1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
16 #include <linux/magic.h>
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
26 * This function is used to map shadow memory for KASAN in uml
28 void kasan_map_memory(void *start, size_t len)
33 MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE,
36 os_info("Couldn't allocate shadow memory: %s\n.",
42 /* Set by make_tempfile() during early boot. */
43 static char *tempdir = NULL;
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)
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) {
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.
69 static char * __init choose_tempdir(void)
71 static const char * const vars[] = {
77 static const char fallback_dir[] = "/tmp";
78 static const char * const tmpfs_dirs[] = {
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')) {
91 if (check_tmpfs(dir) >= 0)
97 os_info("none found\n");
99 for (i = 0; tmpfs_dirs[i]; i++) {
101 if (check_tmpfs(dir) >= 0)
107 os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
109 /* Make a copy since getenv results may not remain valid forever. */
114 * Create an unlinked tempfile in a suitable tempdir. template must be the
115 * basename part of the template with a leading '/'.
117 static int __init make_tempfile(const char *template)
122 if (tempdir == NULL) {
123 tempdir = choose_tempdir();
124 if (tempdir == NULL) {
125 os_warn("Failed to choose tempdir: %s\n",
132 fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
134 * If the running system does not support O_TMPFILE flag then retry
137 if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
138 errno != EOPNOTSUPP))
142 tempname = malloc(strlen(tempdir) + strlen(template) + 1);
143 if (tempname == NULL)
146 strcpy(tempname, tempdir);
147 strcat(tempname, template);
148 fd = mkstemp(tempname);
150 os_warn("open - cannot create %s: %s\n", tempname,
154 if (unlink(tempname) < 0) {
167 #define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
169 static int __init create_tmp_file(unsigned long long len)
174 fd = make_tempfile(TEMPNAME_TEMPLATE);
179 * Seek to len - 1 because writing a character there will
180 * increase the file size by one byte, to the desired length.
182 if (lseek64(fd, len - 1, SEEK_SET) < 0) {
189 err = write(fd, &zero, 1);
198 int __init create_mem_file(unsigned long long len)
202 fd = create_tmp_file(len);
204 err = os_set_exec_close(fd);
207 perror("exec_close");
212 void __init check_tmpexec(void)
215 int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
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) {
222 os_warn("%s\n", strerror(err));
225 os_warn("%s must be not mounted noexec\n", tempdir);
229 munmap(addr, UM_KERN_PAGE_SIZE);