Revert of Reland: Introduce sys_sigprocmask and sys_sigaction.

sandbox/linux/system_headers/i386_linux_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)
-#if !defined(__native_client_nonsfi__)
-#include <asm/sigcontext.h>
-#else
-// In PNaCl toolchain, sigcontext is not defined. So here declare it.
-typedef struct sigaltstack {
-  void* ss_sp;
-  int ss_flags;
-  size_t ss_size;
-} stack_t;
-#endif
-
-/* 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;
-  // Android and PNaCl toolchain's sigset_t has only 32 bits, though Linux
-  // ABI requires 64 bits.
-  union {
-    sigset_t uc_sigmask;
-    uint32_t kernel_sigmask[2];
-  };
-  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_