/*

 * Copyright (C) 2016 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 <stdint.h>

#include <unwindstack/MachineArm.h>

#include <unwindstack/Memory.h>

#include <unwindstack/RegsArm.h>

#include "ArmExidx.h"

#include "ElfInterfaceArm.h"

namespace unwindstack {

bool ElfInterfaceArm::Init(int64_t* load_bias) {

  if (!ElfInterface32::Init(load_bias)) {

    return false;

  }

  load_bias_ = *load_bias;

  return true;

}

bool ElfInterfaceArm::FindEntry(uint32_t pc, uint64_t* entry_offset) {

  if (start_offset_ == 0 || total_entries_ == 0) {

    last_error_.code = ERROR_UNWIND_INFO;

    return false;

  }

  size_t first = 0;

  size_t last = total_entries_;

  while (first < last) {

    size_t current = (first + last) / 2;

    uint32_t addr = addrs_[current];

    if (addr == 0) {

      if (!GetPrel31Addr(start_offset_ + current * 8, &addr)) {

        return false;

      }

      addrs_[current] = addr;

    }

    if (pc == addr) {

      *entry_offset = start_offset_ + current * 8;

      return true;

    }

    if (pc < addr) {

      last = current;

    } else {

      first = current + 1;

    }

  }

  if (last != 0) {

    *entry_offset = start_offset_ + (last - 1) * 8;

    return true;

  }

  last_error_.code = ERROR_UNWIND_INFO;

  return false;

}

bool ElfInterfaceArm::GetPrel31Addr(uint32_t offset, uint32_t* addr) {

  uint32_t data;

  if (!memory_->Read32(offset, &data)) {

    last_error_.code = ERROR_MEMORY_INVALID;

    last_error_.address = offset;

    return false;

  }

  // Sign extend the value if necessary.

  int32_t value = (static_cast<int32_t>(data) << 1) >> 1;

  *addr = offset + value;

  return true;

}

#if !defined(PT_ARM_EXIDX)

#define PT_ARM_EXIDX 0x70000001

#endif

void ElfInterfaceArm::HandleUnknownType(uint32_t type, uint64_t ph_offset, uint64_t ph_filesz) {

  if (type != PT_ARM_EXIDX) {

    return;

  }

  // The offset already takes into account the load bias.

  start_offset_ = ph_offset;

  // Always use filesz instead of memsz. In most cases they are the same,

  // but some shared libraries wind up setting one correctly and not the other.

  total_entries_ = ph_filesz / 8;

}

bool ElfInterfaceArm::Step(uint64_t pc, Regs* regs, Memory* process_memory, bool* finished,

                           bool* is_signal_frame) {

  // Dwarf unwind information is precise about whether a pc is covered or not,

  // but arm unwind information only has ranges of pc. In order to avoid

  // incorrectly doing a bad unwind using arm unwind information for a

  // different function, always try and unwind with the dwarf information first.

  return ElfInterface32::Step(pc, regs, process_memory, finished, is_signal_frame) ||

         StepExidx(pc, regs, process_memory, finished);

}

bool ElfInterfaceArm::StepExidx(uint64_t pc, Regs* regs, Memory* process_memory, bool* finished) {

  // Adjust the load bias to get the real relative pc.

  if (pc < load_bias_) {

    last_error_.code = ERROR_UNWIND_INFO;

    return false;

  }

  pc -= load_bias_;

  RegsArm* regs_arm = reinterpret_cast<RegsArm*>(regs);

  uint64_t entry_offset;

  if (!FindEntry(pc, &entry_offset)) {

    return false;

  }

  ArmExidx arm(regs_arm, memory_.get(), process_memory);

  arm.set_cfa(regs_arm->sp());

  bool return_value = false;

  if (arm.ExtractEntryData(entry_offset) && arm.Eval()) {

    // If the pc was not set, then use the LR registers for the PC.

    if (!arm.pc_set()) {

      (*regs_arm)[ARM_REG_PC] = (*regs_arm)[ARM_REG_LR];

    }

    (*regs_arm)[ARM_REG_SP] = arm.cfa();

    return_value = true;

    // If the pc was set to zero, consider this the final frame.

    *finished = (regs_arm->pc() == 0) ? true : false;

  }

  if (arm.status() == ARM_STATUS_NO_UNWIND) {

    *finished = true;

    return true;

  }

  if (!return_value) {

    switch (arm.status()) {

      case ARM_STATUS_NONE:

      case ARM_STATUS_NO_UNWIND:

      case ARM_STATUS_FINISH:

        last_error_.code = ERROR_NONE;

        break;

      case ARM_STATUS_RESERVED:

      case ARM_STATUS_SPARE:

      case ARM_STATUS_TRUNCATED:

      case ARM_STATUS_MALFORMED:

      case ARM_STATUS_INVALID_ALIGNMENT:

      case ARM_STATUS_INVALID_PERSONALITY:

        last_error_.code = ERROR_UNWIND_INFO;

        break;

      case ARM_STATUS_READ_FAILED:

        last_error_.code = ERROR_MEMORY_INVALID;

        last_error_.address = arm.status_address();

        break;

    }

  }

  return return_value;

}

bool ElfInterfaceArm::GetFunctionName(uint64_t addr, SharedString* name, uint64_t* offset) {

  // For ARM, thumb function symbols have bit 0 set, but the address passed

  // in here might not have this bit set and result in a failure to find

  // the thumb function names. Adjust the address and offset to account

  // for this possible case.

  if (ElfInterface32::GetFunctionName(addr | 1, name, offset)) {

    *offset &= ~1;

    return true;

  }

  return false;

}

}  // namespace unwindstack