Introduce sys_sigprocmask and sys_sigaction.

This is preparation of nacl_helper_nonsfi's secompbpf sandbox
implementation.
PNaCl toolchain's signal ABI is incompatible with Linux's.
For example, the length of sigset_t is shoter than Linux's.
(Android has also same problem).
siginfo_t has different memory layout.
Some signal numbers, including SIGBUS, SIGCHLD and SIGSYS,
or some signal flags are different.
This CL fills the gap, by introducing linux_signal.h and
two syscalls, sys_sigprocmask and sys_sigaction.

Also, as signal.h provides ucontext_t, but PNaCl toolchain
does not provides ucontext_t, this CL re-use the
android_ucontext.h (by renaming it to linux_ucontext.h).

TEST=Ran bots.
BUG=358465
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:linux_chromium_trusty32_rel,linux_arm

Review URL: https://codereview.chromium.org/1077143002

Cr-Commit-Position: refs/heads/master@{#325634}

19 files changed, 319 insertions, 112 deletions

diff --git a/sandbox/linux/BUILD.gn b/sandbox/linux/BUILD.gn
index 21f856b..c42520e 100644
--- a/sandbox/linux/BUILD.gn
+++ b/sandbox/linux/BUILD.gn
@@ -288,15 +288,16 @@ component("sandbox_services") {
 
 source_set("sandbox_services_headers") {
   sources = [
-    "system_headers/android_arm64_ucontext.h",
-    "system_headers/android_arm_ucontext.h",
-    "system_headers/android_i386_ucontext.h",
-    "system_headers/android_ucontext.h",
     "system_headers/arm64_linux_syscalls.h",
+    "system_headers/arm64_linux_ucontext.h",
     "system_headers/arm_linux_syscalls.h",
+    "system_headers/arm_linux_ucontext.h",
+    "system_headers/i386_linux_ucontext.h",
     "system_headers/linux_futex.h",
     "system_headers/linux_seccomp.h",
+    "system_headers/linux_signal.h",
     "system_headers/linux_syscalls.h",
+    "system_headers/linux_ucontext.h",
     "system_headers/x86_32_linux_syscalls.h",
     "system_headers/x86_64_linux_syscalls.h",
   ]
diff --git a/sandbox/linux/sandbox_linux.gypi b/sandbox/linux/sandbox_linux.gypi
index 1cf3b2d..7724223 100644
--- a/sandbox/linux/sandbox_linux.gypi
+++ b/sandbox/linux/sandbox_linux.gypi
@@ -278,18 +278,18 @@
     { 'target_name': 'sandbox_services_headers',
       'type': 'none',
       'sources': [
-        'system_headers/android_arm64_ucontext.h',
-        'system_headers/android_arm_ucontext.h',
-        'system_headers/android_i386_ucontext.h',
-        'system_headers/android_mips_ucontext.h',
-        'system_headers/android_ucontext.h',
         'system_headers/arm64_linux_syscalls.h',
+        'system_headers/arm64_linux_ucontext.h',
         'system_headers/arm_linux_syscalls.h',
+        'system_headers/arm_linux_ucontext.h',
         'system_headers/capability.h',
+        'system_headers/i386_linux_ucontext.h',
         'system_headers/linux_futex.h',
         'system_headers/linux_seccomp.h',
         'system_headers/linux_syscalls.h',
+        'system_headers/linux_ucontext.h',
         'system_headers/mips_linux_syscalls.h',
+        'system_headers/mips_linux_ucontext.h',
         'system_headers/x86_32_linux_syscalls.h',
         'system_headers/x86_64_linux_syscalls.h',
       ],
diff --git a/sandbox/linux/seccomp-bpf/die.cc b/sandbox/linux/seccomp-bpf/die.cc
index 777c9d1..3baf1f1 100644
--- a/sandbox/linux/seccomp-bpf/die.cc
+++ b/sandbox/linux/seccomp-bpf/die.cc
@@ -16,6 +16,8 @@
 #include "base/logging.h"
 #include "base/posix/eintr_wrapper.h"
 #include "sandbox/linux/seccomp-bpf/syscall.h"
+#include "sandbox/linux/services/syscall_wrappers.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 
 namespace sandbox {
 
