libunwindstack/Unwinder.cpp

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <elf.h>
#include <inttypes.h>
#include <stdint.h>
#include <sys/types.h>
#include <unistd.h>

#include <android-base/stringprintf.h>

#include <unwindstack/Elf.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Unwinder.h>

namespace unwindstack {

void Unwinder::FillInFrame(MapInfo* map_info, uint64_t* rel_pc) {
  size_t frame_num = frames_.size();
  frames_.resize(frame_num + 1);
  FrameData* frame = &frames_.at(frame_num);
  frame->num = frame_num;
  frame->pc = regs_->pc();
  frame->sp = regs_->sp();
  frame->rel_pc = frame->pc;

  if (map_info == nullptr) {
    return;
  }

  Elf* elf = map_info->GetElf(process_memory_, true);
  *rel_pc = elf->GetRelPc(regs_->pc(), map_info);
  if (frame_num != 0) {
    // Don't adjust the first frame pc.
    frame->rel_pc = regs_->GetAdjustedPc(*rel_pc, elf);

    // Adjust the original pc.
    frame->pc -= *rel_pc - frame->rel_pc;
  } else {
    frame->rel_pc = *rel_pc;
  }

  frame->map_name = map_info->name;
  frame->map_offset = map_info->elf_offset;
  frame->map_start = map_info->start;
  frame->map_end = map_info->end;

  if (!elf->GetFunctionName(frame->rel_pc, &frame->function_name, &frame->function_offset)) {
    frame->function_name = "";
    frame->function_offset = 0;
  }
}

void Unwinder::Unwind() {
  frames_.clear();

  bool return_address_attempt = false;
  for (; frames_.size() < max_frames_;) {
    MapInfo* map_info = maps_->Find(regs_->pc());

    uint64_t rel_pc;
    FillInFrame(map_info, &rel_pc);

    bool stepped;
    if (map_info == nullptr) {
      stepped = false;
    } else {
      bool finished;
      stepped = map_info->elf->Step(rel_pc + map_info->elf_offset, regs_, process_memory_.get(),
                                    &finished);
      if (stepped && finished) {
        break;
      }
    }
    if (!stepped) {
      if (return_address_attempt) {
        // Remove the speculative frame.
        frames_.pop_back();
        break;
      } else {
        // Steping didn't work, try this secondary method.
        if (!regs_->SetPcFromReturnAddress(process_memory_.get())) {
          break;
        }
        return_address_attempt = true;
      }
    } else {
      return_address_attempt = false;
    }
  }
}

std::string Unwinder::FormatFrame(size_t frame_num) {
  if (frame_num >= frames_.size()) {
    return "";
  }
  return FormatFrame(frames_[frame_num],
                     regs_->MachineType() == EM_ARM || regs_->MachineType() == EM_386);
}

std::string Unwinder::FormatFrame(const FrameData& frame, bool bits32) {
  std::string data;

  if (bits32) {
    data += android::base::StringPrintf("  #%02zu pc %08" PRIx64, frame.num, frame.rel_pc);
  } else {
    data += android::base::StringPrintf("  #%02zu pc %016" PRIx64, frame.num, frame.rel_pc);
  }

  if (frame.map_offset != 0) {
    data += android::base::StringPrintf(" (offset 0x%" PRIx64 ")", frame.map_offset);
  }

  if (frame.map_start == frame.map_end) {
    // No valid map associated with this frame.
    data += "  <unknown>";
  } else if (!frame.map_name.empty()) {
    data += "  " + frame.map_name;
  } else {
    data += android::base::StringPrintf("  <anonymous:%" PRIx64 ">", frame.map_start);
  }
  if (!frame.function_name.empty()) {
    data += " (" + frame.function_name;
    if (frame.function_offset != 0) {
      data += android::base::StringPrintf("+%" PRId64, frame.function_offset);
    }
    data += ')';
  }
  return data;
}

}  // namespace unwindstack