src/developer/debug/zxdb/client/thread_impl.cc

// Copyright 2018 The Fuchsia 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 "src/developer/debug/zxdb/client/thread_impl.h"

#include <inttypes.h>

#include <iostream>
#include <limits>

#include "src/developer/debug/shared/logging/block_timer.h"
#include "src/developer/debug/shared/message_loop.h"
#include "src/developer/debug/shared/zx_status.h"
#include "src/developer/debug/zxdb/client/breakpoint.h"
#include "src/developer/debug/zxdb/client/frame_impl.h"
#include "src/developer/debug/zxdb/client/process_impl.h"
#include "src/developer/debug/zxdb/client/remote_api.h"
#include "src/developer/debug/zxdb/client/session.h"
#include "src/developer/debug/zxdb/client/target_impl.h"
#include "src/developer/debug/zxdb/client/thread_controller.h"
#include "src/developer/debug/zxdb/symbols/process_symbols.h"
#include "src/lib/fxl/logging.h"

namespace zxdb {

ThreadImpl::ThreadImpl(ProcessImpl* process,
                       const debug_ipc::ThreadRecord& record)
    : Thread(process->session()),
      process_(process),
      koid_(record.thread_koid),
      stack_(this),
      weak_factory_(this) {
  SetMetadata(record);
  settings_.set_fallback(&process_->target()->settings());
  settings_.set_name("thread");
}

ThreadImpl::~ThreadImpl() = default;

Process* ThreadImpl::GetProcess() const { return process_; }

uint64_t ThreadImpl::GetKoid() const { return koid_; }

const std::string& ThreadImpl::GetName() const { return name_; }

debug_ipc::ThreadRecord::State ThreadImpl::GetState() const { return state_; }
debug_ipc::ThreadRecord::BlockedReason ThreadImpl::GetBlockedReason() const {
  return blocked_reason_;
}

void ThreadImpl::Pause(std::function<void()> on_paused) {
  // The frames may have been requested when the thread was running which
  // will have marked them "empty but complete." When a pause happens the
  // frames will become available so we want subsequent requests to request
  // them.
  ClearFrames();

  debug_ipc::PauseRequest request;
  request.process_koid = process_->GetKoid();
  request.thread_koid = koid_;
  session()->remote_api()->Pause(
      request, [weak_thread = weak_factory_.GetWeakPtr(),
                on_paused = std::move(on_paused)](const Err& err,
                                                  debug_ipc::PauseReply reply) {
        if (!err.has_error() && weak_thread) {
          // Save the new metadata.
          if (reply.threads.size() == 1 &&
              reply.threads[0].thread_koid == weak_thread->koid_) {
            weak_thread->SetMetadata(reply.threads[0]);
          } else {
            // If the client thread still exists, the agent's record of that
            // thread should have existed at the time the message was sent so
            // there should be no reason the update doesn't match.
            FXL_NOTREACHED();
          }
        }
        on_paused();
      });
}

void ThreadImpl::Continue() {
  debug_ipc::ResumeRequest request;
  request.process_koid = process_->GetKoid();
  request.thread_koids.push_back(koid_);

  if (controllers_.empty()) {
    request.how = debug_ipc::ResumeRequest::How::kContinue;
  } else {
    // When there are thread controllers, ask the most recent one for how to
    // continue.
    //
    // Theoretically we're running with all controllers at once and we want to
    // stop at the first one that triggers, which means we want to compute the
    // most restrictive intersection of all of them.
    //
    // This is annoying to implement and it's difficult to construct a
    // situation where this would be required. The controller that doesn't
    // involve breakpoints is "step in range" and generally ranges refer to
    // code lines that will align. Things like "until" are implemented with
    // breakpoints so can overlap arbitrarily with other operations with no
    // problem.
    //
    // A case where this might show up:
    //  1. Do "step into" which steps through a range of instructions.
    //  2. In the middle of that range is a breakpoint that's hit.
    //  3. The user does "finish." We'll ask the finish controller what to do
    //     and it will say "continue" and the range from step 1 is lost.
    // However, in this case probably does want to end up one stack frame
    // back rather than several instructions after the breakpoint due to the
    // original "step into" command, so even when "wrong" this current behavior
    // isn't necessarily bad.
    controllers_.back()->Log("Continuing with this controller as primary.");
    ThreadController::ContinueOp op = controllers_.back()->GetContinueOp();
    if (op.synthetic_stop_) {
      // Synthetic stop. Skip notifying the backend and broadcast a stop
      // notification for the current state.
      controllers_.back()->Log("Synthetic stop.");
      debug_ipc::MessageLoop::Current()->PostTask(
          FROM_HERE, [thread = weak_factory_.GetWeakPtr()]() {
            if (thread) {
              thread->OnException(debug_ipc::NotifyException::Type::kSynthetic,
                                  {});
            }
          });
      return;
    } else {
      // Dispatch the continuation message.
      request.how = op.how;
      request.range_begin = op.range.begin();
      request.range_end = op.range.end();
    }
  }

