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https://github.com/RGBCube/serenity
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e362b56b4f
The kernel and its static data structures are no longer identity-mapped in the bottom 8MB of the address space, but instead move above 3GB. The first 8MB above 3GB are pseudo-identity-mapped to the bottom 8MB of the physical address space. But things don't have to stay this way! Thanks to Jesse who made an earlier attempt at this, it was really easy to get device drivers working once the page tables were in place! :^) Fixes #734.
78 lines
3 KiB
C++
78 lines
3 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 = 0xc0800000;
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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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extern "C" u32 boot_pdpt;
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extern "C" u32 boot_pd0;
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extern "C" u32 boot_pd3;
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PageDirectory::PageDirectory()
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: m_range_allocator(VirtualAddress(0xc0c00000), 0x3f000000)
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{
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// Adopt the page tables already set up by boot.S
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PhysicalAddress boot_pdpt_paddr(virtual_to_low_physical((u32)&boot_pdpt));
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PhysicalAddress boot_pd0_paddr(virtual_to_low_physical((u32)&boot_pd0));
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PhysicalAddress boot_pd3_paddr(virtual_to_low_physical((u32)&boot_pd3));
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kprintf("MM: boot_pdpt @ P%p\n", boot_pdpt_paddr.get());
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kprintf("MM: boot_pd0 @ P%p\n", boot_pd0_paddr.get());
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kprintf("MM: boot_pd3 @ P%p\n", boot_pd3_paddr.get());
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m_directory_table = PhysicalPage::create(boot_pdpt_paddr, true, false);
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m_directory_pages[0] = PhysicalPage::create(boot_pd0_paddr, true, false);
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m_directory_pages[3] = PhysicalPage::create(boot_pd3_paddr, true, false);
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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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PageDirectoryEntry buffer[4];
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auto* kernel_pd = MM.quickmap_pd(MM.kernel_page_directory(), 0);
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memcpy(buffer, kernel_pd, sizeof(PageDirectoryEntry) * 4);
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auto* new_pd = MM.quickmap_pd(*this, 0);
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memcpy(new_pd, buffer, sizeof(PageDirectoryEntry) * 4);
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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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