949ceedaed
This partially reverts c6ce7c9326.
The munmap part of that change was good, but we can't seal the blocks
since that breaks NewString and other ops that have String members.
69 lines
1.9 KiB
C++
69 lines
1.9 KiB
C++
/*
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* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/String.h>
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#include <LibJS/Bytecode/Block.h>
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#include <LibJS/Bytecode/Op.h>
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#include <sys/mman.h>
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namespace JS::Bytecode {
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NonnullOwnPtr<Block> Block::create()
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{
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return adopt_own(*new Block);
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}
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Block::Block()
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{
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// FIXME: This is not the smartest solution ever. Find something cleverer!
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// The main issue we're working around here is that we don't want pointers into the bytecode stream to become invalidated
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// during code generation due to dynamic buffer resizing. Otherwise we could just use a Vector.
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m_buffer_capacity = 64 * KiB;
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m_buffer = (u8*)mmap(nullptr, m_buffer_capacity, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
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VERIFY(m_buffer != MAP_FAILED);
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}
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Block::~Block()
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{
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Bytecode::InstructionStreamIterator it(instruction_stream());
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while (!it.at_end()) {
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auto& to_destroy = (*it);
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++it;
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Instruction::destroy(const_cast<Instruction&>(to_destroy));
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}
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munmap(m_buffer, m_buffer_capacity);
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}
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void Block::seal()
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{
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// FIXME: mprotect the instruction stream as PROT_READ
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// This is currently not possible because instructions can have destructors (that clean up strings)
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// Instructions should instead be destructor-less and refer to strings in a string table on the Bytecode::Block.
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// It also doesn't work because instructions that have String members use RefPtr internally which must be in writable memory.
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}
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void Block::dump() const
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{
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Bytecode::InstructionStreamIterator it(instruction_stream());
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while (!it.at_end()) {
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warnln("[{:4x}] {}", it.offset(), (*it).to_string());
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++it;
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}
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}
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void Block::grow(size_t additional_size)
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{
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m_buffer_size += additional_size;
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VERIFY(m_buffer_size <= m_buffer_capacity);
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}
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void InstructionStreamIterator::operator++()
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{
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m_offset += dereference().length();
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}
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}
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