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https://github.com/RGBCube/serenity
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b2a52f6208
By designating a committed page pool we can guarantee to have physical pages available for lazy allocation in mappings. However, when forking we will overcommit. The assumption is that worst-case it's better for the fork to die due to insufficient physical memory on COW access than the parent that created the region. If a fork wants to ensure that all memory is available (trigger a commit) then it can use madvise. This also means that fork now can gracefully fail if we don't have enough physical pages available.
92 lines
3.1 KiB
C++
92 lines
3.1 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <Kernel/VM/AnonymousVMObject.h>
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#include <Kernel/VM/MemoryManager.h>
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#include <Kernel/VM/PhysicalPage.h>
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namespace Kernel {
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NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_size(size_t size)
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{
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return adopt(*new AnonymousVMObject(size));
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}
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RefPtr<AnonymousVMObject> AnonymousVMObject::create_for_physical_range(PhysicalAddress paddr, size_t size)
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{
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if (paddr.offset(size) < paddr) {
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dbg() << "Shenanigans! create_for_physical_range(" << paddr << ", " << size << ") would wrap around";
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return nullptr;
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}
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return adopt(*new AnonymousVMObject(paddr, size));
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}
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NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_physical_page(PhysicalPage& page)
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{
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auto vmobject = create_with_size(PAGE_SIZE);
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vmobject->m_physical_pages[0] = page;
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return vmobject;
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}
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AnonymousVMObject::AnonymousVMObject(size_t size, bool initialize_pages)
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: VMObject(size)
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{
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if (initialize_pages) {
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#ifndef MAP_SHARED_ZERO_PAGE_LAZILY
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for (size_t i = 0; i < page_count(); ++i)
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physical_pages()[i] = MM.shared_zero_page();
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#endif
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}
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}
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AnonymousVMObject::AnonymousVMObject(PhysicalAddress paddr, size_t size)
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: VMObject(size)
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{
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ASSERT(paddr.page_base() == paddr);
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for (size_t i = 0; i < page_count(); ++i)
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physical_pages()[i] = PhysicalPage::create(paddr.offset(i * PAGE_SIZE), false, false);
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}
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AnonymousVMObject::AnonymousVMObject(const AnonymousVMObject& other)
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: VMObject(other)
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{
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}
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AnonymousVMObject::~AnonymousVMObject()
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{
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}
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RefPtr<VMObject> AnonymousVMObject::clone()
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{
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return adopt(*new AnonymousVMObject(*this));
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}
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RefPtr<PhysicalPage> AnonymousVMObject::allocate_committed_page(size_t)
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{
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return {};
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}
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}
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