arch/arm/kernel/head-inflate-data.c

   1 /*
   2  * XIP kernel .data segment decompressor
   3  *
   4  * Created by:  Nicolas Pitre, August 2017
   5  * Copyright:   (C) 2017  Linaro Limited
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/init.h>
  13 #include <linux/zutil.h>
  14
  15 /* for struct inflate_state */
  16 #include "../../../lib/zlib_inflate/inftrees.h"
  17 #include "../../../lib/zlib_inflate/inflate.h"
  18 #include "../../../lib/zlib_inflate/infutil.h"
  19
  20 extern char __data_loc[];
  21 extern char _edata_loc[];
  22 extern char _sdata[];
  23
  24 /*
  25  * This code is called very early during the boot process to decompress
  26  * the .data segment stored compressed in ROM. Therefore none of the global
  27  * variables are valid yet, hence no kernel services such as memory
  28  * allocation is available. Everything must be allocated on the stack and
  29  * we must avoid any global data access. We use a temporary stack located
  30  * in the .bss area. The linker script makes sure the .bss is big enough
  31  * to hold our stack frame plus some room for called functions.
  32  *
  33  * We mimic the code in lib/decompress_inflate.c to use the smallest work
  34  * area possible. And because everything is statically allocated on the
  35  * stack then there is no need to clean up before returning.
  36  */
  37
  38 int __init __inflate_kernel_data(void)
  39 {
  40         struct z_stream_s stream, *strm = &stream;
  41         struct inflate_state state;
  42         char *in = __data_loc;
  43         int rc;
  44
  45         /* Check and skip gzip header (assume no filename) */
  46         if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3)
  47                 return -1;
  48         in += 10;
  49
  50         strm->workspace = &state;
  51         strm->next_in = in;
  52         strm->avail_in = _edata_loc - __data_loc;  /* upper bound */
  53         strm->next_out = _sdata;
  54         strm->avail_out = _edata_loc - __data_loc;
  55         zlib_inflateInit2(strm, -MAX_WBITS);
  56         WS(strm)->inflate_state.wsize = 0;
  57         WS(strm)->inflate_state.window = NULL;
  58         rc = zlib_inflate(strm, Z_FINISH);
  59         if (rc == Z_OK || rc == Z_STREAM_END)
  60                 rc = strm->avail_out;  /* should be 0 */
  61         return rc;
  62 }