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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 <os.h>
19
20/*
21 * kasan_map_memory - maps memory from @start with a size of @len.
22 * The allocated memory is filled with zeroes upon success.
23 * @start: the start address of the memory to be mapped
24 * @len: the length of the memory to be mapped
25 *
26 * This function is used to map shadow memory for KASAN in uml
27 */
28void kasan_map_memory(void *start, size_t len)
29{
30 if (mmap(start,
31 len,
32 PROT_READ|PROT_WRITE,
33 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE,
34 -1,
35 0) == MAP_FAILED) {
36 os_info("Couldn't allocate shadow memory: %s\n.",
37 strerror(errno));
38 exit(1);
39 }
40}
41
42/* Set by make_tempfile() during early boot. */
43static char *tempdir = NULL;
44
45/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
46static int __init check_tmpfs(const char *dir)
47{
48 struct statfs st;
49
50 os_info("Checking if %s is on tmpfs...", dir);
51 if (statfs(dir, &st) < 0) {
52 os_info("%s\n", strerror(errno));
53 } else if (st.f_type != TMPFS_MAGIC) {
54 os_info("no\n");
55 } else {
56 os_info("OK\n");
57 return 0;
58 }
59 return -1;
60}
61
62/*
63 * Choose the tempdir to use. We want something on tmpfs so that our memory is
64 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
65 * environment, we use that even if it's not on tmpfs, but we warn the user.
66 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
67 * then we fall back to /tmp.
68 */
69static char * __init choose_tempdir(void)
70{
71 static const char * const vars[] = {
72 "TMPDIR",
73 "TMP",
74 "TEMP",
75 NULL
76 };
77 static const char fallback_dir[] = "/tmp";
78 static const char * const tmpfs_dirs[] = {
79 "/dev/shm",
80 fallback_dir,
81 NULL
82 };
83 int i;
84 const char *dir;
85
86 os_info("Checking environment variables for a tempdir...");
87 for (i = 0; vars[i]; i++) {
88 dir = getenv(vars[i]);
89 if ((dir != NULL) && (*dir != '\0')) {
90 os_info("%s\n", dir);
91 if (check_tmpfs(dir) >= 0)
92 goto done;
93 else
94 goto warn;
95 }
96 }
97 os_info("none found\n");
98
99 for (i = 0; tmpfs_dirs[i]; i++) {
100 dir = tmpfs_dirs[i];
101 if (check_tmpfs(dir) >= 0)
102 goto done;
103 }
104
105 dir = fallback_dir;
106warn:
107 os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
108done:
109 /* Make a copy since getenv results may not remain valid forever. */
110 return strdup(dir);
111}
112
113/*
114 * Create an unlinked tempfile in a suitable tempdir. template must be the
115 * basename part of the template with a leading '/'.
116 */
117static int __init make_tempfile(const char *template)
118{
119 char *tempname;
120 int fd;
121
122 if (tempdir == NULL) {
123 tempdir = choose_tempdir();
124 if (tempdir == NULL) {
125 os_warn("Failed to choose tempdir: %s\n",
126 strerror(errno));
127 return -1;
128 }
129 }
130
131#ifdef O_TMPFILE
132 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
133 /*
134 * If the running system does not support O_TMPFILE flag then retry
135 * without it.
136 */
137 if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
138 errno != EOPNOTSUPP))
139 return fd;
140#endif
141
142 tempname = malloc(strlen(tempdir) + strlen(template) + 1);
143 if (tempname == NULL)
144 return -1;
145
146 strcpy(tempname, tempdir);
147 strcat(tempname, template);
148 fd = mkstemp(tempname);
149 if (fd < 0) {
150 os_warn("open - cannot create %s: %s\n", tempname,
151 strerror(errno));
152 goto out;
153 }
154 if (unlink(tempname) < 0) {
155 perror("unlink");
156 goto close;
157 }
158 free(tempname);
159 return fd;
160close:
161 close(fd);
162out:
163 free(tempname);
164 return -1;
165}
166
167#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
168
169static int __init create_tmp_file(unsigned long long len)
170{
171 int fd, err;
172 char zero;
173
174 fd = make_tempfile(TEMPNAME_TEMPLATE);
175 if (fd < 0)
176 exit(1);
177
178 /*
179 * Seek to len - 1 because writing a character there will
180 * increase the file size by one byte, to the desired length.
