RegisterContext.cpp

//===-- RegisterContext.cpp -----------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "lldb/Target/RegisterContext.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/Value.h"
#include "lldb/Expression/DWARFExpression.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/StackFrame.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/Thread.h"
#include "lldb/Utility/DataExtractor.h"
#include "lldb/Utility/Endian.h"
#include "lldb/Utility/RegisterValue.h"
#include "lldb/Utility/Scalar.h"

using namespace lldb;
using namespace lldb_private;

RegisterContext::RegisterContext(Thread &thread, uint32_t concrete_frame_idx)
    : m_thread(thread), m_concrete_frame_idx(concrete_frame_idx),
      m_stop_id(thread.GetProcess()->GetStopID()) {}

RegisterContext::~RegisterContext() = default;

void RegisterContext::InvalidateIfNeeded(bool force) {
  ProcessSP process_sp(m_thread.GetProcess());
  bool invalidate = force;
  uint32_t process_stop_id = UINT32_MAX;

  if (process_sp)
    process_stop_id = process_sp->GetStopID();
  else
    invalidate = true;

  if (!invalidate)
    invalidate = process_stop_id != GetStopID();

  if (invalidate) {
    InvalidateAllRegisters();
    SetStopID(process_stop_id);
  }
}

const RegisterInfo *
RegisterContext::GetRegisterInfoByName(llvm::StringRef reg_name,
                                       uint32_t start_idx) {
  if (reg_name.empty())
    return nullptr;

  // Generic register names take precedence over specific register names.
  // For example, on x86 we want "sp" to refer to the complete RSP/ESP register
  // rather than the 16-bit SP pseudo-register.
  uint32_t generic_reg = Args::StringToGenericRegister(reg_name);
  if (generic_reg != LLDB_INVALID_REGNUM) {
    const RegisterInfo *reg_info =
        GetRegisterInfo(eRegisterKindGeneric, generic_reg);
    if (reg_info)
      return reg_info;
  }

  const uint32_t num_registers = GetRegisterCount();
  for (uint32_t reg = start_idx; reg < num_registers; ++reg) {
    const RegisterInfo *reg_info = GetRegisterInfoAtIndex(reg);

    if (reg_name.equals_insensitive(reg_info->name) ||
        reg_name.equals_insensitive(reg_info->alt_name))
      return reg_info;
  }

  return nullptr;
}

const RegisterInfo *RegisterContext::GetRegisterInfo(lldb::RegisterKind kind,
                                                     uint32_t num) {
  const uint32_t reg_num = ConvertRegisterKindToRegisterNumber(kind, num);
  if (reg_num == LLDB_INVALID_REGNUM)
    return nullptr;
  return GetRegisterInfoAtIndex(reg_num);
}

const char *RegisterContext::GetRegisterName(uint32_t reg) {
  const RegisterInfo *reg_info = GetRegisterInfoAtIndex(reg);
  if (reg_info)
    return reg_info->name;
  return nullptr;
}

uint64_t RegisterContext::GetPC(uint64_t fail_value) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_PC);
  uint64_t pc = ReadRegisterAsUnsigned(reg, fail_value);

  if (pc != fail_value) {
    TargetSP target_sp = m_thread.CalculateTarget();
    if (target_sp) {
      Target *target = target_sp.get();
      if (target)
        pc = target->GetOpcodeLoadAddress(pc, AddressClass::eCode);
    }
  }

  return pc;
}

uint64_t RegisterContext::GetThreadPointer(uint64_t fail_value) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_TP);
  return ReadRegisterAsUnsigned(reg, fail_value);
}

bool RegisterContext::SetPC(uint64_t pc) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_PC);
  bool success = WriteRegisterFromUnsigned(reg, pc);
  if (success) {
    StackFrameSP frame_sp(
        m_thread.GetFrameWithConcreteFrameIndex(m_concrete_frame_idx));
    if (frame_sp)
      frame_sp->ChangePC(pc);
    else
      m_thread.ClearStackFrames();
  }
  return success;
}

