Add CRASHPAD_SIMULATE_CRASH() and supporting client code

client/simulate_crash_mac.cc

Index: client/simulate_crash_mac.cc
diff --git a/client/simulate_crash_mac.cc b/client/simulate_crash_mac.cc
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "client/simulate_crash_mac.h"
+
+#include <string.h>
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/mac/mach_logging.h"
+#include "base/mac/scoped_mach_port.h"
+#include "base/strings/stringprintf.h"
+#include "build/build_config.h"
+#include "util/mach/exc_client_variants.h"
+#include "util/mach/exception_behaviors.h"
+#include "util/mach/exception_ports.h"
+#include "util/mach/mach_extensions.h"
+
+namespace crashpad {
+
+namespace {
+
+//! \brief Sends an exception message to an exception port in accordance with
+//!     the behavior and thread state flavor it’s registered to receive.
+//!
+//! \param[in] thread, task, exception, code, code_count These parameters will
+//!     be passed to the exception handler as appropriate.
+//! \param[in] cpu_context The value to use for the thread state, if \a behavior
+//!     indicates that the handler should receive a thread state and if the
+//!     supplied thread state matches or can be converted to \a flavor. If \a
+//!     behavior requires a thread state but this argument cannot be converted
+//!     to match \a flavor, `thread_get_state()` will be called to obtain a
+//!     suitable thread state value.
+//! \param[in] handler The Mach exception handler to deliver the exception to.
+//! \param[in] set_state If `true` and \a behavior indicates that the handler
+//!     should receive and return a thread state, a new thread state will be set
+//!     by `thread_set_state()` upon successful completion of the exception
+//!     handler. If `false`, this will be suppressed, even when \a behavior
+//!     indicates that the handler receives and returns a thread state.
+//!
+//! \return `true` if the exception was delivered to the handler and the handler
+//!     indicated success. `false` otherwise, with a warning message logged.
+bool DeliverException(thread_t thread,
+                      task_t task,
+                      exception_type_t exception,
+                      const mach_exception_data_t code,
+                      mach_msg_type_number_t code_count,
+                      const NativeCPUContext* cpu_context,
+                      const ExceptionPorts::ExceptionHandler& handler,
+                      bool set_state) {
+  kern_return_t kr;
+
+  bool handler_wants_state = ExceptionBehaviorHasState(handler.behavior);
+  if (!handler_wants_state) {
+    // Regardless of the passed-in value of |set_state|, if the handler won’t be
+    // dealing with any state at all, no state should be set.
+    set_state = false;
+  }
+
+  // A const version of thread_state_t.
+  typedef const natural_t* ConstThreadState;
+
+  // old_state is only used if the context already captured doesn’t match (or
+  // can’t be converted to) what’s registered for the handler.
+  thread_state_data_t old_state;
+
+  thread_state_flavor_t flavor = handler.flavor;
+  ConstThreadState state;
+  mach_msg_type_number_t state_count;
+  switch (flavor) {
+#if defined(ARCH_CPU_X86_FAMILY)
+    case x86_THREAD_STATE:
+      state = reinterpret_cast<ConstThreadState>(cpu_context);
+      state_count = x86_THREAD_STATE_COUNT;
+      break;
+#if defined(ARCH_CPU_X86)
+    case x86_THREAD_STATE32:
+      state = reinterpret_cast<ConstThreadState>(&cpu_context->uts.ts32);
+      state_count = cpu_context->tsh.count;
+      break;
+#elif defined(ARCH_CPU_X86_64)
+    case x86_THREAD_STATE64:
+      state = reinterpret_cast<ConstThreadState>(&cpu_context->uts.ts64);
+      state_count = cpu_context->tsh.count;
+      break;
+#endif
+#else
+#error Port to your CPU architecture
+#endif
+
+    case THREAD_STATE_NONE:
+      // This is only acceptable if the handler doesn’t have one of the “state”
+      // behaviors. Otherwise, if the kernel were attempting to send an
+      // exception message to this port, it would call thread_getstatus() (known
+      // outside the kernel as thread_get_state()) which would fail because
+      // THREAD_STATE_NONE is not a valid state to get. See 10.9.5
+      // xnu-2422.115.4/osfmk/kern/exception.c exception_deliver() and
+      // xnu-2422.115.4/osfmk/i386/pcb.c machine_thread_get_state().
+      if (!handler_wants_state) {
+        state = nullptr;
+        state_count = 0;
+        break;
+      }
+
+      LOG(WARNING) << "exception handler has unexpected state flavor" << flavor;
+      return false;
+
+    default:
+      if (!handler_wants_state) {
+        // Don’t bother getting any thread state if the handler’s not actually
+        // going to use it.
+        state = nullptr;
+        state_count = 0;
+      } else {
+        state = old_state;
+        state_count = THREAD_STATE_MAX;
+        kr = thread_get_state(thread, flavor, old_state, &state_count);
+        if (kr != KERN_SUCCESS) {
+          MACH_LOG(WARNING, kr) << "thread_get_state";
+          return false;
+        }
+      }
+      break;
+  }
+
+  // new_state is supposed to be an out parameter only, but in case the handler
+  // doesn't touch it, make sure it's initialized to a valid thread state.
