Line data Source code
1 : /* Compress or decompress a section.
2 : Copyright (C) 2015 Red Hat, Inc.
3 : This file is part of elfutils.
4 :
5 : This file is free software; you can redistribute it and/or modify
6 : it under the terms of either
7 :
8 : * the GNU Lesser General Public License as published by the Free
9 : Software Foundation; either version 3 of the License, or (at
10 : your option) any later version
11 :
12 : or
13 :
14 : * the GNU General Public License as published by the Free
15 : Software Foundation; either version 2 of the License, or (at
16 : your option) any later version
17 :
18 : or both in parallel, as here.
19 :
20 : elfutils is distributed in the hope that it will be useful, but
21 : WITHOUT ANY WARRANTY; without even the implied warranty of
22 : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 : General Public License for more details.
24 :
25 : You should have received copies of the GNU General Public License and
26 : the GNU Lesser General Public License along with this program. If
27 : not, see <http://www.gnu.org/licenses/>. */
28 :
29 : #ifdef HAVE_CONFIG_H
30 : # include <config.h>
31 : #endif
32 :
33 : #include <libelf.h>
34 : #include "libelfP.h"
35 : #include "common.h"
36 :
37 : int
38 440 : elf_compress_gnu (Elf_Scn *scn, int inflate, unsigned int flags)
39 : {
40 440 : if (scn == NULL)
41 : return -1;
42 :
43 440 : if ((flags & ~ELF_CHF_FORCE) != 0)
44 : {
45 0 : __libelf_seterrno (ELF_E_INVALID_OPERAND);
46 0 : return -1;
47 : }
48 :
49 440 : bool force = (flags & ELF_CHF_FORCE) != 0;
50 :
51 440 : Elf *elf = scn->elf;
52 : GElf_Ehdr ehdr;
53 440 : if (gelf_getehdr (elf, &ehdr) == NULL)
54 : return -1;
55 :
56 440 : int elfclass = elf->class;
57 440 : int elfdata = ehdr.e_ident[EI_DATA];
58 :
59 : Elf64_Xword sh_flags;
60 : Elf64_Word sh_type;
61 : Elf64_Xword sh_addralign;
62 440 : if (elfclass == ELFCLASS32)
63 : {
64 183 : Elf32_Shdr *shdr = elf32_getshdr (scn);
65 183 : if (shdr == NULL)
66 : return -1;
67 :
68 183 : sh_flags = shdr->sh_flags;
69 183 : sh_type = shdr->sh_type;
70 183 : sh_addralign = shdr->sh_addralign;
71 : }
72 : else
73 : {
74 257 : Elf64_Shdr *shdr = elf64_getshdr (scn);
75 257 : if (shdr == NULL)
76 : return -1;
77 :
78 257 : sh_flags = shdr->sh_flags;
79 257 : sh_type = shdr->sh_type;
80 257 : sh_addralign = shdr->sh_addralign;
81 : }
82 :
83 440 : if ((sh_flags & SHF_ALLOC) != 0)
84 : {
85 0 : __libelf_seterrno (ELF_E_INVALID_SECTION_FLAGS);
86 0 : return -1;
87 : }
88 :
89 440 : if (sh_type == SHT_NULL || sh_type == SHT_NOBITS)
90 : {
91 0 : __libelf_seterrno (ELF_E_INVALID_SECTION_TYPE);
92 0 : return -1;
93 : }
94 :
95 : /* For GNU compression we cannot really know whether the section is
96 : already compressed or not. Just try and see what happens... */
97 : // int compressed = (sh_flags & SHF_COMPRESSED);
98 440 : if (inflate == 1)
99 : {
100 176 : size_t hsize = 4 + 8; /* GNU "ZLIB" + 8 byte size. */
101 : size_t orig_size, new_size, orig_addralign;
102 176 : void *out_buf = __libelf_compress (scn, hsize, elfdata,
103 : &orig_size, &orig_addralign,
104 : &new_size, force);
105 :
106 : /* Compression would make section larger, don't change anything. */
107 176 : if (out_buf == (void *) -1)
108 : return 0;
109 :
110 : /* Compression failed, return error. */
111 147 : if (out_buf == NULL)
112 : return -1;
113 :
114 294 : uint64_t be64_size = htobe64 (orig_size);
115 147 : memmove (out_buf, "ZLIB", 4);
116 294 : memmove (out_buf + 4, &be64_size, sizeof (be64_size));
117 :
118 : /* We don't know anything about sh_entsize, sh_addralign and
119 : sh_flags won't have a SHF_COMPRESSED hint in the GNU format.
