EIC code displayed by LXR master/​include/​lldb/​Target/​ThreadPlan.h	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2026-05-10 08:42:56

 //===-- ThreadPlan.h --------------------------------------------*- C++ -*-===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLDB_TARGET_THREADPLAN_H
 #define LLDB_TARGET_THREADPLAN_H
 
 #include <mutex>
 #include <string>
 
 #include "lldb/Target/Process.h"
 #include "lldb/Target/StopInfo.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Target/Thread.h"
 #include "lldb/Target/ThreadPlanTracer.h"
 #include "lldb/Utility/UserID.h"
 #include "lldb/lldb-private.h"
 
 namespace lldb_private {
 
 //  ThreadPlan:
 //
 //  This is the pure virtual base class for thread plans.
 //
 //  The thread plans provide the "atoms" of behavior that all the logical
 //  process control, either directly from commands or through more complex
 //  composite plans will rely on.
 //
 //  Plan Stack:
 //
 //  The thread maintaining a thread plan stack, and you program the actions of
 //  a particular thread by pushing plans onto the plan stack.  There is always
 //  a "Current" plan, which is the top of the plan stack, though in some cases
 //  a plan may defer to plans higher in the stack for some piece of information
 //  (let us define that the plan stack grows downwards).
 //
 //  The plan stack is never empty, there is always a Base Plan which persists
 //  through the life of the running process.
 //
 //
 //  Creating Plans:
 //
 //  The thread plan is generally created and added to the plan stack through
 //  the QueueThreadPlanFor... API in lldb::Thread.  Those API's will return the
 //  plan that performs the named operation in a manner appropriate for the
 //  current process.  The plans in lldb/source/Target are generic
 //  implementations, but a Process plugin can override them.
 //
 //  ValidatePlan is then called.  If it returns false, the plan is unshipped.
 //  This is a little convenience which keeps us from having to error out of the
 //  constructor.
 //
 //  Then the plan is added to the plan stack.  When the plan is added to the
 //  plan stack its DidPush will get called.  This is useful if a plan wants to
 //  push any additional plans as it is constructed, since you need to make sure
 //  you're already on the stack before you push additional plans.
 //
 //  Completed Plans:
 //
 //  When the target process stops the plans are queried, among other things,
 //  for whether their job is done.  If it is they are moved from the plan stack
 //  to the Completed Plan stack in reverse order from their position on the
 //  plan stack (since multiple plans may be done at a given stop.)  This is
 //  used primarily so that the lldb::Thread::StopInfo for the thread can be set
 //  properly.  If one plan pushes another to achieve part of its job, but it
 //  doesn't want that sub-plan to be the one that sets the StopInfo, then call
 //  SetPrivate on the sub-plan when you create it, and the Thread will pass
 //  over that plan in reporting the reason for the stop.
 //
 //  Discarded plans:
 //
 //  Your plan may also get discarded, i.e. moved from the plan stack to the
 //  "discarded plan stack".  This can happen, for instance, if the plan is
 //  calling a function and the function call crashes and you want to unwind the
 //  attempt to call.  So don't assume that your plan will always successfully
 //  stop.  Which leads to:
 //
 //  Cleaning up after your plans:
 //
 //  When the plan is moved from the plan stack its DidPop method is always
 //  called, no matter why.  Once it is moved off the plan stack it is done, and
 //  won't get a chance to run again.  So you should undo anything that affects
 //  target state in this method.  But be sure to leave the plan able to
 //  correctly fill the StopInfo, however.  N.B. Don't wait to do clean up
 //  target state till the destructor, since that will usually get called when
 //  the target resumes, and you want to leave the target state correct for new
 //  plans in the time between when your plan gets unshipped and the next
 //  resume.
 //
 //  Thread State Checkpoint:
 //
 //  Note that calling functions on target process (ThreadPlanCallFunction)
 //  changes current thread state. The function can be called either by direct
 //  user demand or internally, for example lldb allocates memory on device to
 //  calculate breakpoint condition expression - on Linux it is performed by
 //  calling mmap on device.  ThreadStateCheckpoint saves Thread state (stop
 //  info and completed plan stack) to restore it after completing function
 //  call.
 //
 //  Over the lifetime of the plan, various methods of the ThreadPlan are then
 //  called in response to changes of state in the process we are debugging as
 //  follows:
 //
 //  Resuming:
 //
 //  When the target process is about to be restarted, the plan's WillResume
 //  method is called, giving the plan a chance to prepare for the run.  If
 //  WillResume returns false, then the process is not restarted.  Be sure to