@@ -32,7 +34,10 @@ void Die::ExitGroup() {
   // to a defined state; but we have not way to verify whether we actually
   // succeeded in doing so. Nonetheless, triggering a fatal signal could help
   // us terminate.
-  signal(SIGSEGV, SIG_DFL);
+  struct sigaction sa = {};
+  sa.sa_handler = LINUX_SIG_DFL;
+  sa.sa_flags = LINUX_SA_RESTART;
+  sys_sigaction(LINUX_SIGSEGV, &sa, nullptr);
   Syscall::Call(__NR_prctl, PR_SET_DUMPABLE, (void*)0, (void*)0, (void*)0);
   if (*(volatile char*)0) {
   }
diff --git a/sandbox/linux/seccomp-bpf/syscall.h b/sandbox/linux/seccomp-bpf/syscall.h
index dfb44eb..ccfc88d 100644
--- a/sandbox/linux/seccomp-bpf/syscall.h
+++ b/sandbox/linux/seccomp-bpf/syscall.h
@@ -9,13 +9,9 @@
 #include <stdint.h>
 
 #include "base/macros.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/sandbox_export.h"
 
-// Android's signal.h doesn't define ucontext etc.
-#if defined(OS_ANDROID)
-#include "sandbox/linux/system_headers/android_ucontext.h"
-#endif
-
 namespace sandbox {
 
 // This purely static class can be used to perform system calls with some
diff --git a/sandbox/linux/seccomp-bpf/trap.cc b/sandbox/linux/seccomp-bpf/trap.cc
index 145e624..79b7569 100644
--- a/sandbox/linux/seccomp-bpf/trap.cc
+++ b/sandbox/linux/seccomp-bpf/trap.cc
@@ -17,12 +17,9 @@
 #include "sandbox/linux/bpf_dsl/seccomp_macros.h"
 #include "sandbox/linux/seccomp-bpf/die.h"
 #include "sandbox/linux/seccomp-bpf/syscall.h"
+#include "sandbox/linux/services/syscall_wrappers.h"
 #include "sandbox/linux/system_headers/linux_seccomp.h"
-
-// Android's signal.h doesn't define ucontext etc.
-#if defined(OS_ANDROID)
-#include "sandbox/linux/system_headers/android_ucontext.h"
-#endif
+#include "sandbox/linux/system_headers/linux_signal.h"
 
 namespace {
 
@@ -53,13 +50,13 @@ const char kSandboxDebuggingEnv[] = "CHROME_SANDBOX_DEBUGGING";
 // possibly even worse.
 bool GetIsInSigHandler(const ucontext_t* ctx) {
   // Note: on Android, sigismember does not take a pointer to const.
-  return sigismember(const_cast<sigset_t*>(&ctx->uc_sigmask), SIGBUS);
+  return sigismember(const_cast<sigset_t*>(&ctx->uc_sigmask), LINUX_SIGBUS);
 }
 
