ThreadPlan.h revision 04cc48eb5cff32268a822b57f87590c9dc2643f8
1//===-- ThreadPlan.h --------------------------------------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9 10#ifndef liblldb_ThreadPlan_h_ 11#define liblldb_ThreadPlan_h_ 12 13// C Includes 14// C++ Includes 15#include <string> 16// Other libraries and framework includes 17// Project includes 18#include "lldb/lldb-private.h" 19#include "lldb/Core/UserID.h" 20#include "lldb/Host/Mutex.h" 21#include "lldb/Target/Process.h" 22#include "lldb/Target/Target.h" 23#include "lldb/Target/Thread.h" 24#include "lldb/Target/ThreadPlanTracer.h" 25#include "lldb/Target/StopInfo.h" 26 27namespace lldb_private { 28 29//------------------------------------------------------------------ 30// ThreadPlan: 31// This is the pure virtual base class for thread plans. 32// 33// The thread plans provide the "atoms" of behavior that 34// all the logical process control, either directly from commands or through 35// more complex composite plans will rely on. 36// 37// Plan Stack: 38// 39// The thread maintaining a thread plan stack, and you program the actions of a particular thread 40// by pushing plans onto the plan stack. 41// There is always a "Current" plan, which is the head of the plan stack, though in some cases 42// a plan may defer to plans higher in the stack for some piece of information. 43// 44// The plan stack is never empty, there is always a Base Plan which persists through the life 45// of the running process. 46// 47// 48// Creating Plans: 49// 50// The thread plan is generally created and added to the plan stack through the QueueThreadPlanFor... API 51// in lldb::Thread. Those API's will return the plan that performs the named operation in a manner 52// appropriate for the current process. The plans in lldb/source/Target are generic 53// implementations, but a Process plugin can override them. 54// 55// ValidatePlan is then called. If it returns false, the plan is unshipped. This is a little 56// convenience which keeps us from having to error out of the constructor. 57// 58// Then the plan is added to the plan stack. When the plan is added to the plan stack its DidPush 59// will get called. This is useful if a plan wants to push any additional plans as it is constructed, 60// since you need to make sure you're already on the stack before you push additional plans. 61// 62// Completed Plans: 63// 64// When the target process stops the plans are queried, among other things, for whether their job is done. 65// If it is they are moved from the plan stack to the Completed Plan stack in reverse order from their position 66// on the plan stack (since multiple plans may be done at a given stop.) This is used primarily so that 67// the lldb::Thread::StopInfo for the thread can be set properly. If one plan pushes another to achieve part of 68// its job, but it doesn't want that sub-plan to be the one that sets the StopInfo, then call SetPrivate on the 69// sub-plan when you create it, and the Thread will pass over that plan in reporting the reason for the stop. 70// 71// Discarded plans: 72// 73// Your plan may also get discarded, i.e. moved from the plan stack to the "discarded plan stack". This can 74// happen, for instance, if the plan is calling a function and the function call crashes and you want 75// to unwind the attempt to call. So don't assume that your plan will always successfully stop. Which leads to: 76// 77// Cleaning up after your plans: 78// 79// When the plan is moved from the plan stack its WillPop method is always called, no matter why. Once it is 80// moved off the plan stack it is done, and won't get a chance to run again. So you should 81// undo anything that affects target state in this method. But be sure to leave the plan able to correctly 82// fill the StopInfo, however. 83// N.B. Don't wait to do clean up target state till the destructor, since that will usually get called when 84// the target resumes, and you want to leave the target state correct for new plans in the time between when 85// your plan gets unshipped and the next resume. 