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. */
21 static char *tempdir = NULL;
22
23 /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
check_tmpfs(const char * dir)24 static int __init check_tmpfs(const char *dir)
25 {
26 struct statfs st;
27
28 os_info("Checking if %s is on tmpfs...", dir);
29 if (statfs(dir, &st) < 0) {
30 os_info("%s\n", strerror(errno));
31 } else if (st.f_type != TMPFS_MAGIC) {
32 os_info("no\n");
33 } else {
34 os_info("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 */
choose_tempdir(void)47 static 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 os_info("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 os_info("%s\n", dir);
69 if (check_tmpfs(dir) >= 0)
70 goto done;
71 else
72 goto warn;
73 }
74 }
75 os_info("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;
84 warn:
85 os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
86 done:
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 */
make_tempfile(const char * template)95 static 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 os_warn("Failed to choose tempdir: %s\n",
104 strerror(errno));
105 return -1;
106 }
107 }
108
109 #ifdef O_TMPFILE
110 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
111 /*
112 * If the running system does not support O_TMPFILE flag then retry
113 * without it.
114 */
115 if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
116 errno != EOPNOTSUPP))
117 return fd;
118 #endif
119
120 tempname = malloc(strlen(tempdir) + strlen(template) + 1);
121 if (tempname == NULL)
122 return -1;
123
124 strcpy(tempname, tempdir);
125 strcat(tempname, template);
126 fd = mkstemp(tempname);
127 if (fd < 0) {
128 os_warn("open - cannot create %s: %s\n", tempname,
129 strerror(errno));
130 goto out;
131 }
132 if (unlink(tempname) < 0) {
133 perror("unlink");
134 goto close;
135 }
136 free(tempname);
137 return fd;
138 close:
139 close(fd);
140 out:
141 free(tempname);
142 return -1;
143 }
144
145 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
146
create_tmp_file(unsigned long long len)147 static int __init create_tmp_file(unsigned long long len)
148 {
149 int fd, err;
150 char zero;
151
152 fd = make_tempfile(TEMPNAME_TEMPLATE);
153 if (fd < 0)
154 exit(1);
155
156 /*
157 * Seek to len - 1 because writing a character there will
158 * increase the file size by one byte, to the desired length.
159 */
160 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
161 perror("lseek64");
162 exit(1);
163 }
164
165 zero = 0;
166
167 err = write(fd, &zero, 1);
168 if (err != 1) {
169 perror("write");
170 exit(1);
171 }
172
173 return fd;
174 }
175
create_mem_file(unsigned long long len)176 int __init create_mem_file(unsigned long long len)
177 {
178 int err, fd;
179
180 fd = create_tmp_file(len);
181
182 err = os_set_exec_close(fd);
183 if (err < 0) {
184 errno = -err;
185 perror("exec_close");
186 }
187 return fd;
188 }
189
check_tmpexec(void)190 void __init check_tmpexec(void)
191 {
192 void *addr;
193 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
194
195 addr = mmap(NULL, UM_KERN_PAGE_SIZE,
196 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
197 os_info("Checking PROT_EXEC mmap in %s...", tempdir);
198 if (addr == MAP_FAILED) {
199 err = errno;
200 os_warn("%s\n", strerror(err));
201 close(fd);
202 if (err == EPERM)
203 os_warn("%s must be not mounted noexec\n", tempdir);
204 exit(1);
205 }
206 os_info("OK\n");
207 munmap(addr, UM_KERN_PAGE_SIZE);
208
209 close(fd);
210 }
211