181 */
182 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
183 perror("lseek64");
184 exit(1);
185 }
186
187 zero = 0;
188
189 err = write(fd, &zero, 1);
190 if (err != 1) {
191 perror("write");
192 exit(1);
193 }
194
195 return fd;
196}
197
198int __init create_mem_file(unsigned long long len)
199{
200 int err, fd;
201
202 fd = create_tmp_file(len);
203
204 err = os_set_exec_close(fd);
205 if (err < 0) {
206 errno = -err;
207 perror("exec_close");
208 }
209 return fd;
210}
211
212void __init check_tmpexec(void)
213{
214 void *addr;
215 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
216
217 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
218 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
219 os_info("Checking PROT_EXEC mmap in %s...", tempdir);
220 if (addr == MAP_FAILED) {
221 err = errno;
222 os_warn("%s\n", strerror(err));
223 close(fd);
224 if (err == EPERM)
225 os_warn("%s must be not mounted noexec\n", tempdir);
226 exit(1);
227 }
228 os_info("OK\n");
229 munmap(addr, UM_KERN_PAGE_SIZE);
230
231 close(fd);
232}
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 "kern_constants.h"
18#include "os.h"
19#include "user.h"
20
21/* Modified by which_tmpdir, which is called during early boot */
22static char *default_tmpdir = "/tmp";
23
24/*
25 * Modified when creating the physical memory file and when checking
26 * the tmp filesystem for usability, both happening during early boot.
27 */
28static char *tempdir = NULL;
29
30static void __init find_tempdir(void)
31{
32 const char *dirs[] = { "TMP", "TEMP", "TMPDIR", NULL };
33 int i;
34 char *dir = NULL;
35
36 if (tempdir != NULL)
37 /* We've already been called */
38 return;
39 for (i = 0; dirs[i]; i++) {
40 dir = getenv(dirs[i]);
41 if ((dir != NULL) && (*dir != '\0'))
42 break;
43 }
44 if ((dir == NULL) || (*dir == '\0'))
45 dir = default_tmpdir;
46
47 tempdir = malloc(strlen(dir) + 2);
48 if (tempdir == NULL) {
49 fprintf(stderr, "Failed to malloc tempdir, "
50 "errno = %d\n", errno);
51 return;
52 }
53 strcpy(tempdir, dir);
54 strcat(tempdir, "/");
55}
56
57/*
58 * This will return 1, with the first character in buf being the
59 * character following the next instance of c in the file. This will
60 * read the file as needed. If there's an error, -errno is returned;
61 * if the end of the file is reached, 0 is returned.
62 */
63static int next(int fd, char *buf, size_t size, char c)
64{
65 ssize_t n;
66 size_t len;
67 char *ptr;
68
69 while ((ptr = strchr(buf, c)) == NULL) {
70 n = read(fd, buf, size - 1);
71 if (n == 0)
72 return 0;
73 else if (n < 0)
74 return -errno;
75
76 buf[n] = '\0';
77 }
78
79 ptr++;
80 len = strlen(ptr);
81 memmove(buf, ptr, len + 1);
82
83 /*
84 * Refill the buffer so that if there's a partial string that we care
85 * about, it will be completed, and we can recognize it.
86 */
87 n = read(fd, &buf[len], size - len - 1);
88 if (n < 0)
89 return -errno;
90
91 buf[len + n] = '\0';
92 return 1;
93}
94
95/* which_tmpdir is called only during early boot */
96static int checked_tmpdir = 0;
97
98/*
99 * Look for a tmpfs mounted at /dev/shm. I couldn't find a cleaner
100 * way to do this than to parse /proc/mounts. statfs will return the
101 * same filesystem magic number and fs id for both /dev and /dev/shm
102 * when they are both tmpfs, so you can't tell if they are different
103 * filesystems. Also, there seems to be no other way of finding the
104 * mount point of a filesystem from within it.
105 *
106 * If a /dev/shm tmpfs entry is found, then we switch to using it.
107 * Otherwise, we stay with the default /tmp.
