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  */
kasan_map_memory(void * start,size_t len)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. */
check_tmpfs(const char * dir)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  */
choose_tempdir(void)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  */
make_tempfile(const char * template)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 
create_tmp_file(unsigned long long len)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 
create_mem_file(unsigned long long len)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 
check_tmpexec(void)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