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