/*
This file is part of cpp-ethereum.
cpp-ethereum is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
cpp-ethereum is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file KnownState.cpp
* @author Christian <c@ethdev.com>
* @date 2015
* Contains knowledge about the state of the virtual machine at a specific instruction.
*/
#include "KnownState.h"
#include <functional>
#include <libdevcrypto/SHA3.h>
#include <libevmasm/AssemblyItem.h>
using namespace std;
using namespace dev;
using namespace dev::eth;
ostream& KnownState::stream(ostream& _out) const
{
auto streamExpressionClass = [this](ostream& _out, Id _id)
{
auto const& expr = m_expressionClasses->representative(_id);
_out << " " << dec << _id << ": ";
if (!expr.item)
_out << " no item";
else if (expr.item->type() == UndefinedItem)
_out << " unknown " << int(expr.item->data());
else
_out << *expr.item;
if (expr.sequenceNumber)
_out << "@" << dec << expr.sequenceNumber;
_out << "(";
for (Id arg: expr.arguments)
_out << dec << arg << ",";
_out << ")" << endl;
};
_out << "=== State ===" << endl;
_out << "Stack height: " << dec << m_stackHeight << endl;
_out << "Equivalence classes: " << endl;
for (Id eqClass = 0; eqClass < m_expressionClasses->size(); ++eqClass)
streamExpressionClass(_out, eqClass);
_out << "Stack: " << endl;
for (auto const& it: m_stackElements)
{
_out << " " << dec << it.first << ": ";
streamExpressionClass(_out, it.second);
}
_out << "Storage: " << endl;
for (auto const& it: m_storageContent)
{
_out << " ";
streamExpressionClass(_out, it.first);
_out << ": ";
streamExpressionClass(_out, it.second);
}
_out << "Memory: " << endl;
for (auto const& it: m_memoryContent)
{
_out << " ";
streamExpressionClass(_out, it.first);
_out << ": ";
streamExpressionClass(_out, it.second);
}
return _out;
}
KnownState::StoreOperation KnownState::feedItem(AssemblyItem const& _item, bool _copyItem)
{
StoreOperation op;
if (_item.type() == Tag)
{
// can be ignored
}
else if (_item.type() != Operation)
{
assertThrow(_item.deposit() == 1, InvalidDeposit, "");
setStackElement(++m_stackHeight, m_expressionClasses->find(_item, {}, _copyItem));
}
else
{
Instruction instruction = _item.instruction();
InstructionInfo info = instructionInfo(instruction);
if (SemanticInformation::isDupInstruction(_item))
setStackElement(
m_stackHeight + 1,
stackElement(
m_stackHeight - int(instruction) + int(Instruction::DUP1),
_item.getLocation()
)
);
else if (SemanticInformation::isSwapInstruction(_item))
swapStackElements(
m_stackHeight,
m_stackHeight - 1 - int(instruction) + int(Instruction::SWAP1),
_item.getLocation()
);
else if (instruction != Instruction::POP)
{
vector<Id> arguments(info.args);
for (int i = 0; i < info.args; ++i)
arguments[i] = stackElement(m_stackHeight - i, _item.getLocation());
if (_item.instruction() == Instruction::SSTORE)
op = storeInStorage(arguments[0], arguments[1], _item.getLocation());
else if (_item.instruction() == Instruction::SLOAD)
setStackElement(
m_stackHeight + _item.deposit(),
loadFromStorage(arguments[0], _item.getLocation())
);
else if (_item.instruction() == Instruction::MSTORE)
op = storeInMemory(arguments[0], arguments[1], _item.getLocation());
else if (_item.instruction() == Instruction::MLOAD)
setStackElement(
m_stackHeight + _item.deposit(),
loadFromMemory(arguments[0], _item.getLocation())
);
else if (_item.instruction() == Instruction::SHA3)
setStackElement(
m_stackHeight + _item.deposit(),
applySha3(arguments.at(0), arguments.at(1), _item.getLocation())
);
else
{
if (SemanticInformation::invalidatesMemory(_item.instruction()))
resetMemory();
if (SemanticInformation::invalidatesStorage(_item.instruction()))
resetStorage();
assertThrow(info.ret <= 1, InvalidDeposit, "");
if (info.ret == 1)
setStackElement(
m_stackHeight + _item.deposit(),
m_expressionClasses->find(_item, arguments, _copyItem)
);
}
}
m_stackElements.erase(
m_stackElements.upper_bound(m_stackHeight + _item.deposit()),
m_stackElements.end()
);
m_stackHeight += _item.deposit();
}
return op;
}
void KnownState::reduceToCommonKnowledge(KnownState const& /*_other*/)
{
//@todo
*this = KnownState(m_expressionClasses);
}
bool KnownState::operator==(const KnownState& _other) const
{
//@todo
return (
m_stackElements.empty() &&
_other.m_stackElements.empty() &&
m_storageContent.empty() &&
_other.m_storageContent.empty() &&
m_memoryContent.empty() &&
_other.m_memoryContent.empty()
);
}
ExpressionClasses::Id KnownState::stackElement(int _stackHeight, SourceLocation const& _location)
{
if (m_stackElements.count(_stackHeight))
return m_stackElements.at(_stackHeight);
// Stack element not found (not assigned yet), create new unknown equivalence class.