 //  set an appropriate error value in the Process if you have to do this.
 //  Note, ThreadPlans actually implement DoWillResume, WillResume wraps that
 //  call.
 //
 //  Next the "StopOthers" method of all the threads are polled, and if one
 //  thread's Current plan returns "true" then only that thread gets to run.  If
 //  more than one returns "true" the threads that want to run solo get run one
 //  by one round robin fashion.  Otherwise all are let to run.
 //
 //  Note, the way StopOthers is implemented, the base class implementation just
 //  asks the previous plan.  So if your plan has no opinion about whether it
 //  should run stopping others or not, just don't implement StopOthers, and the
 //  parent will be asked.
 //
 //  Finally, for each thread that is running, it run state is set to the return
 //  of RunState from the thread's Current plan.
 //
 //  Responding to a stop:
 //
 //  When the target process stops, the plan is called in the following stages:
 //
 //  First the thread asks the Current Plan if it can handle this stop by
 //  calling PlanExplainsStop.  If the Current plan answers "true" then it is
 //  asked if the stop should percolate all the way to the user by calling the
 //  ShouldStop method.  If the current plan doesn't explain the stop, then we
 //  query up the plan stack for a plan that does explain the stop.  The plan
 //  that does explain the stop then needs to figure out what to do about the
 //  plans below it in the stack.  If the stop is recoverable, then the plan
 //  that understands it can just do what it needs to set up to restart, and
 //  then continue.  Otherwise, the plan that understood the stop should call
 //  DiscardPlanStack to clean up the stack below it.  Note, plans actually
 //  implement DoPlanExplainsStop, the result is cached in PlanExplainsStop so
 //  the DoPlanExplainsStop itself will only get called once per stop.
 //
 //  Controlling plans:
 //
 //  In the normal case, when we decide to stop, we will  collapse the plan
 //  stack up to the point of the plan that understood the stop reason.
 //  However, if a plan wishes to stay on the stack after an event it didn't
 //  directly handle it can designate itself a "Controlling" plan by responding
 //  true to IsControllingPlan, and then if it wants not to be discarded, it can
 //  return false to OkayToDiscard, and it and all its dependent plans will be
 //  preserved when we resume execution.
 //
 //  The other effect of being a controlling plan is that when the Controlling
 //  plan is
 //  done , if it has set "OkayToDiscard" to false, then it will be popped &
 //  execution will stop and return to the user.  Remember that if OkayToDiscard
 //  is false, the plan will be popped and control will be given to the next
 //  plan above it on the stack  So setting OkayToDiscard to false means the
 //  user will regain control when the ControllingPlan is completed.
 //
 //  Between these two controls this allows things like: a
 //  ControllingPlan/DontDiscard Step Over to hit a breakpoint, stop and return
 //  control to the user, but then when the user continues, the step out
 //  succeeds.  Even more tricky, when the breakpoint is hit, the user can
 //  continue to step in/step over/etc, and finally when they continue, they
 //  will finish up the Step Over.
 //
 //  FIXME: ControllingPlan & OkayToDiscard aren't really orthogonal.
 //  ControllingPlan
 //  designation means that this plan controls it's fate and the fate of plans
 //  below it.  OkayToDiscard tells whether the ControllingPlan wants to stay on
 //  the stack.  I originally thought "ControllingPlan-ness" would need to be a
 //  fixed
 //  characteristic of a ThreadPlan, in which case you needed the extra control.
 //  But that doesn't seem to be true.  So we should be able to convert to only
 //  ControllingPlan status to mean the current "ControllingPlan/DontDiscard".
 //  Then no plans would be ControllingPlans by default, and you would set the
 //  ones you wanted to be "user level" in this way.
 //
 //
 //  Actually Stopping:
 //
 //  If a plan says responds "true" to ShouldStop, then it is asked if it's job
 //  is complete by calling MischiefManaged.  If that returns true, the plan is
 //  popped from the plan stack and added to the Completed Plan Stack.  Then the
 //  next plan in the stack is asked if it ShouldStop, and  it returns "true",
 //  it is asked if it is done, and if yes popped, and so on till we reach a
 //  plan that is not done.
 //
 //  Since you often know in the ShouldStop method whether your plan is
 //  complete, as a convenience you can call SetPlanComplete and the ThreadPlan
 //  implementation of MischiefManaged will return "true", without your having
 //  to redo the calculation when your sub-classes MischiefManaged is called.
 //  If you call SetPlanComplete, you can later use IsPlanComplete to determine
 //  whether the plan is complete.  This is only a convenience for sub-classes,
