Linux kernel mirror (for testing)
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linux
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * decompress.c
4 *
5 * Detect the decompression method based on magic number
6 */
7
8#include <linux/decompress/generic.h>
9
10#include <linux/decompress/bunzip2.h>
11#include <linux/decompress/unlzma.h>
12#include <linux/decompress/unxz.h>
13#include <linux/decompress/inflate.h>
14#include <linux/decompress/unlzo.h>
15#include <linux/decompress/unlz4.h>
16#include <linux/decompress/unzstd.h>
17
18#include <linux/types.h>
19#include <linux/string.h>
20#include <linux/init.h>
21#include <linux/printk.h>
22
23#ifndef CONFIG_DECOMPRESS_GZIP
24# define gunzip NULL
25#endif
26#ifndef CONFIG_DECOMPRESS_BZIP2
27# define bunzip2 NULL
28#endif
29#ifndef CONFIG_DECOMPRESS_LZMA
30# define unlzma NULL
31#endif
32#ifndef CONFIG_DECOMPRESS_XZ
33# define unxz NULL
34#endif
35#ifndef CONFIG_DECOMPRESS_LZO
36# define unlzo NULL
37#endif
38#ifndef CONFIG_DECOMPRESS_LZ4
39# define unlz4 NULL
40#endif
41#ifndef CONFIG_DECOMPRESS_ZSTD
42# define unzstd NULL
43#endif
44
45struct compress_format {
46 unsigned char magic[2];
47 const char *name;
48 decompress_fn decompressor;
49};
50
51static const struct compress_format compressed_formats[] __initconst = {
52 { .magic = {0x1f, 0x8b}, .name = "gzip", .decompressor = gunzip },
53 { .magic = {0x1f, 0x9e}, .name = "gzip", .decompressor = gunzip },
54 { .magic = {0x42, 0x5a}, .name = "bzip2", .decompressor = bunzip2 },
55 { .magic = {0x5d, 0x00}, .name = "lzma", .decompressor = unlzma },
56 { .magic = {0xfd, 0x37}, .name = "xz", .decompressor = unxz },
57 { .magic = {0x89, 0x4c}, .name = "lzo", .decompressor = unlzo },
58 { .magic = {0x02, 0x21}, .name = "lz4", .decompressor = unlz4 },
59 { .magic = {0x28, 0xb5}, .name = "zstd", .decompressor = unzstd },
60 { /* sentinel */ }
61};
62
63decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
64 const char **name)
65{
66 const struct compress_format *cf;
67
68 if (len < 2) {
69 if (name)
70 *name = NULL;
71 return NULL; /* Need at least this much... */
72 }
73
74 pr_debug("Compressed data magic: %#.2x %#.2x\n", inbuf[0], inbuf[1]);
75
76 for (cf = compressed_formats; cf->name; cf++)
77 if (!memcmp(inbuf, cf->magic, 2))
78 break;
79
80 if (name)
81 *name = cf->name;
82 return cf->decompressor;
83}