//@todo check that we do not infer incorrect equivalences when the stack is cleared partially
//in between.
return m_stackElements[_stackHeight] = initialStackElement(_stackHeight, _location);
}
ExpressionClasses::Id KnownState::initialStackElement(
int _stackHeight,
SourceLocation const& _location
)
{
// This is a special assembly item that refers to elements pre-existing on the initial stack.
return m_expressionClasses->find(AssemblyItem(UndefinedItem, u256(_stackHeight), _location));
}
void KnownState::setStackElement(int _stackHeight, Id _class)
{
m_stackElements[_stackHeight] = _class;
}
void KnownState::swapStackElements(
int _stackHeightA,
int _stackHeightB,
SourceLocation const& _location
)
{
assertThrow(_stackHeightA != _stackHeightB, OptimizerException, "Swap on same stack elements.");
// ensure they are created
stackElement(_stackHeightA, _location);
stackElement(_stackHeightB, _location);
swap(m_stackElements[_stackHeightA], m_stackElements[_stackHeightB]);
}
KnownState::StoreOperation KnownState::storeInStorage(
Id _slot,
Id _value,
SourceLocation const& _location)
{
if (m_storageContent.count(_slot) && m_storageContent[_slot] == _value)
// do not execute the storage if we know that the value is already there
return StoreOperation();
m_sequenceNumber++;
decltype(m_storageContent) storageContents;
// Copy over all values (i.e. retain knowledge about them) where we know that this store
// operation will not destroy the knowledge. Specifically, we copy storage locations we know
// are different from _slot or locations where we know that the stored value is equal to _value.
for (auto const& storageItem: m_storageContent)
if (m_expressionClasses->knownToBeDifferent(storageItem.first, _slot) || storageItem.second == _value)
storageContents.insert(storageItem);
m_storageContent = move(storageContents);
AssemblyItem item(Instruction::SSTORE, _location);
Id id = m_expressionClasses->find(item, {_slot, _value}, true, m_sequenceNumber);
StoreOperation operation(StoreOperation::Storage, _slot, m_sequenceNumber, id);
m_storageContent[_slot] = _value;
// increment a second time so that we get unique sequence numbers for writes
m_sequenceNumber++;
return operation;
}
ExpressionClasses::Id KnownState::loadFromStorage(Id _slot, SourceLocation const& _location)
{
if (m_storageContent.count(_slot))
return m_storageContent.at(_slot);
AssemblyItem item(Instruction::SLOAD, _location);
return m_storageContent[_slot] = m_expressionClasses->find(item, {_slot}, true, m_sequenceNumber);
}
KnownState::StoreOperation KnownState::storeInMemory(Id _slot, Id _value, SourceLocation const& _location)
{
if (m_memoryContent.count(_slot) && m_memoryContent[_slot] == _value)
// do not execute the store if we know that the value is already there
return StoreOperation();
m_sequenceNumber++;
decltype(m_memoryContent) memoryContents;
// copy over values at points where we know that they are different from _slot by at least 32
for (auto const& memoryItem: m_memoryContent)
if (m_expressionClasses->knownToBeDifferentBy32(memoryItem.first, _slot))
memoryContents.insert(memoryItem);
m_memoryContent = move(memoryContents);
AssemblyItem item(Instruction::MSTORE, _location);
Id id = m_expressionClasses->find(item, {_slot, _value}, true, m_sequenceNumber);
StoreOperation operation(StoreOperation(StoreOperation::Memory, _slot, m_sequenceNumber, id));
m_memoryContent[_slot] = _value;
// increment a second time so that we get unique sequence numbers for writes
m_sequenceNumber++;
return operation;
}
ExpressionClasses::Id KnownState::loadFromMemory(Id _slot, SourceLocation const& _location)
{
if (m_memoryContent.count(_slot))
return m_memoryContent.at(_slot);
AssemblyItem item(Instruction::MLOAD, _location);
return m_memoryContent[_slot] = m_expressionClasses->find(item, {_slot}, true, m_sequenceNumber);
}
KnownState::Id KnownState::applySha3(
Id _start,
Id _length,
SourceLocation const& _location
)
{
AssemblyItem sha3Item(Instruction::SHA3, _location);
// Special logic if length is a short constant, otherwise we cannot tell.
u256 const* l = m_expressionClasses->knownConstant(_length);
// unknown or too large length
if (!l || *l > 128)
return m_expressionClasses->find(sha3Item, {_start, _length}, true, m_sequenceNumber);
vector<Id> arguments;
for (u256 i = 0; i < *l; i += 32)
{
Id slot = m_expressionClasses->find(
AssemblyItem(Instruction::ADD, _location),
{_start, m_expressionClasses->find(i)}
);
arguments.push_back(loadFromMemory(slot, _location));
}
if (m_knownSha3Hashes.count(arguments))
return m_knownSha3Hashes.at(arguments);
Id v;
// If all arguments are known constants, compute the sha3 here
if (all_of(arguments.begin(), arguments.end(), [this](Id _a) { return !!m_expressionClasses->knownConstant(_a); }))
{
bytes data;
for (Id a: arguments)
data += toBigEndian(*m_expressionClasses->knownConstant(a));
data.resize(size_t(*l));
v = m_expressionClasses->find(AssemblyItem(u256(sha3(data)), _location));
}
else
v = m_expressionClasses->find(sha3Item, {_start, _length}, true, m_sequenceNumber);
return m_knownSha3Hashes[arguments] = v;
}