bool RegisterContext::GetPCForSymbolication(Address &address) {
  addr_t pc = GetPC(LLDB_INVALID_ADDRESS);
  if (pc == LLDB_INVALID_ADDRESS)
    return false;
  TargetSP target_sp = m_thread.CalculateTarget();
  if (!target_sp.get())
    return false;

  if (!BehavesLikeZerothFrame() && pc != 0)
    pc--;
  address.SetLoadAddress(pc, target_sp.get());
  return true;
}

bool RegisterContext::SetPC(Address addr) {
  TargetSP target_sp = m_thread.CalculateTarget();
  Target *target = target_sp.get();

  lldb::addr_t callAddr = addr.GetCallableLoadAddress(target);
  if (callAddr == LLDB_INVALID_ADDRESS)
    return false;

  return SetPC(callAddr);
}

uint64_t RegisterContext::GetSP(uint64_t fail_value) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_SP);
  return ReadRegisterAsUnsigned(reg, fail_value);
}

bool RegisterContext::SetSP(uint64_t sp) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_SP);
  return WriteRegisterFromUnsigned(reg, sp);
}

uint64_t RegisterContext::GetFP(uint64_t fail_value) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_FP);
  return ReadRegisterAsUnsigned(reg, fail_value);
}

bool RegisterContext::SetFP(uint64_t fp) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_FP);
  return WriteRegisterFromUnsigned(reg, fp);
}

uint64_t RegisterContext::GetReturnAddress(uint64_t fail_value) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_RA);
  return ReadRegisterAsUnsigned(reg, fail_value);
}

uint64_t RegisterContext::GetFlags(uint64_t fail_value) {
  uint32_t reg = ConvertRegisterKindToRegisterNumber(eRegisterKindGeneric,
                                                     LLDB_REGNUM_GENERIC_FLAGS);
  return ReadRegisterAsUnsigned(reg, fail_value);
}

uint64_t RegisterContext::ReadRegisterAsUnsigned(uint32_t reg,
                                                 uint64_t fail_value) {
  if (reg != LLDB_INVALID_REGNUM)
    return ReadRegisterAsUnsigned(GetRegisterInfoAtIndex(reg), fail_value);
  return fail_value;
}

uint64_t RegisterContext::ReadRegisterAsUnsigned(const RegisterInfo *reg_info,
                                                 uint64_t fail_value) {
  if (reg_info) {
    RegisterValue value;
    if (ReadRegister(reg_info, value))
      return value.GetAsUInt64();
  }
  return fail_value;
}

bool RegisterContext::WriteRegisterFromUnsigned(uint32_t reg, uint64_t uval) {
  if (reg == LLDB_INVALID_REGNUM)
    return false;
  return WriteRegisterFromUnsigned(GetRegisterInfoAtIndex(reg), uval);
}

bool RegisterContext::WriteRegisterFromUnsigned(const RegisterInfo *reg_info,
                                                uint64_t uval) {
  if (reg_info) {
    RegisterValue value;
    if (value.SetUInt(uval, reg_info->byte_size))
      return WriteRegister(reg_info, value);
  }
  return false;
}

bool RegisterContext::CopyFromRegisterContext(lldb::RegisterContextSP context) {
  uint32_t num_register_sets = context->GetRegisterSetCount();
  // We don't know that two threads have the same register context, so require
  // the threads to be the same.
  if (context->GetThreadID() != GetThreadID())
    return false;

  if (num_register_sets != GetRegisterSetCount())
    return false;

  RegisterContextSP frame_zero_context = m_thread.GetRegisterContext();

  for (uint32_t set_idx = 0; set_idx < num_register_sets; ++set_idx) {
    const RegisterSet *const reg_set = GetRegisterSet(set_idx);

    const uint32_t num_registers = reg_set->num_registers;
    for (uint32_t reg_idx = 0; reg_idx < num_registers; ++reg_idx) {
      const uint32_t reg = reg_set->registers[reg_idx];
      const RegisterInfo *reg_info = GetRegisterInfoAtIndex(reg);
      if (!reg_info || reg_info->value_regs)
        continue;
      RegisterValue reg_value;

