RegisterContextUnwind.h

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//===-- RegisterContextUnwind.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_REGISTERCONTEXTUNWIND_H
#define LLDB_TARGET_REGISTERCONTEXTUNWIND_H
 
#include <vector>
 
#include "lldb/Symbol/SymbolContext.h"
#include "lldb/Symbol/UnwindPlan.h"
#include "lldb/Target/RegisterContext.h"
#include "lldb/Target/RegisterNumber.h"
#include "lldb/Target/UnwindLLDB.h"
#include "lldb/lldb-private.h"
 
namespace lldb_private {
 
class UnwindLLDB;
class ArchitectureArm;
 
class RegisterContextUnwind : public lldb_private::RegisterContext {
public:
  typedef std::shared_ptr<RegisterContextUnwind> SharedPtr;
 
  RegisterContextUnwind(lldb_private::Thread &thread,
                        const SharedPtr &next_frame,
                        lldb_private::SymbolContext &sym_ctx,
                        uint32_t frame_number,
                        lldb_private::UnwindLLDB &unwind_lldb);
 
  ~RegisterContextUnwind() override = default;
 
  void InvalidateAllRegisters() override;
 
  size_t GetRegisterCount() override;
 
  const lldb_private::RegisterInfo *GetRegisterInfoAtIndex(size_t reg) override;
 
  size_t GetRegisterSetCount() override;
 
  const lldb_private::RegisterSet *GetRegisterSet(size_t reg_set) override;
 
  bool ReadRegister(const lldb_private::RegisterInfo *reg_info,
                    lldb_private::RegisterValue &value) override;
 
  bool WriteRegister(const lldb_private::RegisterInfo *reg_info,
                     const lldb_private::RegisterValue &value) override;
 
  bool ReadAllRegisterValues(lldb::WritableDataBufferSP &data_sp) override;
 
  bool WriteAllRegisterValues(const lldb::DataBufferSP &data_sp) override;
 
  uint32_t ConvertRegisterKindToRegisterNumber(lldb::RegisterKind kind,
                                               uint32_t num) override;
 
  bool IsValid() const;
 
  bool IsTrapHandlerFrame() const;
 
  bool GetCFA(lldb::addr_t &cfa);
 
  bool GetStartPC(lldb::addr_t &start_pc);
 
  bool ReadPC(lldb::addr_t &start_pc);
 
  // Indicates whether this frame *behaves* like frame zero -- the currently
  // executing frame -- or not.  This can be true in the middle of the stack
  // above asynchronous trap handlers (sigtramp) for instance.
  bool BehavesLikeZerothFrame() const override;
 
protected:
  // Provide a location for where THIS function saved the CALLER's register
  // value, or a frame "below" this one saved it. That is, this function doesn't
  // modify the register, it may call a function that does & saved it to stack.
  //
  // The ConcreteRegisterLocation type may be set to eRegisterNotAvailable --
  // this will happen for a volatile register being queried mid-stack.  Instead
  // of floating frame 0's contents of that register up the stack (which may or
  // may not be the value of that reg when the function was executing), we won't
  // return any value.
  //
  // If a non-volatile register (a "preserved" register, a callee-preserved
  // register) is requested mid-stack, and no frames "below" the requested stack
  // have saved the register anywhere, it is safe to assume that frame 0's
  // register value is the same.
  lldb_private::UnwindLLDB::RegisterSearchResult SavedLocationForRegister(
      uint32_t lldb_regnum,
      lldb_private::UnwindLLDB::ConcreteRegisterLocation &regloc);
 
private:
  enum FrameType {
    eNormalFrame,
    eTrapHandlerFrame,
    eDebuggerFrame, // a debugger inferior function call frame; we get caller's
                    // registers from debugger
    eSkipFrame,     // The unwind resulted in a bogus frame but may get back on
                    // track so we don't want to give up yet
    eNotAValidFrame // this frame is invalid for some reason - most likely it is
                    // past the top (end) of the stack
  };
 
  // UnwindLLDB needs to pass around references to ConcreteRegisterLocations
  friend class UnwindLLDB;
  // Architecture may need to retrieve caller register values from this frame
  friend class ArchitectureArm;
 
  // Returns true if we have an unwind loop -- the same stack frame unwinding
  // multiple times.
  bool CheckIfLoopingStack();
 
  // Indicates whether this frame is frame zero -- the currently
  // executing frame -- or not.
  bool IsFrameZero() const;
 
  void InitializeZerothFrame();
 
  void InitializeNonZerothFrame();
 
  SharedPtr GetNextFrame() const;
 
  SharedPtr GetPrevFrame() const;
 
  // A SkipFrame occurs when the unwind out of frame 0 didn't go right -- we've
  // got one bogus frame at frame #1.
  // There is a good chance we'll get back on track if we follow the frame
  // pointer chain (or whatever is appropriate
  // on this ABI) so we allow one invalid frame to be in the stack.  Ideally
  // we'll mark this frame specially at some
  // point and indicate to the user that the unwinder had a hiccup.  Often when
  // this happens we will miss a frame of
  // the program's actual stack in the unwind and we want to flag that for the
  // user somehow.
  bool IsSkipFrame() const;
 
  /// Determines if a SymbolContext is a trap handler or not
  ///
  /// Given a SymbolContext, determines if this is a trap handler function
  /// aka asynchronous signal handler.
  ///
  /// \return
  ///     Returns true if the SymbolContext is a trap handler.
  bool IsTrapHandlerSymbol(lldb_private::Process *process,
                           const lldb_private::SymbolContext &m_sym_ctx) const;
 
