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path: root/libavb_user/avb_ops_user.c (plain)
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1/*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Permission is hereby granted, free of charge, to any person
5 * obtaining a copy of this software and associated documentation
6 * files (the "Software"), to deal in the Software without
7 * restriction, including without limitation the rights to use, copy,
8 * modify, merge, publish, distribute, sublicense, and/or sell copies
9 * of the Software, and to permit persons to whom the Software is
10 * furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25#include "avb_ops_user.h"
26
27#include <errno.h>
28#include <fcntl.h>
29#include <linux/fs.h>
30#include <stdlib.h>
31#include <string.h>
32#include <sys/ioctl.h>
33#include <sys/stat.h>
34#include <sys/types.h>
35#include <unistd.h>
36
37#include <cutils/properties.h>
38#include <fs_mgr.h>
39
40#include <libavb_ab/libavb_ab.h>
41
42/* Open the appropriate fstab file and fallback to /fstab.device if
43 * that's what's being used.
44 */
45static struct fstab* open_fstab(void) {
46 struct fstab* fstab = fs_mgr_read_fstab_default();
47
48 if (fstab != NULL) {
49 return fstab;
50 }
51
52 fstab = fs_mgr_read_fstab("/fstab.device");
53 return fstab;
54}
55
56static int open_partition(const char* name, int flags) {
57 char* path;
58 int fd;
59 struct fstab* fstab;
60 struct fstab_rec* record;
61
62 /* We can't use fs_mgr to look up |name| because fstab doesn't list
63 * every slot partition (it uses the slotselect option to mask the
64 * suffix) and |slot| is expected to be of that form, e.g. boot_a.
65 *
66 * We can however assume that there's an entry for the /misc mount
67 * point and use that to get the device file for the misc
68 * partition. From there we'll assume that a by-name scheme is used
69 * so we can just replace the trailing "misc" by the given |name|,
70 * e.g.
71 *
72 * /dev/block/platform/soc.0/7824900.sdhci/by-name/misc ->
73 * /dev/block/platform/soc.0/7824900.sdhci/by-name/boot_a
74 *
75 * If needed, it's possible to relax this assumption in the future
76 * by trawling /sys/block looking for the appropriate sibling of
77 * misc and then finding an entry in /dev matching the sysfs entry.
78 */
79
80 fstab = open_fstab();
81 if (fstab == NULL) {
82 return -1;
83 }
84 record = fs_mgr_get_entry_for_mount_point(fstab, "/misc");
85 if (record == NULL) {
86 fs_mgr_free_fstab(fstab);
87 return -1;
88 }
89 if (strcmp(name, "misc") == 0) {
90 path = strdup(record->blk_device);
91 } else {
92 size_t trimmed_len, name_len;
93 const char* end_slash = strrchr(record->blk_device, '/');
94 if (end_slash == NULL) {
95 fs_mgr_free_fstab(fstab);
96 return -1;
97 }
98 trimmed_len = end_slash - record->blk_device + 1;
99 name_len = strlen(name);
100 path = calloc(trimmed_len + name_len + 1, 1);
101 strncpy(path, record->blk_device, trimmed_len);
102 strncpy(path + trimmed_len, name, name_len);
103 }
104 fs_mgr_free_fstab(fstab);
105
106 fd = open(path, flags);
107 free(path);
108
109 return fd;
110}
111
112static AvbIOResult read_from_partition(AvbOps* ops,
113 const char* partition,
114 int64_t offset,
115 size_t num_bytes,
116 void* buffer,
117 size_t* out_num_read) {
118 int fd;
119 off_t where;
120 ssize_t num_read;
121 AvbIOResult ret;
122
123 fd = open_partition(partition, O_RDONLY);
124 if (fd == -1) {
125 ret = AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION;
126 goto out;
127 }
128
129 if (offset < 0) {
130 uint64_t partition_size;
131 if (ioctl(fd, BLKGETSIZE64, &partition_size) != 0) {
132 avb_errorv(
133 "Error getting size of \"", partition, "\" partition.\n", NULL);
134 ret = AVB_IO_RESULT_ERROR_IO;
135 goto out;
136 }
137 offset = partition_size - (-offset);
138 }
139
140 where = lseek(fd, offset, SEEK_SET);
141 if (where == -1) {
142 avb_error("Error seeking to offset.\n");
143 ret = AVB_IO_RESULT_ERROR_IO;
144 goto out;
145 }
146 if (where != offset) {
147 avb_error("Error seeking to offset.\n");
148 ret = AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION;
149 goto out;
150 }
151
152 /* On Linux, we never get partial reads from block devices (except
153 * for EOF).