120 : Just adjust the sh_size. */
121 147 : if (elfclass == ELFCLASS32)
122 : {
123 73 : Elf32_Shdr *shdr = elf32_getshdr (scn);
124 73 : shdr->sh_size = new_size;
125 : }
126 : else
127 : {
128 74 : Elf64_Shdr *shdr = elf64_getshdr (scn);
129 74 : shdr->sh_size = new_size;
130 : }
131 :
132 147 : __libelf_reset_rawdata (scn, out_buf, new_size, 1, ELF_T_BYTE);
133 :
134 : /* The section is now compressed, we could keep the uncompressed
135 : data around, but since that might have been multiple Elf_Data
136 : buffers let the user uncompress it explicitly again if they
137 : want it to simplify bookkeeping. */
138 147 : scn->zdata_base = NULL;
139 :
140 147 : return 1;
141 : }
142 264 : else if (inflate == 0)
143 : {
144 : /* In theory the user could have constucted a compressed section
145 : by hand. But we always just take the rawdata directly and
146 : decompress that. */
147 264 : Elf_Data *data = elf_rawdata (scn, NULL);
148 264 : if (data == NULL)
149 : return -1;
150 :
151 264 : size_t hsize = 4 + 8; /* GNU "ZLIB" + 8 byte size. */
152 264 : if (data->d_size < hsize || memcmp (data->d_buf, "ZLIB", 4) != 0)
153 : {
154 4 : __libelf_seterrno (ELF_E_NOT_COMPRESSED);
155 4 : return -1;
156 : }
157 :
158 : /* There is a 12-byte header of "ZLIB" followed by
159 : an 8-byte big-endian size. There is only one type and
160 : Alignment isn't preserved separately. */
161 : uint64_t gsize;
162 260 : memcpy (&gsize, data->d_buf + 4, sizeof gsize);
163 520 : gsize = be64toh (gsize);
164 :
165 : /* One more sanity check, size should be bigger than original
166 : data size plus some overhead (4 chars ZLIB + 8 bytes size + 6
167 : bytes zlib stream overhead + 5 bytes overhead max for one 16K
168 : block) and should fit into a size_t. */
169 260 : if (gsize + 4 + 8 + 6 + 5 < data->d_size || gsize > SIZE_MAX)
170 : {
171 0 : __libelf_seterrno (ELF_E_NOT_COMPRESSED);
172 0 : return -1;
173 : }
174 :
175 260 : size_t size = gsize;
176 260 : size_t size_in = data->d_size - hsize;
177 260 : void *buf_in = data->d_buf + hsize;
178 260 : void *buf_out = __libelf_decompress (buf_in, size_in, size);
179 260 : if (buf_out == NULL)
180 : return -1;
181 :
182 : /* We don't know anything about sh_entsize, sh_addralign and
183 : sh_flags won't have a SHF_COMPRESSED hint in the GNU format.
184 : Just adjust the sh_size. */
185 260 : if (elfclass == ELFCLASS32)
186 : {
187 98 : Elf32_Shdr *shdr = elf32_getshdr (scn);
188 98 : shdr->sh_size = size;
189 : }
190 : else
191 : {
192 162 : Elf64_Shdr *shdr = elf64_getshdr (scn);
193 162 : shdr->sh_size = size;
194 : }
195 :
196 260 : __libelf_reset_rawdata (scn, buf_out, size, sh_addralign,
197 : __libelf_data_type (elf, sh_type));
198 :
199 260 : scn->zdata_base = buf_out;
200 :
201 260 : return 1;
202 : }
203 : else
204 : {
205 0 : __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
206 0 : return -1;
207 : }
208 : }
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