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 <kern_util.h> 19 #include <os.h> 20 #include "internal.h" 21 22 /* 23 * kasan_map_memory - maps memory from @start with a size of @len. 24 * The allocated memory is filled with zeroes upon success. 25 * @start: the start address of the memory to be mapped 26 * @len: the length of the memory to be mapped 27 * 28 * This function is used to map shadow memory for KASAN in uml 29 */ 30 void kasan_map_memory(void *start, size_t len) 31 { 32 if (mmap(start, 33 len, 34 PROT_READ|PROT_WRITE, 35 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, 36 -1, 37 0) == MAP_FAILED) { 38 os_info("Couldn't allocate shadow memory: %s\n.", 39 strerror(errno)); 40 exit(1); 41 } 42 43 if (madvise(start, len, MADV_DONTDUMP)) { 44 os_info("Couldn't set MAD_DONTDUMP on shadow memory: %s\n.", 45 strerror(errno)); 46 exit(1); 47 } 48 49 if (madvise(start, len, MADV_DONTFORK)) { 50 os_info("Couldn't set MADV_DONTFORK on shadow memory: %s\n.", 51 strerror(errno)); 52 exit(1); 53 } 54 } 55 56 /* Set by make_tempfile() during early boot. */ 57 char *tempdir = NULL; 58 59 /* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */ 60 static int __init check_tmpfs(const char *dir) 61 { 62 struct statfs st; 63 64 os_info("Checking if %s is on tmpfs...", dir); 65 if (statfs(dir, &st) < 0) { 66 os_info("%s\n", strerror(errno)); 67 } else if (st.f_type != TMPFS_MAGIC) { 68 os_info("no\n"); 69 } else { 70 os_info("OK\n"); 71 return 0; 72 } 73 return -1; 74 } 75 76 /* 77 * Choose the tempdir to use. We want something on tmpfs so that our memory is 78 * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the 79 * environment, we use that even if it's not on tmpfs, but we warn the user. 80 * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found 81 * then we fall back to /tmp. 82 */ 83 static char * __init choose_tempdir(void) 84 { 85 static const char * const vars[] = { 86 "TMPDIR", 87 "TMP", 88 "TEMP", 89 NULL 90 }; 91 static const char fallback_dir[] = "/tmp"; 92 static const char * const tmpfs_dirs[] = { 93 "/dev/shm", 94 fallback_dir, 95 NULL 96 }; 97 int i; 98 const char *dir; 99 100 os_info("Checking environment variables for a tempdir..."); 101 for (i = 0; vars[i]; i++) { 102 dir = getenv(vars[i]); 103 if ((dir != NULL) && (*dir != '\0')) { 104 os_info("%s\n", dir); 105 if (check_tmpfs(dir) >= 0) 106 goto done; 107 else 108 goto warn; 109 } 110 } 111 os_info("none found\n"); 112 113 for (i = 0; tmpfs_dirs[i]; i++) { 114 dir = tmpfs_dirs[i]; 115 if (check_tmpfs(dir) >= 0) 116 goto done; 117 } 118 119 dir = fallback_dir; 120 warn: 121 os_warn("Warning: tempdir %s is not on tmpfs\n", dir); 122 done: 123 /* Make a copy since getenv results may not remain valid forever. */ 124 return strdup(dir); 125 } 126 127 /* 128 * Create an unlinked tempfile in a suitable tempdir. template must be the 129 * basename part of the template with a leading '/'. 130 */ 131 static int __init make_tempfile(const char *template) 132 { 133 char *tempname; 134 int fd; 135 136 if (tempdir == NULL) { 137 tempdir = choose_tempdir(); 138 if (tempdir == NULL) { 139 os_warn("Failed to choose tempdir: %s\n", 140 strerror(errno)); 141 return -1; 142 } 143 } 144 145 #ifdef O_TMPFILE 146 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700); 147 /* 148 * If the running system does not support O_TMPFILE flag then retry 149 * without it. 150 */ 151 if (fd != -1 || (errno != EINVAL && errno != EISDIR && 152 errno != EOPNOTSUPP)) 153 return fd; 154 #endif 155 156 tempname = malloc(strlen(tempdir) + strlen(template) + 1); 157 if (tempname == NULL) 158 return -1; 159 160 strcpy(tempname, tempdir); 161 strcat(tempname, template); 162 fd = mkstemp(tempname); 163 if (fd < 0) { 164 os_warn("open - cannot create %s: %s\n", tempname, 165 strerror(errno)); 166 goto out; 167 } 168 if (unlink(tempname) < 0) { 169 perror("unlink"); 170 goto close; 171 } 172 free(tempname); 173 return fd; 174 close: 175 close(fd); 176 out: 177 free(tempname); 178 return -1; 179 } 180 181 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX" 182 183 static int __init create_tmp_file(unsigned long long len) 184 { 185 int fd, err; 186 char zero; 187 188 fd = make_tempfile(TEMPNAME_TEMPLATE); 189 if (fd < 0) 190 exit(1); 191 192 /* 193 * Seek to len - 1 because writing a character there will 194 * increase the file size by one byte, to the desired length. 195 */ 196 if (lseek64(fd, len - 1, SEEK_SET) < 0) { 197 perror("lseek64"); 198 exit(1); 199 } 200 201 zero = 0; 202 203 err = write(fd, &zero, 1); 204 if (err != 1) { 205 perror("write"); 206 exit(1); 207 } 208 209 return fd; 210 } 211 212 int __init create_mem_file(unsigned long long len) 213 { 214 int err, fd; 215 216 fd = create_tmp_file(len); 217 218 err = os_set_exec_close(fd); 219 if (err < 0) { 220 errno = -err; 221 perror("exec_close"); 222 } 223 return fd; 224 } 225 226 void __init check_tmpexec(void) 227 { 228 void *addr; 229 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE); 230 231 addr = mmap(NULL, UM_KERN_PAGE_SIZE, 232 PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0); 233 os_info("Checking PROT_EXEC mmap in %s...", tempdir); 234 if (addr == MAP_FAILED) { 235 err = errno; 236 os_warn("%s\n", strerror(err)); 237 close(fd); 238 if (err == EPERM) 239 os_warn("%s must be not mounted noexec\n", tempdir); 240 exit(1); 241 } 242 os_info("OK\n"); 243 munmap(addr, UM_KERN_PAGE_SIZE); 244 245 close(fd); 246 } 247