 void SetIsInSigHandler() {
   sigset_t mask;
-  if (sigemptyset(&mask) || sigaddset(&mask, SIGBUS) ||
-      sigprocmask(SIG_BLOCK, &mask, NULL)) {
+  if (sigemptyset(&mask) || sigaddset(&mask, LINUX_SIGBUS) ||
+      sandbox::sys_sigprocmask(LINUX_SIG_BLOCK, &mask, NULL)) {
     SANDBOX_DIE("Failed to block SIGBUS");
   }
 }
@@ -82,10 +79,13 @@ Trap::Trap()
       has_unsafe_traps_(false) {
   // Set new SIGSYS handler
   struct sigaction sa = {};
-  sa.sa_sigaction = SigSysAction;
-  sa.sa_flags = SA_SIGINFO | SA_NODEFER;
-  struct sigaction old_sa;
-  if (sigaction(SIGSYS, &sa, &old_sa) < 0) {
+  // In some toolchain, sa_sigaction is not declared in struct sigaction.
+  // So, here cast the pointer to the sa_handler's type. This works because
+  // |sa_handler| and |sa_sigaction| shares the same memory.
+  sa.sa_handler = reinterpret_cast<void (*)(int)>(SigSysAction);
+  sa.sa_flags = LINUX_SA_SIGINFO | LINUX_SA_NODEFER;
+  struct sigaction old_sa = {};
+  if (sys_sigaction(LINUX_SIGSYS, &sa, &old_sa) < 0) {
     SANDBOX_DIE("Failed to configure SIGSYS handler");
   }
 
@@ -99,8 +99,8 @@ Trap::Trap()
 
   // Unmask SIGSYS
   sigset_t mask;
-  if (sigemptyset(&mask) || sigaddset(&mask, SIGSYS) ||
-      sigprocmask(SIG_UNBLOCK, &mask, NULL)) {
+  if (sigemptyset(&mask) || sigaddset(&mask, LINUX_SIGSYS) ||
+      sys_sigprocmask(LINUX_SIG_UNBLOCK, &mask, NULL)) {
     SANDBOX_DIE("Failed to configure SIGSYS handler");
   }
 }
@@ -120,7 +120,7 @@ bpf_dsl::TrapRegistry* Trap::Registry() {
   return global_trap_;
 }
 
-void Trap::SigSysAction(int nr, siginfo_t* info, void* void_context) {
+void Trap::SigSysAction(int nr, LinuxSigInfo* info, void* void_context) {
   if (!global_trap_) {
     RAW_SANDBOX_DIE(
         "This can't happen. Found no global singleton instance "
@@ -129,7 +129,7 @@ void Trap::SigSysAction(int nr, siginfo_t* info, void* void_context) {
   global_trap_->SigSys(nr, info, void_context);
 }
 
-void Trap::SigSys(int nr, siginfo_t* info, void* void_context) {
+void Trap::SigSys(int nr, LinuxSigInfo* info, void* void_context) {
   // Signal handlers should always preserve "errno". Otherwise, we could
   // trigger really subtle bugs.
   const int old_errno = errno;
@@ -137,7 +137,7 @@ void Trap::SigSys(int nr, siginfo_t* info, void* void_context) {
   // Various sanity checks to make sure we actually received a signal
   // triggered by a BPF filter. If something else triggered SIGSYS
   // (e.g. kill()), there is really nothing we can do with this signal.
-  if (nr != SIGSYS || info->si_code != SYS_SECCOMP || !void_context ||
+  if (nr != LINUX_SIGSYS || info->si_code != SYS_SECCOMP || !void_context ||
       info->si_errno <= 0 ||
       static_cast<size_t>(info->si_errno) > trap_array_size_) {
     // ATI drivers seem to send SIGSYS, so this cannot be FATAL.
diff --git a/sandbox/linux/seccomp-bpf/trap.h b/sandbox/linux/seccomp-bpf/trap.h
index 4073bfe..bbddeb7 100644
--- a/sandbox/linux/seccomp-bpf/trap.h
+++ b/sandbox/linux/seccomp-bpf/trap.h
@@ -5,13 +5,13 @@
 #ifndef SANDBOX_LINUX_SECCOMP_BPF_TRAP_H__
 #define SANDBOX_LINUX_SECCOMP_BPF_TRAP_H__
 
