NonSFI NaCl: Plumb Exception IRT enough for breakpad.

components/nacl/loader/nonsfi/irt_exception_handling.cc

+// Copyright 2014 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.
+
+#include <errno.h>
+#include <signal.h>
+
+#include "base/atomicops.h"
+#include "components/nacl/loader/nonsfi/irt_interfaces.h"
+#include "native_client/src/include/nacl_macros.h"
+#include "native_client/src/trusted/service_runtime/nacl_exception.h"
+#include "native_client/src/trusted/service_runtime/nacl_signal.h"
+
+namespace nacl {
+namespace nonsfi {
+namespace {
+
+// This is NonSFI version of exception handling codebase, NaCl side of
+// things resides in:
+// native_client/src/trusted/service_runtime/linux/nacl_signal.c
+// native_client/src/trusted/service_runtime/sys_exception.c
+
+// Crash signals to handle.  The differences from SFI NaCl are that
+// NonSFI NaCl does not use NACL_THREAD_SUSPEND_SIGNAL (==SIGUSR1),
+// and SIGSYS is reserved for seccomp-bpf.
+static const int kSignals[] = {
+  SIGSTKFLT,
+  SIGINT, SIGQUIT, SIGILL, SIGTRAP, SIGBUS, SIGFPE, SIGSEGV,
+  // Handle SIGABRT in case someone sends it asynchronously using kill().
+  SIGABRT
+};
+
+volatile NaClExceptionHandler signal_handler_function_pointer = NULL;
+
+// Signal handler, responsible for calling the registered handlers.
+static void SignalCatch(int sig, siginfo_t* info, void* uc) {
+  if (signal_handler_function_pointer) {
+    NaClSignalContext signal_context;
+    NaClSignalContextFromHandler(&signal_context, uc);
+    NaClExceptionFrame exception_frame;
+    NaClSignalSetUpExceptionFrame(&exception_frame,
+                                  &signal_context,
+                                  0 /* context_user_addr,
+                                       not useful for NonSFI NaCl. */);
+    signal_handler_function_pointer(&exception_frame.context);
+  }
+  _exit(-1);
+}
+
+static int IrtExceptionHandler(NaClExceptionHandler handler,
+                               NaClExceptionHandler* old_handler) {
+  if (old_handler)
+    *old_handler = signal_handler_function_pointer;
+  signal_handler_function_pointer = handler;
+  return 0;
+}
+
+static int IrtExceptionStack(void* stack, size_t size) {
+  // TODO(uekawa): I think we shouldn't implement this until we really

[Mark Seaborn, 2014/04/24 23:39:27]

Can you state the TODO a bit more formally, please?

i.e. "Implement this function so that the exception stack actually gets used for
running an exception handler.  Currently we don't switch stack, which means we
can't handle stack overflow exceptions."

[Junichi Uekawa, 2014/04/25 01:06:10]

Done.

+  // need it.  IrtThreadCreate allocates sigaltstack already, and

[Mark Seaborn, 2014/04/24 23:39:27]

BTW, this part doesn't reflect the code currently.

[Junichi Uekawa, 2014/04/25 01:06:10]

Done.

+  // there is no legitimate reason I can think of that you would want
+  // to reallocate an altstack. Note that
+  // native_client/src/tests/exception_test/exception_crash_test.c
+  // wants to use this but we are not running that test yet. Instead
+  // of returning an error, ignore and succeed.
+  return 0;
+}
+
+static int IrtExceptionClearFlag(void) {
+  // TODO(uekawa): I think we shouldn't implement this until we really

[Mark Seaborn, 2014/04/24 23:39:27]

Ditto -- can you state it a bit more formally?  i.e. "Implement clear_flag() to
behave like SFI NaCl's implementation, so that a thread can handle a second
exception after handling a first exception"

[Junichi Uekawa, 2014/04/25 01:06:10]

Done.

+  // need it.
+  return -ENOSYS;
+}
+
+}  // namespace
+
+const struct nacl_irt_exception_handling kIrtExceptionHandling = {
+  IrtExceptionHandler,
+  IrtExceptionStack,
+  IrtExceptionClearFlag,
+};
+
+void InitializeSignalHandler() {
+  struct sigaction sa;
+  unsigned int a;
+
+  memset(&sa, 0, sizeof(sa));
+  sigemptyset(&sa.sa_mask);
+  sa.sa_sigaction = SignalCatch;
+  sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
+
+  // Mask all signals we catch to prevent re-entry.
+  for (a = 0; a < NACL_ARRAY_SIZE(kSignals); a++) {
+    sigaddset(&sa.sa_mask, kSignals[a]);
+  }
+
+  // Install all handlers.
+  for (a = 0; a < NACL_ARRAY_SIZE(kSignals); a++) {
+    if (sigaction(kSignals[a], &sa, NULL) != 0)
+      NaClLog(LOG_FATAL, "sigaction to register signals failed.");
+  }
+}
+
+}  // namespace nonsfi
+}  // namespace nacl