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 }
57
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