-#include <signal.h>
 #include <stdint.h>
 
 #include <map>
 
 #include "base/macros.h"
 #include "sandbox/linux/bpf_dsl/trap_registry.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/sandbox_export.h"
 
 namespace sandbox {
@@ -57,11 +57,11 @@ class SANDBOX_EXPORT Trap : public bpf_dsl::TrapRegistry {
   // break subsequent system calls that trigger a SIGSYS.
   ~Trap() = delete;
 
-  static void SigSysAction(int nr, siginfo_t* info, void* void_context);
+  static void SigSysAction(int nr, LinuxSigInfo* info, void* void_context);
 
   // Make sure that SigSys is not inlined in order to get slightly better crash
   // dumps.
-  void SigSys(int nr, siginfo_t* info, void* void_context)
+  void SigSys(int nr, LinuxSigInfo* info, void* void_context)
       __attribute__((noinline));
   // We have a global singleton that handles all of our SIGSYS traps. This
   // variable must never be deallocated after it has been set up initially, as
diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index 475ce3f..883e396 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -27,16 +27,12 @@
 #include "sandbox/linux/services/syscall_wrappers.h"
 #include "sandbox/linux/services/thread_helpers.h"
 #include "sandbox/linux/system_headers/capability.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 
 namespace sandbox {
 
 namespace {
 
-// Signal ABI for some toolchain is incompatible with Linux's. In particular,
-// PNaCl toolchain defines SIGCHLD = 20. So, here, directly define Linux's
-// value.
-const int kLinuxSIGCHLD = 17;
-
 bool IsRunningOnValgrind() { return RUNNING_ON_VALGRIND; }
 
 // Checks that the set of RES-uids and the set of RES-gids have
@@ -96,8 +92,8 @@ bool ChrootToSafeEmptyDir() {
 #endif
 
   pid = clone(ChrootToSelfFdinfo, stack,
-              CLONE_VM | CLONE_VFORK | CLONE_FS | kLinuxSIGCHLD,
-              nullptr, nullptr, nullptr, nullptr);
+              CLONE_VM | CLONE_VFORK | CLONE_FS | LINUX_SIGCHLD, nullptr,
+              nullptr, nullptr, nullptr);
   PCHECK(pid != -1);
 
   int status = -1;
diff --git a/sandbox/linux/services/syscall_wrappers.cc b/sandbox/linux/services/syscall_wrappers.cc
index e793fad..0366051 100644
--- a/sandbox/linux/services/syscall_wrappers.cc
+++ b/sandbox/linux/services/syscall_wrappers.cc
@@ -12,12 +12,14 @@
 #include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <cstring>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/third_party/valgrind/valgrind.h"
 #include "build/build_config.h"
 #include "sandbox/linux/system_headers/capability.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/linux/system_headers/linux_syscalls.h"
 
 namespace sandbox {
@@ -137,4 +139,63 @@ int sys_unshare(int flags) {
   return syscall(__NR_unshare, flags);
 }
 
