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Commit 82866421 authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Fix pc/function name for signal handler frame. 

This refactors the step function slightly to split it up into
distinct pieces since the code needs to handle a signal handler
versus normal step slightly differently.

Add a new error for an invalid elf.

Modify libbacktrace code to handle new error code.

Bug: 130302288

Test: libbacktrace/libunwindstack unit tests.
Change-Id: I3fb9b00c02d2cf2cc5911541bba0346c6f39b8e6
Merged-In: I3fb9b00c02d2cf2cc5911541bba0346c6f39b8e6
(cherry picked from commit d11ed86d)
parent 1dd53f76

libbacktrace/Backtrace.cpp

+2 −0
Original line number Diff line number Diff line
@@ -170,5 +170,7 @@ std::string Backtrace::GetErrorString(BacktraceUnwindError error) { 
      return "Failed to unwind due to invalid unwind information";

    case BACKTRACE_UNWIND_ERROR_REPEATED_FRAME:

      return "Failed to unwind due to same sp/pc repeating";

    case BACKTRACE_UNWIND_ERROR_INVALID_ELF:

      return "Failed to unwind due to invalid elf";

  }

}

libbacktrace/UnwindStack.cpp

+4 −0
Original line number Diff line number Diff line
@@ -89,6 +89,10 @@ bool Backtrace::Unwind(unwindstack::Regs* regs, BacktraceMap* back_map, 
      case unwindstack::ERROR_REPEATED_FRAME:

        error->error_code = BACKTRACE_UNWIND_ERROR_REPEATED_FRAME;

        break;



      case unwindstack::ERROR_INVALID_ELF:

        error->error_code = BACKTRACE_UNWIND_ERROR_INVALID_ELF;

        break;

    }

  }

libbacktrace/include/backtrace/Backtrace.h

+2 −0
Original line number Diff line number Diff line
@@ -64,6 +64,8 @@ enum BacktraceUnwindErrorCode : uint32_t { 
  BACKTRACE_UNWIND_ERROR_UNWIND_INFO,

  // Unwind information stopped due to sp/pc repeating.

  BACKTRACE_UNWIND_ERROR_REPEATED_FRAME,

  // Unwind information stopped due to invalid elf.

  BACKTRACE_UNWIND_ERROR_INVALID_ELF,

};



struct BacktraceUnwindError {

libunwindstack/Elf.cpp

+10 −9
Original line number Diff line number Diff line
@@ -160,7 +160,7 @@ ErrorCode Elf::GetLastErrorCode() { 
  if (valid_) {

    return interface_->LastErrorCode();

  }

  return ERROR_NONE;

  return ERROR_INVALID_ELF;

}



uint64_t Elf::GetLastErrorAddress() {
@@ -170,22 +170,23 @@ uint64_t Elf::GetLastErrorAddress() { 
  return 0;

}



// The relative pc is always relative to the start of the map from which it comes.

bool Elf::Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, Regs* regs, Memory* process_memory,

               bool* finished) {

// The relative pc expectd by this function is relative to the start of the elf.

bool Elf::StepIfSignalHandler(uint64_t rel_pc, Regs* regs, Memory* process_memory) {

  if (!valid_) {

    return false;

  }

  return regs->StepIfSignalHandler(rel_pc, this, process_memory);

}



  // The relative pc expectd by StepIfSignalHandler is relative to the start of the elf.

  if (regs->StepIfSignalHandler(rel_pc, this, process_memory)) {

    *finished = false;

    return true;

// The relative pc is always relative to the start of the map from which it comes.

bool Elf::Step(uint64_t rel_pc, Regs* regs, Memory* process_memory, bool* finished) {

  if (!valid_) {

    return false;

  }



  // Lock during the step which can update information in the object.

  std::lock_guard<std::mutex> guard(lock_);

  return interface_->Step(adjusted_rel_pc, regs, process_memory, finished);

  return interface_->Step(rel_pc, regs, process_memory, finished);

}



bool Elf::IsValidElf(Memory* memory) {

libunwindstack/LocalUnwinder.cpp

+11 −13
Original line number Diff line number Diff line
@@ -111,6 +111,14 @@ bool LocalUnwinder::Unwind(std::vector<LocalFrameData>* frame_info, size_t max_f 
      pc_adjustment = 0;

    }

    step_pc -= pc_adjustment;



    bool finished = false;

    if (elf->StepIfSignalHandler(rel_pc, regs.get(), process_memory_.get())) {

      step_pc = rel_pc;

    } else if (!elf->Step(step_pc, regs.get(), process_memory_.get(), &finished)) {

      finished = true;

    }



    // Skip any locations that are within this library.

    if (num_frames != 0 || !ShouldSkipLibrary(map_info->name)) {

      // Add frame information.
@@ -124,22 +132,12 @@ bool LocalUnwinder::Unwind(std::vector<LocalFrameData>* frame_info, size_t max_f 
      }

      num_frames++;

    }

    if (!elf->valid()) {

      break;

    }

    if (frame_info->size() == max_frames) {

      break;

    }



    adjust_pc = true;

    bool finished;

    if (!elf->Step(rel_pc, step_pc, regs.get(), process_memory_.get(), &finished) || finished) {

      break;

    }

    // pc and sp are the same, terminate the unwind.

    if (cur_pc == regs->pc() && cur_sp == regs->sp()) {

    if (finished || frame_info->size() == max_frames ||

        (cur_pc == regs->pc() && cur_sp == regs->sp())) {

      break;

    }

    adjust_pc = true;

  }

  return num_frames != 0;

}