 //  the logic in lldb::Thread will only call MischiefManaged.
 //
 //  One slightly tricky point is you have to be careful using SetPlanComplete
 //  in PlanExplainsStop because you are not guaranteed that PlanExplainsStop
 //  for a plan will get called before ShouldStop gets called.  If your sub-plan
 //  explained the stop and then popped itself, only your ShouldStop will get
 //  called.
 //
 //  If ShouldStop for any thread returns "true", then the WillStop method of
 //  the Current plan of all threads will be called, the stop event is placed on
 //  the Process's public broadcaster, and control returns to the upper layers
 //  of the debugger.
 //
 //  Reporting the stop:
 //
 //  When the process stops, the thread is given a StopReason, in the form of a
 //  StopInfo object.  If there is a completed plan corresponding to the stop,
 //  then the "actual" stop reason can be suppressed, and instead a
 //  StopInfoThreadPlan object will be cons'ed up from the top completed plan in
 //  the stack.  However, if the plan doesn't want to be the stop reason, then
 //  it can call SetPlanComplete and pass in "false" for the "success"
 //  parameter.  In that case, the real stop reason will be used instead.  One
 //  example of this is the "StepRangeStepIn" thread plan.  If it stops because
 //  of a crash or breakpoint hit, it wants to unship itself, because it isn't
 //  so useful to have step in keep going after a breakpoint hit.  But it can't
 //  be the reason for the stop or no-one would see that they had hit a
 //  breakpoint.
 //
 //  Cleaning up the plan stack:
 //
 //  One of the complications of ControllingPlans is that you may get past the
 //  limits
 //  of a plan without triggering it to clean itself up.  For instance, if you
 //  are doing a ControllingPlan StepOver, and hit a breakpoint in a called
 //  function,
 //  then step over enough times to step out of the initial StepOver range, each
 //  of the step overs will explain the stop & take themselves off the stack,
 //  but control would never be returned to the original StepOver.  Eventually,
 //  the user will continue, and when that continue stops, the old stale
 //  StepOver plan that was left on the stack will get woken up and notice it is
 //  done. But that can leave junk on the stack for a while.  To avoid that, the
 //  plans implement a "IsPlanStale" method, that can check whether it is
 //  relevant anymore.  On stop, after the regular plan negotiation, the
 //  remaining plan stack is consulted and if any plan says it is stale, it and
 //  the plans below it are discarded from the stack.
 //
 //  Automatically Resuming:
 //
 //  If ShouldStop for all threads returns "false", then the target process will
 //  resume.  This then cycles back to Resuming above.
 //
 //  Reporting eStateStopped events when the target is restarted:
 //
 //  If a plan decides to auto-continue the target by returning "false" from
 //  ShouldStop, then it will be asked whether the Stopped event should still be
 //  reported.  For instance, if you hit a breakpoint that is a User set
 //  breakpoint, but the breakpoint callback said to continue the target
 //  process, you might still want to inform the upper layers of lldb that the
 //  stop had happened.  The way this works is every thread gets to vote on
 //  whether to report the stop.  If all votes are eVoteNoOpinion, then the
 //  thread list will decide what to do (at present it will pretty much always
 //  suppress these stopped events.) If there is an eVoteYes, then the event
 //  will be reported regardless of the other votes.  If there is an eVoteNo and
 //  no eVoteYes's, then the event won't be reported.
 //
 //  One other little detail here, sometimes a plan will push another plan onto
 //  the plan stack to do some part of the first plan's job, and it would be
 //  convenient to tell that plan how it should respond to ShouldReportStop.
 //  You can do that by setting the report_stop_vote in the child plan when you
 //  create it.
 //
 //  Suppressing the initial eStateRunning event:
 //
 //  The private process running thread will take care of ensuring that only one
 //  "eStateRunning" event will be delivered to the public Process broadcaster
 //  per public eStateStopped event.  However there are some cases where the
 //  public state of this process is eStateStopped, but a thread plan needs to
 //  restart the target, but doesn't want the running event to be publicly
 //  broadcast.  The obvious example of this is running functions by hand as
 //  part of expression evaluation.  To suppress the running event return
 //  eVoteNo from ShouldReportStop, to force a running event to be reported
 //  return eVoteYes, in general though you should return eVoteNoOpinion which
 //  will allow the ThreadList to figure out the right thing to do.  The
 //  report_run_vote argument to the constructor works like report_stop_vote, and
 //  is a way for a plan to instruct a sub-plan on how to respond to
 //  ShouldReportStop.
 