+  // Otherwise, the thread_set_state() call below would set a garbage thread
+  // state.
+  thread_state_data_t new_state;
+  size_t state_size =
+      sizeof(natural_t) *
+      std::min(state_count, static_cast<unsigned int>(THREAD_STATE_MAX));
+  memcpy(new_state, state, state_size);
+  mach_msg_type_number_t new_state_count = THREAD_STATE_MAX;
+
+  kr = UniversalExceptionRaise(handler.behavior,
+                               handler.port,
+                               thread,
+                               task,
+                               exception,
+                               code,
+                               code_count,
+                               &flavor,
+                               state,
+                               state_count,
+                               new_state,
+                               &new_state_count);
+
+  // The kernel treats a return value of MACH_RCV_PORT_DIED as successful,
+  // although it will not set a new thread state in that case. See 10.9.5
+  // xnu-2422.115.4/osfmk/kern/exception.c exception_deliver(), and the more
+  // elaborate comment at util/mach/exc_server_variants.h
+  // ExcServerSuccessfulReturnValue(). Duplicate that behavior.
+  bool success = kr == KERN_SUCCESS || kr == MACH_RCV_PORT_DIED;
+  MACH_LOG_IF(WARNING, !success, kr) << "UniversalExceptionRaise";
+
+  if (kr == KERN_SUCCESS && set_state) {
+    kr = thread_set_state(thread, flavor, new_state, new_state_count);
+    MACH_LOG_IF(WARNING, kr != KERN_SUCCESS, kr) << "thread_set_state";
+  }
+
+  return success;
+}
+
+}  // namespace
+
+void SimulateCrash(const NativeCPUContext* cpu_context) {
+#if defined(ARCH_CPU_X86)
+  DCHECK_EQ(cpu_context->tsh.flavor,
+            static_cast<thread_state_flavor_t>(x86_THREAD_STATE32));
+  DCHECK_EQ(static_cast<mach_msg_type_number_t>(cpu_context->tsh.count),
+            x86_THREAD_STATE32_COUNT);
+#elif defined(ARCH_CPU_X86_64)
+  DCHECK_EQ(cpu_context->tsh.flavor,
+            static_cast<thread_state_flavor_t>(x86_THREAD_STATE64));
+  DCHECK_EQ(static_cast<mach_msg_type_number_t>(cpu_context->tsh.count),
+            x86_THREAD_STATE64_COUNT);
+#endif
+
+  base::mac::ScopedMachSendRight thread(mach_thread_self());
+  exception_type_t exception = kMachExceptionSimulated;
+  mach_exception_data_type_t codes[] = {0, 0};
+  mach_msg_type_number_t code_count = arraysize(codes);
+
+  // Look up the handler for EXC_CRASH exceptions in the same way that the
+  // kernel would: try a thread handler, then a task handler, and finally a host
+  // handler. 10.9.5 xnu-2422.115.4/osfmk/kern/exception.c exception_triage().
+  const ExceptionPorts::TargetType kTargetTypes[] = {
+      ExceptionPorts::kTargetTypeThread,
+      ExceptionPorts::kTargetTypeTask,
+
+      // This is not expected to succeed, because mach_host_self() doesn’t
+      // return the host_priv port to non-root users, and this is the port
+      // that’s required for host_get_exception_ports().
+      //
+      // See 10.9.5 xnu-2422.115.4/bsd/kern/kern_prot.c set_security_token(),
+      // xnu-2422.115.4/osfmk/kern/task.c host_security_set_task_token(), and
+      // xnu-2422.115.4/osfmk/kern/ipc_host.c host_get_exception_ports().
+      ExceptionPorts::kTargetTypeHost,
+  };
+
+  bool success = false;
+
+  for (size_t target_type_index = 0;
+       !success && target_type_index < arraysize(kTargetTypes);
+       ++target_type_index) {
+    std::vector<ExceptionPorts::ExceptionHandler> handlers;
+    ExceptionPorts exception_ports(kTargetTypes[target_type_index],
+                                   MACH_PORT_NULL);
+    if (exception_ports.GetExceptionPorts(EXC_MASK_CRASH, &handlers)) {
+      DCHECK_LE(handlers.size(), 1u);
+      if (handlers.size() == 1) {
+        DCHECK(handlers[0].mask & EXC_MASK_CRASH);
+        success = DeliverException(thread,
+                                   mach_task_self(),
+                                   exception,
+                                   codes,
+                                   code_count,
+                                   cpu_context,
+                                   handlers[0],
+                                   false);
+      }
+    }
+  }
+
+  LOG_IF(WARNING, !success)
+      << "SimulateCrash did not find an appropriate exception handler";
+}
+
+}  // namespace crashpad