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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 */
20static 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 */
26static char *tempdir = NULL;
27
28static 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 */
61static 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 */
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{
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
138err:
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
144out:
145 close(fd);
146
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;
157 }
158
159 printf("OK\n");
160 default_tmpdir = "/dev/shm";
161 goto out;
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
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;
199close:
200 close(fd);
201out:
202 free(tempname);
203 return -1;
204}
205
206#define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
207
208static 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
243int __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
258void __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}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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/vfs.h>
16#include <linux/magic.h>
17#include <init.h>
18#include <kern_util.h>
19#include <os.h>
20#include "internal.h"
21
22/*
23 * kasan_map_memory - maps memory from @start with a size of @len.
24 * The allocated memory is filled with zeroes upon success.
25 * @start: the start address of the memory to be mapped
26 * @len: the length of the memory to be mapped
27 *
28 * This function is used to map shadow memory for KASAN in uml
29 */
30void kasan_map_memory(void *start, size_t len)
31{
32 if (mmap(start,
33 len,
34 PROT_READ|PROT_WRITE,
35 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE,
36 -1,
37 0) == MAP_FAILED) {
38 os_info("Couldn't allocate shadow memory: %s\n.",
39 strerror(errno));
40 exit(1);
41 }
42
43 if (madvise(start, len, MADV_DONTDUMP)) {
44 os_info("Couldn't set MAD_DONTDUMP on shadow memory: %s\n.",
45 strerror(errno));
46 exit(1);
47 }
48
49 if (madvise(start, len, MADV_DONTFORK)) {
50 os_info("Couldn't set MADV_DONTFORK on shadow memory: %s\n.",
51 strerror(errno));
52 exit(1);
53 }
54}
55
56/* Set by make_tempfile() during early boot. */
57char *tempdir = NULL;
58
59/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
60static int __init check_tmpfs(const char *dir)
61{
62 struct statfs st;
63
64 os_info("Checking if %s is on tmpfs...", dir);
65 if (statfs(dir, &st) < 0) {
66 os_info("%s\n", strerror(errno));
67 } else if (st.f_type != TMPFS_MAGIC) {
68 os_info("no\n");
69 } else {
70 os_info("OK\n");
71 return 0;
72 }
73 return -1;
74}
75
76/*
77 * Choose the tempdir to use. We want something on tmpfs so that our memory is
78 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
79 * environment, we use that even if it's not on tmpfs, but we warn the user.
80 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
81 * then we fall back to /tmp.
82 */
83static char * __init choose_tempdir(void)
84{
85 static const char * const vars[] = {
86 "TMPDIR",
87 "TMP",
88 "TEMP",
89 NULL
90 };
91 static const char fallback_dir[] = "/tmp";
92 static const char * const tmpfs_dirs[] = {
93 "/dev/shm",
94 fallback_dir,
95 NULL
96 };
97 int i;
98 const char *dir;
99
100 os_info("Checking environment variables for a tempdir...");
101 for (i = 0; vars[i]; i++) {
102 dir = getenv(vars[i]);
103 if ((dir != NULL) && (*dir != '\0')) {
104 os_info("%s\n", dir);
105 if (check_tmpfs(dir) >= 0)
106 goto done;
107 else
108 goto warn;
109 }
110 }
111 os_info("none found\n");
112
113 for (i = 0; tmpfs_dirs[i]; i++) {
114 dir = tmpfs_dirs[i];
115 if (check_tmpfs(dir) >= 0)
116 goto done;
117 }
118
119 dir = fallback_dir;
120warn:
121 os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
122done:
123 /* Make a copy since getenv results may not remain valid forever. */
124 return strdup(dir);
125}
126
127/*
128 * Create an unlinked tempfile in a suitable tempdir. template must be the
129 * basename part of the template with a leading '/'.
130 */
131static int __init make_tempfile(const char *template)
132{
133 char *tempname;
134 int fd;
135
136 if (tempdir == NULL) {
137 tempdir = choose_tempdir();
138 if (tempdir == NULL) {
139 os_warn("Failed to choose tempdir: %s\n",
140 strerror(errno));
141 return -1;
142 }
143 }
144
145#ifdef O_TMPFILE
146 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
147 /*
148 * If the running system does not support O_TMPFILE flag then retry
149 * without it.
150 */
151 if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
152 errno != EOPNOTSUPP))
153 return fd;
154#endif
155
156 tempname = malloc(strlen(tempdir) + strlen(template) + 1);
157 if (tempname == NULL)
158 return -1;
159
160 strcpy(tempname, tempdir);
161 strcat(tempname, template);
162 fd = mkstemp(tempname);
163 if (fd < 0) {
164 os_warn("open - cannot create %s: %s\n", tempname,
165 strerror(errno));
166 goto out;
167 }
168 if (unlink(tempname) < 0) {
169 perror("unlink");
170 goto close;
171 }
172 free(tempname);
173 return fd;
174close:
175 close(fd);
176out:
177 free(tempname);
178 return -1;
179}
180
181#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
182
183static int __init create_tmp_file(unsigned long long len)
184{
185 int fd, err;
186 char zero;
187
188 fd = make_tempfile(TEMPNAME_TEMPLATE);
189 if (fd < 0)
190 exit(1);
191
192 /*
193 * Seek to len - 1 because writing a character there will
194 * increase the file size by one byte, to the desired length.
195 */
196 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
197 perror("lseek64");
198 exit(1);
199 }
200
201 zero = 0;
202
203 err = write(fd, &zero, 1);
204 if (err != 1) {
205 perror("write");
206 exit(1);
207 }
208
209 return fd;
210}
211
212int __init create_mem_file(unsigned long long len)
213{
214 int err, fd;
215
216 fd = create_tmp_file(len);
217
218 err = os_set_exec_close(fd);
219 if (err < 0) {
220 errno = -err;
221 perror("exec_close");
222 }
223 return fd;
224}
225
226void __init check_tmpexec(void)
227{
228 void *addr;
229 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
230
231 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
232 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
233 os_info("Checking PROT_EXEC mmap in %s...", tempdir);
234 if (addr == MAP_FAILED) {
235 err = errno;
236 os_warn("%s\n", strerror(err));
237 close(fd);
238 if (err == EPERM)
239 os_warn("%s must be not mounted noexec\n", tempdir);
240 exit(1);
241 }
242 os_info("OK\n");
243 munmap(addr, UM_KERN_PAGE_SIZE);
244
245 close(fd);
246}