lib/decompress_unxz.c - kernel/mindspeed - Git at Google

 /*
  * Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd
  *
  * 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.
  */

 /*
  * Important notes about in-place decompression
  *
  * At least on x86, the kernel is decompressed in place: the compressed data
  * is placed to the end of the output buffer, and the decompressor overwrites
  * most of the compressed data. There must be enough safety margin to
  * guarantee that the write position is always behind the read position.
  *
  * The safety margin for XZ with LZMA2 or BCJ+LZMA2 is calculated below.
  * Note that the margin with XZ is bigger than with Deflate (gzip)!
  *
  * The worst case for in-place decompression is that the beginning of
  * the file is compressed extremely well, and the rest of the file is
  * uncompressible. Thus, we must look for worst-case expansion when the
  * compressor is encoding uncompressible data.
  *
  * The structure of the .xz file in case of a compresed kernel is as follows.
  * Sizes (as bytes) of the fields are in parenthesis.
  *
  *    Stream Header (12)
  *    Block Header:
  *      Block Header (8-12)
  *      Compressed Data (N)
  *      Block Padding (0-3)
  *      CRC32 (4)
  *    Index (8-20)
  *    Stream Footer (12)
  *
  * Normally there is exactly one Block, but let's assume that there are
  * 2-4 Blocks just in case. Because Stream Header and also Block Header
  * of the first Block don't make the decompressor produce any uncompressed
  * data, we can ignore them from our calculations. Block Headers of possible
  * additional Blocks have to be taken into account still. With these
  * assumptions, it is safe to assume that the total header overhead is
  * less than 128 bytes.
  *
  * Compressed Data contains LZMA2 or BCJ+LZMA2 encoded data. Since BCJ
  * doesn't change the size of the data, it is enough to calculate the
  * safety margin for LZMA2.
  *
  * LZMA2 stores the data in chunks. Each chunk has a header whose size is
  * a maximum of 6 bytes, but to get round 2^n numbers, let's assume that
  * the maximum chunk header size is 8 bytes. After the chunk header, there
  * may be up to 64 KiB of actual payload in the chunk. Often the payload is
  * quite a bit smaller though; to be safe, let's assume that an average
  * chunk has only 32 KiB of payload.
  *
  * The maximum uncompressed size of the payload is 2 MiB. The minimum
  * uncompressed size of the payload is in practice never less than the
  * payload size itself. The LZMA2 format would allow uncompressed size
  * to be less than the payload size, but no sane compressor creates such
  * files. LZMA2 supports storing uncompressible data in uncompressed form,
  * so there's never a need to create payloads whose uncompressed size is
  * smaller than the compressed size.
  *
  * The assumption, that the uncompressed size of the payload is never
  * smaller than the payload itself, is valid only when talking about
  * the payload as a whole. It is possible that the payload has parts where
  * the decompressor consumes more input than it produces output. Calculating
  * the worst case for this would be tricky. Instead of trying to do that,
  * let's simply make sure that the decompressor never overwrites any bytes
  * of the payload which it is currently reading.
  *
  * Now we have enough information to calculate the safety margin. We need
  *   - 128 bytes for the .xz file format headers;
  *   - 8 bytes per every 32 KiB of uncompressed size (one LZMA2 chunk header
  *     per chunk, each chunk having average payload size of 32 KiB); and
  *   - 64 KiB (biggest possible LZMA2 chunk payload size) to make sure that
  *     the decompressor never overwrites anything from the LZMA2 chunk
  *     payload it is currently reading.
  *
  * We get the following formula:
  *
  *    safety_margin = 128 + uncompressed_size * 8 / 32768 + 65536
  *                  = 128 + (uncompressed_size >> 12) + 65536
  *
  * For comparison, according to arch/x86/boot/compressed/misc.c, the
  * equivalent formula for Deflate is this:
  *
  *    safety_margin = 18 + (uncompressed_size >> 12) + 32768
  *
  * Thus, when updating Deflate-only in-place kernel decompressor to
  * support XZ, the fixed overhead has to be increased from 18+32768 bytes
  * to 128+65536 bytes.
  */

