v4.19.13 snapshot.
diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
new file mode 100644
index 0000000..b783ac8
--- /dev/null
+++ b/arch/um/kernel/skas/syscall.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/kernel.h>
+#include <linux/ptrace.h>
+#include <linux/seccomp.h>
+#include <kern_util.h>
+#include <sysdep/ptrace.h>
+#include <sysdep/ptrace_user.h>
+#include <sysdep/syscalls.h>
+
+void handle_syscall(struct uml_pt_regs *r)
+{
+ struct pt_regs *regs = container_of(r, struct pt_regs, regs);
+ int syscall;
+
+ /* Initialize the syscall number and default return value. */
+ UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
+ PT_REGS_SET_SYSCALL_RETURN(regs, -ENOSYS);
+
+ if (syscall_trace_enter(regs))
+ goto out;
+
+ /* Do the seccomp check after ptrace; failures should be fast. */
+ if (secure_computing(NULL) == -1)
+ goto out;
+
+ syscall = UPT_SYSCALL_NR(r);
+ if (syscall >= 0 && syscall <= __NR_syscall_max)
+ PT_REGS_SET_SYSCALL_RETURN(regs,
+ EXECUTE_SYSCALL(syscall, regs));
+
+out:
+ syscall_trace_leave(regs);
+}