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// Copyright 2012 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.
#ifndef V8_UTILS_ALLOCATION_H_
#define V8_UTILS_ALLOCATION_H_
#include <new>
#include "include/v8-platform.h"
#include "src/base/address-region.h"
#include "src/base/bounded-page-allocator.h"
#include "src/base/compiler-specific.h"
#include "src/base/platform/memory.h"
#include "src/init/v8.h"
namespace v8 {
namespace base {
class BoundedPageAllocator;
} // namespace base
namespace internal {
class Isolate;
// This file defines memory allocation functions. If a first attempt at an
// allocation fails, these functions call back into the embedder, then attempt
// the allocation a second time. The embedder callback must not reenter V8.
// Superclass for classes managed with new & delete.
class V8_EXPORT_PRIVATE Malloced {
public:
static void* operator new(size_t size);
static void operator delete(void* p);
};
// Function that may release reserved memory regions to allow failed allocations
// to succeed.
V8_EXPORT_PRIVATE void OnCriticalMemoryPressure();
template <typename T>
T* NewArray(size_t size) {
T* result = new (std::nothrow) T[size];
if (V8_UNLIKELY(result == nullptr)) {
OnCriticalMemoryPressure();
result = new (std::nothrow) T[size];
if (result == nullptr) V8::FatalProcessOutOfMemory(nullptr, "NewArray");
}
return result;
}
template <typename T>
T* NewArray(size_t size, T default_val)
requires base::is_trivially_copyable<T>::value
{
T* result = reinterpret_cast<T*>(NewArray<uint8_t>(sizeof(T) * size));
for (size_t i = 0; i < size; ++i) result[i] = default_val;
return result;
}
template <typename T>
void DeleteArray(T* array) {
delete[] array;
}
template <typename T>
struct ArrayDeleter {
void operator()(T* array) { DeleteArray(array); }
};
template <typename T>
using ArrayUniquePtr = std::unique_ptr<T, ArrayDeleter<T>>;
// The normal strdup functions use malloc. These versions of StrDup
// and StrNDup uses new and calls the FatalProcessOutOfMemory handler
// if allocation fails.
V8_EXPORT_PRIVATE char* StrDup(const char* str);
char* StrNDup(const char* str, int n);
// Allocation policy for allocating in the C free store using malloc
// and free. Used as the default policy for lists.
class FreeStoreAllocationPolicy {
public:
template <typename T, typename TypeTag = T[]>
V8_INLINE T* AllocateArray(size_t length) {
return static_cast<T*>(Malloced::operator new(length * sizeof(T)));
}
template <typename T, typename TypeTag = T[]>
V8_INLINE void DeleteArray(T* p, size_t length) {
Malloced::operator delete(p);
}
};
using MallocFn = void* (*)(size_t);
// Performs a malloc, with retry logic on failure. Returns nullptr on failure.
// Call free to release memory allocated with this function.
void* AllocWithRetry(size_t size, MallocFn = base::Malloc);
// Performs a malloc, with retry logic on failure. Returns nullptr on failure.
// Call free to release memory allocated with this function.
base::AllocationResult<void*> AllocAtLeastWithRetry(size_t size);
V8_EXPORT_PRIVATE void* AlignedAllocWithRetry(size_t size, size_t alignment);
V8_EXPORT_PRIVATE void AlignedFree(void* ptr);
// Returns platfrom page allocator instance. Guaranteed to be a valid pointer.
V8_EXPORT_PRIVATE v8::PageAllocator* GetPlatformPageAllocator();
// Returns platfrom virtual memory space instance. Guaranteed to be a valid
// pointer.
V8_EXPORT_PRIVATE v8::VirtualAddressSpace* GetPlatformVirtualAddressSpace();
#ifdef V8_ENABLE_SANDBOX
// Returns the page allocator instance for allocating pages inside the sandbox.
// Guaranteed to be a valid pointer.
V8_EXPORT_PRIVATE v8::PageAllocator* GetSandboxPageAllocator();
#endif
// Returns the appropriate page allocator to use for ArrayBuffer backing
// stores. If the sandbox is enabled, these must be allocated inside the
// sandbox and so this will be the SandboxPageAllocator. Otherwise it will be
// the PlatformPageAllocator.
inline v8::PageAllocator* GetArrayBufferPageAllocator() {
#ifdef V8_ENABLE_SANDBOX
return GetSandboxPageAllocator();
#else
return GetPlatformPageAllocator();
#endif
}
// Sets the given page allocator as the platform page allocator and returns
// the current one. This function *must* be used only for testing purposes.
// It is not thread-safe and the testing infrastructure should ensure that
// the tests do not modify the value simultaneously.
V8_EXPORT_PRIVATE v8::PageAllocator* SetPlatformPageAllocatorForTesting(
v8::PageAllocator* page_allocator);
// Gets the page granularity for AllocatePages and FreePages. Addresses returned
// by AllocatePages are aligned to this size.
V8_EXPORT_PRIVATE size_t AllocatePageSize();
// Gets the granularity at which the permissions and release calls can be made.
