guest_state/include/berberis/guest_state/guest_state_riscv64.h

/*
 * Copyright (C) 2023 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.
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#ifndef BERBERIS_GUEST_STATE_GUEST_STATE_RISCV64_H_
#define BERBERIS_GUEST_STATE_GUEST_STATE_RISCV64_H_

#include <atomic>
#include <cstdint>

#include "berberis/base/dependent_false.h"
#include "berberis/base/macros.h"
#include "berberis/guest_state/guest_addr.h"

namespace berberis {

struct CPUState {
  // x0 to x31.
  uint64_t x[32];
  // f0 to f31. We are using uint64_t because C++ may change values of NaN when they are passed from
  // or to function and RISC-V uses NaN-boxing which would make things problematic.
  uint64_t f[32];
  // RISC-V has five rounding modes, while x86-64 has only four.
  //
  // Extra rounding mode (RMM in RISC-V documentation) is emulated but requires the use of
  // FE_TOWARDZERO mode for correct work.
  //
  // Additionally RISC-V implementation is supposed to support three “illegal” rounding modes and
  // when they are selected all instructions which use rounding mode trigger “undefined instruction”
  // exception.
  //
  // For simplicity we always keep full rounding mode (3 bits) in the frm field and set host
  // rounding mode to appropriate one.
  //
  // Exceptions, on the other hand, couldn't be stored here efficiently, instead we rely on the fact
  // that x86-64 implements all five exceptions that RISC-V needs (and more).
  uint8_t frm : 3;
  GuestAddr insn_addr;
};

template <uint8_t kIndex>
inline uint64_t GetXReg(const CPUState& state) {
  static_assert(kIndex > 0);
  static_assert(kIndex < arraysize(state.x));
  return state.x[kIndex];
}

template <uint8_t kIndex>
inline void SetXReg(CPUState& state, uint64_t val) {
  static_assert(kIndex > 0);
  static_assert(kIndex < arraysize(state.x));
  state.x[kIndex] = val;
}

template <uint8_t kIndex>
inline uint64_t GetFReg(const CPUState& state) {
  static_assert((kIndex) < arraysize(state.f));
  return state.f[kIndex];
}

template <uint8_t kIndex>
inline void SetFReg(CPUState& state, uint64_t val) {
  static_assert((kIndex) < arraysize(state.f));
  state.f[kIndex] = val;
}

enum class RegisterType {
  kReg,
  kFpReg,
};

template <RegisterType register_type, uint8_t kIndex>
inline auto GetReg(const CPUState& state) {
  if constexpr (register_type == RegisterType::kReg) {
    return GetXReg<kIndex>(state);
  } else if constexpr (register_type == RegisterType::kFpReg) {
    return GetFReg<kIndex>(state);
  } else {
    static_assert(kDependentValueFalse<register_type>, "Unsupported register type");
  }
}

template <RegisterType register_type, uint8_t kIndex, typename Register>
inline auto SetReg(CPUState& state, Register val) {
  if constexpr (register_type == RegisterType::kReg) {
    return SetXReg<kIndex>(state, val);
  } else if constexpr (register_type == RegisterType::kFpReg) {
    return SetFReg<kIndex>(state, val);
  } else {
    static_assert(kDependentValueFalse<register_type>, "Unsupported register type");
  }
}

class GuestThread;

// TODO(b/28058920): Refactor into GuestThread.
// Pending signals status state machine:
//   disabled <-> enabled <-> enabled and pending signals present
enum PendingSignalsStatus : uint8_t {
  kPendingSignalsDisabled = 0,  // initial value, must be 0
  kPendingSignalsEnabled,
  kPendingSignalsPresent,  // implies enabled
};

// Track whether we are in generated code or not.
enum GuestThreadResidence : uint8_t {
  kOutsideGeneratedCode = 0,
  kInsideGeneratedCode = 1,
};

struct ThreadState {
  CPUState cpu;

  // Guest thread pointer.
  GuestThread* thread;

  // Keep pending signals status here for fast checking in generated code.
  // Uses enum values from PendingSignalsStatus.
  // TODO(b/28058920): Refactor into GuestThread.
  std::atomic<uint_least8_t> pending_signals_status;

  GuestThreadResidence residence;

  // Arbitrary per-thread data added by instrumentation.
  void* instrument_data;
};

// TODO(b/28058920): Refactor into GuestThread.
inline bool ArePendingSignalsPresent(const ThreadState* state) {
  return state->pending_signals_status.load(std::memory_order_relaxed) == kPendingSignalsPresent;
}

// The ABI names come from
// https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc.

