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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "v8config.h" // NOLINT(build/include_directory)
#if !defined(CPPGC_CAGED_HEAP)
#error "Must be compiled with caged heap enabled"
#endif
#include "src/heap/cppgc/caged-heap.h"
#include "include/cppgc/internal/caged-heap-local-data.h"
#include "src/base/bounded-page-allocator.h"
#include "src/base/logging.h"
#include "src/heap/cppgc/globals.h"
namespace cppgc {
namespace internal {
STATIC_ASSERT(api_constants::kCagedHeapReservationSize ==
kCagedHeapReservationSize);
STATIC_ASSERT(api_constants::kCagedHeapReservationAlignment ==
kCagedHeapReservationAlignment);
namespace {
VirtualMemory ReserveCagedHeap(PageAllocator* platform_allocator) {
DCHECK_NOT_NULL(platform_allocator);
DCHECK_EQ(0u,
kCagedHeapReservationSize % platform_allocator->AllocatePageSize());
static constexpr size_t kAllocationTries = 4;
for (size_t i = 0; i < kAllocationTries; ++i) {
void* hint = reinterpret_cast<void*>(RoundDown(
reinterpret_cast<uintptr_t>(platform_allocator->GetRandomMmapAddr()),
kCagedHeapReservationAlignment));
VirtualMemory memory(platform_allocator, kCagedHeapReservationSize,
kCagedHeapReservationAlignment, hint);
if (memory.IsReserved()) return memory;
}
FATAL("Fatal process out of memory: Failed to reserve memory for caged heap");
UNREACHABLE();
}
class CppgcBoundedPageAllocator final : public v8::base::BoundedPageAllocator {
public:
CppgcBoundedPageAllocator(v8::PageAllocator* page_allocator, Address start,
size_t size, size_t allocate_page_size)
: BoundedPageAllocator(page_allocator, start, size, allocate_page_size) {}
bool FreePages(void* address, size_t size) final {
// BoundedPageAllocator is not guaranteed to allocate zeroed page.
// Specifically it is possible that BPA frees a page and then tries to
// reallocate the same page before the OS has had a chance to asyncroniously
// reclaim that page. In such cases, the contents of the page would not have
// been cleared by the OS and the reallocated page will keep its previous
// contents. To mitigate this problem, CppgcBoundedPageAllocator clears all
// pages before they are freed. This also includes protected guard pages, so
// CppgcBoundedPageAllocator needs to update permissions before clearing.
SetPermissions(address, size, Permission::kReadWrite);
memset(address, 0, size);
return v8::base::BoundedPageAllocator::FreePages(address, size);
}
};
} // namespace
CagedHeap::CagedHeap(HeapBase* heap_base, PageAllocator* platform_allocator)
: reserved_area_(ReserveCagedHeap(platform_allocator)) {
using CagedAddress = CagedHeap::AllocatorType::Address;
DCHECK_NOT_NULL(heap_base);
CHECK(platform_allocator->SetPermissions(
reserved_area_.address(),
RoundUp(sizeof(CagedHeapLocalData), platform_allocator->CommitPageSize()),
PageAllocator::kReadWrite));
auto* local_data =
new (reserved_area_.address()) CagedHeapLocalData(heap_base);
#if defined(CPPGC_YOUNG_GENERATION)
local_data->age_table.Reset(platform_allocator);
#endif
USE(local_data);
const CagedAddress caged_heap_start =
RoundUp(reinterpret_cast<CagedAddress>(reserved_area_.address()) +
sizeof(CagedHeapLocalData),
kPageSize);
const size_t local_data_size_with_padding =
caged_heap_start -
reinterpret_cast<CagedAddress>(reserved_area_.address());
bounded_allocator_ = std::make_unique<CppgcBoundedPageAllocator>(
platform_allocator, caged_heap_start,
reserved_area_.size() - local_data_size_with_padding, kPageSize);
}
} // namespace internal
} // namespace cppgc
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