V8_EXPORT_PRIVATE size_t CommitPageSize();
// Generate a random address to be used for hinting allocation calls.
V8_EXPORT_PRIVATE void* GetRandomMmapAddr();
// Allocates memory. Permissions are set according to the access argument.
// |address| is a hint. |size| and |alignment| must be multiples of
// AllocatePageSize(). Returns the address of the allocated memory, with the
// specified size and alignment, or nullptr on failure.
V8_EXPORT_PRIVATE
V8_WARN_UNUSED_RESULT void* AllocatePages(v8::PageAllocator* page_allocator,
void* address, size_t size,
size_t alignment,
PageAllocator::Permission access);
// Frees memory allocated by a call to AllocatePages. |address| and |size| must
// be multiples of AllocatePageSize().
V8_EXPORT_PRIVATE
void FreePages(v8::PageAllocator* page_allocator, void* address,
const size_t size);
// Releases memory that is no longer needed. The range specified by |address|
// and |size| must be an allocated memory region. |size| and |new_size| must be
// multiples of CommitPageSize(). Memory from |new_size| to |size| is released.
// Released memory is left in an undefined state, so it should not be accessed.
V8_EXPORT_PRIVATE
void ReleasePages(v8::PageAllocator* page_allocator, void* address, size_t size,
size_t new_size);
// Sets permissions according to |access|. |address| and |size| must be
// multiples of CommitPageSize(). Setting permission to kNoAccess may
// cause the memory contents to be lost. Returns true on success, otherwise
// false.
V8_EXPORT_PRIVATE
V8_WARN_UNUSED_RESULT bool SetPermissions(v8::PageAllocator* page_allocator,
void* address, size_t size,
PageAllocator::Permission access);
inline bool SetPermissions(v8::PageAllocator* page_allocator, Address address,
size_t size, PageAllocator::Permission access) {
return SetPermissions(page_allocator, reinterpret_cast<void*>(address), size,
access);
}
// Defines whether the address space reservation is going to be used for
// allocating executable pages.
enum class JitPermission { kNoJit, kMapAsJittable };
// Represents and controls an area of reserved memory.
class VirtualMemory final {
public:
// Empty VirtualMemory object, controlling no reserved memory.
V8_EXPORT_PRIVATE VirtualMemory();
VirtualMemory(const VirtualMemory&) = delete;
VirtualMemory& operator=(const VirtualMemory&) = delete;
// Reserves virtual memory containing an area of the given size that is
// aligned per |alignment| rounded up to the |page_allocator|'s allocate page
// size. The |size| must be aligned with |page_allocator|'s commit page size.
// This may not be at the position returned by address().
V8_EXPORT_PRIVATE VirtualMemory(
v8::PageAllocator* page_allocator, size_t size, void* hint,
size_t alignment = 1,
PageAllocator::Permission permissions = PageAllocator::kNoAccess);
// Construct a virtual memory by assigning it some already mapped address
// and size.
VirtualMemory(v8::PageAllocator* page_allocator, Address address, size_t size)
: page_allocator_(page_allocator), region_(address, size) {
DCHECK_NOT_NULL(page_allocator);
DCHECK(IsAligned(address, page_allocator->AllocatePageSize()));
DCHECK(IsAligned(size, page_allocator->CommitPageSize()));
}
// Releases the reserved memory, if any, controlled by this VirtualMemory
// object.
V8_EXPORT_PRIVATE ~VirtualMemory();
// Move constructor.
VirtualMemory(VirtualMemory&& other) V8_NOEXCEPT { *this = std::move(other); }
// Move assignment operator.
VirtualMemory& operator=(VirtualMemory&& other) V8_NOEXCEPT {
DCHECK(!IsReserved());
page_allocator_ = other.page_allocator_;
region_ = other.region_;
other.Reset();
return *this;
}
// Returns whether the memory has been reserved.
bool IsReserved() const { return region_.begin() != kNullAddress; }
// Initialize or resets an embedded VirtualMemory object.
V8_EXPORT_PRIVATE void Reset();
v8::PageAllocator* page_allocator() { return page_allocator_; }
const base::AddressRegion& region() const { return region_; }
// Returns the start address of the reserved memory.
// If the memory was reserved with an alignment, this address is not
// necessarily aligned. The user might need to round it up to a multiple of
// the alignment to get the start of the aligned block.
Address address() const {
DCHECK(IsReserved());
return region_.begin();
}
Address end() const {
DCHECK(IsReserved());
return region_.end();
}
// Returns the size of the reserved memory. The returned value is only
// meaningful when IsReserved() returns true.
// If the memory was reserved with an alignment, this size may be larger
// than the requested size.
size_t size() const { return region_.size(); }
// Sets permissions according to the access argument. address and size must be
// multiples of CommitPageSize(). Returns true on success, otherwise false.
V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT bool SetPermissions(
Address address, size_t size, PageAllocator::Permission access);
// Recommits discarded pages in the given range with given permissions.
// Discarded pages must be recommitted with their original permissions
// before they are used again. |address| and |size| must be multiples of
// CommitPageSize(). Returns true on success, otherwise false.