      // If we can reconstruct the register from the frame we are copying from,
      // then do so, otherwise use the value from frame 0.
      if (context->ReadRegister(reg_info, reg_value)) {
        WriteRegister(reg_info, reg_value);
      } else if (frame_zero_context->ReadRegister(reg_info, reg_value)) {
        WriteRegister(reg_info, reg_value);
      }
    }
  }
  return true;
}

lldb::tid_t RegisterContext::GetThreadID() const { return m_thread.GetID(); }

uint32_t RegisterContext::NumSupportedHardwareBreakpoints() { return 0; }

uint32_t RegisterContext::SetHardwareBreakpoint(lldb::addr_t addr,
                                                size_t size) {
  return LLDB_INVALID_INDEX32;
}

// Used when parsing DWARF and EH frame information and any other object file
// sections that contain register numbers in them.
uint32_t
RegisterContext::ConvertRegisterKindToRegisterNumber(lldb::RegisterKind kind,
                                                     uint32_t num) {
  const uint32_t num_regs = GetRegisterCount();

  assert(kind < kNumRegisterKinds);
  for (uint32_t reg_idx = 0; reg_idx < num_regs; ++reg_idx) {
    const RegisterInfo *reg_info = GetRegisterInfoAtIndex(reg_idx);

    if (reg_info->kinds[kind] == num)
      return reg_idx;
  }

  return LLDB_INVALID_REGNUM;
}

bool RegisterContext::ClearHardwareBreakpoint(uint32_t hw_idx) { return false; }

uint32_t RegisterContext::NumSupportedHardwareWatchpoints() { return 0; }

uint32_t RegisterContext::SetHardwareWatchpoint(lldb::addr_t addr, size_t size,
                                                bool read, bool write) {
  return LLDB_INVALID_INDEX32;
}

bool RegisterContext::ClearHardwareWatchpoint(uint32_t hw_index) {
  return false;
}

bool RegisterContext::HardwareSingleStep(bool enable) { return false; }

Status RegisterContext::ReadRegisterValueFromMemory(
    const RegisterInfo *reg_info, lldb::addr_t src_addr, uint32_t src_len,
    RegisterValue &reg_value) {
  Status error;
  if (reg_info == nullptr) {
    error.SetErrorString("invalid register info argument.");
    return error;
  }

  // Moving from addr into a register
  //
  // Case 1: src_len == dst_len
  //
  //   |AABBCCDD| Address contents
  //   |AABBCCDD| Register contents
  //
  // Case 2: src_len > dst_len
  //
  //   Status!  (The register should always be big enough to hold the data)
  //
  // Case 3: src_len < dst_len
  //
  //   |AABB| Address contents
  //   |AABB0000| Register contents [on little-endian hardware]
  //   |0000AABB| Register contents [on big-endian hardware]
  const uint32_t dst_len = reg_info->byte_size;

  if (src_len > dst_len) {
    error.SetErrorStringWithFormat(
        "%u bytes is too big to store in register %s (%u bytes)", src_len,
        reg_info->name, dst_len);
    return error;
  }

  ProcessSP process_sp(m_thread.GetProcess());
  if (process_sp) {
    RegisterValue::BytesContainer src(src_len);

    // Read the memory
    const uint32_t bytes_read =
        process_sp->ReadMemory(src_addr, src.data(), src_len, error);

    // Make sure the memory read succeeded...
    if (bytes_read != src_len) {
      if (error.Success()) {
        // This might happen if we read _some_ bytes but not all
        error.SetErrorStringWithFormat("read %u of %u bytes", bytes_read,
                                       src_len);
      }
      return error;
    }

