Revert of Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/system_headers/android_i386_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_I386_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_I386_UCONTEXT_H_
+
+// We do something compatible with glibc. Hopefully, at some point Android will
+// provide that for us, and __BIONIC_HAVE_UCONTEXT_T should be defined.
+// This is mostly copied from breakpad (common/android/include/sys/ucontext.h),
+// except we do use sigset_t for uc_sigmask instead of a custom type.
+
+#if !defined(__BIONIC_HAVE_UCONTEXT_T)
+#include <asm/sigcontext.h>
+
+/* 80-bit floating-point register */
+struct _libc_fpreg {
+  unsigned short significand[4];
+  unsigned short exponent;
+};
+
+/* Simple floating-point state, see FNSTENV instruction */
+struct _libc_fpstate {
+  unsigned long cw;
+  unsigned long sw;
+  unsigned long tag;
+  unsigned long ipoff;
+  unsigned long cssel;
+  unsigned long dataoff;
+  unsigned long datasel;
+  struct _libc_fpreg _st[8];
+  unsigned long status;
+};
+
+typedef uint32_t greg_t;
+
+typedef struct {
+  uint32_t gregs[19];
+  struct _libc_fpstate* fpregs;
+  uint32_t oldmask;
+  uint32_t cr2;
+} mcontext_t;
+
+enum {
+  REG_GS = 0,
+  REG_FS,
+  REG_ES,
+  REG_DS,
+  REG_EDI,
+  REG_ESI,
+  REG_EBP,
+  REG_ESP,
+  REG_EBX,
+  REG_EDX,
+  REG_ECX,
+  REG_EAX,
+  REG_TRAPNO,
+  REG_ERR,
+  REG_EIP,
+  REG_CS,
+  REG_EFL,
+  REG_UESP,
+  REG_SS,
+};
+
+typedef struct ucontext {
+  uint32_t uc_flags;
+  struct ucontext* uc_link;
+  stack_t uc_stack;
+  mcontext_t uc_mcontext;
+  sigset_t uc_sigmask;
+  struct _libc_fpstate __fpregs_mem;
+} ucontext_t;
+
+#else
+#include <sys/ucontext.h>
+#endif  // __BIONIC_HAVE_UCONTEXT_T
+
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_I386_UCONTEXT_H_