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Kernel: Move kernel above the 3GB virtual address mark

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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.
This commit is contained in:
Andreas Kling 2020-01-17 19:59:20 +01:00
parent cee597a728
commit e362b56b4f
17 changed files with 325 additions and 125 deletions
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45
Kernel/VM/PageDirectory.cpp
View file

@ -4,7 +4,7 @@
#include <Kernel/VM/PageDirectory.h>
static const u32 userspace_range_base = 0x01000000;
static const u32 kernelspace_range_base = 0xc0000000;
static const u32 kernelspace_range_base = 0xc0800000;
static HashMap<u32, PageDirectory*>& cr3_map()
{
@ -21,22 +21,23 @@ RefPtr<PageDirectory> PageDirectory::find_by_cr3(u32 cr3)
return cr3_map().get(cr3).value_or({});
}
PageDirectory::PageDirectory(PhysicalAddress paddr)
: m_range_allocator(VirtualAddress(0xc0000000), 0x3f000000)
extern "C" u32 boot_pdpt;
extern "C" u32 boot_pd0;
extern "C" u32 boot_pd3;
PageDirectory::PageDirectory()
: m_range_allocator(VirtualAddress(0xc0c00000), 0x3f000000)
{
m_directory_table = PhysicalPage::create(paddr, true, false);
m_directory_pages[0] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 1), true, false);
m_directory_pages[1] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 2), true, false);
m_directory_pages[2] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 3), true, false);
m_directory_pages[3] = PhysicalPage::create(paddr.offset(PAGE_SIZE * 4), true, false);
table().raw[0] = (u64)m_directory_pages[0]->paddr().as_ptr() | 1;
table().raw[1] = (u64)m_directory_pages[1]->paddr().as_ptr() | 1;
table().raw[2] = (u64)m_directory_pages[2]->paddr().as_ptr() | 1;
table().raw[3] = (u64)m_directory_pages[3]->paddr().as_ptr() | 1;
InterruptDisabler disabler;
cr3_map().set(cr3(), this);
// Adopt the page tables already set up by boot.S
PhysicalAddress boot_pdpt_paddr(virtual_to_low_physical((u32)&boot_pdpt));
PhysicalAddress boot_pd0_paddr(virtual_to_low_physical((u32)&boot_pd0));
PhysicalAddress boot_pd3_paddr(virtual_to_low_physical((u32)&boot_pd3));
kprintf("MM: boot_pdpt @ P%p\n", boot_pdpt_paddr.get());
kprintf("MM: boot_pd0 @ P%p\n", boot_pd0_paddr.get());
kprintf("MM: boot_pd3 @ P%p\n", boot_pd3_paddr.get());
m_directory_table = PhysicalPage::create(boot_pdpt_paddr, true, false);
m_directory_pages[0] = PhysicalPage::create(boot_pd0_paddr, true, false);
m_directory_pages[3] = PhysicalPage::create(boot_pd3_paddr, true, false);
}
PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_range_allocator)
@ -44,7 +45,6 @@ PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_rang
, m_range_allocator(parent_range_allocator ? RangeAllocator(*parent_range_allocator) : RangeAllocator(VirtualAddress(userspace_range_base), kernelspace_range_base - userspace_range_base))
{
// