1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Wrapper around the kernel's pre-boot decompression library.
4 *
5 * Copyright (C) IBM Corporation 2016.
6 */
7
8#include "elf.h"
9#include "page.h"
10#include "string.h"
11#include "stdio.h"
12#include "ops.h"
13#include "reg.h"
14#include "types.h"
15
16/*
17 * The decompressor_*.c files play #ifdef games so they can be used in both
18 * pre-boot and regular kernel code. We need these definitions to make the
19 * includes work.
20 */
21
22#define STATIC static
23#define INIT
24
25/*
26 * The build process will copy the required zlib source files and headers
27 * out of lib/ and "fix" the includes so they do not pull in other kernel
28 * headers.
29 */
30
31#ifdef CONFIG_KERNEL_GZIP
32#	include "decompress_inflate.c"
33#endif
34
35#ifdef CONFIG_KERNEL_XZ
36#	include "xz_config.h"
37#	include "../../../lib/decompress_unxz.c"
38#endif
39
40/* globals for tracking the state of the decompression */
41static unsigned long decompressed_bytes;
42static unsigned long limit;
43static unsigned long skip;
44static char *output_buffer;
45
46/*
47 * flush() is called by __decompress() when the decompressor's scratch buffer is
48 * full.
49 */
50static long flush(void *v, unsigned long buffer_size)
51{
52	unsigned long end = decompressed_bytes + buffer_size;
53	unsigned long size = buffer_size;
54	unsigned long offset = 0;
55	char *in = v;
56	char *out;
57
58	/*
59	 * if we hit our decompression limit, we need to fake an error to abort
60	 * the in-progress decompression.
61	 */
62	if (decompressed_bytes >= limit)
63		return -1;
64
65	/* skip this entire block */
66	if (end <= skip) {
67		decompressed_bytes += buffer_size;
68		return buffer_size;
69	}
70
71	/* skip some data at the start, but keep the rest of the block */
72	if (decompressed_bytes < skip && end > skip) {
73		offset = skip - decompressed_bytes;
74
75		in += offset;
76		size -= offset;
77		decompressed_bytes += offset;
78	}
79
80	out = &output_buffer[decompressed_bytes - skip];
81	size = min(decompressed_bytes + size, limit) - decompressed_bytes;
82
83	memcpy(out, in, size);
84	decompressed_bytes += size;
85
86	return buffer_size;
87}
88
89static void print_err(char *s)
90{
91	/* suppress the "error" when we terminate the decompressor */
92	if (decompressed_bytes >= limit)
93		return;
94
95	printf("Decompression error: '%s'\n\r", s);
96}
97
98/**
99 * partial_decompress - decompresses part or all of a compressed buffer
100 * @inbuf:       input buffer
101 * @input_size:  length of the input buffer
102 * @outbuf:      output buffer
103 * @output_size: length of the output buffer
104 * @skip         number of output bytes to ignore
105 *
106 * This function takes compressed data from inbuf, decompresses and write it to
107 * outbuf. Once output_size bytes are written to the output buffer, or the
108 * stream is exhausted the function will return the number of bytes that were
109 * decompressed. Otherwise it will return whatever error code the decompressor
110 * reported (NB: This is specific to each decompressor type).
111 *
112 * The skip functionality is mainly there so the program and discover
113 * the size of the compressed image so that it can ask firmware (if present)
114 * for an appropriately sized buffer.
115 */
116long partial_decompress(void *inbuf, unsigned long input_size,
117	void *outbuf, unsigned long output_size, unsigned long _skip)
118{
119	int ret;
120
121	/*
122	 * The skipped bytes needs to be included in the size of data we want
123	 * to decompress.
124	 */
125	output_size += _skip;
126
127	decompressed_bytes = 0;
128	output_buffer = outbuf;
129	limit = output_size;
130	skip = _skip;
131
132	ret = __decompress(inbuf, input_size, NULL, flush, outbuf,
133		output_size, NULL, print_err);
134
135	/*
136	 * If decompression was aborted due to an actual error rather than
137	 * a fake error that we used to abort, then we should report it.
138	 */
139	if (decompressed_bytes < limit)
140		return ret;
141
142	return decompressed_bytes - skip;
143}
144