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[lldb] Correctly annotate threads at a bp site as hitting it #82709

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Merged
merged 2 commits into from
Feb 23, 2024
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[lldb] Correctly annotate threads at a bp site as hitting it #82709

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[lldb] Correctly annotate threads at a bp site as hitting it
jasonmolenda Feb 22, 2024
8e10123
Update to address Jim's feedback
jasonmolenda Feb 23, 2024
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21 changes: 14 additions & 7 deletions lldb/include/lldb/Target/Thread.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1163,13 +1163,20 @@ class Thread : public std::enable_shared_from_this<Thread>,

void CalculatePublicStopInfo();

// Ask the thread subclass to set its stop info.
//
// Thread subclasses should call Thread::SetStopInfo(...) with the reason the
// thread stopped.
//
// \return
// True if Thread::SetStopInfo(...) was called, false otherwise.
/// Ask the thread subclass to set its stop info.
///
/// Thread subclasses should call Thread::SetStopInfo(...) with the reason the
/// thread stopped.
///
/// A thread that is sitting at a breakpoint site, but has not yet executed
/// the breakpoint instruction, should have a breakpoint-hit StopInfo set.
/// When execution is resumed, any thread sitting at a breakpoint site will
/// instruction-step over the breakpoint instruction silently, and we will
/// never record this breakpoint as being hit, updating the hit count,
/// possibly executing breakpoint commands or conditions.
///
/// \return
/// True if Thread::SetStopInfo(...) was called, false otherwise.
virtual bool CalculateStopInfo() = 0;

// Gets the temporary resume state for a thread.
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33 changes: 27 additions & 6 deletions lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
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Expand Up @@ -1600,6 +1600,26 @@ bool ProcessGDBRemote::CalculateThreadStopInfo(ThreadGDBRemote *thread) {
// has no stop reason.
thread->GetRegisterContext()->InvalidateIfNeeded(true);
if (!GetThreadStopInfoFromJSON(thread, m_jstopinfo_sp)) {
// If a thread is stopped at a breakpoint site, set that as the stop
// reason even if it hasn't executed the breakpoint instruction yet.
// We will silently step over the breakpoint when we resume execution
// and miss the fact that this thread hit the breakpoint.
const size_t num_thread_ids = m_thread_ids.size();
for (size_t i = 0; i < num_thread_ids; i++) {
if (m_thread_ids[i] == thread->GetID() && m_thread_pcs.size() > i) {
addr_t pc = m_thread_pcs[i];
lldb::BreakpointSiteSP bp_site_sp =
thread->GetProcess()->GetBreakpointSiteList().FindByAddress(pc);
if (bp_site_sp) {
if (bp_site_sp->ValidForThisThread(*thread)) {
thread->SetStopInfo(
StopInfo::CreateStopReasonWithBreakpointSiteID(
*thread, bp_site_sp->GetID()));
return true;
}
}
}
}
thread->SetStopInfo(StopInfoSP());
}
return true;
Expand Down Expand Up @@ -1722,7 +1742,9 @@ ThreadSP ProcessGDBRemote::SetThreadStopInfo(
} else {
bool handled = false;
bool did_exec = false;
if (!reason.empty()) {
// debugserver can send reason = "none" which is equivalent
// to no reason.
if (!reason.empty() && reason != "none") {
if (reason == "trace") {
addr_t pc = thread_sp->GetRegisterContext()->GetPC();
lldb::BreakpointSiteSP bp_site_sp =
Expand Down Expand Up @@ -1864,11 +1886,10 @@ ThreadSP ProcessGDBRemote::SetThreadStopInfo(
lldb::BreakpointSiteSP bp_site_sp =
thread_sp->GetProcess()->GetBreakpointSiteList().FindByAddress(pc);

// If the current pc is a breakpoint site then the StopInfo should be
// set to Breakpoint even though the remote stub did not set it as such.
// This can happen when the thread is involuntarily interrupted (e.g.
// due to stops on other threads) just as it is about to execute the
// breakpoint instruction.
// If a thread is stopped at a breakpoint site, set that as the stop
// reason even if it hasn't executed the breakpoint instruction yet.
// We will silently step over the breakpoint when we resume execution
// and miss the fact that this thread hit the breakpoint.
if (bp_site_sp && bp_site_sp->ValidForThisThread(*thread_sp)) {
thread_sp->SetStopInfo(StopInfo::CreateStopReasonWithBreakpointSiteID(
*thread_sp, bp_site_sp->GetID()));
Expand Down