mem.c (cf9ce948f47640797bd19980e1d99c6d17d0bdc3) mem.c (7473534130c3156d199512c99ff1b796233e8547)
1/*
2 * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6#include <stdio.h>
7#include <stddef.h>
8#include <stdlib.h>

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48 "errno = %d\n", errno);
49 return;
50 }
51 strcpy(tempdir, dir);
52 strcat(tempdir, "/");
53}
54
55/*
1/*
2 * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6#include <stdio.h>
7#include <stddef.h>
8#include <stdlib.h>

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48 "errno = %d\n", errno);
49 return;
50 }
51 strcpy(tempdir, dir);
52 strcat(tempdir, "/");
53}
54
55/*
56 * Remove bytes from the front of the buffer and refill it so that if there's a
57 * partial string that we care about, it will be completed, and we can recognize
58 * it.
59 */
60static int pop(int fd, char *buf, size_t size, size_t npop)
61{
62 ssize_t n;
63 size_t len = strlen(&buf[npop]);
64
65 memmove(buf, &buf[npop], len + 1);
66 n = read(fd, &buf[len], size - len - 1);
67 if (n < 0)
68 return -errno;
69
70 buf[len + n] = '\0';
71 return 1;
72}
73
74/*
56 * This will return 1, with the first character in buf being the
57 * character following the next instance of c in the file. This will
58 * read the file as needed. If there's an error, -errno is returned;
59 * if the end of the file is reached, 0 is returned.
60 */
61static int next(int fd, char *buf, size_t size, char c)
62{
63 ssize_t n;
75 * This will return 1, with the first character in buf being the
76 * character following the next instance of c in the file. This will
77 * read the file as needed. If there's an error, -errno is returned;
78 * if the end of the file is reached, 0 is returned.
79 */
80static int next(int fd, char *buf, size_t size, char c)
81{
82 ssize_t n;
64 size_t len;
65 char *ptr;
66
67 while ((ptr = strchr(buf, c)) == NULL) {
68 n = read(fd, buf, size - 1);
69 if (n == 0)
70 return 0;
71 else if (n < 0)
72 return -errno;
73
74 buf[n] = '\0';
75 }
76
83 char *ptr;
84
85 while ((ptr = strchr(buf, c)) == NULL) {
86 n = read(fd, buf, size - 1);
87 if (n == 0)
88 return 0;
89 else if (n < 0)
90 return -errno;
91
92 buf[n] = '\0';
93 }
94
77 ptr++;
78 len = strlen(ptr);
79 memmove(buf, ptr, len + 1);
95 return pop(fd, buf, size, ptr - buf + 1);
96}
80
97
98/*
99 * Decode an octal-escaped and space-terminated path of the form used by
100 * /proc/mounts. May be used to decode a path in-place. "out" must be at least
101 * as large as the input. The output is always null-terminated. "len" gets the
102 * length of the output, excluding the trailing null. Returns 0 if a full path
103 * was successfully decoded, otherwise an error.
104 */
105static int decode_path(const char *in, char *out, size_t *len)
106{
107 char *first = out;
108 int c;
109 int i;
110 int ret = -EINVAL;
111 while (1) {
112 switch (*in) {
113 case '\0':
114 goto out;
115
116 case ' ':
117 ret = 0;
118 goto out;
119
120 case '\\':
121 in++;
122 c = 0;
123 for (i = 0; i < 3; i++) {
124 if (*in < '0' || *in > '7')
125 goto out;
126 c = (c << 3) | (*in++ - '0');
127 }
128 *(unsigned char *)out++ = (unsigned char) c;
129 break;
130
131 default:
132 *out++ = *in++;
133 break;
134 }
135 }
136
137out:
138 *out = '\0';
139 *len = out - first;
140 return ret;
141}
142
143/*
144 * Computes the length of s when encoded with three-digit octal escape sequences
145 * for the characters in chars.
146 */
147static size_t octal_encoded_length(const char *s, const char *chars)
148{
149 size_t len = strlen(s);
150 while ((s = strpbrk(s, chars)) != NULL) {
151 len += 3;
152 s++;
153 }
154
155 return len;
156}
157
158enum {
159 OUTCOME_NOTHING_MOUNTED,
160 OUTCOME_TMPFS_MOUNT,
161 OUTCOME_NON_TMPFS_MOUNT,
162};
163
164/* Read a line of /proc/mounts data looking for a tmpfs mount at "path". */
165static int read_mount(int fd, char *buf, size_t bufsize, const char *path,
166 int *outcome)
167{
168 int found;
169 int match;
170 char *space;
171 size_t len;
172
173 enum {
174 MATCH_NONE,
175 MATCH_EXACT,
176 MATCH_PARENT,
177 };
178
179 found = next(fd, buf, bufsize, ' ');
180 if (found != 1)
181 return found;
182
81 /*
183 /*
82 * Refill the buffer so that if there's a partial string that we care
83 * about, it will be completed, and we can recognize it.
184 * If there's no following space in the buffer, then this path is
185 * truncated, so it can't be the one we're looking for.
84 */
186 */
85 n = read(fd, &buf[len], size - len - 1);
86 if (n < 0)
87 return -errno;
187 space = strchr(buf, ' ');
188 if (space) {
189 match = MATCH_NONE;
190 if (!decode_path(buf, buf, &len)) {
191 if (!strcmp(buf, path))
192 match = MATCH_EXACT;
193 else if (!strncmp(buf, path, len)
194 && (path[len] == '/' || !strcmp(buf, "/")))
195 match = MATCH_PARENT;
196 }
88
197
89 buf[len + n] = '\0';
