v4.19.13 snapshot.
diff --git a/arch/um/kernel/initrd.c b/arch/um/kernel/initrd.c
new file mode 100644
index 0000000..6f6e789
--- /dev/null
+++ b/arch/um/kernel/initrd.c
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/initrd.h>
+#include <asm/types.h>
+#include <init.h>
+#include <os.h>
+
+/* Changed by uml_initrd_setup, which is a setup */
+static char *initrd __initdata = NULL;
+static int load_initrd(char *filename, void *buf, int size);
+
+int __init read_initrd(void)
+{
+ void *area;
+ long long size;
+ int err;
+
+ if (initrd == NULL)
+ return 0;
+
+ err = os_file_size(initrd, &size);
+ if (err)
+ return 0;
+
+ /*
+ * This is necessary because alloc_bootmem craps out if you
+ * ask for no memory.
+ */
+ if (size == 0) {
+ printk(KERN_ERR "\"%s\" is a zero-size initrd\n", initrd);
+ return 0;
+ }
+
+ area = alloc_bootmem(size);
+
+ if (load_initrd(initrd, area, size) == -1)
+ return 0;
+
+ initrd_start = (unsigned long) area;
+ initrd_end = initrd_start + size;
+ return 0;
+}
+
+static int __init uml_initrd_setup(char *line, int *add)
+{
+ initrd = line;
+ return 0;
+}
+
+__uml_setup("initrd=", uml_initrd_setup,
+"initrd=<initrd image>\n"
+" This is used to boot UML from an initrd image. The argument is the\n"
+" name of the file containing the image.\n\n"
+);
+
+static int load_initrd(char *filename, void *buf, int size)
+{
+ int fd, n;
+
+ fd = os_open_file(filename, of_read(OPENFLAGS()), 0);
+ if (fd < 0) {
+ printk(KERN_ERR "Opening '%s' failed - err = %d\n", filename,
+ -fd);
+ return -1;
+ }
+ n = os_read_file(fd, buf, size);
+ if (n != size) {
+ printk(KERN_ERR "Read of %d bytes from '%s' failed, "
+ "err = %d\n", size,
+ filename, -n);
+ return -1;
+ }
+
+ os_close_file(fd);
+ return 0;
+}