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 */
41 static unsigned long decompressed_bytes;
42 static unsigned long limit;
43 static unsigned long skip;
44 static char *output_buffer;
45 
46 /*
47  * flush() is called by __decompress() when the decompressor's scratch buffer is
48  * full.
49  */
flush(void * v,unsigned long buffer_size)50 static 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 
print_err(char * s)89 static 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  */
partial_decompress(void * inbuf,unsigned long input_size,void * outbuf,unsigned long output_size,unsigned long _skip)116 long 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