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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/vfs.h>
16#include <linux/magic.h>
17#include <init.h>
18#include <os.h>
19
20/* Set by make_tempfile() during early boot. */
21static char *tempdir = NULL;
22
23/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
24static int __init check_tmpfs(const char *dir)
25{
26 struct statfs st;
27
28 printf("Checking if %s is on tmpfs...", dir);
29 if (statfs(dir, &st) < 0) {
30 printf("%s\n", strerror(errno));
31 } else if (st.f_type != TMPFS_MAGIC) {
32 printf("no\n");
33 } else {
34 printf("OK\n");
35 return 0;
36 }
37 return -1;
38}
39
40/*
41 * Choose the tempdir to use. We want something on tmpfs so that our memory is
42 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
43 * environment, we use that even if it's not on tmpfs, but we warn the user.
44 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
45 * then we fall back to /tmp.
46 */
47static char * __init choose_tempdir(void)
48{
49 static const char * const vars[] = {
50 "TMPDIR",
51 "TMP",
52 "TEMP",
53 NULL
54 };
55 static const char fallback_dir[] = "/tmp";
56 static const char * const tmpfs_dirs[] = {
57 "/dev/shm",
58 fallback_dir,
59 NULL
60 };
61 int i;
62 const char *dir;
63
64 printf("Checking environment variables for a tempdir...");
65 for (i = 0; vars[i]; i++) {
66 dir = getenv(vars[i]);
67 if ((dir != NULL) && (*dir != '\0')) {
68 printf("%s\n", dir);
69 if (check_tmpfs(dir) >= 0)
70 goto done;
71 else
72 goto warn;
73 }
74 }
75 printf("none found\n");
76
77 for (i = 0; tmpfs_dirs[i]; i++) {
78 dir = tmpfs_dirs[i];
79 if (check_tmpfs(dir) >= 0)
80 goto done;
81 }
82
83 dir = fallback_dir;
84warn:
85 printf("Warning: tempdir %s is not on tmpfs\n", dir);
86done:
87 /* Make a copy since getenv results may not remain valid forever. */
88 return strdup(dir);
89}
90
91/*
92 * Create an unlinked tempfile in a suitable tempdir. template must be the
93 * basename part of the template with a leading '/'.
94 */
95static int __init make_tempfile(const char *template)
96{
97 char *tempname;
98 int fd;
99
100 if (tempdir == NULL) {
101 tempdir = choose_tempdir();
102 if (tempdir == NULL) {
103 fprintf(stderr, "Failed to choose tempdir: %s\n",
104 strerror(errno));
105 return -1;
106 }
107 }
108
109 tempname = malloc(strlen(tempdir) + strlen(template) + 1);
110 if (tempname == NULL)
111 return -1;
112
113 strcpy(tempname, tempdir);
114 strcat(tempname, template);
115 fd = mkstemp(tempname);
116 if (fd < 0) {
117 fprintf(stderr, "open - cannot create %s: %s\n", tempname,
118 strerror(errno));
119 goto out;
120 }
121 if (unlink(tempname) < 0) {
122 perror("unlink");
123 goto close;
124 }
125 free(tempname);
126 return fd;
127close:
128 close(fd);
129out:
130 free(tempname);
131 return -1;
132}
133
134#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
135
136static int __init create_tmp_file(unsigned long long len)
137{
138 int fd, err;
139 char zero;
140
141 fd = make_tempfile(TEMPNAME_TEMPLATE);
142 if (fd < 0)
143 exit(1);
144
145 err = fchmod(fd, 0777);
146 if (err < 0) {
147 perror("fchmod");
148 exit(1);
149 }
150
151 /*
152 * Seek to len - 1 because writing a character there will
153 * increase the file size by one byte, to the desired length.
154 */
155 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
156 perror("lseek64");
157 exit(1);
158 }
159
160 zero = 0;
161
162 err = write(fd, &zero, 1);
163 if (err != 1) {
164 perror("write");
165 exit(1);
166 }
167
168 return fd;
169}
170
171int __init create_mem_file(unsigned long long len)
172{
173 int err, fd;
174
175 fd = create_tmp_file(len);
176
177 err = os_set_exec_close(fd);
178 if (err < 0) {
179 errno = -err;
180 perror("exec_close");
181 }
182 return fd;
183}
184
185void __init check_tmpexec(void)
186{
187 void *addr;
188 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
189
190 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
191 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
192 printf("Checking PROT_EXEC mmap in %s...", tempdir);
193 if (addr == MAP_FAILED) {
194 err = errno;
195 printf("%s\n", strerror(err));
196 close(fd);
197 if (err == EPERM)
198 printf("%s must be not mounted noexec\n", tempdir);
199 exit(1);
200 }
201 printf("OK\n");
202 munmap(addr, UM_KERN_PAGE_SIZE);
203
204 close(fd);
205}
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 */
29void 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. */
44static char *tempdir = NULL;
45
46/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
47static 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 */
70static 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;
107warn:
108 os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
109done:
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 */
118static 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;
161close:
162 close(fd);
163out:
164 free(tempname);
165 return -1;
166}
167
168#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
169
170static 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
199int __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
213void __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}