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. */ 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 */ 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 */ 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" 146 147 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 } 175 176 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 } 189 190 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