Browse Source
This implements the API defined in <linux/decompress/generic.h> which is used for kernel, initramfs, and initrd decompression. This patch together with the first patch is enough for XZ-compressed initramfs and initrd; XZ-compressed kernel will need arch-specific changes. The buffering requirements described in decompress_unxz.c are stricter than with gzip, so the relevant changes should be done to the arch-specific code when adding support for XZ-compressed kernel. Similarly, the heap size in arch-specific pre-boot code may need to be increased (30 KiB is enough). The XZ decompressor needs memmove(), memeq() (memcmp() == 0), and memzero() (memset(ptr, 0, size)), which aren't available in all arch-specific pre-boot environments. I'm including simple versions in decompress_unxz.c, but a cleaner solution would naturally be nicer. 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>master
Lasse Collin
12 years ago
committed by
Linus Torvalds
9 changed files with 469 additions and 2 deletions
@ -0,0 +1,19 @@
|
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/*
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* Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd |
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* |
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* Author: Lasse Collin <lasse.collin@tukaani.org> |
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* |
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* This file has been put into the public domain. |
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* You can do whatever you want with this file. |
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*/ |
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|
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#ifndef DECOMPRESS_UNXZ_H |
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#define DECOMPRESS_UNXZ_H |
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int unxz(unsigned char *in, int in_size, |
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int (*fill)(void *dest, unsigned int size), |
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int (*flush)(void *src, unsigned int size), |
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unsigned char *out, int *in_used, |
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void (*error)(char *x)); |
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#endif |
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@ -0,0 +1,397 @@
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/*
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* Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd |
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* |
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* Author: Lasse Collin <lasse.collin@tukaani.org> |
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* |
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* This file has been put into the public domain. |
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* You can do whatever you want with this file. |
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*/ |
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/*
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* Important notes about in-place decompression |
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* |
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* At least on x86, the kernel is decompressed in place: the compressed data |
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* is placed to the end of the output buffer, and the decompressor overwrites |
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* most of the compressed data. There must be enough safety margin to |
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* guarantee that the write position is always behind the read position. |
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* |
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* The safety margin for XZ with LZMA2 or BCJ+LZMA2 is calculated below. |
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* Note that the margin with XZ is bigger than with Deflate (gzip)! |
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* |
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* The worst case for in-place decompression is that the beginning of |
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* the file is compressed extremely well, and the rest of the file is |
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* uncompressible. Thus, we must look for worst-case expansion when the |
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* compressor is encoding uncompressible data. |
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* |
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* The structure of the .xz file in case of a compresed kernel is as follows. |
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* Sizes (as bytes) of the fields are in parenthesis. |
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* |
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* Stream Header (12) |
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* Block Header: |
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* Block Header (8-12) |
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* Compressed Data (N) |
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* Block Padding (0-3) |
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* CRC32 (4) |
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* Index (8-20) |
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* Stream Footer (12) |
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* |
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* Normally there is exactly one Block, but let's assume that there are |
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* 2-4 Blocks just in case. Because Stream Header and also Block Header |
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* of the first Block don't make the decompressor produce any uncompressed |
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* data, we can ignore them from our calculations. Block Headers of possible |
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* additional Blocks have to be taken into account still. With these |
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* assumptions, it is safe to assume that the total header overhead is |
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* less than 128 bytes. |
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* |
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* Compressed Data contains LZMA2 or BCJ+LZMA2 encoded data. Since BCJ |
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* doesn't change the size of the data, it is enough to calculate the |
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* safety margin for LZMA2. |
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* |
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* LZMA2 stores the data in chunks. Each chunk has a header whose size is |
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* a maximum of 6 bytes, but to get round 2^n numbers, let's assume that |
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* the maximum chunk header size is 8 bytes. After the chunk header, there |
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* may be up to 64 KiB of actual payload in the chunk. Often the payload is |
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* quite a bit smaller though; to be safe, let's assume that an average |
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* chunk has only 32 KiB of payload. |
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* |
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* The maximum uncompressed size of the payload is 2 MiB. The minimum |
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* uncompressed size of the payload is in practice never less than the |
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* payload size itself. The LZMA2 format would allow uncompressed size |
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* to be less than the payload size, but no sane compressor creates such |
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* files. LZMA2 supports storing uncompressible data in uncompressed form, |
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* so there's never a need to create payloads whose uncompressed size is |
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* smaller than the compressed size. |
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* |
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* The assumption, that the uncompressed size of the payload is never |
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* smaller than the payload itself, is valid only when talking about |
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* the payload as a whole. It is possible that the payload has parts where |
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* the decompressor consumes more input than it produces output. Calculating |
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* the worst case for this would be tricky. Instead of trying to do that, |
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* let's simply make sure that the decompressor never overwrites any bytes |
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* of the payload which it is currently reading. |
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* |
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* Now we have enough information to calculate the safety margin. We need |
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* - 128 bytes for the .xz file format headers; |
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* - 8 bytes per every 32 KiB of uncompressed size (one LZMA2 chunk header |
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* per chunk, each chunk having average payload size of 32 KiB); and |
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* - 64 KiB (biggest possible LZMA2 chunk payload size) to make sure that |
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* the decompressor never overwrites anything from the LZMA2 chunk |
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* payload it is currently reading. |
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* |
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* We get the following formula: |
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* |
