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
17extern char __data_loc[];
18extern char _edata_loc[];
19extern 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
35int __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}