1//===-- RegisterContextLLDB.h --------------------------------------------*- C++
2//-*-===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef lldb_RegisterContextLLDB_h_
11#define lldb_RegisterContextLLDB_h_
12
13#include <vector>
14
15#include "UnwindLLDB.h"
16#include "lldb/Symbol/SymbolContext.h"
17#include "lldb/Symbol/UnwindPlan.h"
18#include "lldb/Target/RegisterContext.h"
19#include "lldb/Target/RegisterNumber.h"
20#include "lldb/lldb-private.h"
21
22namespace lldb_private {
23
24class UnwindLLDB;
25
26class RegisterContextLLDB : public lldb_private::RegisterContext {
27public:
28  typedef std::shared_ptr<RegisterContextLLDB> SharedPtr;
29
30  RegisterContextLLDB(lldb_private::Thread &thread, const SharedPtr &next_frame,
31                      lldb_private::SymbolContext &sym_ctx,
32                      uint32_t frame_number,
33                      lldb_private::UnwindLLDB &unwind_lldb);
34
35  ~RegisterContextLLDB() override = default;
36
37  void InvalidateAllRegisters() override;
38
39  size_t GetRegisterCount() override;
40
41  const lldb_private::RegisterInfo *GetRegisterInfoAtIndex(size_t reg) override;
42
43  size_t GetRegisterSetCount() override;
44
45  const lldb_private::RegisterSet *GetRegisterSet(size_t reg_set) override;
46
47  bool ReadRegister(const lldb_private::RegisterInfo *reg_info,
48                    lldb_private::RegisterValue &value) override;
49
50  bool WriteRegister(const lldb_private::RegisterInfo *reg_info,
51                     const lldb_private::RegisterValue &value) override;
52
53  bool ReadAllRegisterValues(lldb::DataBufferSP &data_sp) override;
54
55  bool WriteAllRegisterValues(const lldb::DataBufferSP &data_sp) override;
56
57  uint32_t ConvertRegisterKindToRegisterNumber(lldb::RegisterKind kind,
58                                               uint32_t num) override;
59
60  bool IsValid() const;
61
62  bool IsTrapHandlerFrame() const;
63
64  bool GetCFA(lldb::addr_t &cfa);
65
66  bool GetStartPC(lldb::addr_t &start_pc);
67
68  bool ReadPC(lldb::addr_t &start_pc);
69
70private:
71  enum FrameType {
72    eNormalFrame,
73    eTrapHandlerFrame,
74    eDebuggerFrame, // a debugger inferior function call frame; we get caller's
75                    // registers from debugger
76    eSkipFrame,     // The unwind resulted in a bogus frame but may get back on
77                    // track so we don't want to give up yet
78    eNotAValidFrame // this frame is invalid for some reason - most likely it is
79                    // past the top (end) of the stack
80  };
81
82  // UnwindLLDB needs to pass around references to RegisterLocations
83  friend class UnwindLLDB;
84
85  // Returns true if we have an unwind loop -- the same stack frame unwinding
86  // multiple times.
87  bool CheckIfLoopingStack();
88
89  // Indicates whether this frame is frame zero -- the currently
90  // executing frame -- or not.
91  bool IsFrameZero() const;
92
93  void InitializeZerothFrame();
94
95  void InitializeNonZerothFrame();
96
97  SharedPtr GetNextFrame() const;
98
99  SharedPtr GetPrevFrame() const;
100
101  // A SkipFrame occurs when the unwind out of frame 0 didn't go right -- we've
102  // got one bogus frame at frame #1.
103  // There is a good chance we'll get back on track if we follow the frame
104  // pointer chain (or whatever is appropriate
105  // on this ABI) so we allow one invalid frame to be in the stack.  Ideally
106  // we'll mark this frame specially at some
107  // point and indicate to the user that the unwinder had a hiccup.  Often when
108  // this happens we will miss a frame of
109  // the program's actual stack in the unwind and we want to flag that for the
110  // user somehow.
111  bool IsSkipFrame() const;
112
113  /// Determines if a SymbolContext is a trap handler or not
114  ///
115  /// Given a SymbolContext, determines if this is a trap handler function
116  /// aka asynchronous signal handler.
117  ///
118  /// \return
119  ///     Returns true if the SymbolContext is a trap handler.
120  bool IsTrapHandlerSymbol(lldb_private::Process *process,
121                           const lldb_private::SymbolContext &m_sym_ctx) const;
122
123  /// Check if the given unwind plan indicates a signal trap handler, and
124  /// update frame type and symbol context if so.
125  void PropagateTrapHandlerFlagFromUnwindPlan(lldb::UnwindPlanSP unwind_plan);
126
127  // Provide a location for where THIS function saved the CALLER's register
128  // value
129  // Or a frame "below" this one saved it, i.e. a function called by this one,
130  // preserved a register that this
131  // function didn't modify/use.
132  //
133  // The RegisterLocation type may be set to eRegisterNotAvailable -- this will
134  // happen for a volatile register
135  // being queried mid-stack.  Instead of floating frame 0's contents of that
136  // register up the stack (which may
137  // or may not be the value of that reg when the function was executing), we
138  // won't return any value.
