#include <virtual-address-space-page-allocator.h>

Inheritance diagram for v8::base::VirtualAddressSpacePageAllocator:

Collaboration diagram for v8::base::VirtualAddressSpacePageAllocator:

Public Types
using	Address = uintptr_t

Public Types inherited from v8::PageAllocator
enum	Permission { kNoAccess , kRead , kReadWrite , kReadWriteExecute , kReadExecute , kNoAccessWillJitLater }

Public Member Functions
	VirtualAddressSpacePageAllocator (v8::VirtualAddressSpace *vas)

	VirtualAddressSpacePageAllocator (const VirtualAddressSpacePageAllocator &)=delete

VirtualAddressSpacePageAllocator &	operator= (const VirtualAddressSpacePageAllocator &)=delete

	~VirtualAddressSpacePageAllocator () override=default

size_t	AllocatePageSize () override

size_t	CommitPageSize () override

void	SetRandomMmapSeed (int64_t seed) override

void *	GetRandomMmapAddr () override

void *	AllocatePages (void *hint, size_t size, size_t alignment, Permission access) override

bool	FreePages (void *address, size_t size) override

bool	ReleasePages (void *address, size_t size, size_t new_size) override

bool	SetPermissions (void *address, size_t size, Permission access) override

bool	RecommitPages (void *address, size_t size, PageAllocator::Permission access) override

bool	DiscardSystemPages (void *address, size_t size) override

bool	DecommitPages (void *address, size_t size) override

bool	SealPages (void *address, size_t size) override

Public Member Functions inherited from v8::PageAllocator
virtual	~PageAllocator ()=default

virtual bool	ReserveForSharedMemoryMapping (void *address, size_t size)

virtual std::unique_ptr< SharedMemory >	AllocateSharedPages (size_t length, const void *original_address)

virtual bool	CanAllocateSharedPages ()

Private Attributes
v8::VirtualAddressSpace *	vas_

std::unordered_map< Address, size_t >	resized_allocations_

Mutex	mutex_

Detailed Description

Definition at line 20 of file virtual-address-space-page-allocator.h.

Member Typedef Documentation

◆ Address

using v8::base::VirtualAddressSpacePageAllocator::Address = uintptr_t

Definition at line 23 of file virtual-address-space-page-allocator.h.

Constructor & Destructor Documentation

◆ VirtualAddressSpacePageAllocator() [1/2]

v8::base::VirtualAddressSpacePageAllocator::VirtualAddressSpacePageAllocator ( v8::VirtualAddressSpace * vas )

explicit

Definition at line 10 of file virtual-address-space-page-allocator.cc.

◆ VirtualAddressSpacePageAllocator() [2/2]

v8::base::VirtualAddressSpacePageAllocator::VirtualAddressSpacePageAllocator ( const VirtualAddressSpacePageAllocator & )

delete

◆ ~VirtualAddressSpacePageAllocator()

v8::base::VirtualAddressSpacePageAllocator::~VirtualAddressSpacePageAllocator ( )

overridedefault

Member Function Documentation

◆ AllocatePages()

void * v8::base::VirtualAddressSpacePageAllocator::AllocatePages	(	void *	address,
		size_t	length,
		size_t	alignment,
		Permission	permissions )

overridevirtual

Allocates memory in range with the given alignment and permission.

Implements v8::PageAllocator.

Definition at line 14 of file virtual-address-space-page-allocator.cc.

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◆ AllocatePageSize()

size_t v8::base::VirtualAddressSpacePageAllocator::AllocatePageSize ( )

inlineoverridevirtual

Gets the page granularity for AllocatePages and FreePages. Addresses and lengths for those calls should be multiples of AllocatePageSize().

Implements v8::PageAllocator.

Definition at line 33 of file virtual-address-space-page-allocator.h.

◆ CommitPageSize()

size_t v8::base::VirtualAddressSpacePageAllocator::CommitPageSize ( )

inlineoverridevirtual

Gets the page granularity for SetPermissions and ReleasePages. Addresses and lengths for those calls should be multiples of CommitPageSize().

Implements v8::PageAllocator.

Definition at line 35 of file virtual-address-space-page-allocator.h.

◆ DecommitPages()

bool v8::base::VirtualAddressSpacePageAllocator::DecommitPages	(	void *	address,
		size_t	size )

overridevirtual

Decommits any wired memory pages in the given range, allowing the OS to reclaim them, and marks the region as inacessible (kNoAccess). The address range stays reserved and can be accessed again later by changing its permissions. However, in that case the memory content is guaranteed to be zero-initialized again. The memory must have been previously allocated by a call to AllocatePages. Returns true on success, false otherwise.

Implements v8::PageAllocator.

Definition at line 71 of file virtual-address-space-page-allocator.cc.

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◆ DiscardSystemPages()

bool v8::base::VirtualAddressSpacePageAllocator::DiscardSystemPages	(	void *	address,
		size_t	size )

overridevirtual

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.

Reimplemented from v8::PageAllocator.

Definition at line 66 of file virtual-address-space-page-allocator.cc.

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◆ FreePages()

bool v8::base::VirtualAddressSpacePageAllocator::FreePages	(	void *	address,
		size_t	length )

overridevirtual

Frees memory in a range that was allocated by a call to AllocatePages.

Implements v8::PageAllocator.

Definition at line 22 of file virtual-address-space-page-allocator.cc.

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◆ GetRandomMmapAddr()

void * v8::base::VirtualAddressSpacePageAllocator::GetRandomMmapAddr ( )

inlineoverridevirtual

Returns a randomized address, suitable for memory allocation under ASLR. The address will be aligned to AllocatePageSize.

Implements v8::PageAllocator.

Definition at line 39 of file virtual-address-space-page-allocator.h.

◆ operator=()

VirtualAddressSpacePageAllocator & v8::base::VirtualAddressSpacePageAllocator::operator= ( const VirtualAddressSpacePageAllocator & )

delete

◆ RecommitPages()

bool v8::base::VirtualAddressSpacePageAllocator::RecommitPages	(	void *	address,
		size_t	length,
		PageAllocator::Permission	permissions )

overridevirtual

Recommits discarded pages in the given range with given permissions. Discarded pages must be recommitted with their original permissions before they are used again.

Reimplemented from v8::PageAllocator.

Definition at line 60 of file virtual-address-space-page-allocator.cc.

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◆ ReleasePages()

bool v8::base::VirtualAddressSpacePageAllocator::ReleasePages	(	void *	address,
		size_t	length,
		size_t	new_length )

overridevirtual

Releases memory in a range that was allocated by a call to AllocatePages.

Implements v8::PageAllocator.

Definition at line 35 of file virtual-address-space-page-allocator.cc.

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◆ SealPages()

bool v8::base::VirtualAddressSpacePageAllocator::SealPages	(	void *	address,
		size_t	length )

overridevirtual

Block any modifications to the given mapping such as changing permissions or unmapping the pages on supported platforms. The address space reservation will exist until the process ends, but it's possible to release the memory using DiscardSystemPages. Note that this might require write permissions to the page as e.g. on Linux, mseal will block discarding sealed anonymous memory.

Reimplemented from v8::PageAllocator.

Definition at line 76 of file virtual-address-space-page-allocator.cc.