    // We now have a memory buffer that contains the part or all of the
    // register value. Set the register value using this memory data.
    // TODO: we might need to add a parameter to this function in case the byte
    // order of the memory data doesn't match the process. For now we are
    // assuming they are the same.
    reg_value.SetFromMemoryData(*reg_info, src.data(), src_len,
                                process_sp->GetByteOrder(), error);
  } else
    error.SetErrorString("invalid process");

  return error;
}

Status RegisterContext::WriteRegisterValueToMemory(
    const RegisterInfo *reg_info, lldb::addr_t dst_addr, uint32_t dst_len,
    const RegisterValue &reg_value) {
  Status error;
  ProcessSP process_sp(m_thread.GetProcess());

  if (!process_sp) {
    error.SetErrorString("invalid process");
    return error;
  }

  if (reg_info == nullptr) {
    error.SetErrorString("Invalid register info argument.");
    return error;
  }

  // TODO: we might need to add a parameter to this function in case the byte
  // order of the memory data doesn't match the process. For now we are
  // assuming they are the same.
  RegisterValue::BytesContainer dst(dst_len);
  const uint32_t bytes_copied = reg_value.GetAsMemoryData(
      *reg_info, dst.data(), dst_len, process_sp->GetByteOrder(), error);

  if (error.Success()) {
    if (bytes_copied == 0) {
      error.SetErrorString("byte copy failed.");
    } else {
      const uint32_t bytes_written =
          process_sp->WriteMemory(dst_addr, dst.data(), bytes_copied, error);
      if (bytes_written != bytes_copied) {
        if (error.Success()) {
          // This might happen if we read _some_ bytes but not all
          error.SetErrorStringWithFormat("only wrote %u of %u bytes",
                                         bytes_written, bytes_copied);
        }
      }
    }
  }

  return error;
}

lldb::ByteOrder RegisterContext::GetByteOrder() {
  // Get the target process whose privileged thread was used for the register
  // read.
  lldb::ByteOrder byte_order = lldb::eByteOrderInvalid;
  lldb_private::Process *process = CalculateProcess().get();

  if (process)
    byte_order = process->GetByteOrder();
  return byte_order;
}

bool RegisterContext::ReadAllRegisterValues(
    lldb_private::RegisterCheckpoint &reg_checkpoint) {
  return ReadAllRegisterValues(reg_checkpoint.GetData());
}

bool RegisterContext::WriteAllRegisterValues(
    const lldb_private::RegisterCheckpoint &reg_checkpoint) {
  return WriteAllRegisterValues(reg_checkpoint.GetData());
}

TargetSP RegisterContext::CalculateTarget() {
  return m_thread.CalculateTarget();
}

ProcessSP RegisterContext::CalculateProcess() {
  return m_thread.CalculateProcess();
}

ThreadSP RegisterContext::CalculateThread() {
  return m_thread.shared_from_this();
}

StackFrameSP RegisterContext::CalculateStackFrame() {
  // Register contexts might belong to many frames if we have inlined functions
  // inside a frame since all inlined functions share the same registers, so we
  // can't definitively say which frame we come from...
  return StackFrameSP();
}

void RegisterContext::CalculateExecutionContext(ExecutionContext &exe_ctx) {
  m_thread.CalculateExecutionContext(exe_ctx);
}

bool RegisterContext::ConvertBetweenRegisterKinds(lldb::RegisterKind source_rk,
                                                  uint32_t source_regnum,
                                                  lldb::RegisterKind target_rk,
                                                  uint32_t &target_regnum) {
  const uint32_t num_registers = GetRegisterCount();
  for (uint32_t reg = 0; reg < num_registers; ++reg) {
    const RegisterInfo *reg_info = GetRegisterInfoAtIndex(reg);

    if (reg_info->kinds[source_rk] == source_regnum) {
      target_regnum = reg_info->kinds[target_rk];
      return (target_regnum != LLDB_INVALID_REGNUM);
    }
  }
  return false;
}