  /// Check if the given unwind plan indicates a signal trap handler, and
  /// update frame type and symbol context if so.
  void PropagateTrapHandlerFlagFromUnwindPlan(
      std::shared_ptr<const UnwindPlan> unwind_plan);
 
  std::optional<UnwindPlan::Row::AbstractRegisterLocation>
  GetAbstractRegisterLocation(uint32_t lldb_regnum, lldb::RegisterKind &kind);
 
  bool ReadRegisterValueFromRegisterLocation(
      lldb_private::UnwindLLDB::ConcreteRegisterLocation regloc,
      const lldb_private::RegisterInfo *reg_info,
      lldb_private::RegisterValue &value);
 
  bool WriteRegisterValueToRegisterLocation(
      lldb_private::UnwindLLDB::ConcreteRegisterLocation regloc,
      const lldb_private::RegisterInfo *reg_info,
      const lldb_private::RegisterValue &value);
 
  /// If the unwind has to the caller frame has failed, try something else
  ///
  /// If lldb is using an assembly language based UnwindPlan for a frame and
  /// the unwind to the caller frame fails, try falling back to a generic
  /// UnwindPlan (architecture default unwindplan) to see if that might work
  /// better.  This is mostly helping to work around problems where the
  /// assembly language inspection fails on hand-written assembly code.
  ///
  /// \return
  ///     Returns true if a fallback unwindplan was found & was installed.
  bool TryFallbackUnwindPlan();
 
  /// Switch to the fallback unwind plan unconditionally without any safety
  /// checks that it is providing better results than the normal unwind plan.
  ///
  /// The only time it is valid to call this method is if the full unwindplan is
  /// found to be fundamentally incorrect/impossible.
  ///
  /// Returns true if it was able to install the fallback unwind plan.
  bool ForceSwitchToFallbackUnwindPlan();
 
  // Get the contents of a general purpose (address-size) register for this
  // frame
  // (usually retrieved from the next frame)
  bool ReadGPRValue(lldb::RegisterKind register_kind, uint32_t regnum,
                    lldb::addr_t &value);
 
  bool ReadGPRValue(const RegisterNumber &reg_num, lldb::addr_t &value);
 
  // Get the Frame Address register for a given frame.
  bool ReadFrameAddress(lldb::RegisterKind register_kind,
                        const UnwindPlan::Row::FAValue &fa,
                        lldb::addr_t &address);
 
  std::shared_ptr<const UnwindPlan> GetFastUnwindPlanForFrame();
 
  std::shared_ptr<const UnwindPlan> GetFullUnwindPlanForFrame();
 
  lldb::UnwindPlanSP TryAdoptArchitectureUnwindPlan();
 
  void UnwindLogMsg(const char *fmt, ...) __attribute__((format(printf, 2, 3)));
 
  void UnwindLogMsgVerbose(const char *fmt, ...)
      __attribute__((format(printf, 2, 3)));
 
  bool IsUnwindPlanValidForCurrentPC(
      std::shared_ptr<const UnwindPlan> unwind_plan_sp);
 
  lldb::addr_t GetReturnAddressHint(int32_t plan_offset);
 
  lldb_private::Thread &m_thread;
 
  ///
  // The following tell us how to retrieve the CALLER's register values (ie the
  // "previous" frame, aka the frame above)
  // i.e. where THIS frame saved them
  ///
 
  std::shared_ptr<const UnwindPlan> m_fast_unwind_plan_sp; // may be NULL
  std::shared_ptr<const UnwindPlan> m_full_unwind_plan_sp;
  std::shared_ptr<const UnwindPlan> m_fallback_unwind_plan_sp; // may be NULL
 
  bool m_all_registers_available; // Can we retrieve all regs or just
                                  // nonvolatile regs?
  int m_frame_type;               // enum FrameType
 
  lldb::addr_t m_cfa;
  lldb::addr_t m_afa;
  lldb_private::Address m_start_pc;
  lldb_private::Address m_current_pc;
 
  /// How far into the function we've executed. 0 if no instructions have been
  /// executed yet, std::nullopt if unknown.
  std::optional<int> m_current_offset;
 
  // How far into the function we've executed. 0 if no instructions have been
  // executed yet, std::nullopt if unknown. On architectures where the return
  // address on the stack points to the instruction after the CALL, this value
  // will have 1 subtracted from it. Otherwise, a function that ends in a CALL
  // will have an offset pointing into the next function's address range.
  // m_current_pc has the actual address of the "current" pc.
  std::optional<int> m_current_offset_backed_up_one;
 
  bool m_behaves_like_zeroth_frame; // this frame behaves like frame zero
 
  lldb_private::SymbolContext &m_sym_ctx;
  bool m_sym_ctx_valid; // if ResolveSymbolContextForAddress fails, don't try to
                        // use m_sym_ctx
 
  uint32_t m_frame_number; // What stack frame this RegisterContext is
 
  std::map<uint32_t, lldb_private::UnwindLLDB::ConcreteRegisterLocation>
      m_registers; // where to find reg values for this frame
 
  lldb_private::UnwindLLDB &m_parent_unwind; // The UnwindLLDB that is creating
                                             // this RegisterContextUnwind
 
  RegisterContextUnwind(const RegisterContextUnwind &) = delete;
  const RegisterContextUnwind &
  operator=(const RegisterContextUnwind &) = delete;
};
 
} // namespace lldb_private
 
#endif // LLDB_TARGET_REGISTERCONTEXTUNWIND_H