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* safety_margin = 128 + uncompressed_size * 8 / 32768 + 65536 |
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* = 128 + (uncompressed_size >> 12) + 65536 |
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* |
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* For comparision, according to arch/x86/boot/compressed/misc.c, the |
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* equivalent formula for Deflate is this: |
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* |
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* safety_margin = 18 + (uncompressed_size >> 12) + 32768 |
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* |
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* Thus, when updating Deflate-only in-place kernel decompressor to |
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* support XZ, the fixed overhead has to be increased from 18+32768 bytes |
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* to 128+65536 bytes. |
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*/ |
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|
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/*
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* STATIC is defined to "static" if we are being built for kernel |
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* decompression (pre-boot code). <linux/decompress/mm.h> will define |
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* STATIC to empty if it wasn't already defined. Since we will need to |
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* know later if we are being used for kernel decompression, we define |
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* XZ_PREBOOT here. |
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*/ |
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#ifdef STATIC |
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# define XZ_PREBOOT |
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#endif |
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#ifdef __KERNEL__ |
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# include <linux/decompress/mm.h> |
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#endif |
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#define XZ_EXTERN STATIC |
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#ifndef XZ_PREBOOT |
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# include <linux/slab.h> |
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# include <linux/xz.h> |
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#else |
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/*
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* Use the internal CRC32 code instead of kernel's CRC32 module, which |
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* is not available in early phase of booting. |
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*/ |
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#define XZ_INTERNAL_CRC32 1 |
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/*
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* For boot time use, we enable only the BCJ filter of the current |
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* architecture or none if no BCJ filter is available for the architecture. |
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*/ |
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#ifdef CONFIG_X86 |
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# define XZ_DEC_X86 |
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#endif |
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#ifdef CONFIG_PPC |
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# define XZ_DEC_POWERPC |
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#endif |
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#ifdef CONFIG_ARM |
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# define XZ_DEC_ARM |
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#endif |
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#ifdef CONFIG_IA64 |
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# define XZ_DEC_IA64 |
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#endif |
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#ifdef CONFIG_SPARC |
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# define XZ_DEC_SPARC |
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#endif |
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/*
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* This will get the basic headers so that memeq() and others |
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* can be defined. |
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*/ |
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#include "xz/xz_private.h" |
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/*
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* Replace the normal allocation functions with the versions from |
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* <linux/decompress/mm.h>. vfree() needs to support vfree(NULL) |
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* when XZ_DYNALLOC is used, but the pre-boot free() doesn't support it. |
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* Workaround it here because the other decompressors don't need it. |
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*/ |
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#undef kmalloc |
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#undef kfree |
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#undef vmalloc |
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#undef vfree |
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#define kmalloc(size, flags) malloc(size) |
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#define kfree(ptr) free(ptr) |
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#define vmalloc(size) malloc(size) |
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#define vfree(ptr) do { if (ptr != NULL) free(ptr); } while (0) |
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/*
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* FIXME: Not all basic memory functions are provided in architecture-specific |
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* files (yet). We define our own versions here for now, but this should be |
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* only a temporary solution. |
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* |
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* memeq and memzero are not used much and any remotely sane implementation |
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* is fast enough. memcpy/memmove speed matters in multi-call mode, but |
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* the kernel image is decompressed in single-call mode, in which only |
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* memcpy speed can matter and only if there is a lot of uncompressible data |
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* (LZMA2 stores uncompressible chunks in uncompressed form). Thus, the |
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* functions below should just be kept small; it's probably not worth |
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* optimizing for speed. |
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*/ |
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#ifndef memeq |
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static bool memeq(const void *a, const void *b, size_t size) |
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{ |
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const uint8_t *x = a; |
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const uint8_t *y = b; |
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size_t i; |
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for (i = 0; i < size; ++i) |
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if (x[i] != y[i]) |
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return false; |
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return true; |
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} |
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#endif |
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#ifndef memzero |
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static void memzero(void *buf, size_t size) |
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{ |
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uint8_t *b = buf; |
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uint8_t *e = b + size; |
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while (b != e) |
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*b++ = '\0'; |
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} |
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#endif |
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#ifndef memmove |
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/* Not static to avoid a conflict with the prototype in the Linux headers. */ |
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void *memmove(void *dest, const void *src, size_t size) |
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{ |
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uint8_t *d = dest; |
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const uint8_t *s = src; |
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size_t i; |
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if (d < s) { |
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for (i = 0; i < size; ++i) |
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d[i] = s[i]; |
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} else if (d > s) { |
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i = size; |
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while (i-- > 0) |
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d[i] = s[i]; |
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} |
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return dest; |
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} |
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#endif |
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/*
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* Since we need memmove anyway, would use it as memcpy too. |
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* Commented out for now to avoid breaking things. |
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*/ |
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/*
