->data.file = (file_info_t *)n->payload;
+		break;
+	case S_IFLNK:
+		n->data.slink_target = (char *)n->payload;
+		break;
+	}
+
+	n->name = (char *)n + size;
+	memcpy(n->name, name, name_len);
+	return n;
+}
+
+static void free_recursive(tree_node_t *n)
+{
+	tree_node_t *it;
+
+	if (S_ISDIR(n->mode)) {
+		while (n->data.dir->children != NULL) {
+			it = n->data.dir->children;
+			n->data.dir->children = it->next;
+
+			free_recursive(it);
+		}
+	}
+
+	free(n);
+}
+
+static tree_node_t *child_by_name(tree_node_t *root, const char *name,
+				  size_t len)
+{
+	tree_node_t *n = root->data.dir->children;
+
+	while (n != NULL) {
+		if (strncmp(n->name, name, len) == 0 && n->name[len] == '\0')
+			break;
+
+		n = n->next;
+	}
+
+	return n;
+}
+
+static tree_node_t *get_parent_node(fstree_t *fs, tree_node_t *root,
+				    const char *path)
+{
+	const char *end;
+	tree_node_t *n;
+
+	for (;;) {
+		if (!S_ISDIR(root->mode)) {
+			errno = ENOTDIR;
+			return NULL;
+		}
+
+		end = strchr(path, '/');
+		if (end == NULL)
+			break;
+
+		n = child_by_name(root, path, end - path);
+
+		if (n == NULL) {
+			n = mknode(root, path, end - path, 0,
+				   S_IFDIR | fs->default_mode,
+				   fs->default_uid, fs->default_gid);
+			if (n == NULL)
+				return NULL;
+
+			n->data.dir->created_implicitly = true;
+		}
+
+		root = n;
+		path = end + 1;
+	}
+
+	return root;
+}
+
+tree_node_t *fstree_add(fstree_t *fs, const char *path, uint16_t mode,
+			uint32_t uid, uint32_t gid, size_t extra_len)
+{
+	tree_node_t *child, *parent;
+	const char *name;
+
+	name = strrchr(path, '/');
+	name = (name == NULL ? path : (name + 1));
+
+	parent = get_parent_node(fs, fs->root, path);
+	if (parent == NULL)
+		return NULL;
+
+	child = child_by_name(parent, name, strlen(name));
+	if (child != NULL) {
+		if (S_ISDIR(child->mode) && S_ISDIR(mode) &&
+		    child->data.dir->created_implicitly) {
+			child->data.dir->created_implicitly = false;
+			return child;
+		}
+
+		errno = EEXIST;
+		return NULL;
+	}
+
+	return mknode(parent, name, strlen(name), extra_len, mode, uid, gid);
+}
+
+tree_node_t *fstree_add_file(fstree_t *fs, const char *path, uint16_t mode,
+			     uint32_t uid, uint32_t gid, uint64_t filesz,
+			     const char *input)
+{
+	tree_node_t *node;
+	size_t count, extra;
+	char *ptr;
+
+	count = filesz / fs->block_size;
+	extra = sizeof(uint32_t) * count + strlen(input) + 1;
+
+	mode &= 07777;
+	node = fstree_add(fs, path, S_IFREG | mode, uid, gid, extra);
+
+	if (node != NULL) {
+		ptr = (char *)(node->data.file->blocksizes + count);
+		strcpy(ptr, input);
+
+		node->data.file->input_file = ptr;
+		node->data.file->size = filesz;
+	}
+	return node;
+}
+
+int fstree_init(fstree_t *fs, size_t block_size, uint32_t mtime,
+		uint16_t default_mode, uint32_t default_uid,
+		uint32_t default_gid)
+{
+	memset(fs, 0, sizeof(*fs));
+
+	fs->default_uid = default_uid;
+	fs->default_gid = default_gid;
+	fs->default_mode = default_mode & 07777;
+	fs->default_mtime = mtime;
+	fs->block_size = block_size;
+
+	fs->root = mknode(NULL, "", 0, 0, S_IFDIR | fs->default_mode,
+			  default_uid, default_gid);
+
+	if (fs->root == NULL) {
+		perror("initializing file system tree");
+		return -1;
+	}
+
+	return 0;
+}
+
+void fstree_cleanup(fstree_t *fs)