 class ThreadPlan : public std::enable_shared_from_this<ThreadPlan>,
                    public UserID {
 public:
   // We use these enums so that we can cast a base thread plan to it's real
   // type without having to resort to dynamic casting.
   enum ThreadPlanKind {
     eKindGeneric,
     eKindNull,
     eKindBase,
     eKindCallFunction,
     eKindPython,
     eKindStepInstruction,
     eKindStepOut,
     eKindStepOverBreakpoint,
     eKindStepOverRange,
     eKindStepInRange,
     eKindRunToAddress,
     eKindStepThrough,
     eKindStepUntil,
     eKindSingleThreadTimeout,
   };
 
   virtual ~ThreadPlan();
 
   /// Returns the name of this thread plan.
   ///
   /// \return
   ///   A const char * pointer to the thread plan's name.
   const char *GetName() const { return m_name.c_str(); }
 
   /// Returns the Thread that is using this thread plan.
   ///
   /// \return
   ///   A  pointer to the thread plan's owning thread.
   Thread &GetThread();
 
   Target &GetTarget();
 
   const Target &GetTarget() const;
 
   /// Clear the Thread* cache.
   ///
   /// This is useful in situations like when a new Thread list is being
   /// generated.
   void ClearThreadCache();
 
   /// Print a description of this thread to the stream \a s.
   /// \a thread.  Don't expect that the result of GetThread is valid in
   /// the description method.  This might get called when the underlying
   /// Thread has not been reported, so we only know the TID and not the thread.
   ///
   /// \param[in] s
   ///    The stream to which to print the description.
   ///
   /// \param[in] level
   ///    The level of description desired.  Note that eDescriptionLevelBrief
   ///    will be used in the stop message printed when the plan is complete.
   virtual void GetDescription(Stream *s, lldb::DescriptionLevel level) = 0;
 
   /// Returns whether this plan could be successfully created.
   ///
   /// \param[in] error
   ///    A stream to which to print some reason why the plan could not be
   ///    created.
   ///    Can be NULL.
   ///
   /// \return
   ///   \b true if the plan should be queued, \b false otherwise.
   virtual bool ValidatePlan(Stream *error) = 0;
 
   bool TracerExplainsStop() {
     if (!m_tracer_sp)
       return false;
     else
       return m_tracer_sp->TracerExplainsStop();
   }
 
   lldb::StateType RunState();
 
   bool PlanExplainsStop(Event *event_ptr);
 
   virtual bool ShouldStop(Event *event_ptr) = 0;
 
   /// Returns whether this thread plan overrides the `ShouldStop` of
   /// subsequently processed plans.
   ///
   /// When processing the thread plan stack, this function gives plans the
   /// ability to continue - even when subsequent plans return true from
   /// `ShouldStop`. \see Thread::ShouldStop
   virtual bool ShouldAutoContinue(Event *event_ptr) { return false; }
 
   // Whether a "stop class" event should be reported to the "outside world".
   // In general if a thread plan is active, events should not be reported.
 
   virtual Vote ShouldReportStop(Event *event_ptr);
 
