lldb/source/Target/ThreadPlanStepOverBreakpoint.cpp

//===-- ThreadPlanStepOverBreakpoint.cpp ----------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "lldb/Target/ThreadPlanStepOverBreakpoint.h"

#include "lldb/Target/Process.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/ThreadList.h"
#include "lldb/Utility/LLDBLog.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/Stream.h"

using namespace lldb;
using namespace lldb_private;

// ThreadPlanStepOverBreakpoint: Single steps over a breakpoint bp_site_sp at
// the pc.

ThreadPlanStepOverBreakpoint::ThreadPlanStepOverBreakpoint(Thread &thread)
    : ThreadPlan(ThreadPlan::eKindStepOverBreakpoint,
                 "Step over breakpoint trap", thread, eVoteNo,
                 eVoteNoOpinion), // We need to report the run since this
                                  // happens first in the thread plan stack when
                                  // stepping over a breakpoint
      m_breakpoint_addr(LLDB_INVALID_ADDRESS), m_auto_continue(false),
      m_reenabled_breakpoint_site(false),
      m_defer_reenable_breakpoint_site(false)

{
  m_breakpoint_addr = thread.GetRegisterContext()->GetPC();
  m_breakpoint_site_id =
      thread.GetProcess()->GetBreakpointSiteList().FindIDByAddress(
          m_breakpoint_addr);
}

ThreadPlanStepOverBreakpoint::~ThreadPlanStepOverBreakpoint() = default;

void ThreadPlanStepOverBreakpoint::GetDescription(
    Stream *s, lldb::DescriptionLevel level) {
  s->Printf("Single stepping past breakpoint site %" PRIu64 " at 0x%" PRIx64,
            m_breakpoint_site_id, (uint64_t)m_breakpoint_addr);
}

bool ThreadPlanStepOverBreakpoint::ValidatePlan(Stream *error) { return true; }

bool ThreadPlanStepOverBreakpoint::DoPlanExplainsStop(Event *event_ptr) {
  StopInfoSP stop_info_sp = GetPrivateStopInfo();
  if (stop_info_sp) {
    StopReason reason = stop_info_sp->GetStopReason();

    Log *log = GetLog(LLDBLog::Step);
    LLDB_LOG(log, "Step over breakpoint stopped for reason: {0}.",
             Thread::StopReasonAsString(reason));

    switch (reason) {
      case eStopReasonTrace:
      case eStopReasonNone:
        return true;
      case eStopReasonBreakpoint:
      {
        // It's a little surprising that we stop here for a breakpoint hit.
        // However, when you single step ONTO a breakpoint we still want to call
        // that a breakpoint hit, and trigger the actions, etc.  Otherwise you
        // would see the PC at the breakpoint without having triggered the
        // actions, then you'd continue, the PC wouldn't change, and you'd see
        // the breakpoint hit, which would be odd. So the lower levels fake 
        // "step onto breakpoint address" and return that as a breakpoint hit.  
        // So our trace step COULD appear as a breakpoint hit if the next 
        // instruction also contained a breakpoint.  We don't want to handle 
        // that, since we really don't know what to do with breakpoint hits.  
        // But make sure we don't set ourselves to auto-continue or we'll wrench
        // control away from the plans that can deal with this.
        // Be careful, however, as we may have "seen a breakpoint under the PC
        // because we stopped without changing the PC, in which case we do want
        // to re-claim this stop so we'll try again.
        lldb::addr_t pc_addr = GetThread().GetRegisterContext()->GetPC();

        if (pc_addr == m_breakpoint_addr) {
          LLDB_LOGF(log,
                    "Got breakpoint stop reason but pc: 0x%" PRIx64
                    "hasn't changed.",
                    pc_addr);
          return true;
        }

        SetAutoContinue(false);
        return false;
      }
      default:
        return false;
    }
  }
  return false;
}

bool ThreadPlanStepOverBreakpoint::ShouldStop(Event *event_ptr) {
  return !ShouldAutoContinue(event_ptr);
}

bool ThreadPlanStepOverBreakpoint::StopOthers() { return true; }

// This thread plan does a single instruction step over a breakpoint instruction
// and needs to not resume other threads, so return false to stop the
// ThreadPlanSingleThreadTimeout from timing out and trying to resume all
// threads. If all threads gets resumed before we disable, single step and
// re-enable the breakpoint, we can miss breakpoints on other threads.
bool ThreadPlanStepOverBreakpoint::SupportsResumeOthers() { return false; }

StateType ThreadPlanStepOverBreakpoint::GetPlanRunState() {
  return eStateStepping;
}

bool ThreadPlanStepOverBreakpoint::DoWillResume(StateType resume_state,
                                                bool current_plan) {
  if (current_plan) {
    BreakpointSiteSP bp_site_sp(
        m_process.GetBreakpointSiteList().FindByAddress(m_breakpoint_addr));
    if (bp_site_sp && m_process.IsBreakpointSiteEnabled(*bp_site_sp)) {
      llvm::consumeError(m_process.ExecuteBreakpointSiteAction(
          *bp_site_sp, Process::BreakpointAction::Disable,
          /*forbid_delay=*/false));
      m_reenabled_breakpoint_site = false;
    }
  }
  return true;
}

bool ThreadPlanStepOverBreakpoint::WillStop() {
  ReenableBreakpointSite();
  return true;
}

void ThreadPlanStepOverBreakpoint::DidPop() { ReenableBreakpointSite(); }

bool ThreadPlanStepOverBreakpoint::MischiefManaged() {
  lldb::addr_t pc_addr = GetThread().GetRegisterContext()->GetPC();

  if (pc_addr == m_breakpoint_addr) {
    // If we are still at the PC of our breakpoint, then for some reason we
    // didn't get a chance to run.
    return false;
  } else {
    Log *log = GetLog(LLDBLog::Step);
    LLDB_LOGF(log, "Completed step over breakpoint plan.");
    // Otherwise, re-enable the breakpoint we were stepping over, and we're
    // done.
    ReenableBreakpointSite();
    ThreadPlan::MischiefManaged();
    return true;
  }
}

void ThreadPlanStepOverBreakpoint::ReenableBreakpointSite() {
  if (!m_reenabled_breakpoint_site) {
    m_reenabled_breakpoint_site = true;

    if (m_defer_reenable_breakpoint_site) {
      // Let ThreadList track all threads stepping over this breakpoint.
      // It will re-enable the breakpoint only when ALL threads have finished.
      m_process.GetThreadList().ThreadFinishedSteppingOverBreakpoint(
          m_breakpoint_addr, GetThread().GetID());
    } else {
      // Default behavior: re-enable the breakpoint directly.
      if (BreakpointSiteSP bp_site_sp =
              m_process.GetBreakpointSiteList().FindByAddress(
                  m_breakpoint_addr))
        llvm::consumeError(m_process.ExecuteBreakpointSiteAction(
            *bp_site_sp, Process::BreakpointAction::Enable,
            /*forbid_delay=*/false));
    }
  }
}
void ThreadPlanStepOverBreakpoint::ThreadDestroyed() {
  ReenableBreakpointSite();
}

void ThreadPlanStepOverBreakpoint::SetAutoContinue(bool do_it) {
  m_auto_continue = do_it;
}

bool ThreadPlanStepOverBreakpoint::ShouldAutoContinue(Event *event_ptr) {
  return m_auto_continue;
}

bool ThreadPlanStepOverBreakpoint::IsPlanStale() {
  return GetThread().GetRegisterContext()->GetPC() != m_breakpoint_addr;
}