+{
+	free_recursive(fs->root);
+	memset(fs, 0, sizeof(*fs));
+}
diff --git a/lib/fstree/fstree_from_file.c b/lib/fstree/fstree_from_file.c
new file mode 100644
index 0000000..66d71a2
--- /dev/null
+++ b/lib/fstree/fstree_from_file.c
@@ -0,0 +1,436 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "fstree.h"
+
+#include <sys/sysmacros.h>
+#include <sys/types.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+#include <ctype.h>
+#include <errno.h>
+
+static int add_dir(fstree_t *fs, const char *filename, size_t line_num,
+		   const char *path, uint16_t mode, uint32_t uid,
+		   uint32_t gid, const char *extra)
+{
+	if (extra != NULL && *extra != '\0') {
+		fprintf(stderr, "%s: %zu: WARNING: ignoring extra arguments\n",
+			filename, line_num);
+	}
+
+	if (fstree_add(fs, path, S_IFDIR | mode, uid, gid, 0) == NULL) {
+		fprintf(stderr, "%s: %zu: mkdir -p %s: %s\n",
+			filename, line_num, path, strerror(errno));
+		return -1;
+	}
+
+	return 0;
+}
+
+static int add_slink(fstree_t *fs, const char *filename, size_t line_num,
+		     const char *path, uint16_t mode, uint32_t uid,
+		     uint32_t gid, const char *extra)
+{
+	tree_node_t *node;
+	(void)mode;
+
+	if (extra == NULL || *extra == '\0') {
+		fprintf(stderr, "%s: %zu: missing symlink target\n",
+			filename, line_num);
+		return -1;
+	}
+
+	node = fstree_add(fs, path, S_IFLNK | 0777, uid, gid,
+			  strlen(extra) + 1);
+
+	if (node == NULL) {
+		fprintf(stderr, "%s: %zu: ln -s %s %s\n",
+			filename, line_num, extra, path);
+		return -1;
+	}
+
+	strcpy(node->data.slink_target, extra);
+	return 0;
+}
+
+static int add_device(fstree_t *fs, const char *filename, size_t line_num,
+		      const char *path, uint16_t mode, uint32_t uid,
+		      uint32_t gid, const char *extra)
+{
+	unsigned int maj = 0, min = 0;
+	tree_node_t *node;
+
+	if (extra == NULL || *extra == '\0') {
+		fprintf(stderr, "%s: %zu: missing device type\n",
+			filename, line_num);
+		return -1;
+	}
+
+	if ((*extra == 'c' || *extra == 'C') && isspace(extra[1])) {
+		mode |= S_IFCHR;
+	} else if ((*extra == 'b' || *extra == 'B') && isspace(extra[1])) {
+		mode |= S_IFBLK;
+	} else {
+		fprintf(stderr, "%s: %zu: unsupported device type",
+			filename, line_num);
+		return -1;
+	}
+
+	++extra;
+	while (isspace(*extra))
+		++extra;
+
+	if (!isdigit(*extra))
+		goto fail_devno;
+
+	while (isdigit(*extra))
+		maj = maj * 10 + *(extra++) - '0';
+
+	if (*(extra++) != ':')
+		goto fail_devno;
+
+	if (!isdigit(*extra))
+		goto fail_devno;
+
+	while (isdigit(*extra))
+		min = min * 10 + *(extra++) - '0';
+
+	while (isspace(*extra))
+		++extra;
+
+	if (*extra != '\0') {
+		fprintf(stderr, "%s: %zu: WARNING: ignoring extra arguments\n",
+			filename, line_num);
+	}
+
+	node = fstree_add(fs, path, mode, uid, gid, 0);
+	if (node == NULL) {
+		fprintf(stderr, "%s: %zu: mknod %s %c %u %u: %s\n",
+			filename, line_num, path, S_ISCHR(mode) ? 'c' : 'b',
+			maj, min, strerror(errno));
+		return -1;
+	}
+
+	node->data.devno = makedev(maj, min);
+	return 0;
+fail_devno:
+	fprintf(stderr, "%s: %zu: error in device number format\n",
+		filename, line_num);
+	return -1;
+}
+
+static int add_pipe(fstree_t *fs, const char *filename, size_t line_num,
+		    const char *path, uint16_t mode, uint32_t uid,
