Liam Appelbe
4f98a2dc9f
Change-Id: I1f56687bf140faae113b2a4d2f34192cb87b68f7 TEST=DuplicateRXVirtualMemory Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/303960 Auto-Submit: Liam Appelbe <liama@google.com> Reviewed-by: Martin Kustermann <kustermann@google.com> Commit-Queue: Liam Appelbe <liama@google.com>
90 lines
3.3 KiB
C++
90 lines
3.3 KiB
C++
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#include "vm/virtual_memory.h"
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#include "platform/assert.h"
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#include "platform/utils.h"
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#if defined(DART_HOST_OS_MACOS)
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#include <mach/mach.h>
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#endif
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namespace dart {
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bool VirtualMemory::InSamePage(uword address0, uword address1) {
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return (Utils::RoundDown(address0, PageSize()) ==
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Utils::RoundDown(address1, PageSize()));
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}
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void VirtualMemory::Truncate(intptr_t new_size) {
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ASSERT(Utils::IsAligned(new_size, PageSize()));
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ASSERT(new_size <= size());
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if (reserved_.size() ==
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region_.size()) { // Don't create holes in reservation.
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if (FreeSubSegment(reinterpret_cast<void*>(start() + new_size),
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size() - new_size)) {
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reserved_.set_size(new_size);
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if (AliasOffset() != 0) {
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FreeSubSegment(reinterpret_cast<void*>(alias_.start() + new_size),
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alias_.size() - new_size);
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}
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}
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}
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region_.Subregion(region_, 0, new_size);
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alias_.Subregion(alias_, 0, new_size);
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}
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VirtualMemory* VirtualMemory::ForImagePage(void* pointer, uword size) {
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// Memory for precompilated instructions was allocated by the embedder, so
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// create a VirtualMemory without allocating.
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MemoryRegion region(pointer, size);
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MemoryRegion reserved(nullptr, 0); // null reservation indicates VM should
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// not attempt to free this memory.
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VirtualMemory* memory = new VirtualMemory(region, region, reserved);
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ASSERT(!memory->vm_owns_region());
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return memory;
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}
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VirtualMemory* VirtualMemory::DuplicateRX() {
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#if defined(DART_HOST_OS_MACOS)
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// Mac is special cased because iOS doesn't allow allocating new executable
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// memory, so the default approach would fail. We are allowed to make new
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// mappings of existing executable memory using vm_remap though, which is
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// effectively the same for non-writable memory.
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const mach_port_t task = mach_task_self();
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const vm_address_t source_address = reinterpret_cast<vm_address_t>(address());
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const vm_size_t mem_size = size();
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vm_prot_t current_protection = VM_PROT_READ | VM_PROT_EXECUTE;
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vm_prot_t max_protection = current_protection;
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vm_address_t target_address = 0;
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kern_return_t status =
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vm_remap(task, &target_address, mem_size,
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/*mask=*/0,
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/*flags=anywhere*/ 1, task, source_address,
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/*copy=*/true, ¤t_protection, &max_protection,
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/*inheritance=*/VM_INHERIT_NONE);
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if (status != KERN_SUCCESS) {
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return nullptr;
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}
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const MemoryRegion region(reinterpret_cast<void*>(target_address), mem_size);
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return new VirtualMemory(region, region);
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#else // defined(DART_HOST_OS_MACOS)
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// TODO(liama): Use dual mapping on platforms where it's supported.
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VirtualMemory* const memory = VirtualMemory::Allocate(
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size(), /*is_executable=*/true, /*is_compressed=*/false,
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"VirtualMemory::DuplicateRX");
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if (memory == nullptr) {
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return nullptr;
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}
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// This is safe because the old memory can't overlap with the new memory.
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memcpy(memory->address(), address(), size()); // NOLINT
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memory->Protect(kReadExecute);
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return memory;
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#endif // defined(DART_HOST_OS_MACOS)
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}
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} // namespace dart
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