 /*
  * STATIC is defined to "static" if we are being built for kernel
  * decompression (pre-boot code). <linux/decompress/mm.h> will define
  * STATIC to empty if it wasn't already defined. Since we will need to
  * know later if we are being used for kernel decompression, we define
  * XZ_PREBOOT here.
  */
 #ifdef STATIC
 #	define XZ_PREBOOT
 #endif
 #ifdef __KERNEL__
 #	include <linux/decompress/mm.h>
 #endif
 #define XZ_EXTERN STATIC

 #ifndef XZ_PREBOOT
 #	include <linux/slab.h>
 #	include <linux/xz.h>
 #else
 /*
  * Use the internal CRC32 code instead of kernel's CRC32 module, which
  * is not available in early phase of booting.
  */
 #define XZ_INTERNAL_CRC32 1

 /*
  * For boot time use, we enable only the BCJ filter of the current
  * architecture or none if no BCJ filter is available for the architecture.
  */
 #ifdef CONFIG_X86
 #	define XZ_DEC_X86
 #endif
 #ifdef CONFIG_PPC
 #	define XZ_DEC_POWERPC
 #endif
 #ifdef CONFIG_ARM
 #	define XZ_DEC_ARM
 #endif
 #ifdef CONFIG_IA64
 #	define XZ_DEC_IA64
 #endif
 #ifdef CONFIG_SPARC
 #	define XZ_DEC_SPARC
 #endif

 /*
  * This will get the basic headers so that memeq() and others
  * can be defined.
  */
 #include "xz/xz_private.h"

 /*
  * Replace the normal allocation functions with the versions from
  * <linux/decompress/mm.h>. vfree() needs to support vfree(NULL)
  * when XZ_DYNALLOC is used, but the pre-boot free() doesn't support it.
  * Workaround it here because the other decompressors don't need it.
  */
 #undef kmalloc
 #undef kfree
 #undef vmalloc
 #undef vfree
 #define kmalloc(size, flags) malloc(size)
 #define kfree(ptr) free(ptr)
 #define vmalloc(size) malloc(size)
 #define vfree(ptr) do { if (ptr != NULL) free(ptr); } while (0)

 /*
  * FIXME: Not all basic memory functions are provided in architecture-specific
  * files (yet). We define our own versions here for now, but this should be
  * only a temporary solution.
  *
  * memeq and memzero are not used much and any remotely sane implementation
  * is fast enough. memcpy/memmove speed matters in multi-call mode, but
  * the kernel image is decompressed in single-call mode, in which only
  * memcpy speed can matter and only if there is a lot of uncompressible data
  * (LZMA2 stores uncompressible chunks in uncompressed form). Thus, the
  * functions below should just be kept small; it's probably not worth
  * optimizing for speed.
  */

 #ifndef memeq
 static bool memeq(const void *a, const void *b, size_t size)
 {
 	const uint8_t *x = a;
 	const uint8_t *y = b;
 	size_t i;

 	for (i = 0; i < size; ++i)
 		if (x[i] != y[i])
 			return false;

 	return true;
 }
 #endif

 #ifndef memzero
 static void memzero(void *buf, size_t size)
 {
 	uint8_t *b = buf;
 	uint8_t *e = b + size;

 	while (b != e)
 		*b++ = '\0';
 }
 #endif

 #ifndef memmove
 /* Not static to avoid a conflict with the prototype in the Linux headers. */
 void *memmove(void *dest, const void *src, size_t size)
 {
 	uint8_t *d = dest;
 	const uint8_t *s = src;
 	size_t i;

 	if (d < s) {
 		for (i = 0; i < size; ++i)
 			d[i] = s[i];
 	} else if (d > s) {
 		i = size;
 		while (i-- > 0)
 			d[i] = s[i];
 	}

 	return dest;
 }
 #endif

 /*
  * Since we need memmove anyway, would use it as memcpy too.
  * Commented out for now to avoid breaking things.
  */
 /*
 #ifndef memcpy
 #	define memcpy memmove
 #endif
 */

 #include "xz/xz_crc32.c"
 #include "xz/xz_dec_stream.c"
 #include "xz/xz_dec_lzma2.c"
 #include "xz/xz_dec_bcj.c"