+		    uint32_t gid, const char *extra)
+{
+	if (extra != NULL && *extra != '\0') {
+		fprintf(stderr, "%s: %zu: WARNING: ignoring extra arguments\n",
+			filename, line_num);
+	}
+
+	if (fstree_add(fs, path, S_IFIFO | mode, uid, gid, 0) == NULL) {
+		fprintf(stderr, "%s: %zu: mkfifo %s: %s\n",
+			filename, line_num, path, strerror(errno));
+		return -1;
+	}
+
+	return 0;
+}
+
+static int add_socket(fstree_t *fs, const char *filename, size_t line_num,
+		      const char *path, uint16_t mode, uint32_t uid,
+		      uint32_t gid, const char *extra)
+{
+	if (extra != NULL && *extra != '\0') {
+		fprintf(stderr, "%s: %zu: WARNING: ignoring extra arguments\n",
+			filename, line_num);
+	}
+
+	if (fstree_add(fs, path, S_IFSOCK | mode, uid, gid, 0) == NULL) {
+		fprintf(stderr, "%s: %zu: creating Unix socket %s: %s\n",
+			filename, line_num, path, strerror(errno));
+		return -1;
+	}
+
+	return 0;
+}
+
+static int add_file(fstree_t *fs, const char *filename, size_t line_num,
+		    const char *path, uint16_t mode, uint32_t uid,
+		    uint32_t gid, const char *extra)
+{
+	char *infile = NULL;
+	tree_node_t *node;
+	const char *ptr;
+	struct stat sb;
+	int ret;
+
+	ptr = strrchr(filename, '/');
+
+	if (extra == NULL || *extra == '\0') {
+		if (ptr == NULL) {
+			extra = path;
+		} else {
+			ret = asprintf(&infile, "%.*s/%s",
+				       (int)(filename - ptr), filename, path);
+			if (ret < 0)
+				goto fail_asprintf;
+		}
+	} else if (*extra != '/' && ptr != NULL) {
+		ret = asprintf(&infile, "%.*s/%s",
+			       (int)(filename - ptr), filename, extra);
+		if (ret < 0)
+			goto fail_asprintf;
+	}
+
+	if (infile != NULL)
+		extra = infile;
+
+	if (stat(extra, &sb) != 0) {
+		fprintf(stderr, "%s: %zu: stat %s: %s\n", filename, line_num,
+			extra, strerror(errno));
+		goto fail;
+	}
+
+	node = fstree_add_file(fs, path, mode, uid, gid, sb.st_size, extra);
+
+	if (node == NULL) {
+		fprintf(stderr, "%s: %zu: adding %s as %s: %s\n",
+			filename, line_num, extra, path, strerror(errno));
+		goto fail;
+	}
+
+	free(infile);
+	return 0;
+fail:
+	free(infile);
+	return -1;
+fail_asprintf:
+	fprintf(stderr, "%s: %zu: pasting together file path: %s\n",
+		filename, line_num, strerror(errno));
+	return -1;
+}
+
+static const struct {
+	const char *keyword;
+	int (*callback)(fstree_t *fs, const char *filename, size_t line_num,
+			const char *path, uint16_t mode, uint32_t uid,
+			uint32_t gid, const char *extra);
+} file_list_hooks[] = {
+	{ "dir", add_dir },
+	{ "slink", add_slink },
+	{ "nod", add_device },
+	{ "pipe", add_pipe },
+	{ "pipe", add_socket },
+	{ "file", add_file },
+};
+
+#define NUM_HOOKS (sizeof(file_list_hooks) / sizeof(file_list_hooks[0]))
+
+static void trim_line(char *line)
+{
+	size_t i;
+
+	for (i = 0; isspace(line[i]); ++i)
+		;
+
+	if (line[i] == '#') {
+		line[0] = '\0';
+		return;
+	}
+
+	if (i > 0)
+		memmove(line, line + i, strlen(line + i) + 1);
+
+	i = strlen(line);
+	while (i > 0 && isspace(line[i - 1]))
+		--i;
+
+	line[i] = '\0';
+}
+
+static int handle_line(fstree_t *fs, const char *filename,
+		       size_t line_num, char *line)
+{
+	const char *path, *extra = NULL, *msg = NULL;
+	unsigned int mode = 0, uid = 0, gid = 0, x;
+	char keyword[16];
+	size_t i;
+