139  //
140  // If a non-volatile register (a "preserved" register) is requested mid-stack
141  // and no frames "below" the requested
142  // stack have saved the register anywhere, it is safe to assume that frame 0's
143  // register values are still the same
144  // as the requesting frame's.
145  lldb_private::UnwindLLDB::RegisterSearchResult
146  SavedLocationForRegister(uint32_t lldb_regnum,
147                           lldb_private::UnwindLLDB::RegisterLocation &regloc);
148
149  bool ReadRegisterValueFromRegisterLocation(
150      lldb_private::UnwindLLDB::RegisterLocation regloc,
151      const lldb_private::RegisterInfo *reg_info,
152      lldb_private::RegisterValue &value);
153
154  bool WriteRegisterValueToRegisterLocation(
155      lldb_private::UnwindLLDB::RegisterLocation regloc,
156      const lldb_private::RegisterInfo *reg_info,
157      const lldb_private::RegisterValue &value);
158
159  /// If the unwind has to the caller frame has failed, try something else
160  ///
161  /// If lldb is using an assembly language based UnwindPlan for a frame and
162  /// the unwind to the caller frame fails, try falling back to a generic
163  /// UnwindPlan (architecture default unwindplan) to see if that might work
164  /// better.  This is mostly helping to work around problems where the
165  /// assembly language inspection fails on hand-written assembly code.
166  ///
167  /// \return
168  ///     Returns true if a fallback unwindplan was found & was installed.
169  bool TryFallbackUnwindPlan();
170
171  /// Switch to the fallback unwind plan unconditionally without any safety
172  /// checks that it is providing better results than the normal unwind plan.
173  ///
174  /// The only time it is valid to call this method is if the full unwindplan is
175  /// found to be fundamentally incorrect/impossible.
176  ///
177  /// Returns true if it was able to install the fallback unwind plan.
178  bool ForceSwitchToFallbackUnwindPlan();
179
180  // Get the contents of a general purpose (address-size) register for this
181  // frame
182  // (usually retrieved from the next frame)
183  bool ReadGPRValue(lldb::RegisterKind register_kind, uint32_t regnum,
184                    lldb::addr_t &value);
185
186  bool ReadGPRValue(const RegisterNumber &reg_num, lldb::addr_t &value);
187
188  // Get the Frame Address register for a given frame.
189  bool ReadFrameAddress(lldb::RegisterKind register_kind,
190                          UnwindPlan::Row::FAValue &fa, lldb::addr_t &address);
191
192  lldb::UnwindPlanSP GetFastUnwindPlanForFrame();
193
194  lldb::UnwindPlanSP GetFullUnwindPlanForFrame();
195
196  void UnwindLogMsg(const char *fmt, ...) __attribute__((format(printf, 2, 3)));
197
198  void UnwindLogMsgVerbose(const char *fmt, ...)
199      __attribute__((format(printf, 2, 3)));
200
201  bool IsUnwindPlanValidForCurrentPC(lldb::UnwindPlanSP unwind_plan_sp,
202                                     int &valid_pc_offset);
203
204  lldb::addr_t GetReturnAddressHint(int32_t plan_offset);
205
206  lldb_private::Thread &m_thread;
207
208  ///
209  // The following tell us how to retrieve the CALLER's register values (ie the
210  // "previous" frame, aka the frame above)
211  // i.e. where THIS frame saved them
212  ///
213
214  lldb::UnwindPlanSP m_fast_unwind_plan_sp; // may be NULL
215  lldb::UnwindPlanSP m_full_unwind_plan_sp;
216  lldb::UnwindPlanSP m_fallback_unwind_plan_sp; // may be NULL
217
218  bool m_all_registers_available; // Can we retrieve all regs or just
219                                  // nonvolatile regs?
220  int m_frame_type;               // enum FrameType
221
222  lldb::addr_t m_cfa;
223  lldb::addr_t m_afa;
224  lldb_private::Address m_start_pc;
225  lldb_private::Address m_current_pc;
226
227  int m_current_offset; // how far into the function we've executed; -1 if
228                        // unknown
229                        // 0 if no instructions have been executed yet.
230
231  int m_current_offset_backed_up_one; // how far into the function we've
232                                      // executed; -1 if unknown
233  // 0 if no instructions have been executed yet.
234  // On architectures where the return address on the stack points
235  // to the instruction after the CALL, this value will have 1
236  // subtracted from it.  Else a function that ends in a CALL will
237  // have an offset pointing into the next function's address range.
238  // m_current_pc has the actual address of the "current" pc.
239
240  lldb_private::SymbolContext &m_sym_ctx;
241  bool m_sym_ctx_valid; // if ResolveSymbolContextForAddress fails, don't try to
242                        // use m_sym_ctx
243
244  uint32_t m_frame_number; // What stack frame this RegisterContext is
245
246  std::map<uint32_t, lldb_private::UnwindLLDB::RegisterLocation>
247      m_registers; // where to find reg values for this frame
248
249  lldb_private::UnwindLLDB &m_parent_unwind; // The UnwindLLDB that is creating
250                                             // this RegisterContextLLDB
251
252  // For RegisterContextLLDB only
253
254  DISALLOW_COPY_AND_ASSIGN(RegisterContextLLDB);
255};
256
257} // namespace lldb_private
258
259#endif // lldb_RegisterContextLLDB_h_
260