WIP: Implement seccomp-bpf sandbox for nacl_helper_nonsfi.

sandbox/linux/system_headers/linux_signal.h

+// Copyright 2015 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_SYSTEM_HEADERS_LINUX_SIGNAL_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_SIGNAL_H_
+
+// NOTE: On some toolchains, signal related ABI is incompatible with Linux's.
+// So, here we declare necessary macros, structs and functions in Linux ABI.
+
+#include <stdint.h>
+
+#define LINUX_SIGBUS 7
+#define LINUX_SIGSYS 31
+
+#define LINUX_SIG_BLOCK 0
+#define LINUX_SIG_UNBLOCK 1
+
+#define LINUX_SA_SIGINFO 4
+#define LINUX_SA_NODEFER 0x40000000
+
+#define LINUX_SIG_DFL 0
+
+struct arch_sigsys {
+  void* ip;
+  int nr;
+  unsigned int arch;
+};
+
+typedef struct {
+  int si_signo;
+  int si_errno;
+  int si_code;
+  struct {
+    struct arch_sigsys _sigsys;
+  } _sifields;
+} linux_siginfo_t;
+
+// Linux sigset_t is 64 bits.
+typedef struct {
+  uint32_t sig[2];
+} linux_sigset_t;
+
+struct linux_sigaction {
+  // Traling '_' is to avoid name confliction defined by some toolchains.
+  union {
+    void (*sa_handler_)(int);
+    void (*sa_sigaction_)(int, linux_siginfo_t*, void*);
+  };
+  uint32_t sa_flags;
+  void (*sa_restorer)(void);
+  linux_sigset_t sa_mask;
+};
+
+#endif