+	/* isolate keyword */
+	for (i = 0; isalpha(line[i]); ++i)
+		;
+
+	if (i >= sizeof(keyword) || i == 0 || !isspace(line[i]))
+		goto fail_ent;
+
+	memcpy(keyword, line, i);
+	keyword[i] = '\0';
+
+	while (isspace(line[i]))
+		++i;
+
+	/* isolate path */
+	path = line + i;
+
+	for (; line[i] != '\0'; ++i) {
+		/* TODO: escape sequences to support spaces in path */
+
+		if (isspace(line[i]))
+			break;
+	}
+
+	if (!isspace(line[i]))
+		goto fail_ent;
+
+	line[i++] = '\0';
+	while (isspace(line[i]))
+		++i;
+
+	/* mode */
+	if (!isdigit(line[i]))
+		goto fail_mode;
+
+	for (; isdigit(line[i]); ++i) {
+		if (line[i] > '7')
+			goto fail_mode;
+
+		mode = (mode << 3) | (line[i] - '0');
+
+		if (mode > 07777)
+			goto fail_mode_bits;
+	}
+
+	if (!isspace(line[i]))
+		goto fail_ent;
+
+	while (isspace(line[i]))
+		++i;
+
+	/* uid */
+	if (!isdigit(line[i]))
+		goto fail_uid_gid;
+
+	for (; isdigit(line[i]); ++i) {
+		x = line[i] - '0';
+
+		if (uid > (0xFFFFFFFF - x) / 10)
+			goto fail_ov;
+
+		uid = uid * 10 + x;
+	}
+
+	if (!isspace(line[i]))
+		goto fail_ent;
+
+	while (isspace(line[i]))
+		++i;
+
+	/* gid */
+	if (!isdigit(line[i]))
+		goto fail_uid_gid;
+
+	for (; isdigit(line[i]); ++i) {
+		x = line[i] - '0';
+
+		if (gid > (0xFFFFFFFF - x) / 10)
+			goto fail_ov;
+
+		gid = gid * 10 + x;
+	}
+
+	/* extra */
+	if (isspace(line[i])) {
+		while (isspace(line[i]))
+			++i;
+
+		if (line[i] != '\0')
+			extra = line + i;
+	}
+
+	/* forward to callback */
+	for (i = 0; i < NUM_HOOKS; ++i) {
+		if (strcmp(file_list_hooks[i].keyword, keyword) == 0) {
+			return file_list_hooks[i].callback(fs, filename,
+							   line_num, path,
+							   mode, uid, gid,
+							   extra);
+		}
+	}
+
+	fprintf(stderr, "%s: %zu: unknown entry type '%s'.\n", filename,
+		line_num, keyword);
+	return -1;
+fail_ov:
+	msg = "numeric overflow";
+	goto fail_ent;
+fail_uid_gid:
+	msg = "uid & gid must be decimal numbers";
+	goto out_desc;
+fail_mode:
+	msg = "mode must be an octal number";
+	goto out_desc;
+fail_mode_bits:
+	msg = "you can only set the permission bits in the mode";
+	goto out_desc;
+fail_ent:
+	msg = "error in entry description";
+	goto out_desc;
+out_desc:
+	fprintf(stderr, "%s: %zu: %s.\n", filename, line_num, msg);
+	fputs("expected: <type> <path> <mode> <uid> <gid> [<extra>]\n",
+	      stderr);
+	return -1;
+}
+
+int fstree_from_file(fstree_t *fs, const char *filename)
+{
+	FILE *fp = fopen(filename, "rb");
+	size_t n, line_num = 0;
+	ssize_t ret;
+	char *line;
+
+	if (fp == NULL) {
+		perror(filename);
+		return -1;
+	}
+
+	for (;;) {
+		line = NULL;
+		n = 0;
+		errno = 0;
+
+		ret = getline(&line, &n, fp);
+		++line_num;
+
+		if (ret < 0) {
+			if (errno == 0) {
+				free(line);
+				break;
+			}
+
+			perror(filename);
+			goto fail_line;
+		}
+
+		trim_line(line);
+
+		if (line[0] == '\0') {
+			free(line);
+			continue;
+		}
+
+		if (handle_line(fs, filename, line_num, line))
+			goto fail_line;
+
+		free(line);
+	}
+
+	fclose(fp);
+	return 0;
+fail_line:
+	free(line);
+	fclose(fp);
+	return -1;
+}
diff --git a/lib/fstree/fstree_sort.c b/lib/fstree/fstree_sort.c
new file mode 100644
index 0000000..9f07c92
--- /dev/null
+++ b/lib/fstree/fstree_sort.c
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "fstree.h"