V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT bool RecommitPages(
Address address, size_t size, PageAllocator::Permission access);
// Resizes the reservation starting at |address| to |new_size| and commits the
// additional memory range with the |access| permissions.
V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT bool Resize(
Address address, size_t new_size, PageAllocator::Permission access);
// Frees memory in the given [address, address + size) range. address and size
// should be operating system page-aligned. The next write to this
// memory area brings the memory transparently back. This should be treated as
// a hint to the OS that the pages are no longer needed. It does not guarantee
// that the pages will be discarded immediately or at all.
V8_EXPORT_PRIVATE bool DiscardSystemPages(Address address, size_t size);
// Releases memory after |free_start|. Returns the number of bytes released.
V8_EXPORT_PRIVATE size_t Release(Address free_start);
// Frees all memory.
V8_EXPORT_PRIVATE void Free();
bool InVM(Address address, size_t size) const {
return region_.contains(address, size);
}
private:
// Page allocator that controls the virtual memory.
v8::PageAllocator* page_allocator_ = nullptr;
base::AddressRegion region_;
};
// Represents a VirtualMemory reservation along with a BoundedPageAllocator that
// can be used to allocate within the reservation.
//
// Virtual memory cages are used for the pointer compression cage, the code
// ranges (on platforms that require code ranges), and trusted ranges (when the
// sandbox is enabled). They are configurable via ReservationParams.
//
// +-----------+------------ ~~~ --+- ~~~ -+
// | ... | ... | ... |
// +-----------+------------ ~~~ --+- ~~~ -+
// ^ ^
// cage base allocatable base
//
// <------------------->
// allocatable size
// <------------------------------->
// cage size
// <--------------------------------------->
// reservation size
//
// - The reservation is made using ReservationParams::page_allocator.
// - cage base is the start of the virtual memory reservation and the base
// address of the cage.
// - allocatable base is the cage base rounded up to the nearest
// ReservationParams::page_size, and is the start of the allocatable area for
// the BoundedPageAllocator.
// - cage size is the size of the area from cage base to the end of the
// allocatable area.
//
// - The reservation size is configured by ReservationParams::reservation_size
// but it might be actually bigger if we end up over-reserving the virtual
// address space.
//
// Additionally,
// - The alignment of the cage base is configured by
// ReservationParams::base_alignment.
// - The page size of the BoundedPageAllocator is configured by
// ReservationParams::page_size.
// - A hint for the value of start can be passed by
// ReservationParams::requested_start_hint and it must be aligned to
// ReservationParams::base_alignment.
//
// The configuration is subject to the following alignment requirements.
// Below, AllocatePageSize is short for
// ReservationParams::page_allocator->AllocatePageSize().
//
// - The reservation size must be AllocatePageSize-aligned.
// - If the base alignment is not kAnyBaseAlignment then the base alignment
// must be AllocatePageSize-aligned.
// - The base alignment may be kAnyBaseAlignment to denote any alignment is
// acceptable. In this case the base bias size does not need to be aligned.
class VirtualMemoryCage {
public:
VirtualMemoryCage();
virtual ~VirtualMemoryCage();
VirtualMemoryCage(const VirtualMemoryCage&) = delete;
VirtualMemoryCage& operator=(VirtualMemoryCage&) = delete;
VirtualMemoryCage(VirtualMemoryCage&& other) V8_NOEXCEPT;
VirtualMemoryCage& operator=(VirtualMemoryCage&& other) V8_NOEXCEPT;
Address base() const { return base_; }
size_t size() const { return size_; }
base::AddressRegion region() const {
return base::AddressRegion{base_, size_};
}
base::BoundedPageAllocator* page_allocator() const {
return page_allocator_.get();
}
VirtualMemory* reservation() { return &reservation_; }
const VirtualMemory* reservation() const { return &reservation_; }
bool IsReserved() const {
DCHECK_EQ(base_ != kNullAddress, reservation_.IsReserved());
DCHECK_EQ(base_ != kNullAddress, size_ != 0);
return reservation_.IsReserved();
}
struct ReservationParams {
// The allocator to use to reserve the virtual memory.
v8::PageAllocator* page_allocator;
// See diagram above.
size_t reservation_size;
size_t base_alignment;
size_t page_size;
Address requested_start_hint;
PageAllocator::Permission permissions;
base::PageInitializationMode page_initialization_mode;
base::PageFreeingMode page_freeing_mode;
static constexpr size_t kAnyBaseAlignment = 1;
};
// A number of attempts is made to try to reserve a region that satisfies the
// constraints in params, but this may fail. The base address may be different
// than the one requested.
// If an existing reservation is provided, it will be used for this cage
// instead. The caller retains ownership of the reservation and is responsible
// for keeping the memory reserved during the lifetime of this object.
bool InitReservation(
const ReservationParams& params,
base::AddressRegion existing_reservation = base::AddressRegion());
void Free();
protected:
Address base_ = kNullAddress;
size_t size_ = 0;
std::unique_ptr<base::BoundedPageAllocator> page_allocator_;
VirtualMemory reservation_;
};
} // namespace internal
} // namespace v8
#endif // V8_UTILS_ALLOCATION_H_