  ClearFrames();
  session()->remote_api()->Resume(
      request, [](const Err& err, debug_ipc::ResumeReply) {});
}

void ThreadImpl::ContinueWith(std::unique_ptr<ThreadController> controller,
                              std::function<void(const Err&)> on_continue) {
  ThreadController* controller_ptr = controller.get();

  // Add it first so that its presence will be noted by anything its
  // initialization function does.
  controllers_.push_back(std::move(controller));

  controller_ptr->InitWithThread(
      this, [this, controller_ptr,
             on_continue = std::move(on_continue)](const Err& err) {
        if (err.has_error()) {
          controller_ptr->Log("InitWithThread failed.");
          NotifyControllerDone(controller_ptr);  // Remove the controller.
        } else {
          controller_ptr->Log("Initialized, continuing...");
          Continue();
        }
        on_continue(err);
      });
}

void ThreadImpl::JumpTo(uint64_t new_address,
                        std::function<void(const Err&)> cb) {
  // The register to set.
  debug_ipc::WriteRegistersRequest request;
  request.process_koid = process_->GetKoid();
  request.thread_koid = koid_;
  request.registers.emplace_back(
      GetSpecialRegisterID(session()->arch(),
                           debug_ipc::SpecialRegisterType::kIP),
      new_address);

  // The "jump" command updates the thread's location so we need to recompute
  // the stack. So once the jump is complete we re-request the thread's
  // status.
  //
  // This could be made faster by requesting status immediately after sending
  // the update so we don't have to wait for two round-trips, but that
  // complicates the callback logic and this feature is not performance-
  // sensitive.
  //
  // Another approach is to make the register request message able to
  // optionally request a stack backtrace and include that in the reply.
  session()->remote_api()->WriteRegisters(
      request, [thread = weak_factory_.GetWeakPtr(), cb = std::move(cb)](
                   const Err& err, debug_ipc::WriteRegistersReply reply) {
        if (err.has_error()) {
          cb(err);  // Transport error.
        } else if (reply.status != 0) {
          cb(Err("Could not set thread instruction pointer. Error %d (%s).",
                 reply.status,
                 debug_ipc::ZxStatusToString(
                     static_cast<uint32_t>(reply.status))));
        } else if (!thread) {
          cb(Err("Thread destroyed."));
        } else {
          // Success, update the current stack before issuing the callback.
          thread->SyncFramesForStack(std::move(cb));
        }
      });
}

void ThreadImpl::NotifyControllerDone(ThreadController* controller) {
  controller->Log("Controller done, removing.");

  // We expect to have few controllers so brute-force is sufficient.
  for (auto cur = controllers_.begin(); cur != controllers_.end(); ++cur) {
    if (cur->get() == controller) {
      controllers_.erase(cur);
      return;
    }
  }
  FXL_NOTREACHED();  // Notification for unknown controller.
}

void ThreadImpl::StepInstruction() {
  debug_ipc::ResumeRequest request;
  request.process_koid = process_->GetKoid();
  request.thread_koids.push_back(koid_);
  request.how = debug_ipc::ResumeRequest::How::kStepInstruction;
  session()->remote_api()->Resume(
      request, [](const Err& err, debug_ipc::ResumeReply) {});
}

const Stack& ThreadImpl::GetStack() const { return stack_; }

Stack& ThreadImpl::GetStack() { return stack_; }

void ThreadImpl::ReadRegisters(
    std::vector<debug_ipc::RegisterCategory::Type> cats_to_get,
    std::function<void(const Err&, const RegisterSet&)> callback) {
  debug_ipc::ReadRegistersRequest request;
  request.process_koid = process_->GetKoid();
  request.thread_koid = koid_;
  request.categories = std::move(cats_to_get);

  session()->remote_api()->ReadRegisters(
      request, [thread = weak_factory_.GetWeakPtr(), callback](
                   const Err& err, debug_ipc::ReadRegistersReply reply) {
        thread->registers_ = std::make_unique<RegisterSet>(
            thread->session()->arch(), std::move(reply.categories));
        if (callback)
          callback(err, *thread->registers_.get());
      });
}

void ThreadImpl::SetMetadata(const debug_ipc::ThreadRecord& record) {
  FXL_DCHECK(koid_ == record.thread_koid);

  name_ = record.name;
  state_ = record.state;
  blocked_reason_ = record.blocked_reason;

  stack_.SetFrames(record.stack_amount, record.frames);
}

void ThreadImpl::OnException(
    debug_ipc::NotifyException::Type type,
    const std::vector<fxl::WeakPtr<Breakpoint>>& hit_breakpoints) {
  TIME_BLOCK();
#if defined(DEBUG_THREAD_CONTROLLERS)
  ThreadController::LogRaw(
      "----------\r\nGot %s exception @ 0x%" PRIx64 " in %s",
      debug_ipc::NotifyException::TypeToString(type), stack_[0]->GetAddress(),
      ThreadController::FrameFunctionNameForLog(stack_[0]).c_str());
#endif

