decompressors: add XZ decompressor module

In userspace, the .lzma format has become mostly a legacy file format that
got superseded by the .xz format.  Similarly, LZMA Utils was superseded by
XZ Utils.

These patches add support for XZ decompression into the kernel.  Most of
the code is as is from XZ Embedded <http://tukaani.org/xz/embedded.html>.
It was written for the Linux kernel but is usable in other projects too.

Advantages of XZ over the current LZMA code in the kernel:
  - Nice API that can be used by other kernel modules; it's
    not limited to kernel, initramfs, and initrd decompression.
  - Integrity check support (CRC32)
  - BCJ filters improve compression of executable code on
    certain architectures. These together with LZMA2 can
    produce a few percent smaller kernel or Squashfs images
    than plain LZMA without making the decompression slower.

This patch: Add the main decompression code (xz_dec), testing module
(xz_dec_test), wrapper script (xz_wrap.sh) for the xz command line tool,
and documentation.  The xz_dec module is enough to have a usable XZ
decompressor e.g.  for Squashfs.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alain Knaff <alain@knaff.lu>
Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 220 insertions, 0 deletions

diff --git a/lib/xz/xz_dec_test.c b/lib/xz/xz_dec_test.c
new file mode 100644
index 00000000000..da28a19d6c9
--- /dev/null
+++ b/lib/xz/xz_dec_test.c
@@ -0,0 +1,220 @@
+/*
+ * XZ decoder tester
+ *
+ * Author: Lasse Collin <lasse.collin@tukaani.org>
+ *
+ * This file has been put into the public domain.
+ * You can do whatever you want with this file.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/crc32.h>
+#include <linux/xz.h>
+
+/* Maximum supported dictionary size */
+#define DICT_MAX (1 << 20)
+
+/* Device name to pass to register_chrdev(). */
+#define DEVICE_NAME "xz_dec_test"
+
+/* Dynamically allocated device major number */
+static int device_major;
+
+/*
+ * We reuse the same decoder state, and thus can decode only one
+ * file at a time.
+ */
+static bool device_is_open;
+
+/* XZ decoder state */
+static struct xz_dec *state;
+
+/*
+ * Return value of xz_dec_run(). We need to avoid calling xz_dec_run() after
+ * it has returned XZ_STREAM_END, so we make this static.
+ */
+static enum xz_ret ret;
+
+/*
+ * Input and output buffers. The input buffer is used as a temporary safe
+ * place for the data coming from the userspace.
+ */
+static uint8_t buffer_in[1024];
+static uint8_t buffer_out[1024];
+
+/*
+ * Structure to pass the input and output buffers to the XZ decoder.
+ * A few of the fields are never modified so we initialize them here.
+ */
+static struct xz_buf buffers = {
+	.in = buffer_in,
+	.out = buffer_out,
+	.out_size = sizeof(buffer_out)
+};
+
+/*
+ * CRC32 of uncompressed data. This is used to give the user a simple way
+ * to check that the decoder produces correct output.
+ */
+static uint32_t crc;
+
+static int xz_dec_test_open(struct inode *i, struct file *f)
+{
+	if (device_is_open)
+		return -EBUSY;
+
+	device_is_open = true;
+
+	xz_dec_reset(state);
+	ret = XZ_OK;
+	crc = 0xFFFFFFFF;
+
+	buffers.in_pos = 0;
+	buffers.in_size = 0;
+	buffers.out_pos = 0;
+
+	printk(KERN_INFO DEVICE_NAME ": opened\n");
+	return 0;
+}
+
+static int xz_dec_test_release(struct inode *i, struct file *f)
+{
+	device_is_open = false;
+
+	if (ret == XZ_OK)
+		printk(KERN_INFO DEVICE_NAME ": input was truncated\n");