90 return 1;
198 found = pop(fd, buf, bufsize, space - buf + 1);
199 if (found != 1)
200 return found;
201
202 switch (match) {
203 case MATCH_EXACT:
204 if (!strncmp(buf, "tmpfs", strlen("tmpfs")))
205 *outcome = OUTCOME_TMPFS_MOUNT;
206 else
207 *outcome = OUTCOME_NON_TMPFS_MOUNT;
208 break;
209
210 case MATCH_PARENT:
211 /* This mount obscures any previous ones. */
212 *outcome = OUTCOME_NOTHING_MOUNTED;
213 break;
214 }
215 }
216
217 return next(fd, buf, bufsize, '\n');
91}
92
93/* which_tmpdir is called only during early boot */
94static int checked_tmpdir = 0;
95
96/*
97 * Look for a tmpfs mounted at /dev/shm. I couldn't find a cleaner
98 * way to do this than to parse /proc/mounts. statfs will return the
99 * same filesystem magic number and fs id for both /dev and /dev/shm
100 * when they are both tmpfs, so you can't tell if they are different
101 * filesystems. Also, there seems to be no other way of finding the
102 * mount point of a filesystem from within it.
103 *
104 * If a /dev/shm tmpfs entry is found, then we switch to using it.
105 * Otherwise, we stay with the default /tmp.
106 */
107static void which_tmpdir(void)
108{
218}
219
220/* which_tmpdir is called only during early boot */
221static int checked_tmpdir = 0;
222
223/*
224 * Look for a tmpfs mounted at /dev/shm. I couldn't find a cleaner
225 * way to do this than to parse /proc/mounts. statfs will return the
226 * same filesystem magic number and fs id for both /dev and /dev/shm
227 * when they are both tmpfs, so you can't tell if they are different
228 * filesystems. Also, there seems to be no other way of finding the
229 * mount point of a filesystem from within it.
230 *
231 * If a /dev/shm tmpfs entry is found, then we switch to using it.
232 * Otherwise, we stay with the default /tmp.
233 */
234static void which_tmpdir(void)
235{
109 int fd, found;
110 char buf[128] = { '\0' };
236 int fd;
237 int found;
238 int outcome;
239 char *path;
240 char *buf;
241 size_t bufsize;
111
112 if (checked_tmpdir)
113 return;
114
115 checked_tmpdir = 1;
116
117 printf("Checking for tmpfs mount on /dev/shm...");
118
242
243 if (checked_tmpdir)
244 return;
245
246 checked_tmpdir = 1;
247
248 printf("Checking for tmpfs mount on /dev/shm...");
249
250 path = realpath("/dev/shm", NULL);
251 if (!path) {
252 printf("failed to check real path, errno = %d\n", errno);
253 return;
254 }
255 printf("%s...", path);
256
257 /*
258 * The buffer needs to be able to fit the full octal-escaped path, a
259 * space, and a trailing null in order to successfully decode it.
260 */
261 bufsize = octal_encoded_length(path, " \t\n\\") + 2;
262
263 if (bufsize < 128)
264 bufsize = 128;
265
266 buf = malloc(bufsize);
267 if (!buf) {
268 printf("malloc failed, errno = %d\n", errno);
269 goto out;
270 }
271 buf[0] = '\0';
272
119 fd = open("/proc/mounts", O_RDONLY);
120 if (fd < 0) {
121 printf("failed to open /proc/mounts, errno = %d\n", errno);
273 fd = open("/proc/mounts", O_RDONLY);
274 if (fd < 0) {
275 printf("failed to open /proc/mounts, errno = %d\n", errno);
122 return;
276 goto out1;
123 }
124
277 }
278
279 outcome = OUTCOME_NOTHING_MOUNTED;
125 while (1) {
280 while (1) {
126 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
281 found = read_mount(fd, buf, bufsize, path, &outcome);
127 if (found != 1)
128 break;
282 if (found != 1)
283 break;
129
130 if (!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
131 goto found;
132
133 found = next(fd, buf, ARRAY_SIZE(buf), '\n');
134 if (found != 1)
135 break;
136 }
137
284 }
285
138err:
139 if (found == 0)
140 printf("nothing mounted on /dev/shm\n");
141 else if (found < 0)
286 if (found < 0) {
142 printf("read returned errno %d\n", -found);
287 printf("read returned errno %d\n", -found);
288 } else {
289 switch (outcome) {
290 case OUTCOME_TMPFS_MOUNT:
291 printf("OK\n");
292 default_tmpdir = "/dev/shm";
293 break;
143
294
144out:
145 close(fd);
295 case OUTCOME_NON_TMPFS_MOUNT:
296 printf("not tmpfs\n");
297 break;
146
298
147 return;
148
149found:
150 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
151 if (found != 1)
152 goto err;
153
154 if (strncmp(buf, "tmpfs", strlen("tmpfs"))) {
155 printf("not tmpfs\n");
156 goto out;
299 default:
300 printf("nothing mounted on /dev/shm\n");
301 break;
302 }
157 }
158
303 }
304
159 printf("OK\n");
160 default_tmpdir = "/dev/shm";
161 goto out;
305 close(fd);
306out1:
307 free(buf);
308out:
309 free(path);
162}
163
164static int __init make_tempfile(const char *template, char **out_tempname,
165 int do_unlink)
166{
167 char *tempname;
168 int fd;
169

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311
312static int __init make_tempfile(const char *template, char **out_tempname,
313 int do_unlink)
314{
315 char *tempname;
316 int fd;
317

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