Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/system_headers/android_arm_ucontext.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_SYSTEM_HEADERS_ANDROID_ARM_UCONTEXT_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM_UCONTEXT_H_
-
-#if !defined(__BIONIC_HAVE_UCONTEXT_T)
-#include <asm/sigcontext.h>
-
-// We also need greg_t for the sandbox, include it in this header as well.
-typedef unsigned long greg_t;
-
-//typedef unsigned long sigset_t;
-typedef struct ucontext {
-  unsigned long   uc_flags;
-  struct ucontext  *uc_link;
-  stack_t     uc_stack;
-  struct sigcontext uc_mcontext;
-  sigset_t    uc_sigmask;
-  /* Allow for uc_sigmask growth.  Glibc uses a 1024-bit sigset_t.  */
-  int     __not_used[32 - (sizeof (sigset_t) / sizeof (int))];
-  /* Last for extensibility.  Eight byte aligned because some
-     coprocessors require eight byte alignment.  */
-  unsigned long   uc_regspace[128] __attribute__((__aligned__(8)));
-} ucontext_t;
-
-#else
-#include <sys/ucontext.h>
-#endif  // __BIONIC_HAVE_UCONTEXT_T
-
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM_UCONTEXT_H_