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