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295 lines
12 KiB
C++
295 lines
12 KiB
C++
// Copyright 2014 Citra Emulator Project
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#pragma once
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#include <array>
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#include <cstring>
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#include <type_traits>
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#include "common/common_types.h"
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namespace Kernel {
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/*
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* This class defines the SVC ABI, and provides a wrapper template for translating between ARM
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* registers and SVC parameters and return value. The SVC context class should inherit from this
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* class using CRTP (`class SVC : public SVCWrapper<SVC> {...}`), and use the Wrap() template to
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* convert a SVC function interface to a void()-type function that interacts with registers
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* interface GetReg() and SetReg().
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*/
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template <typename Context>
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class SVCWrapper {
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protected:
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template <auto F>
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void Wrap() {
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WrapHelper<decltype(F)>::Call(*static_cast<Context*>(this), F);
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};
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private:
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// A special param index represents the return value
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static constexpr std::size_t INDEX_RETURN = ~(std::size_t)0;
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struct ParamSlot {
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// whether the slot is used for a param
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bool used;
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// index of a param in the function signature, starting from 0, or special value
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// INDEX_RETURN
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std::size_t param_index;
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// index of a 32-bit word within the param
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std::size_t word_index;
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};
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// Size in words of the given type in ARM ABI
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template <typename T>
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static constexpr std::size_t WordSize() {
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static_assert(std::is_trivially_copyable_v<T>);
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if constexpr (std::is_pointer_v<T>) {
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return 1;
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} else if constexpr (std::is_same_v<T, bool>) {
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return 1;
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} else {
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return (sizeof(T) - 1) / 4 + 1;
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}
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}
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// Size in words of the given type in ARM ABI with pointer removed
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template <typename T>
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static constexpr std::size_t OutputWordSize() {
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if constexpr (std::is_pointer_v<T>) {
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return WordSize<std::remove_pointer_t<T>>();
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} else {
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return 0;
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}
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}
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// Describes the register assignments of a SVC
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struct SVCABI {
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static constexpr std::size_t RegCount = 8;
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// Register assignments for input params.
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// For example, in[0] records which input param and word r0 stores
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std::array<ParamSlot, RegCount> in{};
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// Register assignments for output params.
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// For example, out[0] records which output param (with pointer removed) and word r0 stores
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std::array<ParamSlot, RegCount> out{};
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// Search the register assignments for a word of a param
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constexpr std::size_t GetRegisterIndex(std::size_t param_index,
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std::size_t word_index) const {
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for (std::size_t slot = 0; slot < RegCount; ++slot) {
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if (in[slot].used && in[slot].param_index == param_index &&
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in[slot].word_index == word_index) {
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return slot;
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}
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if (out[slot].used && out[slot].param_index == param_index &&
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out[slot].word_index == word_index) {
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return slot;
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}
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}
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// should throw, but gcc bugs out here
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return 0x12345678;
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}
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};
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// Generates ABI info for a given SVC signature R(Context::)(T...)
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template <typename R, typename... T>
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static constexpr SVCABI GetSVCABI() {
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constexpr std::size_t param_count = sizeof...(T);
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std::array<bool, param_count> param_is_output{{std::is_pointer_v<T>...}};
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std::array<std::size_t, param_count> param_size{{WordSize<T>()...}};
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std::array<std::size_t, param_count> output_param_size{{OutputWordSize<T>()...}};
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std::array<bool, param_count> param_need_align{
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{(std::is_same_v<T, u64> || std::is_same_v<T, s64>)...}};
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// derives ARM ABI, which assigns all params to r0~r3 and then stack
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std::array<ParamSlot, 4> armabi_reg{};
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std::array<ParamSlot, 4> armabi_stack{};
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std::size_t reg_pos = 0;
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std::size_t stack_pos = 0;
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for (std::size_t i = 0; i < param_count; ++i) {
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if (param_need_align[i]) {
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reg_pos += reg_pos % 2;
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}
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for (std::size_t j = 0; j < param_size[i]; ++j) {
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if (reg_pos == 4) {
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armabi_stack[stack_pos++] = ParamSlot{true, i, j};
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} else {
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armabi_reg[reg_pos++] = ParamSlot{true, i, j};
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}
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}
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}
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// now derives SVC ABI which is a modified version of ARM ABI
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SVCABI mod_abi{};
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std::size_t out_pos = 0; // next available output register
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// assign return value to output registers
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if constexpr (!std::is_void_v<R>) {
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for (std::size_t j = 0; j < WordSize<R>(); ++j) {
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mod_abi.out[out_pos++] = {true, INDEX_RETURN, j};
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}
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}
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// assign output params (pointer-type params) to output registers
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for (std::size_t i = 0; i < param_count; ++i) {
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if (param_is_output[i]) {
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for (std::size_t j = 0; j < output_param_size[i]; ++j) {
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mod_abi.out[out_pos++] = ParamSlot{true, i, j};
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}
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}
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}
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// assign input params (non-pointer-type params) to input registers
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stack_pos = 0; // next available stack param
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for (std::size_t k = 0; k < mod_abi.in.size(); ++k) {
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if (k < armabi_reg.size() && armabi_reg[k].used &&
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!param_is_output[armabi_reg[k].param_index]) {
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// If this is within the ARM ABI register range and it is a used input param, use
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// the same register position
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mod_abi.in[k] = armabi_reg[k];
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} else {
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// Otherwise, assign it with the next available stack input
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// If all stack inputs have been allocated, this would do nothing
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// and leaves the slot unused.