86// 87// Over the lifetime of the plan, various methods of the ThreadPlan are then called in response to changes of state in 88// the process we are debugging as follows: 89// 90// Resuming: 91// 92// When the target process is about to be restarted, the plan's WillResume method is called, 93// giving the plan a chance to prepare for the run. If WillResume returns false, then the 94// process is not restarted. Be sure to set an appropriate error value in the Process if 95// you have to do this. Note, ThreadPlans actually implement DoWillResume, WillResume wraps that call. 96// 97// Next the "StopOthers" method of all the threads are polled, and if one thread's Current plan 98// returns "true" then only that thread gets to run. If more than one returns "true" the threads that want to run solo 99// get run one by one round robin fashion. Otherwise all are let to run. 100// 101// Note, the way StopOthers is implemented, the base class implementation just asks the previous plan. So if your plan 102// has no opinion about whether it should run stopping others or not, just don't implement StopOthers, and the parent 103// will be asked. 104// 105// Finally, for each thread that is running, it run state is set to the return of RunState from the 106// thread's Current plan. 107// 108// Responding to a stop: 109// 110// When the target process stops, the plan is called in the following stages: 111// 112// First the thread asks the Current Plan if it can handle this stop by calling PlanExplainsStop. 113// If the Current plan answers "true" then it is asked if the stop should percolate all the way to the 114// user by calling the ShouldStop method. If the current plan doesn't explain the stop, then we query down 115// the plan stack for a plan that does explain the stop. The plan that does explain the stop then needs to 116// figure out what to do about the plans below it in the stack. If the stop is recoverable, then the plan that 117// understands it can just do what it needs to set up to restart, and then continue. 118// Otherwise, the plan that understood the stop should call DiscardPlanStack to clean up the stack below it. 119// Note, plans actually implement DoPlanExplainsStop, the result is cached in PlanExplainsStop so the DoPlanExplainsStop 120// itself will only get called once per stop. 121// 122// Master plans: 123// 124// In the normal case, when we decide to stop, we will collapse the plan stack up to the point of the plan that understood 125// the stop reason. However, if a plan wishes to stay on the stack after an event it didn't directly handle 126// it can designate itself a "Master" plan by responding true to IsMasterPlan, and then if it wants not to be 127// discarded, it can return true to OkayToDiscard, and it and all its dependent plans will be preserved when 128// we resume execution. 129// 130// The other effect of being a master plan is that when the Master plan is done , if it has set "OkayToDiscard" to false, 131// then it will be popped & execution will stop and return to the user. Remember that if OkayToDiscard is false, the 132// plan will be popped and control will be given to the next plan above it on the stack So setting OkayToDiscard to 133// false means the user will regain control when the MasterPlan is completed. 134// 135// Between these two controls this allows things like: a MasterPlan/DontDiscard Step Over to hit a breakpoint, stop and 136// return control to the user, but then when the user continues, the step out succeeds. 137// Even more tricky, when the breakpoint is hit, the user can continue to step in/step over/etc, and finally when they 138// continue, they will finish up the Step Over. 139// 140// FIXME: MasterPlan & OkayToDiscard aren't really orthogonal. MasterPlan designation means that this plan controls 141// it's fate and the fate of plans below it. OkayToDiscard tells whether the MasterPlan wants to stay on the stack. I 142// originally thought "MasterPlan-ness" would need to be a fixed characteristic of a ThreadPlan, in which case you needed 143// the extra control. But that doesn't seem to be true. So we should be able to convert to only MasterPlan status to mean 144// the current "MasterPlan/DontDiscard". Then no plans would be MasterPlans by default, and you would set the ones you 145// wanted to be "user level" in this way. 146// 147// 148// Actually Stopping: 149// 150// If a plan says responds "true" to ShouldStop, then it is asked if it's job is complete by calling 151// MischiefManaged. If that returns true, the thread is popped from the plan stack and added to the 152// Completed Plan Stack. Then the next plan in the stack is asked if it ShouldStop, and it returns "true", 153// it is asked if it is done, and if yes popped, and so on till we reach a plan that is not done. 154// 155// Since you often know in the ShouldStop method whether your plan is complete, as a convenience you can call 156// SetPlanComplete and the ThreadPlan implementation of MischiefManaged will return "true", without your having 157// to redo the calculation when your sub-classes MischiefManaged is called. If you call SetPlanComplete, you can 158// later use IsPlanComplete to determine whether the plan is complete. This is only a convenience for sub-classes, 159// the logic in lldb::Thread will only call MischiefManaged. 