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>
9 #include <unistd.h>
10 #include <errno.h>
11 #include <fcntl.h>
12 #include <string.h>
13 #include <sys/stat.h>
14 #include <sys/mman.h>
15 #include <sys/param.h>
16 #include <init.h>
17 #include <os.h>
18
19 /* Modified by which_tmpdir, which is called during early boot */
20 static char *default_tmpdir = "/tmp";
21
22 /*
23 * Modified when creating the physical memory file and when checking
24 * the tmp filesystem for usability, both happening during early boot.
25 */
26 static char *tempdir = NULL;
27
find_tempdir(void)28 static void __init find_tempdir(void)
29 {
30 const char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
31 int i;
32 char *dir = NULL;
33
34 if (tempdir != NULL)
35 /* We've already been called */
36 return;
37 for (i = 0; dirs[i]; i++) {
38 dir = getenv(dirs[i]);
39 if ((dir != NULL) && (*dir != '\0'))
40 break;
41 }
42 if ((dir == NULL) || (*dir == '\0'))
43 dir = default_tmpdir;
44
45 tempdir = malloc(strlen(dir) + 2);
46 if (tempdir == NULL) {
47 fprintf(stderr, "Failed to malloc tempdir, "
48 "errno = %d\n", errno);
49 return;
50 }
51 strcpy(tempdir, dir);
52 strcat(tempdir, "/");
53 }
54
55 /*
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 */
next(int fd,char * buf,size_t size,char c)61 static int next(int fd, char *buf, size_t size, char c)
62 {
63 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
77 ptr++;
78 len = strlen(ptr);
79 memmove(buf, ptr, len + 1);
80
81 /*
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.
84 */
85 n = read(fd, &buf[len], size - len - 1);
86 if (n < 0)
87 return -errno;
88
89 buf[len + n] = '\0';
90 return 1;
91 }
92
93 /* which_tmpdir is called only during early boot */
94 static 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 */
which_tmpdir(void)107 static void which_tmpdir(void)
108 {
109 int fd, found;
110 char buf[128] = { '\0' };
111
112 if (checked_tmpdir)
113 return;
114
115 checked_tmpdir = 1;
116
117 printf("Checking for tmpfs mount on /dev/shm...");
118
119 fd = open("/proc/mounts", O_RDONLY);
120 if (fd < 0) {
121 printf("failed to open /proc/mounts, errno = %d\n", errno);
122 return;
123 }
124
125 while (1) {
126 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
127 if (found != 1)
128 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
138 err:
139 if (found == 0)
140 printf("nothing mounted on /dev/shm\n");
141 else if (found < 0)
142 printf("read returned errno %d\n", -found);
143
144 out:
145 close(fd);
146
147 return;
148
149 found:
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;
157 }
158
159 printf("OK\n");
160 default_tmpdir = "/dev/shm";
161 goto out;
162 }
163
make_tempfile(const char * template,char ** out_tempname,int do_unlink)164 static int __init make_tempfile(const char *template, char **out_tempname,
165 int do_unlink)
166 {
167 char *tempname;
168 int fd;
169
170 which_tmpdir();
171 tempname = malloc(MAXPATHLEN);
172 if (tempname == NULL)
173 return -1;
174
175 find_tempdir();
176 if ((tempdir == NULL) || (strlen(tempdir) >= MAXPATHLEN))
177 goto out;
178
179 if (template[0] != '/')
180 strcpy(tempname, tempdir);
181 else
182 tempname[0] = '\0';
183 strncat(tempname, template, MAXPATHLEN-1-strlen(tempname));
184 fd = mkstemp(tempname);
185 if (fd < 0) {
186 fprintf(stderr, "open - cannot create %s: %s\n", tempname,
187 strerror(errno));
188 goto out;
189 }
190 if (do_unlink && (unlink(tempname) < 0)) {
191 perror("unlink");
192 goto close;
193 }
194 if (out_tempname) {
195 *out_tempname = tempname;
196 } else
197 free(tempname);
198 return fd;
199 close:
200 close(fd);
201 out:
202 free(tempname);
203 return -1;
204 }
205
206 #define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
207
create_tmp_file(unsigned long long len)208 static int __init create_tmp_file(unsigned long long len)
209 {
210 int fd, err;
211 char zero;
212
213 fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
214 if (fd < 0)
215 exit(1);
216
217 err = fchmod(fd, 0777);
218 if (err < 0) {
219 perror("fchmod");
220 exit(1);
221 }
222
223 /*
224 * Seek to len - 1 because writing a character there will
225 * increase the file size by one byte, to the desired length.
226 */
227 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
228 perror("lseek64");
229 exit(1);
230 }
231
232 zero = 0;
233
234 err = write(fd, &zero, 1);
235 if (err != 1) {
236 perror("write");
237 exit(1);
238 }
239
240 return fd;
241 }
242
create_mem_file(unsigned long long len)243 int __init create_mem_file(unsigned long long len)
244 {
245 int err, fd;
246
247 fd = create_tmp_file(len);
248
249 err = os_set_exec_close(fd);
250 if (err < 0) {
251 errno = -err;
252 perror("exec_close");
253 }
254 return fd;
255 }
256
257
check_tmpexec(void)258 void __init check_tmpexec(void)
259 {
260 void *addr;
261 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
262
263 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
264 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
265 printf("Checking PROT_EXEC mmap in %s...",tempdir);
266 fflush(stdout);
267 if (addr == MAP_FAILED) {
268 err = errno;
269 perror("failed");
270 close(fd);
271 if (err == EPERM)
272 printf("%s must be not mounted noexec\n",tempdir);
273 exit(1);
274 }
275 printf("OK\n");
276 munmap(addr, UM_KERN_PAGE_SIZE);
277
278 close(fd);
279 }
280