lib/decompress.c

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