+
+#include <string.h>
+
+static tree_node_t *sort_list(tree_node_t *head)
+{
+	tree_node_t *it, *prev, *lhs, *rhs;
+	size_t i, count = 0;
+
+	for (it = head; it != NULL; it = it->next)
+		++count;
+
+	if (count < 2)
+		return head;
+
+	prev = NULL;
+	it = head;
+
+	for (i = 0; i < count / 2; ++i) {
+		prev = it;
+		it = it->next;
+	}
+
+	prev->next = NULL;
+
+	lhs = sort_list(head);
+	rhs = sort_list(it);
+
+	head = NULL;
+	prev = NULL;
+
+	while (lhs != NULL && rhs != NULL) {
+		if (strcmp(lhs->name, rhs->name) <= 0) {
+			it = lhs;
+			lhs = lhs->next;
+		} else {
+			it = rhs;
+			rhs = rhs->next;
+		}
+
+		it->next = NULL;
+
+		if (prev != NULL) {
+			prev->next = it;
+			prev = it;
+		} else {
+			prev = head = it;
+		}
+	}
+
+	it = (lhs != NULL ? lhs : rhs);
+
+	if (prev != NULL) {
+		prev->next = it;
+	} else {
+		head = it;
+	}
+
+	return head;
+}
+
+static void sort_directory(tree_node_t *n)
+{
+	n->data.dir->children = sort_list(n->data.dir->children);
+
+	for (n = n->data.dir->children; n != NULL; n = n->next) {
+		if (S_ISDIR(n->mode))
+			sort_directory(n);
+	}
+}
+
+void fstree_sort(fstree_t *fs)
+{
+	sort_directory(fs->root);
+}
diff --git a/m4/compiler.m4 b/m4/compiler.m4
new file mode 100644
index 0000000..058c73f
--- /dev/null
+++ b/m4/compiler.m4
@@ -0,0 +1,40 @@
+dnl Copyright (C) 2008-2011 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson
+dnl -- derivated from coreutils m4/warnings.m4
+
+# UL_AS_VAR_APPEND(VAR, VALUE)
+# ----------------------------
+# Provide the functionality of AS_VAR_APPEND if Autoconf does not have it.
+m4_ifdef([AS_VAR_APPEND],
+[m4_copy([AS_VAR_APPEND], [UL_AS_VAR_APPEND])],
+[m4_define([UL_AS_VAR_APPEND],
+[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])
+
+# UL_ADD_WARN(COMPILER_OPTION [, VARNAME])
+# ------------------------
+# Adds parameter to WARN_CFLAGS (or to $VARNAME) if the compiler supports it.
+AC_DEFUN([UL_WARN_ADD], [
+  m4_define([warnvarname], m4_default([$2],WARN_CFLAGS))
+  AS_VAR_PUSHDEF([ul_Warn], [ul_cv_warn_$1])dnl
+  AC_CACHE_CHECK([whether compiler handles $1], m4_defn([ul_Warn]), [
+    # store AC_LANG_WERROR status, then turn it on
+    save_ac_[]_AC_LANG_ABBREV[]_werror_flag="${ac_[]_AC_LANG_ABBREV[]_werror_flag}"
+    AC_LANG_WERROR
+
+    ul_save_CPPFLAGS="$CPPFLAGS"
+    CPPFLAGS="-Werror ${CPPFLAGS} $1"
+    AC_PREPROC_IFELSE([AC_LANG_PROGRAM([])],
+                      [AS_VAR_SET(ul_Warn, [yes])],
+                      [AS_VAR_SET(ul_Warn, [no])])
+    # restore AC_LANG_WERROR
+    ac_[]_AC_LANG_ABBREV[]_werror_flag="${save_ac_[]_AC_LANG_ABBREV[]_werror_flag}"
+
+    CPPFLAGS="$ul_save_CPPFLAGS"
+  ])
+  AS_VAR_IF(ul_Warn, [yes], [UL_AS_VAR_APPEND(warnvarname, [" $1"])])
+])
+
diff --git a/mkfs/Makemodule.am b/mkfs/Makemodule.am
new file mode 100644
index 0000000..1d062b9
--- /dev/null
+++ b/mkfs/Makemodule.am
@@ -0,0 +1,5 @@
+mksquashfs_SOURCES = mkfs/mksquashfs.c mkfs/options.c mkfs/options.h
+mksquashfs_SOURCES += include/squashfs.h
+mksquashfs_LDADD = libfstree.a
+
+bin_PROGRAMS += mksquashfs
diff --git a/mkfs/mksquashfs.c b/mkfs/mksquashfs.c
new file mode 100644
index 0000000..bc2a215
--- /dev/null
+++ b/mkfs/mksquashfs.c
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "squashfs.h"