// Integer register ABI names.

constexpr uint8_t RA = 1;    // Return address - caller saved.
constexpr uint8_t SP = 2;    // Stack pointer - callee saved.
constexpr uint8_t GP = 3;    // Global pointer.
constexpr uint8_t TP = 4;    // Thread pointer.
constexpr uint8_t T0 = 5;    // Temporary register 0 - caller saved.
constexpr uint8_t T1 = 6;    // Temporary register 1 - caller saved.
constexpr uint8_t T2 = 7;    // Temporary register 2 - caller saved.
constexpr uint8_t FP = 8;    // Frame pointer - callee saved.
constexpr uint8_t S0 = 8;    // Saved register 0 - callee saved.
constexpr uint8_t S1 = 9;    // Saved register 1 - callee saved.
constexpr uint8_t A0 = 10;   // Argument register / return value 0 - caller saved.
constexpr uint8_t A1 = 11;   // Argument register / return value 1 - caller saved.
constexpr uint8_t A2 = 12;   // Argument register 2 - caller saved.
constexpr uint8_t A3 = 13;   // Argument register 3 - caller saved.
constexpr uint8_t A4 = 14;   // Argument register 4 - caller saved.
constexpr uint8_t A5 = 15;   // Argument register 5 - caller saved.
constexpr uint8_t A6 = 16;   // Argument register 6 - caller saved.
constexpr uint8_t A7 = 17;   // Argument register 7 - caller saved.
constexpr uint8_t S2 = 18;   // Saved register 2 - callee saved.
constexpr uint8_t S3 = 19;   // Saved register 3 - callee saved.
constexpr uint8_t S4 = 20;   // Saved register 4 - callee saved.
constexpr uint8_t S5 = 21;   // Saved register 5 - callee saved.
constexpr uint8_t S6 = 22;   // Saved register 6 - callee saved.
constexpr uint8_t S7 = 23;   // Saved register 7 - callee saved.
constexpr uint8_t S8 = 24;   // Saved register 8 - callee saved.
constexpr uint8_t S9 = 25;   // Saved register 9 - callee saved.
constexpr uint8_t S10 = 26;  // Saved register 10 - callee saved.
constexpr uint8_t S11 = 27;  // Saved register 11 - callee saved.
constexpr uint8_t T3 = 28;   // Temporary register 3 - caller saved.
constexpr uint8_t T4 = 29;   // Temporary register 4 - caller saved.
constexpr uint8_t T5 = 30;   // Temporary register 5 - caller saved.
constexpr uint8_t T6 = 31;   // Temporary register 6 - caller saved.

// Floating point register ABI names.

constexpr uint8_t FT0 = 0;    // FP Temporary register 0 - caller saved.
constexpr uint8_t FT1 = 1;    // FP Temporary register 1 - caller saved.
constexpr uint8_t FT2 = 2;    // FP Temporary register 2 - caller saved.
constexpr uint8_t FT3 = 3;    // FP Temporary register 3 - caller saved.
constexpr uint8_t FT4 = 4;    // FP Temporary register 4 - caller saved.
constexpr uint8_t FT5 = 5;    // FP Temporary register 5 - caller saved.
constexpr uint8_t FT6 = 6;    // FP Temporary register 6 - caller saved.
constexpr uint8_t FT7 = 7;    // FP Temporary register 7 - caller saved.
constexpr uint8_t FS0 = 8;    // FP Saved register 0 - callee saved.
constexpr uint8_t FS1 = 9;    // FP Saved register 1 - callee saved.
constexpr uint8_t FA0 = 10;   // FP Argument register / return value 0 - caller saved.
constexpr uint8_t FA1 = 11;   // FP Argument register / return value 1 - caller saved.
constexpr uint8_t FA2 = 12;   // FP Argument register 2 - caller saved.
constexpr uint8_t FA3 = 13;   // FP Argument register 3 - caller saved.
constexpr uint8_t FA4 = 14;   // FP Argument register 4 - caller saved.
constexpr uint8_t FA5 = 15;   // FP Argument register 5 - caller saved.
constexpr uint8_t FA6 = 16;   // FP Argument register 6 - caller saved.
constexpr uint8_t FA7 = 17;   // FP Argument register 7 - caller saved.
constexpr uint8_t FS2 = 18;   // FP Saved register 2 - calle saved.
constexpr uint8_t FS3 = 19;   // FP Saved register 3 - callee saved.
constexpr uint8_t FS4 = 20;   // FP Saved register 4 - callee saved.
constexpr uint8_t FS5 = 21;   // FP Saved register 5 - callee saved.
constexpr uint8_t FS6 = 22;   // FP Saved register 6 - callee saved.
constexpr uint8_t FS7 = 23;   // FP Saved register 7 - callee saved.
constexpr uint8_t FS8 = 24;   // FP Saved register 8 - callee saved.
constexpr uint8_t FS9 = 25;   // FP Saved register 9 - callee saved.
constexpr uint8_t FS10 = 26;  // FP Saved register 10 - callee saved.
constexpr uint8_t FS11 = 27;  // FP Saved register 11 - callee saved.
constexpr uint8_t FT8 = 28;   // FP Temporary register 8 - caller saved.
constexpr uint8_t FT9 = 29;   // FP Temporary register 9 - caller saved.
constexpr uint8_t FT10 = 30;  // FP Temporary register 10 - caller saved.
constexpr uint8_t FT11 = 31;  // FP Temporary register 11 - caller saved.

}  // namespace berberis

#endif  // BERBERIS_GUEST_STATE_GUEST_STATE_RISCV64_H_