 #endif /* XZ_PREBOOT */

 /* Size of the input and output buffers in multi-call mode */
 #define XZ_IOBUF_SIZE 4096

 /*
  * This function implements the API defined in <linux/decompress/generic.h>.
  *
  * This wrapper will automatically choose single-call or multi-call mode
  * of the native XZ decoder API. The single-call mode can be used only when
  * both input and output buffers are available as a single chunk, i.e. when
  * fill() and flush() won't be used.
  */
 STATIC int INIT unxz(unsigned char *in, int in_size,
 		     int (*fill)(void *dest, unsigned int size),
 		     int (*flush)(void *src, unsigned int size),
 		     unsigned char *out, int *in_used,
 		     void (*error)(char *x))
 {
 	struct xz_buf b;
 	struct xz_dec *s;
 	enum xz_ret ret;
 	bool must_free_in = false;

 #if XZ_INTERNAL_CRC32
 	xz_crc32_init();
 #endif

 	if (in_used != NULL)
 		*in_used = 0;

 	if (fill == NULL && flush == NULL)
 		s = xz_dec_init(XZ_SINGLE, 0);
 	else
 		s = xz_dec_init(XZ_DYNALLOC, (uint32_t)-1);

 	if (s == NULL)
 		goto error_alloc_state;

 	if (flush == NULL) {
 		b.out = out;
 		b.out_size = (size_t)-1;
 	} else {
 		b.out_size = XZ_IOBUF_SIZE;
 		b.out = malloc(XZ_IOBUF_SIZE);
 		if (b.out == NULL)
 			goto error_alloc_out;
 	}

 	if (in == NULL) {
 		must_free_in = true;
 		in = malloc(XZ_IOBUF_SIZE);
 		if (in == NULL)
 			goto error_alloc_in;
 	}

 	b.in = in;
 	b.in_pos = 0;
 	b.in_size = in_size;
 	b.out_pos = 0;

 	if (fill == NULL && flush == NULL) {
 		ret = xz_dec_run(s, &b);
 	} else {
 		do {
 			if (b.in_pos == b.in_size && fill != NULL) {
 				if (in_used != NULL)
 					*in_used += b.in_pos;

 				b.in_pos = 0;

 				in_size = fill(in, XZ_IOBUF_SIZE);
 				if (in_size < 0) {
 					/*
 					 * This isn't an optimal error code
 					 * but it probably isn't worth making
 					 * a new one either.
 					 */
 					ret = XZ_BUF_ERROR;
 					break;
 				}

 				b.in_size = in_size;
 			}

 			ret = xz_dec_run(s, &b);

 			if (flush != NULL && (b.out_pos == b.out_size
 					|| (ret != XZ_OK && b.out_pos > 0))) {
 				/*
 				 * Setting ret here may hide an error
 				 * returned by xz_dec_run(), but probably
 				 * it's not too bad.
 				 */
 				if (flush(b.out, b.out_pos) != (int)b.out_pos)
 					ret = XZ_BUF_ERROR;

 				b.out_pos = 0;
 			}
 		} while (ret == XZ_OK);

 		if (must_free_in)
 			free(in);

 		if (flush != NULL)
 			free(b.out);
 	}

 	if (in_used != NULL)
 		*in_used += b.in_pos;

 	xz_dec_end(s);

 	switch (ret) {
 	case XZ_STREAM_END:
 		return 0;

 	case XZ_MEM_ERROR:
 		/* This can occur only in multi-call mode. */
 		error("XZ decompressor ran out of memory");
 		break;

 	case XZ_FORMAT_ERROR:
 		error("Input is not in the XZ format (wrong magic bytes)");
 		break;

 	case XZ_OPTIONS_ERROR:
 		error("Input was encoded with settings that are not "
 				"supported by this XZ decoder");
 		break;

 	case XZ_DATA_ERROR:
 	case XZ_BUF_ERROR:
 		error("XZ-compressed data is corrupt");
 		break;

 	default:
 		error("Bug in the XZ decompressor");
 		break;
 	}

 	return -1;

 error_alloc_in:
 	if (flush != NULL)
 		free(b.out);

 error_alloc_out:
 	xz_dec_end(s);

 error_alloc_state:
 	error("XZ decompressor ran out of memory");
 	return -1;
 }

 /*
  * This macro is used by architecture-specific files to decompress
  * the kernel image.
  */
 #define decompress unxz
	/*
	* Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd
	*
	* 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.
	*/

