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https://github.com/RGBCube/serenity
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be5f42adea
This patch introduces the concept of shadow bits. For every byte of
memory there is a corresponding shadow byte that contains metadata
about that memory.
Initially, the only metadata is whether the byte has been initialized
or not. That's represented by the least significant shadow bit.
Shadow bits travel together with regular values throughout the entire
CPU and MMU emulation. There are two main helper classes to facilitate
this: ValueWithShadow and ValueAndShadowReference.
ValueWithShadow<T> is basically a struct { T value; T shadow; } whereas
ValueAndShadowReference<T> is struct { T& value; T& shadow; }.
The latter is used as a wrapper around general-purpose registers, since
they can't use the plain ValueWithShadow memory as we need to be able
to address individual 8-bit and 16-bit subregisters (EAX, AX, AL, AH.)
Whenever a computation is made using uninitialized inputs, the result
is tainted and becomes uninitialized as well. This allows us to track
this state as it propagates throughout memory and registers.
This patch doesn't yet keep track of tainted flags, that will be an
important upcoming improvement to this.
I'm sure I've messed up some things here and there, but it seems to
basically work, so we have a place to start! :^)
125 lines
4.2 KiB
C++
125 lines
4.2 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "ValueWithShadow.h"
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#include <AK/HashMap.h>
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#include <AK/NonnullOwnPtrVector.h>
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#include <AK/OwnPtr.h>
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#include <AK/Types.h>
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#include <LibX86/Instruction.h>
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namespace UserspaceEmulator {
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class SharedBufferRegion;
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class SoftMMU {
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public:
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class Region {
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public:
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virtual ~Region() { }
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u32 base() const { return m_base; }
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u32 size() const { return m_size; }
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u32 end() const { return m_base + m_size; }
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bool contains(u32 address) const { return address >= base() && address < end(); }
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virtual void write8(u32 offset, ValueWithShadow<u8>) = 0;
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virtual void write16(u32 offset, ValueWithShadow<u16>) = 0;
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virtual void write32(u32 offset, ValueWithShadow<u32>) = 0;
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virtual ValueWithShadow<u8> read8(u32 offset) = 0;
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virtual ValueWithShadow<u16> read16(u32 offset) = 0;
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virtual ValueWithShadow<u32> read32(u32 offset) = 0;
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virtual u8* cacheable_ptr([[maybe_unused]] u32 offset) { return nullptr; }
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virtual bool is_shared_buffer() const { return false; }
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virtual bool is_mmap() const { return false; }
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bool is_stack() const { return m_stack; }
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void set_stack(bool b) { m_stack = b; }
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bool is_text() const { return m_text; }
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void set_text(bool b) { m_text = b; }
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protected:
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Region(u32 base, u32 size)
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: m_base(base)
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, m_size(size)
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{
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}
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private:
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u32 m_base { 0 };
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u32 m_size { 0 };
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bool m_stack { false };
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bool m_text { false };
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};
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ValueWithShadow<u8> read8(X86::LogicalAddress);
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ValueWithShadow<u16> read16(X86::LogicalAddress);
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ValueWithShadow<u32> read32(X86::LogicalAddress);
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void write8(X86::LogicalAddress, ValueWithShadow<u8>);
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void write16(X86::LogicalAddress, ValueWithShadow<u16>);
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void write32(X86::LogicalAddress, ValueWithShadow<u32>);
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Region* find_region(X86::LogicalAddress);
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void add_region(NonnullOwnPtr<Region>);
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void remove_region(Region&);
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void set_tls_region(NonnullOwnPtr<Region>);
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void copy_to_vm(FlatPtr destination, const void* source, size_t);
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void copy_from_vm(void* destination, const FlatPtr source, size_t);
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ByteBuffer copy_buffer_from_vm(const FlatPtr source, size_t);
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SharedBufferRegion* shbuf_region(int shbuf_id);
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template<typename Callback>
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void for_each_region(Callback callback)
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{
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if (m_tls_region) {
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if (callback(*m_tls_region) == IterationDecision::Break)
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return;
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}
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for (auto& region : m_regions) {
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if (callback(region) == IterationDecision::Break)
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return;
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}
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}
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private:
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OwnPtr<Region> m_tls_region;
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NonnullOwnPtrVector<Region> m_regions;
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HashMap<int, Region*> m_shbuf_regions;
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};
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}
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