160// 161// One slightly tricky point is you have to be careful using SetPlanComplete in PlanExplainsStop because you 162// are not guaranteed that PlanExplainsStop for a plan will get called before ShouldStop gets called. If your sub-plan 163// explained the stop and then popped itself, only your ShouldStop will get called. 164// 165// If ShouldStop for any thread returns "true", then the WillStop method of the Current plan of 166// all threads will be called, the stop event is placed on the Process's public broadcaster, and 167// control returns to the upper layers of the debugger. 168// 169// Reporting the stop: 170// 171// When the process stops, the thread is given a StopReason, in the form of a StopInfo object. If there is a completed 172// plan corresponding to the stop, then the "actual" stop reason will be suppressed, and instead a StopInfoThreadPlan 173// object will be cons'ed up from the highest completed plan in the stack. However, if the plan doesn't want to be 174// the stop reason, then it can call SetPlanComplete and pass in "false" for the "success" parameter. In that case, 175// the real stop reason will be used instead. One exapmle of this is the "StepRangeStepIn" thread plan. If it stops 176// because of a crash or breakpoint hit, it wants to unship itself, because it isn't so useful to have step in keep going 177// 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. 178// 179// Cleaning up the plan stack: 180// 181// One of the complications of MasterPlans is that you may get past the limits of a plan without triggering it to clean 182// itself up. For instance, if you are doing a MasterPlan StepOver, and hit a breakpoint in a called function, then 183// step over enough times to step out of the initial StepOver range, each of the step overs will explain the stop & 184// take themselves off the stack, but control would never be returned to the original StepOver. Eventually, the user 185// will continue, and when that continue stops, the old stale StepOver plan that was left on the stack will get woken 186// up and notice it is done. But that can leave junk on the stack for a while. To avoid that, the plans implement a 187// "IsPlanStale" method, that can check whether it is relevant anymore. On stop, after the regular plan negotiation, 188// the remaining plan stack is consulted and if any plan says it is stale, it and the plans below it are discarded from 189// the stack. 190// 191// Automatically Resuming: 192// 193// If ShouldStop for all threads returns "false", then the target process will resume. This then cycles back to 194// Resuming above. 195// 196// Reporting eStateStopped events when the target is restarted: 197// 198// If a plan decides to auto-continue the target by returning "false" from ShouldStop, then it will be asked 199// whether the Stopped event should still be reported. For instance, if you hit a breakpoint that is a User set 200// breakpoint, but the breakpoint callback said to continue the target process, you might still want to inform 201// the upper layers of lldb that the stop had happened. 202// The way this works is every thread gets to vote on whether to report the stop. If all votes are eVoteNoOpinion, 203// then the thread list will decide what to do (at present it will pretty much always suppress these stopped events.) 204// If there is an eVoteYes, then the event will be reported regardless of the other votes. If there is an eVoteNo 205// and no eVoteYes's, then the event won't be reported. 206// 207// One other little detail here, sometimes a plan will push another plan onto the plan stack to do some part of 208// the first plan's job, and it would be convenient to tell that plan how it should respond to ShouldReportStop. 209// You can do that by setting the stop_vote in the child plan when you create it. 210// 211// Suppressing the initial eStateRunning event: 212// 213// The private process running thread will take care of ensuring that only one "eStateRunning" event will be 214// delivered to the public Process broadcaster per public eStateStopped event. However there are some cases 215// where the public state of this process is eStateStopped, but a thread plan needs to restart the target, but 216// doesn't want the running event to be publically broadcast. The obvious example of this is running functions 217// by hand as part of expression evaluation. To suppress the running event return eVoteNo from ShouldReportStop, 218// to force a running event to be reported return eVoteYes, in general though you should return eVoteNoOpinion 219// which will allow the ThreadList to figure out the right thing to do. 220// The run_vote argument to the constructor works like stop_vote, and is a way for a plan to instruct a sub-plan 221// on how to respond to ShouldReportStop. 