Added support for greylisting of system calls.

sandbox/linux/seccomp-bpf/syscall.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__
+#define SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__
+
+#include <signal.h>
+#include <stdint.h>
+
+namespace playground2 {
+
+// We have to make sure that we have a single "magic" return address for
+// our system calls, which we can check from within a BPF filter. This
+// works by writing a little bit of asm() code that a) enters the kernel, and
+// that also b) can be invoked in a way that computes this return address.
+// Passing "nr" as "-1" computes the "magic" return address. Passing any
+// other value invokes the appropriate system call.
+intptr_t SandboxSyscall(int nr, ...);
+
+}  // namespace
+
+#endif  // SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__