You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
397 lines
11 KiB
397 lines
11 KiB
/*
|
|
* 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, long in_size,
|
|
long (*fill)(void *dest, unsigned long size),
|
|
long (*flush)(void *src, unsigned long size),
|
|
unsigned char *out, long *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) != (long)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
|
|
|