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 <os.h> 19 20 /* 21 * kasan_map_memory - maps memory from @start with a size of @len. 22 * The allocated memory is filled with zeroes upon success. 23 * @start: the start address of the memory to be mapped 24 * @len: the length of the memory to be mapped 25 * 26 * This function is used to map shadow memory for KASAN in uml 27 */ 28 void kasan_map_memory(void *start, size_t len) 29 { 30 if (mmap(start, 31 len, 32 PROT_READ|PROT_WRITE, 33 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, 34 -1, 35 0) == MAP_FAILED) { 36 os_info("Couldn't allocate shadow memory: %s\n.", 37 strerror(errno)); 38 exit(1); 39 } 40 } 41 42 /* Set by make_tempfile() during early boot. */ 43 static char *tempdir = NULL; 44 45 /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */ 46 static int __init check_tmpfs(const char *dir) 47 { 48 struct statfs st; 49 50 os_info("Checking if %s is on tmpfs...", dir); 51 if (statfs(dir, &st) < 0) { 52 os_info("%s\n", strerror(errno)); 53 } else if (st.f_type != TMPFS_MAGIC) { 54 os_info("no\n"); 55 } else { 56 os_info("OK\n"); 57 return 0; 58 } 59 return -1; 60 } 61 62 /* 63 * Choose the tempdir to use. We want something on tmpfs so that our memory is 64 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the 65 * environment, we use that even if it's not on tmpfs, but we warn the user. 66 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found 67 * then we fall back to /tmp. 68 */ 69 static char * __init choose_tempdir(void) 70 { 71 static const char * const vars[] = { 72 "TMPDIR", 73 "TMP", 74 "TEMP", 75 NULL 76 }; 77 static const char fallback_dir[] = "/tmp"; 78 static const char * const tmpfs_dirs[] = { 79 "/dev/shm", 80 fallback_dir, 81 NULL 82 }; 83 int i; 84 const char *dir; 85 86 os_info("Checking environment variables for a tempdir..."); 87 for (i = 0; vars[i]; i++) { 88 dir = getenv(vars[i]); 89 if ((dir != NULL) && (*dir != '\0')) { 90 os_info("%s\n", dir); 91 if (check_tmpfs(dir) >= 0) 92 goto done; 93 else 94 goto warn; 95 } 96 } 97 os_info("none found\n"); 98 99 for (i = 0; tmpfs_dirs[i]; i++) { 100 dir = tmpfs_dirs[i]; 101 if (check_tmpfs(dir) >= 0) 102 goto done; 103 } 104 105 dir = fallback_dir; 106 warn: 107 os_warn("Warning: tempdir %s is not on tmpfs\n", dir); 108 done: 109 /* Make a copy since getenv results may not remain valid forever. */ 110 return strdup(dir); 111 } 112 113 /* 114 * Create an unlinked tempfile in a suitable tempdir. template must be the 115 * basename part of the template with a leading '/'. 116 */ 117 static int __init make_tempfile(const char *template) 118 { 119 char *tempname; 120 int fd; 121 122 if (tempdir == NULL) { 123 tempdir = choose_tempdir(); 124 if (tempdir == NULL) { 125 os_warn("Failed to choose tempdir: %s\n", 126 strerror(errno)); 127 return -1; 128 } 129 } 130 131 #ifdef O_TMPFILE 132 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700); 133 /* 134 * If the running system does not support O_TMPFILE flag then retry 135 * without it. 136 */ 137 if (fd != -1 || (errno != EINVAL && errno != EISDIR && 138 errno != EOPNOTSUPP)) 139 return fd; 140 #endif 141 142 tempname = malloc(strlen(tempdir) + strlen(template) + 1); 143 if (tempname == NULL) 144 return -1; 145 146 strcpy(tempname, tempdir); 147 strcat(tempname, template); 148 fd = mkstemp(tempname); 149 if (fd < 0) { 150 os_warn("open - cannot create %s: %s\n", tempname, 151 strerror(errno)); 152 goto out; 153 } 154 if (unlink(tempname) < 0) { 155 perror("unlink"); 156 goto close; 157 } 158 free(tempname); 159 return fd; 160 close: 161 close(fd); 162 out: 163 free(tempname); 164 return -1; 165 } 166 167 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX" 168 169 static int __init create_tmp_file(unsigned long long len) 170 { 171 int fd, err; 172 char zero; 173 174 fd = make_tempfile(TEMPNAME_TEMPLATE); 175 if (fd < 0) 176 exit(1); 177 178 /* 179 * Seek to len - 1 because writing a character there will 180 * increase the file size by one byte, to the desired length. 181 */ 182 if (lseek64(fd, len - 1, SEEK_SET) < 0) { 183 perror("lseek64"); 184 exit(1); 185 } 186 187 zero = 0; 188 189 err = write(fd, &zero, 1); 190 if (err != 1) { 191 perror("write"); 192 exit(1); 193 } 194 195 return fd; 196 } 197 198 int __init create_mem_file(unsigned long long len) 199 { 200 int err, fd; 201 202 fd = create_tmp_file(len); 203 204 err = os_set_exec_close(fd); 205 if (err < 0) { 206 errno = -err; 207 perror("exec_close"); 208 } 209 return fd; 210 } 211 212 void __init check_tmpexec(void) 213 { 214 void *addr; 215 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE); 216 217 addr = mmap(NULL, UM_KERN_PAGE_SIZE, 218 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0); 219 os_info("Checking PROT_EXEC mmap in %s...", tempdir); 220 if (addr == MAP_FAILED) { 221 err = errno; 222 os_warn("%s\n", strerror(err)); 223 close(fd); 224 if (err == EPERM) 225 os_warn("%s must be not mounted noexec\n", tempdir); 226 exit(1); 227 } 228 os_info("OK\n"); 229 munmap(addr, UM_KERN_PAGE_SIZE); 230 231 close(fd); 232 } 233