+int sys_sigprocmask(int how, const sigset_t* set, decltype(nullptr) oldset) {
+  // In some toolchain (in particular Android and PNaCl toolchain),
+  // sigset_t is 32 bits, but Linux ABI requires 64 bits.
+  uint64_t linux_value = 0;
+  std::memcpy(&linux_value, set, std::min(sizeof(sigset_t), sizeof(uint64_t)));
+  return syscall(__NR_rt_sigprocmask, how, &linux_value, nullptr,
+                 sizeof(linux_value));
+}
+
+// struct sigaction is different ABI from the Linux's.
+struct KernelSigAction {
+  void (*kernel_handler)(int);
+  uint32_t sa_flags;
+  void (*sa_restorer)(void);
+  uint64_t sa_mask;
+};
+
+// On X86_64 arch, it is necessary to set sa_restorer always.
+#if defined(ARCH_CPU_X86_64)
+#if !defined(SA_RESTORER)
+#define SA_RESTORER 0x04000000
+#endif
+
+static void sys_rt_sigreturn() {
+  syscall(__NR_rt_sigreturn);
+}
+#endif
+
+int sys_sigaction(int signum,
+                  const struct sigaction* act,
+                  struct sigaction* oldact) {
+  KernelSigAction kernel_act = {};
+  if (act) {
+    kernel_act.kernel_handler = act->sa_handler;
+    std::memcpy(&kernel_act.sa_mask, &act->sa_mask,
+                std::min(sizeof(kernel_act.sa_mask), sizeof(act->sa_mask)));
+    kernel_act.sa_flags = act->sa_flags;
+
+#if defined(ARCH_CPU_X86_64)
+    if (!(kernel_act.sa_flags & SA_RESTORER)) {
+      kernel_act.sa_flags |= SA_RESTORER;
+      kernel_act.sa_restorer = sys_rt_sigreturn;
+    }
+#endif
+  }
+
+  KernelSigAction kernel_oldact = {};
+  int result = syscall(__NR_rt_sigaction, signum, act ? &kernel_act : nullptr,
+                       oldact ? &kernel_oldact : nullptr, sizeof(uint64_t));
+  if (result == 0 && oldact) {
+    oldact->sa_handler = kernel_oldact.kernel_handler;
+    sigemptyset(&oldact->sa_mask);
+    std::memcpy(&oldact->sa_mask, &kernel_oldact.sa_mask,
+                std::min(sizeof(kernel_act.sa_mask), sizeof(act->sa_mask)));
+    oldact->sa_flags = kernel_oldact.sa_flags;
+  }
+  return result;
+}
+
 }  // namespace sandbox
diff --git a/sandbox/linux/services/syscall_wrappers.h b/sandbox/linux/services/syscall_wrappers.h
index 4558adf..581425a 100644
--- a/sandbox/linux/services/syscall_wrappers.h
+++ b/sandbox/linux/services/syscall_wrappers.h
@@ -5,6 +5,7 @@
 #ifndef SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
 #define SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
 
+#include <signal.h>
 #include <stdint.h>
 #include <sys/types.h>
 
@@ -66,6 +67,17 @@ SANDBOX_EXPORT int sys_chroot(const char* path);
 // Some libcs do not expose a unshare wrapper.
 SANDBOX_EXPORT int sys_unshare(int flags);
 
+// Some libcs do not expose a sigprocmask. Note that oldset must be a nullptr,
+// because of some ABI gap between toolchain's and Linux's.
+SANDBOX_EXPORT int sys_sigprocmask(int how,
+                                   const sigset_t* set,
+                                   decltype(nullptr) oldset);
+
+// Some libcs do not expose a sigaction().
+SANDBOX_EXPORT int sys_sigaction(int signum,
+                                 const struct sigaction* act,
+                                 struct sigaction* oldact);
+
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_SYSCALL_WRAPPERS_H_
diff --git a/sandbox/linux/services/syscall_wrappers_unittest.cc b/sandbox/linux/services/syscall_wrappers_unittest.cc
index 6a70beb..1878ff3 100644
--- a/sandbox/linux/services/syscall_wrappers_unittest.cc
+++ b/sandbox/linux/services/syscall_wrappers_unittest.cc
@@ -8,11 +8,13 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
+#include <cstring>
 
 #include "base/logging.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/third_party/valgrind/valgrind.h"
 #include "build/build_config.h"
+#include "sandbox/linux/system_headers/linux_signal.h"
 #include "sandbox/linux/tests/test_utils.h"
 #include "sandbox/linux/tests/unit_tests.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -80,6 +82,18 @@ TEST(SyscallWrappers, GetRESGid) {
   EXPECT_EQ(sgid, sys_sgid);
 }
 
