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
  17 #include <linux/types.h>
  18 #include <linux/string.h>
  19 #include <linux/init.h>
  20 #include <linux/printk.h>
  21
  22 #ifndef CONFIG_DECOMPRESS_GZIP
  23 # define gunzip NULL
  24 #endif
  25 #ifndef CONFIG_DECOMPRESS_BZIP2
  26 # define bunzip2 NULL
  27 #endif
  28 #ifndef CONFIG_DECOMPRESS_LZMA
  29 # define unlzma NULL
  30 #endif
  31 #ifndef CONFIG_DECOMPRESS_XZ
  32 # define unxz NULL
  33 #endif
  34 #ifndef CONFIG_DECOMPRESS_LZO
  35 # define unlzo NULL
  36 #endif
  37 #ifndef CONFIG_DECOMPRESS_LZ4
  38 # define unlz4 NULL
  39 #endif
  40
  41 struct compress_format {
  42         unsigned char magic[2];
  43         const char *name;
  44         decompress_fn decompressor;
  45 };
  46
  47 static const struct compress_format compressed_formats[] __initconst = {
  48         { {0x1f, 0x8b}, "gzip", gunzip },
  49         { {0x1f, 0x9e}, "gzip", gunzip },
  50         { {0x42, 0x5a}, "bzip2", bunzip2 },
  51         { {0x5d, 0x00}, "lzma", unlzma },
  52         { {0xfd, 0x37}, "xz", unxz },
  53         { {0x89, 0x4c}, "lzo", unlzo },
  54         { {0x02, 0x21}, "lz4", unlz4 },
  55         { {0, 0}, NULL, NULL }
  56 };
  57
  58 decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
  59                                 const char **name)
  60 {
  61         const struct compress_format *cf;
  62
  63         if (len < 2) {
  64                 if (name)
  65                         *name = NULL;
  66                 return NULL;    /* Need at least this much... */
  67         }
  68
  69         pr_debug("Compressed data magic: %#.2x %#.2x\n", inbuf[0], inbuf[1]);
  70
  71         for (cf = compressed_formats; cf->name; cf++) {
  72                 if (!memcmp(inbuf, cf->magic, 2))
  73                         break;
  74
  75         }
  76         if (name)
  77                 *name = cf->name;
  78         return cf->decompressor;
  79 }