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. */
21static char *tempdir = NULL;
22
23/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
24static 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 */
47static 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;
84warn:
85	printf("Warning: tempdir %s is not on tmpfs\n", dir);
86done:
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 */
95static 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;
127close:
128	close(fd);
129out:
130	free(tempname);
131	return -1;
132}
133
134#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
135
136static 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
171int __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
185void __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