   Vote ShouldReportRun(Event *event_ptr);
 
   virtual void SetStopOthers(bool new_value);
 
   virtual bool StopOthers();
 
   // Returns true if the thread plan supports ThreadPlanSingleThreadTimeout to
   // resume other threads after timeout. If the thread plan returns false it
   // will prevent ThreadPlanSingleThreadTimeout from being created when this
   // thread plan is alive.
   virtual bool SupportsResumeOthers() { return true; }
 
   virtual bool ShouldRunBeforePublicStop() { return false; }
 
   // This is the wrapper for DoWillResume that does generic ThreadPlan logic,
   // then calls DoWillResume.
   bool WillResume(lldb::StateType resume_state, bool current_plan);
 
   virtual bool WillStop() = 0;
 
   bool IsControllingPlan() { return m_is_controlling_plan; }
 
   // Returns true if this plan is a leaf plan, meaning the plan will be popped
   // during each stop if it does not explain the stop and re-pushed before
   // resuming to stay at the top of the stack.
   virtual bool IsLeafPlan() { return false; }
 
   bool SetIsControllingPlan(bool value) {
     bool old_value = m_is_controlling_plan;
     m_is_controlling_plan = value;
     return old_value;
   }
 
   virtual bool OkayToDiscard();
 
   void SetOkayToDiscard(bool value) { m_okay_to_discard = value; }
 
   // The base class MischiefManaged does some cleanup - so you have to call it
   // in your MischiefManaged derived class.
   virtual bool MischiefManaged();
 
   virtual void ThreadDestroyed() {
     // Any cleanup that a plan might want to do in case the thread goes away in
     // the middle of the plan being queued on a thread can be done here.
   }
 
   bool GetPrivate() { return m_plan_private; }
 
   void SetPrivate(bool input) { m_plan_private = input; }
 
   virtual void DidPush();
 
   virtual void DidPop();
 
   ThreadPlanKind GetKind() const { return m_kind; }
 
   bool IsPlanComplete();
 
   void SetPlanComplete(bool success = true);
 
   virtual bool IsPlanStale() { return false; }
 
   bool PlanSucceeded() { return m_plan_succeeded; }
 
   virtual bool IsBasePlan() { return false; }
 
   lldb::ThreadPlanTracerSP &GetThreadPlanTracer() { return m_tracer_sp; }
 
   void SetThreadPlanTracer(lldb::ThreadPlanTracerSP new_tracer_sp) {
     m_tracer_sp = new_tracer_sp;
   }
 
   void DoTraceLog() {
     if (m_tracer_sp && m_tracer_sp->TracingEnabled())
       m_tracer_sp->Log();
   }
 
   // If the completion of the thread plan stepped out of a function, the return
   // value of the function might have been captured by the thread plan
   // (currently only ThreadPlanStepOut does this.) If so, the ReturnValueObject
   // can be retrieved from here.
 
   virtual lldb::ValueObjectSP GetReturnValueObject() {
     return lldb::ValueObjectSP();
   }
 
   // If the thread plan managing the evaluation of a user expression lives
   // longer than the command that instigated the expression (generally because
   // the expression evaluation hit a breakpoint, and the user regained control
   // at that point) a subsequent process control command step/continue/etc.
   // might complete the expression evaluations.  If so, the result of the
   // expression evaluation will show up here.
 
   virtual lldb::ExpressionVariableSP GetExpressionVariable() {
     return lldb::ExpressionVariableSP();
   }
 
   // If a thread plan stores the state before it was run, then you might want
   // to restore the state when it is done.  This will do that job. This is
   // mostly useful for artificial plans like CallFunction plans.
 
   virtual void RestoreThreadState() {}
 
   virtual bool IsVirtualStep() { return false; }
 
   bool SetIterationCount(size_t count) {
     if (m_takes_iteration_count) {
       // Don't tell me to do something 0 times...
       if (count == 0)
         return false;
       m_iteration_count = count;
     }
     return m_takes_iteration_count;
   }
 
   virtual lldb::StateType GetPlanRunState() = 0;
 
 protected:
   // Constructors and Destructors
   ThreadPlan(ThreadPlanKind kind, const char *name, Thread &thread,
              Vote report_stop_vote, Vote report_run_vote);
 
