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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.
108 lines
3.9 KiB
C++
108 lines
3.9 KiB
C++
/*
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* Copyright (c) 2020-2023, 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/AbstractOperations.h>
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#include <LibJS/Runtime/BigInt.h>
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#include <LibJS/Runtime/BigIntConstructor.h>
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#include <LibJS/Runtime/BigIntObject.h>
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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/VM.h>
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#include <LibJS/Runtime/ValueInlines.h>
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namespace JS {
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JS_DEFINE_ALLOCATOR(BigIntConstructor);
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static const Crypto::SignedBigInteger BIGINT_ONE { 1 };
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BigIntConstructor::BigIntConstructor(Realm& realm)
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: NativeFunction(realm.vm().names.BigInt.as_string(), realm.intrinsics().function_prototype())
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{
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}
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void BigIntConstructor::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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// 21.2.2.3 BigInt.prototype, https://tc39.es/ecma262/#sec-bigint.prototype
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define_direct_property(vm.names.prototype, realm.intrinsics().bigint_prototype(), 0);
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u8 attr = Attribute::Writable | Attribute::Configurable;
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define_native_function(realm, vm.names.asIntN, as_int_n, 2, attr);
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define_native_function(realm, vm.names.asUintN, as_uint_n, 2, attr);
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define_direct_property(vm.names.length, Value(1), Attribute::Configurable);
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}
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// 21.2.1.1 BigInt ( value ), https://tc39.es/ecma262/#sec-bigint-constructor-number-value
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ThrowCompletionOr<Value> BigIntConstructor::call()
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{
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auto& vm = this->vm();
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auto value = vm.argument(0);
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// 2. Let prim be ? ToPrimitive(value, number).
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auto primitive = TRY(value.to_primitive(vm, Value::PreferredType::Number));
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// 3. If Type(prim) is Number, return ? NumberToBigInt(prim).
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if (primitive.is_number())
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return TRY(number_to_bigint(vm, primitive));
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// 4. Otherwise, return ? ToBigInt(prim).
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return TRY(primitive.to_bigint(vm));
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}
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// 21.2.1.1 BigInt ( value ), https://tc39.es/ecma262/#sec-bigint-constructor-number-value
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ThrowCompletionOr<NonnullGCPtr<Object>> BigIntConstructor::construct(FunctionObject&)
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{
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return vm().throw_completion<TypeError>(ErrorType::NotAConstructor, "BigInt");
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}
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// 21.2.2.1 BigInt.asIntN ( bits, bigint ), https://tc39.es/ecma262/#sec-bigint.asintn
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JS_DEFINE_NATIVE_FUNCTION(BigIntConstructor::as_int_n)
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{
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// 1. Set bits to ? ToIndex(bits).
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auto bits = TRY(vm.argument(0).to_index(vm));
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// 2. Set bigint to ? ToBigInt(bigint).
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auto bigint = TRY(vm.argument(1).to_bigint(vm));
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// 3. Let mod be ℝ(bigint) modulo 2^bits.
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// FIXME: For large values of `bits`, this can likely be improved with a SignedBigInteger API to
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// drop the most significant bits.
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auto bits_shift_left = BIGINT_ONE.shift_left(bits);
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auto mod = modulo(bigint->big_integer(), bits_shift_left);
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// 4. If mod ≥ 2^(bits-1), return ℤ(mod - 2^bits); otherwise, return ℤ(mod).
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// NOTE: Some of the below conditionals are non-standard, but are to protect SignedBigInteger from
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// allocating an absurd amount of memory if `bits - 1` overflows to NumericLimits<size_t>::max.
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if ((bits == 0) && (mod >= BIGINT_ONE))
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return BigInt::create(vm, mod.minus(bits_shift_left));
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if ((bits > 0) && (mod >= BIGINT_ONE.shift_left(bits - 1)))
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return BigInt::create(vm, mod.minus(bits_shift_left));
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return BigInt::create(vm, mod);
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}
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// 21.2.2.2 BigInt.asUintN ( bits, bigint ), https://tc39.es/ecma262/#sec-bigint.asuintn
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JS_DEFINE_NATIVE_FUNCTION(BigIntConstructor::as_uint_n)
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{
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// 1. Set bits to ? ToIndex(bits).
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auto bits = TRY(vm.argument(0).to_index(vm));
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// 2. Set bigint to ? ToBigInt(bigint).
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auto bigint = TRY(vm.argument(1).to_bigint(vm));
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// 3. Return the BigInt value that represents ℝ(bigint) modulo 2bits.
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// FIXME: For large values of `bits`, this can likely be improved with a SignedBigInteger API to
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// drop the most significant bits.
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return BigInt::create(vm, modulo(bigint->big_integer(), BIGINT_ONE.shift_left(bits)));
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}
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}
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