+TEST(SyscallWrappers, LinuxSigSet) {
+  sigset_t sigset;
+  ASSERT_EQ(0, sigemptyset(&sigset));
+  ASSERT_EQ(0, sigaddset(&sigset, LINUX_SIGSEGV));
+  ASSERT_EQ(0, sigaddset(&sigset, LINUX_SIGBUS));
+  uint64_t linux_sigset = 0;
+  std::memcpy(&linux_sigset, &sigset,
+              std::min(sizeof(sigset), sizeof(linux_sigset)));
+  EXPECT_EQ((1ULL << (LINUX_SIGSEGV - 1)) | (1ULL << (LINUX_SIGBUS - 1)),
+            linux_sigset);
+}
+
 }  // namespace
 
 }  // namespace sandbox
diff --git a/sandbox/linux/system_headers/android_arm_ucontext.h b/sandbox/linux/system_headers/android_arm_ucontext.h
deleted file mode 100644
index a380499..0000000
--- a/sandbox/linux/system_headers/android_arm_ucontext.h
+++ /dev/null
@@ -1,32 +0,0 @@
-// 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_
diff --git a/sandbox/linux/system_headers/android_ucontext.h b/sandbox/linux/system_headers/android_ucontext.h
deleted file mode 100644
index 8e873be..0000000
--- a/sandbox/linux/system_headers/android_ucontext.h
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright (c) 2013 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_UCONTEXT_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_UCONTEXT_H_
-
-#if defined(__ANDROID__)
-
-#if defined(__arm__)
-#include "sandbox/linux/system_headers/android_arm_ucontext.h"
-#elif defined(__i386__)
-#include "sandbox/linux/system_headers/android_i386_ucontext.h"
-#elif defined(__x86_64__)
-#include "sandbox/linux/system_headers/android_x86_64_ucontext.h"
-#elif defined(__mips__)
-#include "sandbox/linux/system_headers/android_mips_ucontext.h"
-#elif defined(__aarch64__)
-#include "sandbox/linux/system_headers/android_arm64_ucontext.h"
-#else
-#error "No support for your architecture in Android header"
-#endif
-
-#else  // __ANDROID__
-#error "Android header file included on non Android."
-#endif  // __ANDROID__
-
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_UCONTEXT_H_
diff --git a/sandbox/linux/system_headers/android_arm64_ucontext.h b/sandbox/linux/system_headers/arm64_linux_ucontext.h
index df2b66a..46e0407 100644
--- a/sandbox/linux/system_headers/android_arm64_ucontext.h
+++ b/sandbox/linux/system_headers/arm64_linux_ucontext.h
@@ -2,8 +2,8 @@
 // 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_ARM64_UCONTEXT_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM64_UCONTEXT_H_
+#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_ARM64_LINUX_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_ARM64_LINUX_UCONTEXT_H_
 
 #if !defined(__BIONIC_HAVE_UCONTEXT_T)
 #include <asm/sigcontext.h>
@@ -26,4 +26,4 @@ struct ucontext_t {
 #include <sys/ucontext.h>
 #endif  // __BIONIC_HAVE_UCONTEXT_T
 
