Line data Source code
1 : /* Update data structures for changes and write them out.
2 : Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006, 2015 Red Hat, Inc.
3 : This file is part of elfutils.
4 : Contributed by Ulrich Drepper <drepper@redhat.com>, 1999.
5 :
6 : This file is free software; you can redistribute it and/or modify
7 : it under the terms of either
8 :
9 : * the GNU Lesser General Public License as published by the Free
10 : Software Foundation; either version 3 of the License, or (at
11 : your option) any later version
12 :
13 : or
14 :
15 : * the GNU General Public License as published by the Free
16 : Software Foundation; either version 2 of the License, or (at
17 : your option) any later version
18 :
19 : or both in parallel, as here.
20 :
21 : elfutils is distributed in the hope that it will be useful, but
22 : WITHOUT ANY WARRANTY; without even the implied warranty of
23 : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
24 : General Public License for more details.
25 :
26 : You should have received copies of the GNU General Public License and
27 : the GNU Lesser General Public License along with this program. If
28 : not, see <http://www.gnu.org/licenses/>. */
29 :
30 : #ifdef HAVE_CONFIG_H
31 : # include <config.h>
32 : #endif
33 :
34 : #include <libelf.h>
35 : #include <fcntl.h>
36 : #include <unistd.h>
37 : #include <sys/mman.h>
38 : #include <sys/stat.h>
39 :
40 : #include "libelfP.h"
41 :
42 :
43 : static off_t
44 308 : write_file (Elf *elf, off_t size, int change_bo, size_t shnum)
45 : {
46 308 : int class = elf->class;
47 :
48 : /* Check the mode bits now, before modification might change them. */
49 : struct stat st;
50 616 : if (unlikely (fstat (elf->fildes, &st) != 0))
51 : {
52 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
53 0 : return -1;
54 : }
55 :
56 : /* Adjust the size in any case. We do this even if we use `write'.
57 : We cannot do this if this file is in an archive. We also don't
58 : do it *now* if we are shortening the file since this would
59 : prevent programs to use the data of the file in generating the
60 : new file. We truncate the file later in this case. */
61 308 : if (elf->parent == NULL
62 308 : && (elf->maximum_size == ~((size_t) 0)
63 308 : || (size_t) size > elf->maximum_size)
64 292 : && unlikely (ftruncate (elf->fildes, size) != 0))
65 : {
66 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
67 0 : return -1;
68 : }
69 :
70 : /* Try to map the file if this isn't done yet. */
71 308 : if (elf->map_address == NULL && elf->cmd == ELF_C_WRITE_MMAP)
72 : {
73 85 : elf->map_address = mmap (NULL, size, PROT_READ | PROT_WRITE,
74 : MAP_SHARED, elf->fildes, 0);
75 85 : if (unlikely (elf->map_address == MAP_FAILED))
76 0 : elf->map_address = NULL;
77 : else
78 85 : elf->flags |= ELF_F_MMAPPED;
79 : }
80 :
81 308 : if (elf->map_address != NULL)
82 : {
83 : /* When using mmap we want to make sure the file content is
84 : really there. Only using ftruncate might mean the file is
85 : extended, but space isn't allocated yet. This might cause a
86 : SIGBUS once we write into the mmapped space and the disk is
87 : full. In glibc posix_fallocate is required to extend the
88 : file and allocate enough space even if the underlying
89 : filesystem would normally return EOPNOTSUPP. But other
90 : implementations might not work as expected. And the glibc
91 : fallback case might fail (with unexpected errnos) in some cases.
