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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 <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}
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}