+#include "options.h"
+#include "fstree.h"
+
+#include <sys/sysmacros.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+#include <ctype.h>
+
+static void print_tree(int level, tree_node_t *node)
+{
+	tree_node_t *n;
+	int i;
+
+	for (i = 1; i < level; ++i) {
+		fputs("|  ", stdout);
+	}
+
+	if (level)
+		fputs("+- ", stdout);
+
+	if (S_ISDIR(node->mode)) {
+		fprintf(stdout, "%s/ (%u, %u, 0%o)\n", node->name,
+			node->uid, node->gid, node->mode & 07777);
+
+		for (n = node->data.dir->children; n != NULL; n = n->next) {
+			print_tree(level + 1, n);
+		}
+
+		if (node->data.dir->children != NULL) {
+			for (i = 0; i < level; ++i)
+				fputs("|  ", stdout);
+
+			if (level)
+				fputc('\n', stdout);
+		}
+	} else {
+		fprintf(stdout, "%s (%u, %u, 0%o)\n", node->name,
+			node->uid, node->gid, node->mode & 07777);
+	}
+}
+
+
+int main(int argc, char **argv)
+{
+	options_t opt;
+	fstree_t fs;
+
+	process_command_line(&opt, argc, argv);
+
+	if (fstree_init(&fs, opt.blksz, opt.def_mtime, opt.def_mode,
+			opt.def_uid, opt.def_gid)) {
+		return EXIT_FAILURE;
+	}
+
+	if (fstree_from_file(&fs, opt.infile)) {
+		fstree_cleanup(&fs);
+		return EXIT_FAILURE;
+	}
+
+	fstree_sort(&fs);
+
+	print_tree(0, fs.root);
+
+	fstree_cleanup(&fs);
+	return EXIT_SUCCESS;
+}
diff --git a/mkfs/options.c b/mkfs/options.c
new file mode 100644
index 0000000..513e76a
--- /dev/null
+++ b/mkfs/options.c
@@ -0,0 +1,295 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "squashfs.h"
+#include "options.h"
+#include "config.h"
+
+#include <stdlib.h>
+#include <getopt.h>
+#include <unistd.h>
+#include <limits.h>
+#include <string.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <stdio.h>
+
+static struct option long_opts[] = {
+	{ "compressor", required_argument, NULL, 'c' },
+	{ "block-size", required_argument, NULL, 'b' },
+	{ "dev-block-size", required_argument, NULL, 'B' },
+	{ "defaults", required_argument, NULL, 'd' },
+	{ "force", no_argument, NULL, 'f' },
+	{ "version", no_argument, NULL, 'V' },
+	{ "help", no_argument, NULL, 'h' },
+};
+
+static const char *short_opts = "c:b:B:d:fhV";
+
+enum {
+	DEF_UID = 0,
+	DEF_GID,
+	DEF_MODE,
+	DEF_MTIME,
+};
+
+static const char *defaults[] = {
+	[DEF_UID] = "uid",
+	[DEF_GID] = "gid",
+	[DEF_MODE] = "mode",
+	[DEF_MTIME] = "mtime",
+	NULL
+};
+
+#define LICENSE_SHORT "GPLv3+"
+#define LICENSE_LONG "GNU GPL version 3 or later"
+#define LICENSE_URL "https://gnu.org/licenses/gpl.html"
+
+extern char *__progname;
+
+static const char *version_string =
+"%s (%s) %s\n"
+"Copyright (c) 2019 David Oberhollenzer\n"
+"License " LICENSE_SHORT ": " LICENSE_LONG " <" LICENSE_URL ">.\n"
+"This is free software: you are free to change and redistribute it.\n"
+"There is NO WARRANTY, to the extent permitted by law.\n"
+"\n"
+"Written by David Oberhollenzer.\n";
+
+static const char *help_string =
+"Usage: %s [OPTIONS] <file-list> <squashfs-file>\n"
+"\n"
+"<file-list> is a file containing newline separated entries that describe\n"
+"the files to be included in the squashfs image:\n"
+"\n"
+"# a comment\n"
+"file <path> <mode> <uid> <gid> [<location>]\n"
+"dir <path> <mode> <uid> <gid>\n"
+"nod <path> <mode> <uid> <gid> <dev_type> <maj> <min>\n"
+"slink <path> <mode> <uid> <gid> <target>\n"