92 : So we only report an error when the call fails and errno is
93 : ENOSPC. Otherwise we ignore the error and treat it as just hint. */
94 93 : if (elf->parent == NULL
95 93 : && (elf->maximum_size == ~((size_t) 0)
96 93 : || (size_t) size > elf->maximum_size)
97 91 : && unlikely (posix_fallocate (elf->fildes, 0, size) != 0))
98 0 : if (errno == ENOSPC)
99 : {
100 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
101 0 : return -1;
102 : }
103 :
104 : /* The file is mmaped. */
105 93 : if ((class == ELFCLASS32
106 38 : ? __elf32_updatemmap (elf, change_bo, shnum)
107 131 : : __elf64_updatemmap (elf, change_bo, shnum)) != 0)
108 : /* Some problem while writing. */
109 0 : size = -1;
110 : }
111 : else
112 : {
113 : /* The file is not mmaped. */
114 215 : if ((class == ELFCLASS32
115 96 : ? __elf32_updatefile (elf, change_bo, shnum)
116 311 : : __elf64_updatefile (elf, change_bo, shnum)) != 0)
117 : /* Some problem while writing. */
118 0 : size = -1;
119 : }
120 :
121 : /* Reduce the file size if necessary. */
122 308 : if (size != -1
123 308 : && elf->parent == NULL
124 308 : && elf->maximum_size != ~((size_t) 0)
125 308 : && (size_t) size < elf->maximum_size
126 12 : && unlikely (ftruncate (elf->fildes, size) != 0))
127 : {
128 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
129 0 : size = -1;
130 : }
131 :
132 : /* POSIX says that ftruncate and write may clear the S_ISUID and S_ISGID
133 : mode bits. So make sure we restore them afterwards if they were set.
134 : This is not atomic if someone else chmod's the file while we operate. */
135 308 : if (size != -1
136 308 : && unlikely (st.st_mode & (S_ISUID | S_ISGID))
137 : /* fchmod ignores the bits we cannot change. */
138 0 : && unlikely (fchmod (elf->fildes, st.st_mode) != 0))
139 : {
140 0 : __libelf_seterrno (ELF_E_WRITE_ERROR);
141 0 : size = -1;
142 : }
143 :
144 308 : if (size != -1 && elf->parent == NULL)
145 308 : elf->maximum_size = size;
146 :
147 : return size;
148 : }
149 :
150 :
151 : off_t
152 364 : elf_update (Elf *elf, Elf_Cmd cmd)
153 : {
154 : size_t shnum;
155 : off_t size;
156 364 : int change_bo = 0;
157 :
158 728 : if (cmd != ELF_C_NULL
159 364 : && cmd != ELF_C_WRITE
160 9 : && unlikely (cmd != ELF_C_WRITE_MMAP))
161 : {
162 0 : __libelf_seterrno (ELF_E_INVALID_CMD);
163 0 : return -1;
164 : }
165 :
166 364 : if (elf == NULL)
167 : return -1;
168 :
169 364 : if (elf->kind != ELF_K_ELF)
170 : {
171 0 : __libelf_seterrno (ELF_E_INVALID_HANDLE);
172 0 : return -1;
173 : }
174 :
175 : rwlock_wrlock (elf->lock);
176 :
177 : /* Make sure we have an ELF header. */
178 364 : if (elf->state.elf.ehdr == NULL)
179 : {
180 0 : __libelf_seterrno (ELF_E_WRONG_ORDER_EHDR);
181 0 : size = -1;
182 0 : goto out;
183 : }
184 :
185 : /* Determine the number of sections. */
186 728 : shnum = (elf->state.elf.scns_last->cnt == 0
187 : ? 0
188 364 : : 1 + elf->state.elf.scns_last->data[elf->state.elf.scns_last->cnt - 1].index);
189 :
190 : /* Update the ELF descriptor. First, place the program header. It
191 : will come right after the ELF header. The count the size of all
192 : sections and finally place the section table. */
193 728 : size = (elf->class == ELFCLASS32
194 : ? __elf32_updatenull_wrlock (elf, &change_bo, shnum)
195 364 : : __elf64_updatenull_wrlock (elf, &change_bo, shnum));
196 364 : if (likely (size != -1)
197 : /* See whether we actually have to write out the data. */
198 364 : && (cmd == ELF_C_WRITE || cmd == ELF_C_WRITE_MMAP))
199 : {
200 616 : if (elf->cmd != ELF_C_RDWR
201 308 : && elf->cmd != ELF_C_RDWR_MMAP
202 278 : && elf->cmd != ELF_C_WRITE
203 85 : && unlikely (elf->cmd != ELF_C_WRITE_MMAP))
204 : {
205 0 : __libelf_seterrno (ELF_E_UPDATE_RO);
206 0 : size = -1;
207 : }
208 308 : else if (unlikely (elf->fildes == -1))
209 : {
210 : /* We closed the file already. */
211 0 : __libelf_seterrno (ELF_E_FD_DISABLED);
212 0 : size = -1;
213 : }
214 : else
215 308 : size = write_file (elf, size, change_bo, shnum);
216 : }
217 :
218 : out:
219 : rwlock_unlock (elf->lock);
220 :
221 : return size;
222 : }
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