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_ARM64_UCONTEXT_H_
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ARM64_LINUX_UCONTEXT_H_
diff --git a/sandbox/linux/system_headers/arm_linux_ucontext.h b/sandbox/linux/system_headers/arm_linux_ucontext.h
new file mode 100644
index 0000000..0eb723a
--- /dev/null
+++ b/sandbox/linux/system_headers/arm_linux_ucontext.h
@@ -0,0 +1,67 @@
+// 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_ARM_LINUX_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_ARM_LINUX_UCONTEXT_H_
+
+#if !defined(__BIONIC_HAVE_UCONTEXT_T)
+#if !defined(__native_client_nonsfi__)
+#include <asm/sigcontext.h>
+#else
+// In PNaCl toolchain, sigcontext and stack_t is not defined. So here declare
+// them.
+struct sigcontext {
+  unsigned long trap_no;
+  unsigned long error_code;
+  unsigned long oldmask;
+  unsigned long arm_r0;
+  unsigned long arm_r1;
+  unsigned long arm_r2;
+  unsigned long arm_r3;
+  unsigned long arm_r4;
+  unsigned long arm_r5;
+  unsigned long arm_r6;
+  unsigned long arm_r7;
+  unsigned long arm_r8;
+  unsigned long arm_r9;
+  unsigned long arm_r10;
+  unsigned long arm_fp;
+  unsigned long arm_ip;
+  unsigned long arm_sp;
+  unsigned long arm_lr;
+  unsigned long arm_pc;
+  unsigned long arm_cpsr;
+  unsigned long fault_address;
+};
+
+typedef struct sigaltstack {
+  void* ss_sp;
+  int ss_flags;
+  size_t ss_size;
+} stack_t;
+
+#endif
+
+// 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_ARM_LINUX_UCONTEXT_H_
diff --git a/sandbox/linux/system_headers/android_i386_ucontext.h b/sandbox/linux/system_headers/i386_linux_ucontext.h
index 868016b..61d9f7a 100644
--- a/sandbox/linux/system_headers/android_i386_ucontext.h
+++ b/sandbox/linux/system_headers/i386_linux_ucontext.h
@@ -11,7 +11,16 @@
 // 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 {
@@ -68,7 +77,12 @@ typedef struct ucontext {
   struct ucontext* uc_link;
   stack_t uc_stack;
   mcontext_t uc_mcontext;
-  sigset_t uc_sigmask;
+  // 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;
 
diff --git a/sandbox/linux/system_headers/linux_signal.h b/sandbox/linux/system_headers/linux_signal.h
new file mode 100644
index 0000000..5db7fc5
--- /dev/null
+++ b/sandbox/linux/system_headers/linux_signal.h
@@ -0,0 +1,73 @@
+// 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
+// (not undefined, but defined different values and in different memory
+// layouts). So, fill the gap here.
+
+#if defined(__native_client_nonsfi__)
+#if !defined(__i386__) && !defined(__arm__)
+#error "Unsupported platform"
+#endif
+
+#include <signal.h>
+
+#define LINUX_SIGBUS 7    // 10 in PNaCl toolchain.
+#define LINUX_SIGSEGV 11  // 11 in PNaCl toolchain. Defined for consistency.
+#define LINUX_SIGCHLD 17  // 20 in PNaCl toolchain.
+#define LINUX_SIGSYS 31   // 12 in PNaCl toolchain.
+
+#define LINUX_SIG_BLOCK 0    // 1 in PNaCl toolchain.
+#define LINUX_SIG_UNBLOCK 1  // 2 in PNaCl toolchain.
+
+#define LINUX_SA_SIGINFO 4           // 2 in PNaCl toolchain.
+#define LINUX_SA_NODEFER 0x40000000  // Undefined in PNaCl toolchain.
+#define LINUX_SA_RESTART 0x10000000  // Undefined in PNaCl toolchain.
+
+#define LINUX_SIG_DFL 0  // In PNaCl toolchain, unneeded cast is applied.
+
+struct LinuxSigInfo {
+  int si_signo;
+  int si_errno;
+  int si_code;
+
+  // Extra data is followed by the |si_code|. The length depends on the
+  // signal number.
+  char _sifields[1];
+};
+
+#include "sandbox/linux/system_headers/linux_ucontext.h"
+
+#else  // !defined(__native_client_nonsfi__)
+
+// Just alias the toolchain's value.
+#include <signal.h>
+
+#define LINUX_SIGBUS SIGBUS
+#define LINUX_SIGSEGV SIGSEGV
+#define LINUX_SIGCHLD SIGCHLD
+#define LINUX_SIGSYS SIGSYS
+
+#define LINUX_SIG_BLOCK SIG_BLOCK
+#define LINUX_SIG_UNBLOCK SIG_UNBLOCK
+
+#define LINUX_SA_SIGINFO SA_SIGINFO
+#define LINUX_SA_NODEFER SA_NODEFER
+#define LINUX_SA_RESTART SA_RESTART
+
+#define LINUX_SIG_DFL SIG_DFL
+
+typedef siginfo_t LinuxSigInfo;
+
+#if defined(__ANDROID__)
+// Android's signal.h doesn't define ucontext etc.
+#include "sandbox/linux/system_headers/linux_ucontext.h"
+#endif  // defined(__ANDROID__)
+
+#endif  // !defined(__native_client_nonsfi__)
+
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_SIGNAL_H_
diff --git a/sandbox/linux/system_headers/linux_ucontext.h b/sandbox/linux/system_headers/linux_ucontext.h
new file mode 100644
index 0000000..ea4d8a6
--- /dev/null
+++ b/sandbox/linux/system_headers/linux_ucontext.h
@@ -0,0 +1,28 @@
+// Copyright (c) 2013 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_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_UCONTEXT_H_
+
+#if defined(__ANDROID__) || defined(__native_client_nonsfi__)
+
+#if defined(__arm__)
+#include "sandbox/linux/system_headers/arm_linux_ucontext.h"
+#elif defined(__i386__)
+#include "sandbox/linux/system_headers/i386_linux_ucontext.h"
+#elif defined(__x86_64__)
+#include "sandbox/linux/system_headers/x86_64_linux_ucontext.h"
+#elif defined(__mips__)
+#include "sandbox/linux/system_headers/mips_linux_ucontext.h"
+#elif defined(__aarch64__)
+#include "sandbox/linux/system_headers/arm64_linux_ucontext.h"
+#else
+#error "No support for your architecture in Android or PNaCl header"
+#endif
+
+#else  // defined(__ANDROID__) || defined(__native_client_nonsfi__)
+#error "The header file included on non Android and non PNaCl."
+#endif  // defined(__ANDROID__) || defined(__native_client_nonsfi__)
+
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_UCONTEXT_H_
diff --git a/sandbox/linux/system_headers/android_mips_ucontext.h b/sandbox/linux/system_headers/mips_linux_ucontext.h
index ec3aa63..27b3763 100644
--- a/sandbox/linux/system_headers/android_mips_ucontext.h
+++ b/sandbox/linux/system_headers/mips_linux_ucontext.h
@@ -2,8 +2,8 @@
 // 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_MIPS_UCONTEXT_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_MIPS_UCONTEXT_H_
+#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_MIPS_LINUX_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_MIPS_LINUX_UCONTEXT_H_
 