+"pipe <path> <mode> <uid> <gid>\n"
+"sock <path> <mode> <uid> <gid>\n"
+"\n"
+"<path>       Absolute path of the entry in the image.\n"
+"<location>   If given, location of the input file. Either absolute or relative\n"
+"             to the description file. If omitted, the image path is used,\n"
+"             relative to the description file.\n"
+"<target>     Symlink target.\n"
+"<mode>       Mode/permissions of the entry.\n"
+"<uid>        Numeric user id.\n"
+"<gid>        Numeric group id.\n"
+"<dev_type>   Device type (b=block, c=character).\n"
+"<maj>        Major number of a device special file.\n"
+"<min>        Minor number of a device special file.\n"
+"\n"
+"Example:\n"
+"# A simple squashfs image\n"
+"dir /dev 0755 0 0\n"
+"nod /dev/console 0600 0 0 c 5 1\n"
+"dir /root 0700 0 0\n"
+"dir /sbin 0755 0 0\n"
+"\n"
+"# Add a file. Input is relative to this listing.\n"
+"file /sbin/init 0755 0 0 ../init/sbin/init\n"
+"\n"
+"# Read from ./bin/bash. /bin is created implicitly with default attributes.\n"
+"file /bin/bash 0755 0 0"
+"\n"
+"Possible options:\n"
+"\n"
+"  --compressor, -c <name>     Select the compressor to use.\n"
+"                              directories (defaults to 'xz').\n"
+"  --block-size, -b <size>     Block size to use for Squashfs image.\n"
+"                              Defaults to %u.\n"
+"  --dev-block-size, -B <size> Device block size to padd the image to.\n"
+"                              Defaults to %u.\n"
+"  --defaults, -d <options>    A comma seperated list of default values for\n"
+"                              implicitly created directories.\n"
+"\n"
+"                              Possible options:\n"
+"                                 uid=<value>    0 if not set.\n"
+"                                 gid=<value>    0 if not set.\n"
+"                                 mode=<value>   0755 if not set.\n"
+"                                 mtime=<value>  0 if not set.\n"
+"\n"
+"  --force, -f                 Overwrite the output file if it exists.\n"
+"  --help, -h                  Print help text and exit.\n"
+"  --version, -V               Print version information and exit.\n"
+"\n";
+
+static const char *compressors[] = {
+	[SQFS_COMP_GZIP] = "gzip",
+	[SQFS_COMP_LZMA] = "lzma",
+	[SQFS_COMP_LZO] = "lzo",
+	[SQFS_COMP_XZ] = "xz",
+	[SQFS_COMP_LZ4] = "lz4",
+	[SQFS_COMP_ZSTD] = "zstd",
+};
+
+static long read_number(const char *name, const char *str, long min, long max)
+{
+	long base = 10, result = 0;
+	int x;
+
+	if (str[0] == '0') {
+		if (str[1] == 'x' || str[1] == 'X') {
+			base = 16;
+			str += 2;
+		} else {
+			base = 8;
+		}
+	}
+
+	if (!isxdigit(*str))
+		goto fail_num;
+
+	while (isxdigit(*str)) {
+		x = *(str++);
+
+		if (isupper(x)) {
+			x = x - 'A' + 10;
+		} else if (islower(x)) {
+			x = x - 'a' + 10;
+		} else {
+			x -= '0';
+		}
+
+		if (x >= base)
+			goto fail_num;
+
+		if (result > (LONG_MAX - x) / base)
+			goto fail_ov;
+
+		result = result * base + x;
+	}
+
+	if (result < min)
+		goto fail_uf;
+
+	if (result > max)
+		goto fail_ov;
+
+	return result;
+fail_num:
+	fprintf(stderr, "%s: expected numeric value > 0\n", name);
+	goto fail;
+fail_uf:
+	fprintf(stderr, "%s: number to small\n", name);
+	goto fail;
+fail_ov:
+	fprintf(stderr, "%s: number to large\n", name);
+	goto fail;
+fail:
+	exit(EXIT_FAILURE);
+}
+
+static void process_defaults(options_t *opt, char *subopts)
+{
+	char *value;
+	int i;
+
+	while (*subopts != '\0') {
+		i = getsubopt(&subopts, (char *const *)defaults, &value);
+
+		if (value == NULL) {
+			fprintf(stderr, "Missing value for option %s\n",
+				defaults[i]);
+			exit(EXIT_FAILURE);
+		}
+
+		switch (i) {
+		case DEF_UID:
+			opt->def_uid = read_number("Default user ID", value,
+						   0, 0xFFFFFFFF);
+			break;
+		case DEF_GID:
+			opt->def_gid = read_number("Default group ID", value,
+						   0, 0xFFFFFFFF);
+			break;
+		case DEF_MODE:
+			opt->def_mode = read_number("Default permissions",
+						    value, 0, 0xFFFFFFFF);
+			break;
+		case DEF_MTIME:
+			opt->def_mtime = read_number("Default mtime", value,
+						     0, 0xFFFFFFFF);
+			break;
+		default:
+			fprintf(stderr, "Unknown option '%s'\n", value);
+			exit(EXIT_FAILURE);
+		}
+	}
+}
+
+void process_command_line(options_t *opt, int argc, char **argv)
+{
+	int i;
+
+	opt->def_uid = 0;
+	opt->def_gid = 0;
+	opt->def_mode = 0755;
+	opt->def_mtime = 0;
+	opt->outmode = O_WRONLY | O_CREAT | O_EXCL;
+	opt->compressor = SQFS_COMP_XZ;
+	opt->blksz = SQFS_DEFAULT_BLOCK_SIZE;
+	opt->devblksz = SQFS_DEVBLK_SIZE;
+	opt->infile = NULL;
+	opt->outfile = NULL;
+
+	for (;;) {
+		i = getopt_long(argc, argv, short_opts, long_opts, NULL);
+		if (i == -1)
+			break;
+
+		switch (i) {
+		case 'c':
+			for (i = SQFS_COMP_MIN; i <= SQFS_COMP_MAX; ++i) {
+				if (strcmp(compressors[i], optarg) == 0) {
+					opt->compressor = i;
+					break;
+				}
+			}
+			break;
+		case 'b':
+			opt->blksz = read_number("Block size", optarg,
+						 1024, 0xFFFFFFFF);
+			break;
+		case 'B':
+			opt->devblksz = read_number("Device block size", optarg,
+						    4096, 0xFFFFFFFF);
+			break;
+		case 'd':
+			process_defaults(opt, optarg);
+			break;
+		case 'f':
+			opt->outmode = O_WRONLY | O_CREAT | O_TRUNC;
+			break;
+		case 'h':
+			printf(help_string, __progname,
+			       SQFS_DEFAULT_BLOCK_SIZE, SQFS_DEVBLK_SIZE);
+
+			fputs("Available compressors:\n", stdout);
+
+			for (i = SQFS_COMP_MIN; i <= SQFS_COMP_MAX; ++i)
+				printf("\t%s\n", compressors[i]);
+
+			exit(EXIT_SUCCESS);
+		case 'V':
+			printf(version_string, __progname,
+			       PACKAGE_NAME, PACKAGE_VERSION);
+			exit(EXIT_SUCCESS);
+		default:
+			goto fail_arg;
+		}
+	}
+
+	if ((optind + 1) >= argc) {
+		fputs("Missing arguments: input and output files.\n", stderr);
+		goto fail_arg;
+	}
+
+	opt->infile = argv[optind++];
+	opt->outfile = argv[optind++];
+	return;
+fail_arg:
+	fprintf(stderr, "Try `%s --help' for more information.\n", __progname);
+	exit(EXIT_FAILURE);
+}
diff --git a/mkfs/options.h b/mkfs/options.h
new file mode 100644
index 0000000..dc11250
--- /dev/null
+++ b/mkfs/options.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef OPTIONS_H
+#define OPTIONS_H
+
+typedef struct {
+	unsigned int def_uid;
+	unsigned int def_gid;
+	unsigned int def_mode;
+	unsigned int def_mtime;
+	int outmode;
+	int compressor;
+	int blksz;
+	int devblksz;
+	const char *infile;
+	const char *outfile;
+} options_t;
+
+void process_command_line(options_t *opt, int argc, char **argv);
+
+#endif /* OPTIONS_H */