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#ifndef memcpy |
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# define memcpy memmove |
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#endif |
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*/ |
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#include "xz/xz_crc32.c" |
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#include "xz/xz_dec_stream.c" |
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#include "xz/xz_dec_lzma2.c" |
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#include "xz/xz_dec_bcj.c" |
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#endif /* XZ_PREBOOT */ |
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/* Size of the input and output buffers in multi-call mode */ |
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#define XZ_IOBUF_SIZE 4096 |
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/*
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* This function implements the API defined in <linux/decompress/generic.h>. |
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* |
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* This wrapper will automatically choose single-call or multi-call mode |
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* of the native XZ decoder API. The single-call mode can be used only when |
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* both input and output buffers are available as a single chunk, i.e. when |
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* fill() and flush() won't be used. |
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*/ |
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STATIC int INIT unxz(unsigned char *in, int in_size, |
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int (*fill)(void *dest, unsigned int size), |
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int (*flush)(void *src, unsigned int size), |
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unsigned char *out, int *in_used, |
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void (*error)(char *x)) |
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{ |
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struct xz_buf b; |
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struct xz_dec *s; |
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enum xz_ret ret; |
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bool must_free_in = false; |
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#if XZ_INTERNAL_CRC32 |
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xz_crc32_init(); |
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#endif |
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if (in_used != NULL) |
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*in_used = 0; |
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if (fill == NULL && flush == NULL) |
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s = xz_dec_init(XZ_SINGLE, 0); |
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else |
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s = xz_dec_init(XZ_DYNALLOC, (uint32_t)-1); |
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if (s == NULL) |
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goto error_alloc_state; |
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if (flush == NULL) { |
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b.out = out; |
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b.out_size = (size_t)-1; |
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} else { |
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b.out_size = XZ_IOBUF_SIZE; |
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b.out = malloc(XZ_IOBUF_SIZE); |
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if (b.out == NULL) |
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goto error_alloc_out; |
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} |
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if (in == NULL) { |
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must_free_in = true; |
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in = malloc(XZ_IOBUF_SIZE); |
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if (in == NULL) |
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goto error_alloc_in; |
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} |
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b.in = in; |
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b.in_pos = 0; |
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b.in_size = in_size; |
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b.out_pos = 0; |
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if (fill == NULL && flush == NULL) { |
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ret = xz_dec_run(s, &b); |
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} else { |
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do { |
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if (b.in_pos == b.in_size && fill != NULL) { |
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if (in_used != NULL) |
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*in_used += b.in_pos; |
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b.in_pos = 0; |
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in_size = fill(in, XZ_IOBUF_SIZE); |
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if (in_size < 0) { |
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/*
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* This isn't an optimal error code |
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* but it probably isn't worth making |
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* a new one either. |
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*/ |
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ret = XZ_BUF_ERROR; |
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break; |
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} |
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b.in_size = in_size; |
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} |
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ret = xz_dec_run(s, &b); |
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if (flush != NULL && (b.out_pos == b.out_size |
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|| (ret != XZ_OK && b.out_pos > 0))) { |
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/*
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* Setting ret here may hide an error |
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* returned by xz_dec_run(), but probably |
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* it's not too bad. |
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*/ |
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if (flush(b.out, b.out_pos) != (int)b.out_pos) |
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ret = XZ_BUF_ERROR; |
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b.out_pos = 0; |
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} |
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} while (ret == XZ_OK); |
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if (must_free_in) |
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free(in); |
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if (flush != NULL) |
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free(b.out); |
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} |
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if (in_used != NULL) |
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*in_used += b.in_pos; |
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xz_dec_end(s); |
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switch (ret) { |
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case XZ_STREAM_END: |
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return 0; |
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case XZ_MEM_ERROR: |
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/* This can occur only in multi-call mode. */ |
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error("XZ decompressor ran out of memory"); |
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break; |
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case XZ_FORMAT_ERROR: |
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error("Input is not in the XZ format (wrong magic bytes)"); |
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break; |
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case XZ_OPTIONS_ERROR: |
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error("Input was encoded with settings that are not " |
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"supported by this XZ decoder"); |
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break; |
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case XZ_DATA_ERROR: |
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case XZ_BUF_ERROR: |
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error("XZ-compressed data is corrupt"); |
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break; |
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default: |
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error("Bug in the XZ decompressor"); |
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break; |
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} |
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return -1; |
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error_alloc_in: |
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if (flush != NULL) |
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free(b.out); |
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error_alloc_out: |
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xz_dec_end(s); |
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error_alloc_state: |
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error("XZ decompressor ran out of memory"); |
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return -1; |
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} |
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/*
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* This macro is used by architecture-specific files to decompress |
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* the kernel image. |
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*/ |
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#define decompress unxz |
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