	/*
	* Important notes about in-place decompression
	*
	* At least on x86, the kernel is decompressed in place: the compressed data
	* is placed to the end of the output buffer, and the decompressor overwrites
	* most of the compressed data. There must be enough safety margin to
	* guarantee that the write position is always behind the read position.
	*
	* The safety margin for XZ with LZMA2 or BCJ+LZMA2 is calculated below.
	* Note that the margin with XZ is bigger than with Deflate (gzip)!
	*
	* The worst case for in-place decompression is that the beginning of
	* the file is compressed extremely well, and the rest of the file is
	* uncompressible. Thus, we must look for worst-case expansion when the
	* compressor is encoding uncompressible data.
	*
	* The structure of the .xz file in case of a compresed kernel is as follows.
	* Sizes (as bytes) of the fields are in parenthesis.
	*
	* Stream Header (12)
	* Block Header:
	* Block Header (8-12)
	* Compressed Data (N)
	* Block Padding (0-3)
	* CRC32 (4)
	* Index (8-20)
	* Stream Footer (12)
	*
	* Normally there is exactly one Block, but let's assume that there are
	* 2-4 Blocks just in case. Because Stream Header and also Block Header
	* of the first Block don't make the decompressor produce any uncompressed
	* data, we can ignore them from our calculations. Block Headers of possible
	* additional Blocks have to be taken into account still. With these
	* assumptions, it is safe to assume that the total header overhead is
	* less than 128 bytes.
	*
	* Compressed Data contains LZMA2 or BCJ+LZMA2 encoded data. Since BCJ
	* doesn't change the size of the data, it is enough to calculate the
	* safety margin for LZMA2.
	*
	* LZMA2 stores the data in chunks. Each chunk has a header whose size is
	* a maximum of 6 bytes, but to get round 2^n numbers, let's assume that
	* the maximum chunk header size is 8 bytes. After the chunk header, there
	* may be up to 64 KiB of actual payload in the chunk. Often the payload is
	* quite a bit smaller though; to be safe, let's assume that an average
	* chunk has only 32 KiB of payload.
	*
	* The maximum uncompressed size of the payload is 2 MiB. The minimum
	* uncompressed size of the payload is in practice never less than the
	* payload size itself. The LZMA2 format would allow uncompressed size
	* to be less than the payload size, but no sane compressor creates such
	* files. LZMA2 supports storing uncompressible data in uncompressed form,
	* so there's never a need to create payloads whose uncompressed size is
	* smaller than the compressed size.
	*
	* The assumption, that the uncompressed size of the payload is never
	* smaller than the payload itself, is valid only when talking about
	* the payload as a whole. It is possible that the payload has parts where
	* the decompressor consumes more input than it produces output. Calculating
	* the worst case for this would be tricky. Instead of trying to do that,
	* let's simply make sure that the decompressor never overwrites any bytes
	* of the payload which it is currently reading.
	*
	* Now we have enough information to calculate the safety margin. We need
	* - 128 bytes for the .xz file format headers;
	* - 8 bytes per every 32 KiB of uncompressed size (one LZMA2 chunk header
	* per chunk, each chunk having average payload size of 32 KiB); and
	* - 64 KiB (biggest possible LZMA2 chunk payload size) to make sure that
	* the decompressor never overwrites anything from the LZMA2 chunk
	* payload it is currently reading.
	*
	* We get the following formula:
	*
	* safety_margin = 128 + uncompressed_size * 8 / 32768 + 65536
	* = 128 + (uncompressed_size >> 12) + 65536
	*
	* For comparison, according to arch/x86/boot/compressed/misc.c, the
	* equivalent formula for Deflate is this:
	*
	* safety_margin = 18 + (uncompressed_size >> 12) + 32768
	*
	* Thus, when updating Deflate-only in-place kernel decompressor to
	* support XZ, the fixed overhead has to be increased from 18+32768 bytes
	* to 128+65536 bytes.
	*/