   // Classes that inherit from ThreadPlan can see and modify these
 
   virtual bool DoWillResume(lldb::StateType resume_state, bool current_plan) {
     return true;
   }
 
   virtual bool DoPlanExplainsStop(Event *event_ptr) = 0;
 
   // This pushes a plan onto the plan stack of the current plan's thread.
   // Also sets the plans to private and not controlling plans.  A plan pushed by
   // another thread plan is never either of the above.
   void PushPlan(lldb::ThreadPlanSP &thread_plan_sp) {
     GetThread().PushPlan(thread_plan_sp);
     thread_plan_sp->SetPrivate(true);
     thread_plan_sp->SetIsControllingPlan(false);
   }
 
   // This gets the previous plan to the current plan (for forwarding requests).
   // This is mostly a formal requirement, it allows us to make the Thread's
   // GetPreviousPlan protected, but only friend ThreadPlan to thread.
 
   ThreadPlan *GetPreviousPlan() { return GetThread().GetPreviousPlan(this); }
 
   // This forwards the private Thread::GetPrivateStopInfo which is generally
   // what ThreadPlan's need to know.
 
   lldb::StopInfoSP GetPrivateStopInfo() {
     return GetThread().GetPrivateStopInfo();
   }
 
   void SetStopInfo(lldb::StopInfoSP stop_reason_sp) {
     GetThread().SetStopInfo(stop_reason_sp);
   }
 
   bool IsUsuallyUnexplainedStopReason(lldb::StopReason);
 
   Status m_status;
   Process &m_process;
   lldb::tid_t m_tid;
   Vote m_report_stop_vote;
   Vote m_report_run_vote;
   bool m_takes_iteration_count;
   bool m_could_not_resolve_hw_bp;
   int32_t m_iteration_count = 1;
 
 private:
   void CachePlanExplainsStop(bool does_explain) {
     m_cached_plan_explains_stop = does_explain ? eLazyBoolYes : eLazyBoolNo;
   }
 
   // For ThreadPlan only
   static lldb::user_id_t GetNextID();
 
   Thread *m_thread; // Stores a cached value of the thread, which is set to
                     // nullptr when the thread resumes.  Don't use this anywhere
                     // but ThreadPlan::GetThread().
   ThreadPlanKind m_kind;
   std::string m_name;
   std::recursive_mutex m_plan_complete_mutex;
   LazyBool m_cached_plan_explains_stop;
   bool m_plan_complete;
   bool m_plan_private;
   bool m_okay_to_discard;
   bool m_is_controlling_plan;
   bool m_plan_succeeded;
 
   lldb::ThreadPlanTracerSP m_tracer_sp;
 
   ThreadPlan(const ThreadPlan &) = delete;
   const ThreadPlan &operator=(const ThreadPlan &) = delete;
 };
 
 // ThreadPlanNull:
 // Threads are assumed to always have at least one plan on the plan stack. This
 // is put on the plan stack when a thread is destroyed so that if you
 // accidentally access a thread after it is destroyed you won't crash. But
 // asking questions of the ThreadPlanNull is definitely an error.
 
 class ThreadPlanNull : public ThreadPlan {
 public:
   ThreadPlanNull(Thread &thread);
   ~ThreadPlanNull() override;
 
   void GetDescription(Stream *s, lldb::DescriptionLevel level) override;
 
   bool ValidatePlan(Stream *error) override;
 
   bool ShouldStop(Event *event_ptr) override;
 
   bool MischiefManaged() override;
 
   bool WillStop() override;
 
   bool IsBasePlan() override { return true; }
 
   bool OkayToDiscard() override { return false; }
 
   const Status &GetStatus() { return m_status; }
 
 protected:
   bool DoPlanExplainsStop(Event *event_ptr) override;
 
   lldb::StateType GetPlanRunState() override;
 
   ThreadPlanNull(const ThreadPlanNull &) = delete;
   const ThreadPlanNull &operator=(const ThreadPlanNull &) = delete;
 };
 
 } // namespace lldb_private
 
 #endif // LLDB_TARGET_THREADPLAN_H

This page was automatically generated by the 2.3.7 LXR engine. The LXR team