 // 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.
@@ -48,4 +48,4 @@ typedef struct ucontext {
 #include <sys/ucontext.h>
 #endif  // __BIONIC_HAVE_UCONTEXT_T
 
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_MIPS_UCONTEXT_H_
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_MIPS_LINUX_UCONTEXT_H_
diff --git a/sandbox/linux/system_headers/android_x86_64_ucontext.h b/sandbox/linux/system_headers/x86_64_linux_ucontext.h
index 778e6d0..57b8919 100644
--- a/sandbox/linux/system_headers/android_x86_64_ucontext.h
+++ b/sandbox/linux/system_headers/x86_64_linux_ucontext.h
@@ -2,8 +2,8 @@
 // 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_X86_64_UCONTEXT_H_
-#define SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_X86_64_UCONTEXT_H_
+#ifndef SANDBOX_LINUX_SYSTEM_HEADERS_X86_64_LINUX_UCONTEXT_H_
+#define SANDBOX_LINUX_SYSTEM_HEADERS_X86_64_LINUX_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.
@@ -85,4 +85,4 @@ typedef struct ucontext {
 #include <sys/ucontext.h>
 #endif  // __BIONIC_HAVE_UCONTEXT_T
 
-#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_ANDROID_X86_64_UCONTEXT_H_
+#endif  // SANDBOX_LINUX_SYSTEM_HEADERS_X86_64_LINUX_UCONTEXT_H_