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 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 */
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 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;
84 warn:
85 printf("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 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;
127 close:
128 close(fd);
129 out:
130 free(tempname);
131 return -1;
132 }
133
134 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
135
create_tmp_file(unsigned long long len)136 static 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
create_mem_file(unsigned long long len)171 int __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
check_tmpexec(void)185 void __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 }
206