+
+	printk(KERN_INFO DEVICE_NAME ": closed\n");
+	return 0;
+}
+
+/*
+ * Decode the data given to us from the userspace. CRC32 of the uncompressed
+ * data is calculated and is printed at the end of successful decoding. The
+ * uncompressed data isn't stored anywhere for further use.
+ *
+ * The .xz file must have exactly one Stream and no Stream Padding. The data
+ * after the first Stream is considered to be garbage.
+ */
+static ssize_t xz_dec_test_write(struct file *file, const char __user *buf,
+				 size_t size, loff_t *pos)
+{
+	size_t remaining;
+
+	if (ret != XZ_OK) {
+		if (size > 0)
+			printk(KERN_INFO DEVICE_NAME ": %zu bytes of "
+					"garbage at the end of the file\n",
+					size);
+
+		return -ENOSPC;
+	}
+
+	printk(KERN_INFO DEVICE_NAME ": decoding %zu bytes of input\n",
+			size);
+
+	remaining = size;
+	while ((remaining > 0 || buffers.out_pos == buffers.out_size)
+			&& ret == XZ_OK) {
+		if (buffers.in_pos == buffers.in_size) {
+			buffers.in_pos = 0;
+			buffers.in_size = min(remaining, sizeof(buffer_in));
+			if (copy_from_user(buffer_in, buf, buffers.in_size))
+				return -EFAULT;
+
+			buf += buffers.in_size;
+			remaining -= buffers.in_size;
+		}
+
+		buffers.out_pos = 0;
+		ret = xz_dec_run(state, &buffers);
+		crc = crc32(crc, buffer_out, buffers.out_pos);
+	}
+
+	switch (ret) {
+	case XZ_OK:
+		printk(KERN_INFO DEVICE_NAME ": XZ_OK\n");
+		return size;
+
+	case XZ_STREAM_END:
+		printk(KERN_INFO DEVICE_NAME ": XZ_STREAM_END, "
+				"CRC32 = 0x%08X\n", ~crc);
+		return size - remaining - (buffers.in_size - buffers.in_pos);
+
+	case XZ_MEMLIMIT_ERROR:
+		printk(KERN_INFO DEVICE_NAME ": XZ_MEMLIMIT_ERROR\n");
+		break;
+
+	case XZ_FORMAT_ERROR:
+		printk(KERN_INFO DEVICE_NAME ": XZ_FORMAT_ERROR\n");
+		break;
+
+	case XZ_OPTIONS_ERROR:
+		printk(KERN_INFO DEVICE_NAME ": XZ_OPTIONS_ERROR\n");
+		break;
+
+	case XZ_DATA_ERROR:
+		printk(KERN_INFO DEVICE_NAME ": XZ_DATA_ERROR\n");
+		break;
+
+	case XZ_BUF_ERROR:
+		printk(KERN_INFO DEVICE_NAME ": XZ_BUF_ERROR\n");
+		break;
+
+	default:
+		printk(KERN_INFO DEVICE_NAME ": Bug detected!\n");
+		break;
+	}
+
+	return -EIO;
+}
+
+/* Allocate the XZ decoder state and register the character device. */
+static int __init xz_dec_test_init(void)
+{
+	static const struct file_operations fileops = {
+		.owner = THIS_MODULE,
+		.open = &xz_dec_test_open,
+		.release = &xz_dec_test_release,
+		.write = &xz_dec_test_write
+	};
+
+	state = xz_dec_init(XZ_PREALLOC, DICT_MAX);
+	if (state == NULL)
+		return -ENOMEM;
+
+	device_major = register_chrdev(0, DEVICE_NAME, &fileops);
+	if (device_major < 0) {
+		xz_dec_end(state);
+		return device_major;
+	}
+
+	printk(KERN_INFO DEVICE_NAME ": module loaded\n");
+	printk(KERN_INFO DEVICE_NAME ": Create a device node with "
+			"'mknod " DEVICE_NAME " c %d 0' and write .xz files "
+			"to it.\n", device_major);
+	return 0;
+}
+
+static void __exit xz_dec_test_exit(void)
+{
+	unregister_chrdev(device_major, DEVICE_NAME);
+	xz_dec_end(state);
+	printk(KERN_INFO DEVICE_NAME ": module unloaded\n");
+}
+
+module_init(xz_dec_test_init);
+module_exit(xz_dec_test_exit);
+
+MODULE_DESCRIPTION("XZ decompressor tester");
+MODULE_VERSION("1.0");
+MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org>");
+
+/*
+ * This code is in the public domain, but in Linux it's simplest to just
+ * say it's GPL and consider the authors as the copyright holders.
+ */
+MODULE_LICENSE("GPL");