108 */
109static void which_tmpdir(void)
110{
111 int fd, found;
112 char buf[128] = { '\0' };
113
114 if (checked_tmpdir)
115 return;
116
117 checked_tmpdir = 1;
118
119 printf("Checking for tmpfs mount on /dev/shm...");
120
121 fd = open("/proc/mounts", O_RDONLY);
122 if (fd < 0) {
123 printf("failed to open /proc/mounts, errno = %d\n", errno);
124 return;
125 }
126
127 while (1) {
128 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
129 if (found != 1)
130 break;
131
132 if (!strncmp(buf, "/dev/shm", strlen("/dev/shm")))
133 goto found;
134
135 found = next(fd, buf, ARRAY_SIZE(buf), '\n');
136 if (found != 1)
137 break;
138 }
139
140err:
141 if (found == 0)
142 printf("nothing mounted on /dev/shm\n");
143 else if (found < 0)
144 printf("read returned errno %d\n", -found);
145
146out:
147 close(fd);
148
149 return;
150
151found:
152 found = next(fd, buf, ARRAY_SIZE(buf), ' ');
153 if (found != 1)
154 goto err;
155
156 if (strncmp(buf, "tmpfs", strlen("tmpfs"))) {
157 printf("not tmpfs\n");
158 goto out;
159 }
160
161 printf("OK\n");
162 default_tmpdir = "/dev/shm";
163 goto out;
164}
165
166static int __init make_tempfile(const char *template, char **out_tempname,
167 int do_unlink)
168{
169 char *tempname;
170 int fd;
171
172 which_tmpdir();
173 tempname = malloc(MAXPATHLEN);
174 if (tempname == NULL)
175 return -1;
176
177 find_tempdir();
178 if ((tempdir == NULL) || (strlen(tempdir) >= MAXPATHLEN))
179 goto out;
180
181 if (template[0] != '/')
182 strcpy(tempname, tempdir);
183 else
184 tempname[0] = '\0';
185 strncat(tempname, template, MAXPATHLEN-1-strlen(tempname));
186 fd = mkstemp(tempname);
187 if (fd < 0) {
188 fprintf(stderr, "open - cannot create %s: %s\n", tempname,
189 strerror(errno));
190 goto out;
191 }
192 if (do_unlink && (unlink(tempname) < 0)) {
193 perror("unlink");
194 goto close;
195 }
196 if (out_tempname) {
197 *out_tempname = tempname;
198 } else
199 free(tempname);
200 return fd;
201close:
202 close(fd);
203out:
204 free(tempname);
205 return -1;
206}
207
208#define TEMPNAME_TEMPLATE "vm_file-XXXXXX"
209
210static int __init create_tmp_file(unsigned long long len)
211{
212 int fd, err;
213 char zero;
214
215 fd = make_tempfile(TEMPNAME_TEMPLATE, NULL, 1);
216 if (fd < 0)
217 exit(1);
218
219 err = fchmod(fd, 0777);
220 if (err < 0) {
221 perror("fchmod");
222 exit(1);
223 }
224
225 /*
226 * Seek to len - 1 because writing a character there will
227 * increase the file size by one byte, to the desired length.
228 */
229 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
230 perror("lseek64");
231 exit(1);
232 }
233
234 zero = 0;
235
236 err = write(fd, &zero, 1);
237 if (err != 1) {
238 perror("write");
239 exit(1);
240 }
241
242 return fd;
243}
244
245int __init create_mem_file(unsigned long long len)
246{
247 int err, fd;
248
249 fd = create_tmp_file(len);
250
251 err = os_set_exec_close(fd);
252 if (err < 0) {
253 errno = -err;
254 perror("exec_close");
255 }
256 return fd;
257}
258
259
260void __init check_tmpexec(void)
261{
262 void *addr;
263 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
264
265 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
266 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
267 printf("Checking PROT_EXEC mmap in %s...",tempdir);
268 fflush(stdout);
269 if (addr == MAP_FAILED) {
270 err = errno;
271 perror("failed");
272 close(fd);
273 if (err == EPERM)
274 printf("%s must be not mounted noexec\n",tempdir);
275 exit(1);
276 }
277 printf("OK\n");
278 munmap(addr, UM_KERN_PAGE_SIZE);
279
280 close(fd);
281}