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
  45 struct compress_format {
  46         unsigned char magic[2];
  47         const char *name;
  48         decompress_fn decompressor;
  49 };
  50
  51 static 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
  63 decompress_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 }