platform_system_core/libunwindstack/Regs.cpp

/*
 * 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 <stdint.h>
#include <sys/ptrace.h>
#include <sys/uio.h>

#include <vector>

#include <unwindstack/Elf.h>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Regs.h>
#include <unwindstack/RegsArm.h>
#include <unwindstack/RegsArm64.h>
#include <unwindstack/RegsMips.h>
#include <unwindstack/RegsMips64.h>
#include <unwindstack/RegsX86.h>
#include <unwindstack/RegsX86_64.h>
#include <unwindstack/UserArm.h>
#include <unwindstack/UserArm64.h>
#include <unwindstack/UserMips.h>
#include <unwindstack/UserMips64.h>
#include <unwindstack/UserX86.h>
#include <unwindstack/UserX86_64.h>

namespace unwindstack {

// The largest user structure.
constexpr size_t MAX_USER_REGS_SIZE = sizeof(mips64_user_regs) + 10;

// This function assumes that reg_data is already aligned to a 64 bit value.
// If not this could crash with an unaligned access.
Regs* Regs::RemoteGet(pid_t pid) {
  // Make the buffer large enough to contain the largest registers type.
  std::vector<uint64_t> buffer(MAX_USER_REGS_SIZE / sizeof(uint64_t));
  struct iovec io;
  io.iov_base = buffer.data();
  io.iov_len = buffer.size() * sizeof(uint64_t);

  if (ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, reinterpret_cast<void*>(&io)) == -1) {
    return nullptr;
  }

  switch (io.iov_len) {
  case sizeof(x86_user_regs):
    return RegsX86::Read(buffer.data());
  case sizeof(x86_64_user_regs):
    return RegsX86_64::Read(buffer.data());
  case sizeof(arm_user_regs):
    return RegsArm::Read(buffer.data());
  case sizeof(arm64_user_regs):
    return RegsArm64::Read(buffer.data());
  case sizeof(mips_user_regs):
    return RegsMips::Read(buffer.data());
  case sizeof(mips64_user_regs):
    return RegsMips64::Read(buffer.data());
  }
  return nullptr;
}

Regs* Regs::CreateFromUcontext(ArchEnum arch, void* ucontext) {
  switch (arch) {
    case ARCH_X86:
      return RegsX86::CreateFromUcontext(ucontext);
    case ARCH_X86_64:
      return RegsX86_64::CreateFromUcontext(ucontext);
    case ARCH_ARM:
      return RegsArm::CreateFromUcontext(ucontext);
    case ARCH_ARM64:
      return RegsArm64::CreateFromUcontext(ucontext);
    case ARCH_MIPS:
      return RegsMips::CreateFromUcontext(ucontext);
    case ARCH_MIPS64:
      return RegsMips64::CreateFromUcontext(ucontext);
    case ARCH_UNKNOWN:
    default:
      return nullptr;
  }
}

ArchEnum Regs::CurrentArch() {
#if defined(__arm__)
  return ARCH_ARM;
#elif defined(__aarch64__)
  return ARCH_ARM64;
#elif defined(__i386__)
  return ARCH_X86;
#elif defined(__x86_64__)
  return ARCH_X86_64;
#else
  abort();
#endif
}

Regs* Regs::CreateFromLocal() {
  Regs* regs;
#if defined(__arm__)
  regs = new RegsArm();
#elif defined(__aarch64__)
  regs = new RegsArm64();
#elif defined(__i386__)
  regs = new RegsX86();
#elif defined(__x86_64__)
  regs = new RegsX86_64();
#else
  abort();
#endif
  return regs;
}

uint64_t GetPcAdjustment(uint64_t rel_pc, Elf* elf, ArchEnum arch) {
  switch (arch) {
    case ARCH_ARM: {
      if (!elf->valid()) {
        return 2;
      }

      uint64_t load_bias = elf->GetLoadBias();
      if (rel_pc < load_bias) {
        if (rel_pc < 2) {
          return 0;
        }
        return 2;
      }
      uint64_t adjusted_rel_pc = rel_pc - load_bias;
      if (adjusted_rel_pc < 5) {
        if (adjusted_rel_pc < 2) {
          return 0;
        }
        return 2;
      }

      if (adjusted_rel_pc & 1) {
        // This is a thumb instruction, it could be 2 or 4 bytes.
        uint32_t value;
        if (!elf->memory()->ReadFully(adjusted_rel_pc - 5, &value, sizeof(value)) ||
            (value & 0xe000f000) != 0xe000f000) {
          return 2;
        }
      }
      return 4;
    }
  case ARCH_ARM64: {
    if (rel_pc < 4) {
      return 0;
    }
    return 4;
  }
  case ARCH_MIPS:
  case ARCH_MIPS64: {
    if (rel_pc < 8) {
      return 0;
    }
    // For now, just assume no compact branches
    return 8;
  }
  case ARCH_X86:
  case ARCH_X86_64: {
    if (rel_pc == 0) {
      return 0;
    }
    return 1;
  }
  case ARCH_UNKNOWN:
    return 0;
  }
}

}  // namespace unwindstack