154 */
155 num_read = read(fd, buffer, num_bytes);
156 if (num_read == -1) {
157 avb_error("Error reading data.\n");
158 ret = AVB_IO_RESULT_ERROR_IO;
159 goto out;
160 }
161 if (out_num_read != NULL) {
162 *out_num_read = num_read;
163 }
164
165 ret = AVB_IO_RESULT_OK;
166
167out:
168 if (fd != -1) {
169 if (close(fd) != 0) {
170 avb_error("Error closing file descriptor.\n");
171 }
172 }
173 return ret;
174}
175
176static AvbIOResult write_to_partition(AvbOps* ops,
177 const char* partition,
178 int64_t offset,
179 size_t num_bytes,
180 const void* buffer) {
181 int fd;
182 off_t where;
183 ssize_t num_written;
184 AvbIOResult ret;
185
186 fd = open_partition(partition, O_WRONLY);
187 if (fd == -1) {
188 avb_errorv("Error opening \"", partition, "\" partition.\n", NULL);
189 ret = AVB_IO_RESULT_ERROR_IO;
190 goto out;
191 }
192
193 where = lseek(fd, offset, SEEK_SET);
194 if (where == -1) {
195 avb_error("Error seeking to offset.\n");
196 ret = AVB_IO_RESULT_ERROR_IO;
197 goto out;
198 }
199 if (where != offset) {
200 avb_error("Error seeking to offset.\n");
201 ret = AVB_IO_RESULT_ERROR_RANGE_OUTSIDE_PARTITION;
202 goto out;
203 }
204
205 /* On Linux, we never get partial writes on block devices. */
206 num_written = write(fd, buffer, num_bytes);
207 if (num_written == -1) {
208 avb_error("Error writing data.\n");
209 ret = AVB_IO_RESULT_ERROR_IO;
210 goto out;
211 }
212
213 ret = AVB_IO_RESULT_OK;
214
215out:
216 if (fd != -1) {
217 if (close(fd) != 0) {
218 avb_error("Error closing file descriptor.\n");
219 }
220 }
221 return ret;
222}
223
224AvbOps* avb_ops_user_new(void) {
225 AvbOps* ops;
226
227 ops = calloc(1, sizeof(AvbOps));
228 if (ops == NULL) {
229 avb_error("Error allocating memory for AvbOps.\n");
230 goto out;
231 }
232
233 ops->ab_ops = calloc(1, sizeof(AvbABOps));
234 if (ops->ab_ops == NULL) {
235 avb_error("Error allocating memory for AvbABOps.\n");
236 free(ops);
237 goto out;
238 }
239 ops->ab_ops->ops = ops;
240
241 ops->read_from_partition = read_from_partition;
242 ops->write_to_partition = write_to_partition;
243 ops->ab_ops->read_ab_metadata = avb_ab_data_read;
244 ops->ab_ops->write_ab_metadata = avb_ab_data_write;
245
246out:
247 return ops;
248}
249
250void avb_ops_user_free(AvbOps* ops) {
251 free(ops->ab_ops);
252 free(ops);
253}
254
generated by cgit at 2024-05-18 14:16:21 (GMT)