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