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 */
30 void 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
44 /* Set by make_tempfile() during early boot. */
45 static char *tempdir = NULL;
46
47 /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
48 static int __init check_tmpfs(const char *dir)
49 {
50 struct statfs st;
51
52 os_info("Checking if %s is on tmpfs...", dir);
53 if (statfs(dir, &st) < 0) {
54 os_info("%s\n", strerror(errno));
55 } else if (st.f_type != TMPFS_MAGIC) {
56 os_info("no\n");
57 } else {
58 os_info("OK\n");
59 return 0;
60 }
61 return -1;
62 }
63
64 /*
65 * Choose the tempdir to use. We want something on tmpfs so that our memory is
66 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
67 * environment, we use that even if it's not on tmpfs, but we warn the user.
68 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
69 * then we fall back to /tmp.
70 */
71 static char * __init choose_tempdir(void)
72 {
73 static const char * const vars[] = {
74 "TMPDIR",
75 "TMP",
76 "TEMP",
77 NULL
78 };
79 static const char fallback_dir[] = "/tmp";
80 static const char * const tmpfs_dirs[] = {
81 "/dev/shm",
82 fallback_dir,
83 NULL
84 };
85 int i;
86 const char *dir;
87
88 os_info("Checking environment variables for a tempdir...");
89 for (i = 0; vars[i]; i++) {
90 dir = getenv(vars[i]);
91 if ((dir != NULL) && (*dir != '\0')) {
92 os_info("%s\n", dir);
93 if (check_tmpfs(dir) >= 0)
94 goto done;
95 else
96 goto warn;
97 }
98 }
99 os_info("none found\n");
100
101 for (i = 0; tmpfs_dirs[i]; i++) {
102 dir = tmpfs_dirs[i];
103 if (check_tmpfs(dir) >= 0)
104 goto done;
105 }
106
107 dir = fallback_dir;
108 warn:
109 os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
110 done:
111 /* Make a copy since getenv results may not remain valid forever. */
112 return strdup(dir);
113 }
114
115 /*
116 * Create an unlinked tempfile in a suitable tempdir. template must be the
117 * basename part of the template with a leading '/'.
118 */
119 static int __init make_tempfile(const char *template)
120 {
121 char *tempname;
122 int fd;
123
124 if (tempdir == NULL) {
125 tempdir = choose_tempdir();
126 if (tempdir == NULL) {
127 os_warn("Failed to choose tempdir: %s\n",
128 strerror(errno));
129 return -1;
130 }
131 }
132
133 #ifdef O_TMPFILE
134 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
135 /*
136 * If the running system does not support O_TMPFILE flag then retry
137 * without it.
138 */
139 if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
140 errno != EOPNOTSUPP))
141 return fd;
142 #endif
143
144 tempname = malloc(strlen(tempdir) + strlen(template) + 1);
145 if (tempname == NULL)
146 return -1;
147
148 strcpy(tempname, tempdir);
149 strcat(tempname, template);
150 fd = mkstemp(tempname);
151 if (fd < 0) {
152 os_warn("open - cannot create %s: %s\n", tempname,
153 strerror(errno));
154 goto out;
155 }
156 if (unlink(tempname) < 0) {
157 perror("unlink");
158 goto close;
159 }
160 free(tempname);
161 return fd;
162 close:
163 close(fd);
164 out:
165 free(tempname);
166 return -1;
167 }
168
169 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
170
171 static int __init create_tmp_file(unsigned long long len)
172 {
173 int fd, err;
174 char zero;
175
176 fd = make_tempfile(TEMPNAME_TEMPLATE);
177 if (fd < 0)
178 exit(1);
179
180 /*
181 * Seek to len - 1 because writing a character there will
182 * increase the file size by one byte, to the desired length.
183 */
184 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
185 perror("lseek64");
186 exit(1);
187 }
188
189 zero = 0;
190
191 err = write(fd, &zero, 1);
192 if (err != 1) {
193 perror("write");
194 exit(1);
195 }
196
197 return fd;
198 }
199
200 int __init create_mem_file(unsigned long long len)
201 {
202 int err, fd;
203
204 fd = create_tmp_file(len);
205
206 err = os_set_exec_close(fd);
207 if (err < 0) {
208 errno = -err;
209 perror("exec_close");
210 }
211 return fd;
212 }
213
214 void __init check_tmpexec(void)
215 {
216 void *addr;
217 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
218
219 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
220 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
221 os_info("Checking PROT_EXEC mmap in %s...", tempdir);
222 if (addr == MAP_FAILED) {
223 err = errno;
224 os_warn("%s\n", strerror(err));
225 close(fd);
226 if (err == EPERM)
227 os_warn("%s must be not mounted noexec\n", tempdir);
228 exit(1);
229 }
230 os_info("OK\n");
231 munmap(addr, UM_KERN_PAGE_SIZE);
232
233 close(fd);
234 }
235
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.