3c74dc9f4d
This patch adds two macros to declare per-type allocators: - JS_DECLARE_ALLOCATOR(TypeName) - JS_DEFINE_ALLOCATOR(TypeName) When used, they add a type-specific CellAllocator that the Heap will delegate allocation requests to. The result of this is that GC objects of the same type always end up within the same HeapBlock, drastically reducing the ability to perform type confusion attacks. It also improves HeapBlock utilization, since each block now has cells sized exactly to the type used within that block. (Previously we only had a handful of block sizes available, and most GC allocations ended up with a large amount of slack in their tails.) There is a small performance hit from this, but I'm sure we can make up for it elsewhere. Note that the old size-based allocators still exist, and we fall back to them for any type that doesn't have its own CellAllocator.
106 lines
3.7 KiB
C++
106 lines
3.7 KiB
C++
/*
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* Copyright (c) 2020, Matthew Olsson <mattco@serenityos.org>
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* Copyright (c) 2022-2023, Linus Groh <linusg@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 <LibJS/Runtime/Error.h>
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#include <LibJS/Runtime/GlobalObject.h>
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#include <LibJS/Runtime/SymbolConstructor.h>
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namespace JS {
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JS_DEFINE_ALLOCATOR(SymbolConstructor);
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SymbolConstructor::SymbolConstructor(Realm& realm)
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: NativeFunction(realm.vm().names.Symbol.as_string(), realm.intrinsics().function_prototype())
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{
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}
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void SymbolConstructor::initialize(Realm& realm)
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{
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auto& vm = this->vm();
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Base::initialize(realm);
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// 20.4.2.9 Symbol.prototype, https://tc39.es/ecma262/#sec-symbol.prototype
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define_direct_property(vm.names.prototype, realm.intrinsics().symbol_prototype(), 0);
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u8 attr = Attribute::Writable | Attribute::Configurable;
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define_native_function(realm, vm.names.for_, for_, 1, attr);
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define_native_function(realm, vm.names.keyFor, key_for, 1, attr);
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#define __JS_ENUMERATE(SymbolName, snake_name) \
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define_direct_property(vm.names.SymbolName, vm.well_known_symbol_##snake_name(), 0);
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JS_ENUMERATE_WELL_KNOWN_SYMBOLS
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#undef __JS_ENUMERATE
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define_direct_property(vm.names.length, Value(0), Attribute::Configurable);
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}
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// 20.4.1.1 Symbol ( [ description ] ), https://tc39.es/ecma262/#sec-symbol-description
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ThrowCompletionOr<Value> SymbolConstructor::call()
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{
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auto& vm = this->vm();
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auto description = vm.argument(0);
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// 2. If description is undefined, let descString be undefined.
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// 3. Else, let descString be ? ToString(description).
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auto description_string = description.is_undefined()
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? Optional<String> {}
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: TRY(description.to_string(vm));
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// 4. Return a new Symbol whose [[Description]] is descString.
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return Symbol::create(vm, move(description_string), false);
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}
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// 20.4.1.1 Symbol ( [ description ] ), https://tc39.es/ecma262/#sec-symbol-description
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ThrowCompletionOr<NonnullGCPtr<Object>> SymbolConstructor::construct(FunctionObject&)
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{
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// 1. If NewTarget is not undefined, throw a TypeError exception.
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return vm().throw_completion<TypeError>(ErrorType::NotAConstructor, "Symbol");
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}
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// 20.4.2.2 Symbol.for ( key ), https://tc39.es/ecma262/#sec-symbol.for
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JS_DEFINE_NATIVE_FUNCTION(SymbolConstructor::for_)
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{
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// 1. Let stringKey be ? ToString(key).
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auto string_key = TRY(vm.argument(0).to_string(vm));
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// 2. For each element e of the GlobalSymbolRegistry List, do
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auto result = vm.global_symbol_registry().get(string_key);
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if (result.has_value()) {
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// a. If SameValue(e.[[Key]], stringKey) is true, return e.[[Symbol]].
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return result.value();
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}
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// 3. Assert: GlobalSymbolRegistry does not currently contain an entry for stringKey.
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VERIFY(!result.has_value());
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// 4. Let newSymbol be a new unique Symbol value whose [[Description]] value is stringKey.
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auto new_symbol = Symbol::create(vm, string_key, true);
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// 5. Append the Record { [[Key]]: stringKey, [[Symbol]]: newSymbol } to the GlobalSymbolRegistry List.
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vm.global_symbol_registry().set(string_key, new_symbol);
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// 6. Return newSymbol.
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return new_symbol;
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}
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// 20.4.2.6 Symbol.keyFor ( sym ), https://tc39.es/ecma262/#sec-symbol.keyfor
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JS_DEFINE_NATIVE_FUNCTION(SymbolConstructor::key_for)
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{
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auto argument = vm.argument(0);
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// 1. If sym is not a Symbol, throw a TypeError exception.
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if (!argument.is_symbol())
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return vm.throw_completion<TypeError>(ErrorType::NotASymbol, argument.to_string_without_side_effects());
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// 2. Return KeyForSymbol(sym).
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auto key = argument.as_symbol().key();
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return key.has_value()
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? PrimitiveString::create(vm, key.release_value())
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: js_undefined();
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}
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}
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