v4.19.13 snapshot.
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
new file mode 100644
index 0000000..e162a95
--- /dev/null
+++ b/arch/um/os-Linux/mem.c
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/vfs.h>
+#include <linux/magic.h>
+#include <init.h>
+#include <os.h>
+
+/* Set by make_tempfile() during early boot. */
+static char *tempdir = NULL;
+
+/* Check if dir is on tmpfs. Return 0 if yes, -1 if no or error. */
+static int __init check_tmpfs(const char *dir)
+{
+ struct statfs st;
+
+ os_info("Checking if %s is on tmpfs...", dir);
+ if (statfs(dir, &st) < 0) {
+ os_info("%s\n", strerror(errno));
+ } else if (st.f_type != TMPFS_MAGIC) {
+ os_info("no\n");
+ } else {
+ os_info("OK\n");
+ return 0;
+ }
+ return -1;
+}
+
+/*
+ * Choose the tempdir to use. We want something on tmpfs so that our memory is
+ * not subject to the host's vm.dirty_ratio. If a tempdir is specified in the
+ * environment, we use that even if it's not on tmpfs, but we warn the user.
+ * Otherwise, we try common tmpfs locations, and if no tmpfs directory is found
+ * then we fall back to /tmp.
+ */
+static char * __init choose_tempdir(void)
+{
+ static const char * const vars[] = {
+ "TMPDIR",
+ "TMP",
+ "TEMP",
+ NULL
+ };
+ static const char fallback_dir[] = "/tmp";
+ static const char * const tmpfs_dirs[] = {
+ "/dev/shm",
+ fallback_dir,
+ NULL
+ };
+ int i;
+ const char *dir;
+
+ os_info("Checking environment variables for a tempdir...");
+ for (i = 0; vars[i]; i++) {
+ dir = getenv(vars[i]);
+ if ((dir != NULL) && (*dir != '\0')) {
+ os_info("%s\n", dir);
+ if (check_tmpfs(dir) >= 0)
+ goto done;
+ else
+ goto warn;
+ }
+ }
+ os_info("none found\n");
+
+ for (i = 0; tmpfs_dirs[i]; i++) {
+ dir = tmpfs_dirs[i];
+ if (check_tmpfs(dir) >= 0)
+ goto done;
+ }
+
+ dir = fallback_dir;
+warn:
+ os_warn("Warning: tempdir %s is not on tmpfs\n", dir);
+done:
+ /* Make a copy since getenv results may not remain valid forever. */
+ return strdup(dir);
+}
+
+/*
+ * Create an unlinked tempfile in a suitable tempdir. template must be the
+ * basename part of the template with a leading '/'.
+ */
+static int __init make_tempfile(const char *template)
+{
+ char *tempname;
+ int fd;
+
+ if (tempdir == NULL) {
+ tempdir = choose_tempdir();
+ if (tempdir == NULL) {
+ os_warn("Failed to choose tempdir: %s\n",
+ strerror(errno));
+ return -1;
+ }
+ }
+
+#ifdef O_TMPFILE
+ fd = open(tempdir, O_CLOEXEC | O_RDWR | O_EXCL | O_TMPFILE, 0700);
+ /*
+ * If the running system does not support O_TMPFILE flag then retry
+ * without it.
+ */
+ if (fd != -1 || (errno != EINVAL && errno != EISDIR &&
+ errno != EOPNOTSUPP))
+ return fd;
+#endif
+
+ tempname = malloc(strlen(tempdir) + strlen(template) + 1);
+ if (tempname == NULL)
+ return -1;
+
+ strcpy(tempname, tempdir);
+ strcat(tempname, template);
+ fd = mkstemp(tempname);
+ if (fd < 0) {
+ os_warn("open - cannot create %s: %s\n", tempname,
+ strerror(errno));
+ goto out;
+ }
+ if (unlink(tempname) < 0) {
+ perror("unlink");
+ goto close;
+ }
+ free(tempname);
+ return fd;
+close:
+ close(fd);
+out:
+ free(tempname);
+ return -1;
+}
+
+#define TEMPNAME_TEMPLATE "/vm_file-XXXXXX"
+
+static int __init create_tmp_file(unsigned long long len)
+{
+ int fd, err;
+ char zero;
+
+ fd = make_tempfile(TEMPNAME_TEMPLATE);
+ if (fd < 0)
+ exit(1);
+
+ /*
+ * Seek to len - 1 because writing a character there will
+ * increase the file size by one byte, to the desired length.
+ */
+ if (lseek64(fd, len - 1, SEEK_SET) < 0) {
+ perror("lseek64");
+ exit(1);
+ }
+
+ zero = 0;
+
+ err = write(fd, &zero, 1);
+ if (err != 1) {
+ perror("write");
+ exit(1);
+ }
+
+ return fd;
+}
+
+int __init create_mem_file(unsigned long long len)
+{
+ int err, fd;
+
+ fd = create_tmp_file(len);
+
+ err = os_set_exec_close(fd);
+ if (err < 0) {
+ errno = -err;
+ perror("exec_close");
+ }
+ return fd;
+}
+
+void __init check_tmpexec(void)
+{
+ void *addr;
+ int err, fd = create_tmp_file(UM_KERN_PAGE_SIZE);
+
+ addr = mmap(NULL, UM_KERN_PAGE_SIZE,
+ PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE, fd, 0);
+ os_info("Checking PROT_EXEC mmap in %s...", tempdir);
+ if (addr == MAP_FAILED) {
+ err = errno;
+ os_warn("%s\n", strerror(err));
+ close(fd);
+ if (err == EPERM)
+ os_warn("%s must be not mounted noexec\n", tempdir);
+ exit(1);
+ }
+ os_info("OK\n");
+ munmap(addr, UM_KERN_PAGE_SIZE);
+
+ close(fd);
+}