LXR linux/lib/decompress.c

   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        { {0x1f, 0x8b}, "gzip", gunzip },
  53        { {0x1f, 0x9e}, "gzip", gunzip },
  54        { {0x42, 0x5a}, "bzip2", bunzip2 },
  55        { {0x5d, 0x00}, "lzma", unlzma },
  56        { {0xfd, 0x37}, "xz", unxz },
  57        { {0x89, 0x4c}, "lzo", unlzo },
  58        { {0x02, 0x21}, "lz4", unlz4 },
  59        { {0x28, 0xb5}, "zstd", unzstd },
  60        { {0, 0}, NULL, NULL }
  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        }
  81        if (name)
  82                *name = cf->name;
  83        return cf->decompressor;
  84}
  85