312297ac38
After compiling bytecode, we should mark the memory read-only. This currently does not work because it breaks instruction destruction. I'm adding this anyway with a FIXME so we don't forget about it. :^)
66 lines
1.8 KiB
C++
66 lines
1.8 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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}
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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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}
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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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