	/*
	* STATIC is defined to "static" if we are being built for kernel
	* decompression (pre-boot code). <linux/decompress/mm.h> will define
	* STATIC to empty if it wasn't already defined. Since we will need to
	* know later if we are being used for kernel decompression, we define
	* XZ_PREBOOT here.
	*/
	#ifdef STATIC
	# define XZ_PREBOOT
	#endif
	#ifdef __KERNEL__
	# include <linux/decompress/mm.h>
	#endif
	#define XZ_EXTERN STATIC

	#ifndef XZ_PREBOOT
	# include <linux/slab.h>
	# include <linux/xz.h>
	#else
	/*
	* Use the internal CRC32 code instead of kernel's CRC32 module, which
	* is not available in early phase of booting.
	*/
	#define XZ_INTERNAL_CRC32 1

	/*
	* For boot time use, we enable only the BCJ filter of the current
	* architecture or none if no BCJ filter is available for the architecture.
	*/
	#ifdef CONFIG_X86
	# define XZ_DEC_X86
	#endif
	#ifdef CONFIG_PPC
	# define XZ_DEC_POWERPC
	#endif
	#ifdef CONFIG_ARM
	# define XZ_DEC_ARM
	#endif
	#ifdef CONFIG_IA64
	# define XZ_DEC_IA64
	#endif
	#ifdef CONFIG_SPARC
	# define XZ_DEC_SPARC
	#endif

	/*
	* This will get the basic headers so that memeq() and others
	* can be defined.
	*/
	#include "xz/xz_private.h"

	/*
	* Replace the normal allocation functions with the versions from
	* <linux/decompress/mm.h>. vfree() needs to support vfree(NULL)
	* when XZ_DYNALLOC is used, but the pre-boot free() doesn't support it.
	* Workaround it here because the other decompressors don't need it.
	*/
	#undef kmalloc
	#undef kfree
	#undef vmalloc
	#undef vfree
	#define kmalloc(size, flags) malloc(size)
	#define kfree(ptr) free(ptr)
	#define vmalloc(size) malloc(size)
	#define vfree(ptr) do { if (ptr != NULL) free(ptr); } while (0)

	/*
	* FIXME: Not all basic memory functions are provided in architecture-specific
	* files (yet). We define our own versions here for now, but this should be
	* only a temporary solution.
	*
	* memeq and memzero are not used much and any remotely sane implementation
	* is fast enough. memcpy/memmove speed matters in multi-call mode, but
	* the kernel image is decompressed in single-call mode, in which only
	* memcpy speed can matter and only if there is a lot of uncompressible data
	* (LZMA2 stores uncompressible chunks in uncompressed form). Thus, the
	* functions below should just be kept small; it's probably not worth
	* optimizing for speed.
	*/

	#ifndef memeq
	static bool memeq(const void a, const void b, size_t size)
	{
	const uint8_t *x = a;
	const uint8_t *y = b;
	size_t i;

	for (i = 0; i < size; ++i)
	if (x[i] != y[i])
	return false;

	return true;
	}
	#endif

	#ifndef memzero
	static void memzero(void *buf, size_t size)
	{
	uint8_t *b = buf;
	uint8_t *e = b + size;

	while (b != e)
	*b++ = '\0';
	}
	#endif

	#ifndef memmove
	/* Not static to avoid a conflict with the prototype in the Linux headers. */
	void memmove(void dest, const void *src, size_t size)
	{
	uint8_t *d = dest;
	const uint8_t *s = src;
	size_t i;

	if (d < s) {
	for (i = 0; i < size; ++i)
	d[i] = s[i];
	} else if (d > s) {
	i = size;
	while (i-- > 0)
	d[i] = s[i];
	}

	return dest;
	}
	#endif

	/*
	* Since we need memmove anyway, would use it as memcpy too.
	* Commented out for now to avoid breaking things.
	*/
	/*
	#ifndef memcpy
	# define memcpy memmove
	#endif
	*/

	#include "xz/xz_crc32.c"
	#include "xz/xz_dec_stream.c"
	#include "xz/xz_dec_lzma2.c"
	#include "xz/xz_dec_bcj.c"

