v4.19.13 snapshot.
diff --git a/arch/um/kernel/exitcode.c b/arch/um/kernel/exitcode.c
new file mode 100644
index 0000000..546302e
--- /dev/null
+++ b/arch/um/kernel/exitcode.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+
+/*
+ * If read and write race, the read will still atomically read a valid
+ * value.
+ */
+int uml_exitcode = 0;
+
+static int exitcode_proc_show(struct seq_file *m, void *v)
+{
+ int val;
+
+ /*
+ * Save uml_exitcode in a local so that we don't need to guarantee
+ * that sprintf accesses it atomically.
+ */
+ val = uml_exitcode;
+ seq_printf(m, "%d\n", val);
+ return 0;
+}
+
+static int exitcode_proc_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, exitcode_proc_show, NULL);
+}
+
+static ssize_t exitcode_proc_write(struct file *file,
+ const char __user *buffer, size_t count, loff_t *pos)
+{
+ char *end, buf[sizeof("nnnnn\0")];
+ size_t size;
+ int tmp;
+
+ size = min(count, sizeof(buf));
+ if (copy_from_user(buf, buffer, size))
+ return -EFAULT;
+
+ tmp = simple_strtol(buf, &end, 0);
+ if ((*end != '\0') && !isspace(*end))
+ return -EINVAL;
+
+ uml_exitcode = tmp;
+ return count;
+}
+
+static const struct file_operations exitcode_proc_fops = {
+ .owner = THIS_MODULE,
+ .open = exitcode_proc_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+ .write = exitcode_proc_write,
+};
+
+static int make_proc_exitcode(void)
+{
+ struct proc_dir_entry *ent;
+
+ ent = proc_create("exitcode", 0600, NULL, &exitcode_proc_fops);
+ if (ent == NULL) {
+ printk(KERN_WARNING "make_proc_exitcode : Failed to register "
+ "/proc/exitcode\n");
+ return 0;
+ }
+ return 0;
+}
+
+__initcall(make_proc_exitcode);