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
38 476 : elf_compress_gnu (Elf_Scn *scn, int inflate, unsigned int flags)
39 : {
40 476 : if (scn == NULL)
41 : return -1;
42 :
43 476 : if ((flags & ~ELF_CHF_FORCE) != 0)
44 : {
45 0 : __libelf_seterrno (ELF_E_INVALID_OPERAND);
46 0 : return -1;
47 : }
48 :
49 476 : bool force = (flags & ELF_CHF_FORCE) != 0;
50 :
51 476 : Elf *elf = scn->elf;
52 : GElf_Ehdr ehdr;
53 476 : if (gelf_getehdr (elf, &ehdr) == NULL)
54 : return -1;
55 :
56 476 : int elfclass = elf->class;
57 476 : int elfdata = ehdr.e_ident[EI_DATA];
58 :
59 : Elf64_Xword sh_flags;
60 : Elf64_Word sh_type;
61 : Elf64_Xword sh_addralign;
62 476 : 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 : {
74 293 : Elf64_Shdr *shdr = elf64_getshdr (scn);
75 293 : if (shdr == NULL)
76 : return -1;
77 :
78 293 : sh_flags = shdr->sh_flags;
79 293 : sh_type = shdr->sh_type;
80 293 : sh_addralign = shdr->sh_addralign;
81 : }
82 :
83 : /* Allocated sections, or sections that are already are compressed
84 : cannot (also) be GNU compressed. */
85 476 : if ((sh_flags & SHF_ALLOC) != 0 || (sh_flags & SHF_COMPRESSED))
86 : {
87 0 : __libelf_seterrno (ELF_E_INVALID_SECTION_FLAGS);
88 0 : return -1;
89 : }
90 :
91 476 : if (sh_type == SHT_NULL || sh_type == SHT_NOBITS)
92 : {
93 0 : __libelf_seterrno (ELF_E_INVALID_SECTION_TYPE);
94 0 : return -1;
95 : }
96 :
97 : /* For GNU compression we cannot really know whether the section is
98 : already compressed or not. Just try and see what happens... */
99 : // int compressed = (sh_flags & SHF_COMPRESSED);
100 476 : if (inflate == 1)
101 : {
102 180 : size_t hsize = 4 + 8; /* GNU "ZLIB" + 8 byte size. */
103 : size_t orig_size, new_size, orig_addralign;
104 180 : void *out_buf = __libelf_compress (scn, hsize, elfdata,
105 : &orig_size, &orig_addralign,
106 : &new_size, force);
107 :
108 : /* Compression would make section larger, don't change anything. */
109 180 : if (out_buf == (void *) -1)
110 : return 0;
111 :
112 : /* Compression failed, return error. */
113 151 : if (out_buf == NULL)
114 : return -1;
115 :
116 302 : uint64_t be64_size = htobe64 (orig_size);
117 151 : memmove (out_buf, "ZLIB", 4);
118 302 : memmove (out_buf + 4, &be64_size, sizeof (be64_size));
119 :
120 : /* We don't know anything about sh_entsize, sh_addralign and
121 : sh_flags won't have a SHF_COMPRESSED hint in the GNU format.
122 : Just adjust the sh_size. */
123 151 : if (elfclass == ELFCLASS32)
124 : {
125 73 : Elf32_Shdr *shdr = elf32_getshdr (scn);
126 73 : shdr->sh_size = new_size;
127 : }
128 : else
129 : {
130 78 : Elf64_Shdr *shdr = elf64_getshdr (scn);
131 78 : shdr->sh_size = new_size;
132 : }
133 :
134 151 : __libelf_reset_rawdata (scn, out_buf, new_size, 1, ELF_T_BYTE);
135 :
136 : /* The section is now compressed, we could keep the uncompressed
137 : data around, but since that might have been multiple Elf_Data
138 : buffers let the user uncompress it explicitly again if they
139 : want it to simplify bookkeeping. */
140 151 : scn->zdata_base = NULL;
141 :
142 151 : return 1;
143 : }
144 296 : else if (inflate == 0)
145 : {
146 : /* In theory the user could have constucted a compressed section
147 : by hand. And in practice they do. For example when copying
148 : a section from one file to another using elf_newdata. So we
149 : have to use elf_getdata (not elf_rawdata). */
150 296 : Elf_Data *data = elf_getdata (scn, NULL);
151 296 : if (data == NULL)
152 : return -1;
153 :
154 296 : size_t hsize = 4 + 8; /* GNU "ZLIB" + 8 byte size. */
155 296 : if (data->d_size < hsize || memcmp (data->d_buf, "ZLIB", 4) != 0)
156 : {
157 12 : __libelf_seterrno (ELF_E_NOT_COMPRESSED);
158 12 : return -1;
159 : }
160 :
161 : /* There is a 12-byte header of "ZLIB" followed by
162 : an 8-byte big-endian size. There is only one type and
163 : Alignment isn't preserved separately. */
164 : uint64_t gsize;
165 284 : memcpy (&gsize, data->d_buf + 4, sizeof gsize);
166 568 : gsize = be64toh (gsize);
167 :
168 : /* One more sanity check, size should be bigger than original
169 : data size plus some overhead (4 chars ZLIB + 8 bytes size + 6
170 : bytes zlib stream overhead + 5 bytes overhead max for one 16K
171 : block) and should fit into a size_t. */
172 284 : if (gsize + 4 + 8 + 6 + 5 < data->d_size || gsize > SIZE_MAX)
173 : {
174 0 : __libelf_seterrno (ELF_E_NOT_COMPRESSED);
175 0 : return -1;
176 : }
177 :
178 284 : size_t size = gsize;
179 284 : size_t size_in = data->d_size - hsize;
180 284 : void *buf_in = data->d_buf + hsize;
181 284 : void *buf_out = __libelf_decompress (buf_in, size_in, size);
182 284 : if (buf_out == NULL)
183 : return -1;
184 :
185 : /* We don't know anything about sh_entsize, sh_addralign and
186 : sh_flags won't have a SHF_COMPRESSED hint in the GNU format.
187 : Just adjust the sh_size. */
188 284 : if (elfclass == ELFCLASS32)
189 : {
190 98 : Elf32_Shdr *shdr = elf32_getshdr (scn);
191 98 : shdr->sh_size = size;
192 : }
193 : else
194 : {
195 186 : Elf64_Shdr *shdr = elf64_getshdr (scn);
196 186 : shdr->sh_size = size;
197 : }
198 :
199 284 : __libelf_reset_rawdata (scn, buf_out, size, sh_addralign,
200 : __libelf_data_type (elf, sh_type, sh_addralign));
201 :
202 284 : scn->zdata_base = buf_out;
203 :
204 284 : return 1;
205 : }
206 : else
207 : {
208 0 : __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
209 0 : return -1;
210 : }
211 : }
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