222// 223//------------------------------------------------------------------ 224 225class ThreadPlan : 226 public UserID 227{ 228public: 229 typedef enum 230 { 231 eAllThreads, 232 eSomeThreads, 233 eThisThread 234 } ThreadScope; 235 236 // We use these enums so that we can cast a base thread plan to it's real type without having to resort 237 // to dynamic casting. 238 typedef enum 239 { 240 eKindGeneric, 241 eKindBase, 242 eKindCallFunction, 243 eKindStepInstruction, 244 eKindStepOut, 245 eKindStepOverBreakpoint, 246 eKindStepOverRange, 247 eKindStepInRange, 248 eKindRunToAddress, 249 eKindStepThrough, 250 eKindStepUntil, 251 eKindTestCondition 252 253 } ThreadPlanKind; 254 255 //------------------------------------------------------------------ 256 // Constructors and Destructors 257 //------------------------------------------------------------------ 258 ThreadPlan (ThreadPlanKind kind, 259 const char *name, 260 Thread &thread, 261 Vote stop_vote, 262 Vote run_vote); 263 264 virtual 265 ~ThreadPlan(); 266 267 //------------------------------------------------------------------ 268 /// Returns the name of this thread plan. 269 /// 270 /// @return 271 /// A const char * pointer to the thread plan's name. 272 //------------------------------------------------------------------ 273 const char * 274 GetName () const 275 { 276 return m_name.c_str(); 277 } 278 279 //------------------------------------------------------------------ 280 /// Returns the Thread that is using this thread plan. 281 /// 282 /// @return 283 /// A pointer to the thread plan's owning thread. 284 //------------------------------------------------------------------ 285 Thread & 286 GetThread() 287 { 288 return m_thread; 289 } 290 291 const Thread & 292 GetThread() const 293 { 294 return m_thread; 295 } 296 297 Target & 298 GetTarget() 299 { 300 return m_thread.GetProcess()->GetTarget(); 301 } 302 303 const Target & 304 GetTarget() const 305 { 306 return m_thread.GetProcess()->GetTarget(); 307 } 308 309 //------------------------------------------------------------------ 310 /// Print a description of this thread to the stream \a s. 311 /// \a thread. 312 /// 313 /// @param[in] s 314 /// The stream to which to print the description. 315 /// 316 /// @param[in] level 317 /// The level of description desired. Note that eDescriptionLevelBrief 318 /// will be used in the stop message printed when the plan is complete. 319 //------------------------------------------------------------------ 320 virtual void 321 GetDescription (Stream *s, 322 lldb::DescriptionLevel level) = 0; 323 324 //------------------------------------------------------------------ 325 /// Returns whether this plan could be successfully created. 326 /// 327 /// @param[in] error 328 /// A stream to which to print some reason why the plan could not be created. 329 /// Can be NULL. 330 /// 331 /// @return 332 /// \b true if the plan should be queued, \b false otherwise. 333 //------------------------------------------------------------------ 334 virtual bool 335 ValidatePlan (Stream *error) = 0; 336 337 bool 338 TracerExplainsStop () 339 { 340 if (!m_tracer_sp) 341 return false; 342 else 343 return m_tracer_sp->TracerExplainsStop(); 344 } 345 346 347 lldb::StateType 348 RunState (); 349 350 bool 351 PlanExplainsStop (Event *event_ptr); 352 353 virtual bool 354 ShouldStop (Event *event_ptr) = 0; 355 356 virtual bool 357 ShouldAutoContinue (Event *event_ptr) 358 { 359 return false; 360 } 361 362 // Whether a "stop class" event should be reported to the "outside world". In general 363 // if a thread plan is active, events should not be reported. 364 365 virtual Vote 366 ShouldReportStop (Event *event_ptr); 367 368 virtual Vote 369 ShouldReportRun (Event *event_ptr); 370 371 virtual void 372 SetStopOthers (bool new_value); 373 374 virtual bool 375 StopOthers (); 376 377 // This is the wrapper for DoWillResume that does generic ThreadPlan logic, then 378 // calls DoWillResume. 379 bool 380 WillResume (lldb::StateType resume_state, bool current_plan); 381 382 virtual bool 383 WillStop () = 0; 384 385 bool 386 IsMasterPlan() 387 { 388 return m_is_master_plan; 389 } 390 391 bool 392 SetIsMasterPlan (bool value) 393 { 394 bool old_value = m_is_master_plan; 395 m_is_master_plan = value; 396 return old_value; 397 } 398 399 virtual bool 400 OkayToDiscard(); 401 402 void 403 SetOkayToDiscard (bool value) 404 { 405 m_okay_to_discard = value; 406 } 407 408 // The base class MischiefManaged does some cleanup - so you have to call it 409 // in your MischiefManaged derived class. 