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