  // When any controller says "stop" it takes precendence and the thread will
  // stop no matter what any other controllers say.
  bool should_stop = false;

  // Set when any controller says "continue". If no controller says "stop" we
  // need to differentiate the case where there are no controllers or all
  // controllers say "unexpected" (thread should stop), from where one or more
  // said "continue" (thread should continue, any "unexpected" votes are
  // ignored).
  bool have_continue = false;

  auto controller_iter = controllers_.begin();
  while (controller_iter != controllers_.end()) {
    ThreadController* controller = controller_iter->get();
    switch (controller->OnThreadStop(type, hit_breakpoints)) {
      case ThreadController::kContinue:
        // Try the next controller.
        controller->Log("Reported continue on exception.");
        have_continue = true;
        controller_iter++;
        break;
      case ThreadController::kStopDone:
        // Once a controller tells us to stop, we assume the controller no
        // longer applies and delete it.
        //
        // Need to continue with checking all controllers even though we know
        // we should stop at this point. Multiple controllers should say
        // "stop" at the same time and we need to be able to delete all that
        // no longer apply (say you did "finish", hit a breakpoint, and then
        // "finish" again, both finish commands would be active and you would
        // want them both to be completed when the current frame actually
        // finishes).
        controller->Log(
            "Reported stop on exception, stopping and removing it.");
        controller_iter = controllers_.erase(controller_iter);
        should_stop = true;
        break;
      case ThreadController::kUnexpected:
        // An unexpected exception means the controller is still active but
        // doesn't know what to do with this exception.
        controller->Log("Reported unexpected exception.");
        controller_iter++;
        break;
    }
  }

  if (!have_continue) {
    // No controller voted to continue (maybe all active controllers reported
    // "unexpected") or there was no controller. Such cases should stop.
    should_stop = true;
  }

  // The existence of any non-internal breakpoints being hit means the thread
  // should always stop. This check happens after notifying the controllers so
  // if a controller triggers, it's counted as a "hit" (otherwise, doing
  // "run until" to a line with a normal breakpoint on it would keep the "run
  // until" operation active even after it was hit).
  //
  // Also, filter out internal breakpoints in the notification sent to the
  // observers.
  std::vector<fxl::WeakPtr<Breakpoint>> external_breakpoints;
  for (auto& hit : hit_breakpoints) {
    if (!hit)
      continue;

    if (!hit->IsInternal()) {
      external_breakpoints.push_back(hit);
      should_stop = true;
      break;
    }
  }

  // Non-debug exceptions also mean the thread should always stop (check this
  // after running the controllers for the same reason as the breakpoint check
  // above).
  if (type == debug_ipc::NotifyException::Type::kGeneral)
    should_stop = true;

  if (should_stop) {
    // Stay stopped and notify the observers.
    for (auto& observer : observers())
      observer.OnThreadStopped(this, type, external_breakpoints);
  } else {
    // Controllers all say to continue.
    Continue();
  }
}

void ThreadImpl::SyncFramesForStack(std::function<void(const Err&)> callback) {
  debug_ipc::ThreadStatusRequest request;
  request.process_koid = process_->GetKoid();
  request.thread_koid = koid_;

  session()->remote_api()->ThreadStatus(
      request,
      [callback = std::move(callback), thread = weak_factory_.GetWeakPtr()](
          const Err& err, debug_ipc::ThreadStatusReply reply) {
        if (err.has_error()) {
          callback(err);
          return;
        }

        if (!thread) {
          callback(Err("Thread destroyed."));
          return;
        }

        thread->SetMetadata(reply.record);
        callback(Err());
      });
}

std::unique_ptr<Frame> ThreadImpl::MakeFrameForStack(
    const debug_ipc::StackFrame& input, Location location) {
  return std::make_unique<FrameImpl>(this, input, std::move(location));
}

Location ThreadImpl::GetSymbolizedLocationForStackFrame(
    const debug_ipc::StackFrame& input) {
  auto vect =
      GetProcess()->GetSymbols()->ResolveInputLocation(InputLocation(input.ip));

  // Symbolizing an address should always give exactly one result.
  FXL_DCHECK(vect.size() == 1u);
  return vect[0];
}

void ThreadImpl::ClearFrames() {
  if (stack_.ClearFrames()) {
    for (auto& observer : observers())
      observer.OnThreadFramesInvalidated(this);
  }
}

}  // namespace zxdb