1 files changed, 210 insertions, 0 deletions
diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
new file mode 100644
index 000000000..3c1b77474
--- /dev/null
+++ b/arch/um/os-Linux/mem.c
@@ -0,0 +1,210 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ */
+
+#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);
+}