citra/src/common/code_block.h

// Copyright 2013 Dolphin Emulator Project
// Licensed under GPLv2
// Refer to the license.txt file included.

#pragma once

#include "common_types.h"
#include "memory_util.h"

// Everything that needs to generate code should inherit from this.
// You get memory management for free, plus, you can use all emitter functions without
// having to prefix them with gen-> or something similar.
// Example implementation:
// class JIT : public CodeBlock<ARMXEmitter> {}
template<class T> class CodeBlock : public T, NonCopyable
{
private:
    // A privately used function to set the executable RAM space to something invalid.
    // For debugging usefulness it should be used to set the RAM to a host specific breakpoint instruction
    virtual void PoisonMemory() = 0;

protected:
    u8 *region;
    size_t region_size;

public:
    CodeBlock() : region(nullptr), region_size(0) {}
    virtual ~CodeBlock() { if (region) FreeCodeSpace(); }

    // Call this before you generate any code.
    void AllocCodeSpace(int size)
    {
        region_size = size;
        region = (u8*)AllocateExecutableMemory(region_size);
        T::SetCodePtr(region);
    }

    // Always clear code space with breakpoints, so that if someone accidentally executes
    // uninitialized, it just breaks into the debugger.
    void ClearCodeSpace()
    {
        PoisonMemory();
        ResetCodePtr();
    }

    // Call this when shutting down. Don't rely on the destructor, even though it'll do the job.
    void FreeCodeSpace()
    {
#ifdef __SYMBIAN32__
        ResetExecutableMemory(region);
#else
        FreeMemoryPages(region, region_size);
#endif
        region = nullptr;
        region_size = 0;
    }

    bool IsInSpace(const u8 *ptr)
    {
        return (ptr >= region) && (ptr < (region + region_size));
    }

    // Cannot currently be undone. Will write protect the entire code region.
    // Start over if you need to change the code (call FreeCodeSpace(), AllocCodeSpace()).
    void WriteProtect()
    {
        WriteProtectMemory(region, region_size, true);
    }

    void ResetCodePtr()
    {
        T::SetCodePtr(region);
    }

    size_t GetSpaceLeft() const
    {
        return region_size - (T::GetCodePtr() - region);
    }

    u8 *GetBasePtr() {
        return region;
    }

    size_t GetOffset(const u8 *ptr) const {
        return ptr - region;
    }
};