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// Loop until an input stack param is found
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while (stack_pos < armabi_stack.size() &&
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(!armabi_stack[stack_pos].used ||
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param_is_output[armabi_stack[stack_pos].param_index])) {
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++stack_pos;
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}
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// Reassign the stack param to the free register
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if (stack_pos < armabi_stack.size()) {
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mod_abi.in[k] = armabi_stack[stack_pos++];
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}
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}
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}
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return mod_abi;
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}
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template <std::size_t param_index, std::size_t word_size, std::size_t... indices>
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static constexpr std::array<std::size_t, word_size> GetRegIndicesImpl(
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SVCABI abi, std::index_sequence<indices...>) {
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return {{abi.GetRegisterIndex(param_index, indices)...}};
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}
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// Gets assigned register index for the param_index-th param of word_size in a function with
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// signature R(Context::)(Ts...)
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template <std::size_t param_index, std::size_t word_size, typename R, typename... Ts>
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static constexpr std::array<std::size_t, word_size> GetRegIndices() {
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constexpr SVCABI abi = GetSVCABI<R, Ts...>();
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return GetRegIndicesImpl<param_index, word_size>(abi,
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std::make_index_sequence<word_size>{});
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}
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// Gets the value for the param_index-th param of word_size in a function with signature
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// R(Context::)(Ts...)
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// T is the param type, which must be a non-pointer as it is an input param.
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// Must hold: Ts[param_index] == T
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template <std::size_t param_index, typename T, typename R, typename... Ts>
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static void GetParam(Context& context, T& value) {
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static_assert(!std::is_pointer_v<T>, "T should not be a pointer");
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constexpr auto regi = GetRegIndices<param_index, WordSize<T>(), R, Ts...>();
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if constexpr (std::is_class_v<T> || std::is_union_v<T>) {
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std::array<u32, WordSize<T>()> buf;
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for (std::size_t i = 0; i < WordSize<T>(); ++i) {
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buf[i] = context.GetReg(regi[i]);
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}
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std::memcpy(&value, &buf, sizeof(T));
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} else if constexpr (WordSize<T>() == 2) {
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u64 l = context.GetReg(regi[0]);
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u64 h = context.GetReg(regi[1]);
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value = static_cast<T>(l | (h << 32));
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} else if constexpr (std::is_same_v<T, bool>) {
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// TODO: Is this correct or should only test the lowest byte?
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value = context.GetReg(regi[0]) != 0;
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} else {
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value = static_cast<T>(context.GetReg(regi[0]));
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}
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}
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// Sets the value for the param_index-th param of word_size in a function with signature
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// R(Context::)(Ts...)
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// T is the param type with pointer removed, which was originally a pointer-type output param
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// Must hold: (Ts[param_index] == T*) || (R==T && param_index == INDEX_RETURN)
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template <std::size_t param_index, typename T, typename R, typename... Ts>
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static void SetParam(Context& context, const T& value) {
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static_assert(!std::is_pointer_v<T>, "T should have pointer removed before passing in");
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constexpr auto regi = GetRegIndices<param_index, WordSize<T>(), R, Ts...>();
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if constexpr (std::is_class_v<T> || std::is_union_v<T>) {
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std::array<u32, WordSize<T>()> buf;
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std::memcpy(&buf, &value, sizeof(T));
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for (std::size_t i = 0; i < WordSize<T>(); ++i) {
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context.SetReg(regi[i], buf[i]);
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}
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} else if constexpr (WordSize<T>() == 2) {
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u64 u = static_cast<u64>(value);
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context.SetReg(regi[0], static_cast<u32>(u & 0xFFFFFFFF));
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context.SetReg(regi[1], static_cast<u32>(u >> 32));
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} else {
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u32 u = static_cast<u32>(value);
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context.SetReg(regi[0], u);
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}
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}
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template <typename SVCT, typename R, typename... Ts>
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struct WrapPass;
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template <typename SVCT, typename R, typename T, typename... Ts>
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struct WrapPass<SVCT, R, T, Ts...> {
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// Do I/O for the param T in function R(Context::svc)(Us..., T, Ts...) and then move on to
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// the next param.
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// Us are params whose I/O is already handled.
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// T is the current param to do I/O.
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// Ts are params whose I/O is not handled yet.
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template <typename... Us>
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static void Call(Context& context, SVCT svc, Us... u) {
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static_assert(std::is_same_v<SVCT, R (Context::*)(Us..., T, Ts...)>);
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constexpr std::size_t current_param_index = sizeof...(Us);
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if constexpr (std::is_pointer_v<T>) {
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using OutputT = std::remove_pointer_t<T>;
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OutputT output;
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WrapPass<SVCT, R, Ts...>::Call(context, svc, u..., &output);
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SetParam<current_param_index, OutputT, R, Us..., T, Ts...>(context, output);
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} else {
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T input;
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GetParam<current_param_index, T, R, Us..., T, Ts...>(context, input);
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WrapPass<SVCT, R, Ts...>::Call(context, svc, u..., input);
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}
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}
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};
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template <typename SVCT, typename R>
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struct WrapPass<SVCT, R /*empty for T, Ts...*/> {
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// Call function R(Context::svc)(Us...) and transfer the return value to registers
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template <typename... Us>
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static void Call(Context& context, SVCT svc, Us... u) {
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static_assert(std::is_same_v<SVCT, R (Context::*)(Us...)>);
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if constexpr (std::is_void_v<R>) {
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(context.*svc)(u...);
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} else {
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R r = (context.*svc)(u...);
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SetParam<INDEX_RETURN, R, R, Us...>(context, r);
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}
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}
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};
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template <typename T>
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struct WrapHelper;
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template <typename R, typename... T>
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struct WrapHelper<R (Context::*)(T...)> {
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static void Call(Context& context, R (Context::*svc)(T...)) {
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WrapPass<decltype(svc), R, T...>::Call(context, svc /*Empty for Us*/);
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}
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};
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};
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} // namespace Kernel
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