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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * XIP kernel .data segment decompressor
   4  *
   5  * Created by:  Nicolas Pitre, August 2017
   6  * Copyright:   (C) 2017  Linaro Limited
   7  */
   8
   9 #include <linux/init.h>
  10 #include <linux/zutil.h>
  11 #include "head.h"
  12
  13 /* for struct inflate_state */
  14 #include "../../../lib/zlib_inflate/inftrees.h"
  15 #include "../../../lib/zlib_inflate/inflate.h"
  16 #include "../../../lib/zlib_inflate/infutil.h"
  17
  18 /*
  19  * This code is called very early during the boot process to decompress
  20  * the .data segment stored compressed in ROM. Therefore none of the global
  21  * variables are valid yet, hence no kernel services such as memory
  22  * allocation is available. Everything must be allocated on the stack and
  23  * we must avoid any global data access. We use a temporary stack located
  24  * in the .bss area. The linker script makes sure the .bss is big enough
  25  * to hold our stack frame plus some room for called functions.
  26  *
  27  * We mimic the code in lib/decompress_inflate.c to use the smallest work
  28  * area possible. And because everything is statically allocated on the
  29  * stack then there is no need to clean up before returning.
  30  */
  31
  32 int __init __inflate_kernel_data(void)
  33 {
  34         struct z_stream_s stream, *strm = &stream;
  35         struct inflate_state state;
  36         char *in = __data_loc;
  37         int rc;
  38
  39         /* Check and skip gzip header (assume no filename) */
  40         if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3)
  41                 return -1;
  42         in += 10;
  43
  44         strm->workspace = &state;
  45         strm->next_in = in;
  46         strm->avail_in = _edata_loc - __data_loc;  /* upper bound */
  47         strm->next_out = _sdata;
  48         strm->avail_out = _edata_loc - __data_loc;
  49         zlib_inflateInit2(strm, -MAX_WBITS);
  50         WS(strm)->inflate_state.wsize = 0;
  51         WS(strm)->inflate_state.window = NULL;
  52         rc = zlib_inflate(strm, Z_FINISH);
  53         if (rc == Z_OK || rc == Z_STREAM_END)
  54                 rc = strm->avail_out;  /* should be 0 */
  55         return rc;
  56 }