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  */
kasan_map_memory(void * start,size_t len)28 void 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. */
43 static char *tempdir = NULL;
44 
45 /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
check_tmpfs(const char * dir)46 static 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  */
choose_tempdir(void)69 static 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;
106 warn:
107 	os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
108 done:
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  */
make_tempfile(const char * template)117 static 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;
160 close:
161 	close(fd);
162 out:
163 	free(tempname);
164 	return -1;
165 }
166 
167 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
168 
create_tmp_file(unsigned long long len)169 static 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 
create_mem_file(unsigned long long len)198 int __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 
check_tmpexec(void)212 void __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 }
233