410 virtual bool 411 MischiefManaged (); 412 413 virtual void 414 ThreadDestroyed () 415 { 416 // Any cleanup that a plan might want to do in case the thread goes away 417 // in the middle of the plan being queued on a thread can be done here. 418 } 419 420 bool 421 GetPrivate () 422 { 423 return m_plan_private; 424 } 425 426 void 427 SetPrivate (bool input) 428 { 429 m_plan_private = input; 430 } 431 432 virtual void 433 DidPush(); 434 435 virtual void 436 WillPop(); 437 438 // This pushes \a plan onto the plan stack of the current plan's thread. 439 void 440 PushPlan (lldb::ThreadPlanSP &thread_plan_sp) 441 { 442 m_thread.PushPlan (thread_plan_sp); 443 } 444 445 ThreadPlanKind GetKind() const 446 { 447 return m_kind; 448 } 449 450 bool 451 IsPlanComplete(); 452 453 void 454 SetPlanComplete (bool success = true); 455 456 virtual bool 457 IsPlanStale () 458 { 459 return false; 460 } 461 462 bool 463 PlanSucceeded () 464 { 465 return m_plan_succeeded; 466 } 467 468 virtual bool 469 IsBasePlan() 470 { 471 return false; 472 } 473 474 lldb::ThreadPlanTracerSP & 475 GetThreadPlanTracer() 476 { 477 return m_tracer_sp; 478 } 479 480 void 481 SetThreadPlanTracer (lldb::ThreadPlanTracerSP new_tracer_sp) 482 { 483 m_tracer_sp = new_tracer_sp; 484 } 485 486 void 487 DoTraceLog () 488 { 489 if (m_tracer_sp && m_tracer_sp->TracingEnabled()) 490 m_tracer_sp->Log(); 491 } 492 493 // Some thread plans hide away the actual stop info which caused any particular stop. For 494 // instance the ThreadPlanCallFunction restores the original stop reason so that stopping and 495 // calling a few functions won't lose the history of the run. 496 // This call can be implemented to get you back to the real stop info. 497 virtual lldb::StopInfoSP 498 GetRealStopInfo () 499 { 500 return m_thread.GetStopInfo (); 501 } 502 503 virtual lldb::ValueObjectSP 504 GetReturnValueObject () 505 { 506 return lldb::ValueObjectSP(); 507 } 508 509 // If a thread plan stores the state before it was run, then you might 510 // want to restore the state when it is done. This will do that job. 511 // This is mostly useful for artificial plans like CallFunction plans. 512 513 virtual bool 514 RestoreThreadState() 515 { 516 // Nothing to do in general. 517 return true; 518 } 519 520 virtual bool 521 IsVirtualStep() 522 { 523 return false; 524 } 525 526protected: 527 //------------------------------------------------------------------ 528 // Classes that inherit from ThreadPlan can see and modify these 529 //------------------------------------------------------------------ 530 531 virtual bool 532 DoWillResume (lldb::StateType resume_state, bool current_plan) { return true; }; 533 534 virtual bool 535 DoPlanExplainsStop (Event *event_ptr) = 0; 536 537 // This gets the previous plan to the current plan (for forwarding requests). 538 // This is mostly a formal requirement, it allows us to make the Thread's 539 // GetPreviousPlan protected, but only friend ThreadPlan to thread. 540 541 ThreadPlan * 542 GetPreviousPlan () 543 { 544 return m_thread.GetPreviousPlan (this); 545 } 546 547 // This forwards the private Thread::GetPrivateStopInfo which is generally what 548 // ThreadPlan's need to know. 549 550 lldb::StopInfoSP 551 GetPrivateStopInfo() 552 { 553 return m_thread.GetPrivateStopInfo (); 554 } 555 556 void 557 SetStopInfo (lldb::StopInfoSP stop_reason_sp) 558 { 559 m_thread.SetStopInfo (stop_reason_sp); 560 } 561 562 void 563 CachePlanExplainsStop (bool does_explain) 564 { 565 m_cached_plan_explains_stop = does_explain ? eLazyBoolYes : eLazyBoolNo; 566 } 567 568 LazyBool 569 GetCachedPlanExplainsStop () const 570 { 571 return m_cached_plan_explains_stop; 572 } 573 574 virtual lldb::StateType 575 GetPlanRunState () = 0; 576 577 Thread &m_thread; 578 Vote m_stop_vote; 579 Vote m_run_vote; 580 581private: 582 //------------------------------------------------------------------ 583 // For ThreadPlan only 584 //------------------------------------------------------------------ 585 static lldb::user_id_t GetNextID (); 586 587 ThreadPlanKind m_kind; 588 std::string m_name; 589 Mutex m_plan_complete_mutex; 590 LazyBool m_cached_plan_explains_stop; 591 bool m_plan_complete; 592 bool m_plan_private; 593 bool m_okay_to_discard; 594 bool m_is_master_plan; 595 bool m_plan_succeeded; 596 597 lldb::ThreadPlanTracerSP m_tracer_sp; 598 599private: 600 DISALLOW_COPY_AND_ASSIGN(ThreadPlan); 601}; 602 603 604} // namespace lldb_private 605 606#endif // liblldb_ThreadPlan_h_ 607