/*

 * Copyright (C) 2018 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 <stdint.h>

#include <string.h>

#include <sys/mman.h>

#include <string>

#include <vector>

#include <android-base/file.h>

#include <unwindstack/Global.h>

#include <unwindstack/MapInfo.h>

#include <unwindstack/Maps.h>

#include <unwindstack/Memory.h>

namespace unwindstack {

Global::Global(std::shared_ptr<Memory>& memory) : memory_(memory) {}

Global::Global(std::shared_ptr<Memory>& memory, std::vector<std::string>& search_libs)

    : memory_(memory), search_libs_(search_libs) {}

void Global::SetArch(ArchEnum arch) {

  if (arch_ == ARCH_UNKNOWN) {

    arch_ = arch;

    ProcessArch();

  }

}

bool Global::Searchable(const std::string& name) {

  if (search_libs_.empty()) {

    return true;

  }

  if (name.empty()) {

    return false;

  }

  std::string base_name = android::base::Basename(name);

  for (const std::string& lib : search_libs_) {

    if (base_name == lib) {

      return true;

    }

  }

  return false;

}

void Global::FindAndReadVariable(Maps* maps, const char* var_str) {

  std::string variable(var_str);

  // When looking for global variables, do not arbitrarily search every

  // readable map. Instead look for a specific pattern that must exist.

  // The pattern should be a readable map, followed by a read-write

  // map with a non-zero offset.

  // For example:

  //   f0000-f1000 0 r-- /system/lib/libc.so

  //   f1000-f2000 1000 r-x /system/lib/libc.so

  //   f2000-f3000 2000 rw- /system/lib/libc.so

  // This also works:

  //   f0000-f2000 0 r-- /system/lib/libc.so

  //   f2000-f3000 2000 rw- /system/lib/libc.so

  // It is also possible to see empty maps after the read-only like so:

  //   f0000-f1000 0 r-- /system/lib/libc.so

  //   f1000-f2000 0 ---

  //   f2000-f3000 1000 r-x /system/lib/libc.so

  //   f3000-f4000 2000 rw- /system/lib/libc.so

  MapInfo* map_zero = nullptr;

  for (const auto& info : *maps) {

    if ((info->flags() & (PROT_READ | PROT_WRITE)) == (PROT_READ | PROT_WRITE) &&

        map_zero != nullptr && Searchable(info->name()) && info->name() == map_zero->name()) {

      Elf* elf = map_zero->GetElf(memory_, arch());

      uint64_t ptr;

      if (elf->GetGlobalVariableOffset(variable, &ptr) && ptr != 0) {

        uint64_t offset_end = info->offset() + info->end() - info->start();

        if (ptr >= info->offset() && ptr < offset_end) {

          ptr = info->start() + ptr - info->offset();

          if (ReadVariableData(ptr)) {

            break;

          }

        }

      }

    } else if (info->offset() == 0 && !info->name().empty()) {

      map_zero = info.get();

    }

  }

}

}  // namespace unwindstack