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52deb09382
Introduce one more (CPU) indirection layer in the paging code: the page directory pointer table (PDPT). Each PageDirectory now has 4 separate PageDirectoryEntry arrays, governing 1 GB of VM each. A really neat side-effect of this is that we can now share the physical page containing the >=3GB kernel-only address space metadata between all processes, instead of lazily cloning it on page faults. This will give us access to the NX (No eXecute) bit, allowing us to prevent execution of memory that's not supposed to be executed.
89 lines
3.4 KiB
C++
89 lines
3.4 KiB
C++
#include <Kernel/Process.h>
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#include <Kernel/Thread.h>
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#include <Kernel/VM/MemoryManager.h>
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#include <Kernel/VM/PageDirectory.h>
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static const u32 userspace_range_base = 0x01000000;
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static const u32 kernelspace_range_base = 0xc0000000;
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static HashMap<u32, PageDirectory*>& cr3_map()
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{
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ASSERT_INTERRUPTS_DISABLED();
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static HashMap<u32, PageDirectory*>* map;
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if (!map)
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map = new HashMap<u32, PageDirectory*>;
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return *map;
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}
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RefPtr<PageDirectory> PageDirectory::find_by_cr3(u32 cr3)
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{
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InterruptDisabler disabler;
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return cr3_map().get(cr3).value_or({});
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}
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PageDirectory::PageDirectory(PhysicalAddress paddr)
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: m_range_allocator(VirtualAddress(0xc0000000), 0x3f000000)
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{
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m_directory_table = PhysicalPage::create(paddr, true, false);
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m_directory_pages[0] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 1), true, false);
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m_directory_pages[1] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 2), true, false);
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m_directory_pages[2] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 3), true, false);
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m_directory_pages[3] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 4), true, false);
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table().raw[0] = (u64)m_directory_pages[0]->paddr().as_ptr() | 1;
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table().raw[1] = (u64)m_directory_pages[1]->paddr().as_ptr() | 1;
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table().raw[2] = (u64)m_directory_pages[2]->paddr().as_ptr() | 1;
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table().raw[3] = (u64)m_directory_pages[3]->paddr().as_ptr() | 1;
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InterruptDisabler disabler;
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cr3_map().set(cr3(), this);
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}
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PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_range_allocator)
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: m_process(&process)
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, m_range_allocator(parent_range_allocator ? RangeAllocator(*parent_range_allocator) : RangeAllocator(VirtualAddress(userspace_range_base), kernelspace_range_base - userspace_range_base))
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{
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// Set up a userspace page directory
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m_directory_table = MM.allocate_supervisor_physical_page();
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m_directory_pages[0] = MM.allocate_supervisor_physical_page();
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m_directory_pages[1] = MM.allocate_supervisor_physical_page();
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m_directory_pages[2] = MM.allocate_supervisor_physical_page();
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// Share the top 1 GB of kernel-only mappings (>=3GB or >=0xc0000000)
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m_directory_pages[3] = MM.kernel_page_directory().m_directory_pages[3];
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table().raw[0] = (u64)m_directory_pages[0]->paddr().as_ptr() | 1;
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table().raw[1] = (u64)m_directory_pages[1]->paddr().as_ptr() | 1;
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table().raw[2] = (u64)m_directory_pages[2]->paddr().as_ptr() | 1;
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table().raw[3] = (u64)m_directory_pages[3]->paddr().as_ptr() | 1;
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// Clone bottom 8 MB of mappings from kernel_page_directory
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table().directory(0)[0].copy_from({}, MM.kernel_page_directory().table().directory(0)[0]);
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table().directory(0)[1].copy_from({}, MM.kernel_page_directory().table().directory(0)[1]);
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table().directory(0)[2].copy_from({}, MM.kernel_page_directory().table().directory(0)[2]);
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table().directory(0)[3].copy_from({}, MM.kernel_page_directory().table().directory(0)[3]);
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InterruptDisabler disabler;
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cr3_map().set(cr3(), this);
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}
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PageDirectory::~PageDirectory()
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{
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#ifdef MM_DEBUG
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dbgprintf("MM: ~PageDirectory K%x\n", this);
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#endif
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InterruptDisabler disabler;
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cr3_map().remove(cr3());
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}
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void PageDirectory::flush(VirtualAddress vaddr)
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{
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#ifdef MM_DEBUG
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dbgprintf("MM: Flush page V%p\n", vaddr.get());
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#endif
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if (!current)
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return;
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if (this == &MM.kernel_page_directory() || ¤t->process().page_directory() == this)
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MM.flush_tlb(vaddr);
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}
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