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https://github.com/LadybirdBrowser/ladybird
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d4ed658429
The plan is to start caching compiled JS bytecode on disk. Before loading anything from a cache we need confidence that the bytes are structurally well-formed, since a corrupted or tampered-with cache file could otherwise hand the interpreter an out-of-bounds jump or a constant-pool index that points past the end of the table. This commit lays down the scaffolding for that validator. The walker lives in Rust (Libraries/LibJS/Rust/src/bytecode/validator.rs) so that it can share the existing Bytecode.def-driven layout machinery with the encoder. C++ calls into it through cbindgen, the same way the rest of the Rust pipeline is wired up. For now, the validator only does Pass 1: walk the byte stream, verify each instruction is 8-byte aligned, the opcode byte is in range, and the reported length keeps us inside the buffer. The length lookup is generated from Bytecode.def so fixed-length and variable-length instructions stay in sync with the rest of the codegen automatically. Per-field bounds checks (operands, labels, table indices, cache indices) and structural extras (basic block offsets, exception handlers, source map) come in follow-up commits. The validator runs after every successful compilation in debug and sanitizer builds, gated on !NDEBUG || HAS_ADDRESS_SANITIZER, so we get an extra sanity check on every executable the encoder produces without paying for it in release builds. Failure trips a VERIFY_NOT_REACHED with the offset, opcode, and error category logged via dbgln().
28 lines
609 B
C++
28 lines
609 B
C++
/*
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* Copyright (c) 2026-present, the Ladybird developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Error.h>
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#include <LibJS/Forward.h>
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namespace JS::Bytecode {
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class Executable;
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// Whether the bytecode being validated still has m_cache fields stored as
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// indices (BeforeFixup) or has had Executable::fixup_cache_pointers() rewrite
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// them into live pointers (AfterFixup). Cache fields are only range-checked
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// in the BeforeFixup case.
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enum class CacheState : u8 {
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BeforeFixup,
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AfterFixup,
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};
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ErrorOr<void> validate_bytecode(Executable const&, CacheState);
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}
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