	#endif /* XZ_PREBOOT */

	/* Size of the input and output buffers in multi-call mode */
	#define XZ_IOBUF_SIZE 4096

	/*
	* This function implements the API defined in <linux/decompress/generic.h>.
	*
	* This wrapper will automatically choose single-call or multi-call mode
	* of the native XZ decoder API. The single-call mode can be used only when
	* both input and output buffers are available as a single chunk, i.e. when
	* fill() and flush() won't be used.
	*/
	STATIC int INIT unxz(unsigned char *in, int in_size,
	int (fill)(void dest, unsigned int size),
	int (flush)(void src, unsigned int size),
	unsigned char out, int in_used,
	void (error)(char x))
	{
	struct xz_buf b;
	struct xz_dec *s;
	enum xz_ret ret;
	bool must_free_in = false;

	#if XZ_INTERNAL_CRC32
	xz_crc32_init();
	#endif

	if (in_used != NULL)
	*in_used = 0;

	if (fill == NULL && flush == NULL)
	s = xz_dec_init(XZ_SINGLE, 0);
	else
	s = xz_dec_init(XZ_DYNALLOC, (uint32_t)-1);

	if (s == NULL)
	goto error_alloc_state;

	if (flush == NULL) {
	b.out = out;
	b.out_size = (size_t)-1;
	} else {
	b.out_size = XZ_IOBUF_SIZE;
	b.out = malloc(XZ_IOBUF_SIZE);
	if (b.out == NULL)
	goto error_alloc_out;
	}

	if (in == NULL) {
	must_free_in = true;
	in = malloc(XZ_IOBUF_SIZE);
	if (in == NULL)
	goto error_alloc_in;
	}

	b.in = in;
	b.in_pos = 0;
	b.in_size = in_size;
	b.out_pos = 0;

	if (fill == NULL && flush == NULL) {
	ret = xz_dec_run(s, &b);
	} else {
	do {
	if (b.in_pos == b.in_size && fill != NULL) {
	if (in_used != NULL)
	*in_used += b.in_pos;

	b.in_pos = 0;

	in_size = fill(in, XZ_IOBUF_SIZE);
	if (in_size < 0) {
	/*
	* This isn't an optimal error code
	* but it probably isn't worth making
	* a new one either.
	*/
	ret = XZ_BUF_ERROR;
	break;
	}

	b.in_size = in_size;
	}

	ret = xz_dec_run(s, &b);

	if (flush != NULL && (b.out_pos == b.out_size
	\|\| (ret != XZ_OK && b.out_pos > 0))) {
	/*
	* Setting ret here may hide an error
	* returned by xz_dec_run(), but probably
	* it's not too bad.
	*/
	if (flush(b.out, b.out_pos) != (int)b.out_pos)
	ret = XZ_BUF_ERROR;

	b.out_pos = 0;
	}
	} while (ret == XZ_OK);

	if (must_free_in)
	free(in);

	if (flush != NULL)
	free(b.out);
	}

	if (in_used != NULL)
	*in_used += b.in_pos;

	xz_dec_end(s);

	switch (ret) {
	case XZ_STREAM_END:
	return 0;

	case XZ_MEM_ERROR:
	/* This can occur only in multi-call mode. */
	error("XZ decompressor ran out of memory");
	break;

	case XZ_FORMAT_ERROR:
	error("Input is not in the XZ format (wrong magic bytes)");
	break;

	case XZ_OPTIONS_ERROR:
	error("Input was encoded with settings that are not "
	"supported by this XZ decoder");
	break;

	case XZ_DATA_ERROR:
	case XZ_BUF_ERROR:
	error("XZ-compressed data is corrupt");
	break;

	default:
	error("Bug in the XZ decompressor");
	break;
	}

	return -1;

	error_alloc_in:
	if (flush != NULL)
	free(b.out);

	error_alloc_out:
	xz_dec_end(s);

	error_alloc_state:
	error("XZ decompressor ran out of memory");
	return -1;
	}

	/*
	* This macro is used by architecture-specific files to decompress
	* the kernel image.
	*/
	#define decompress unxz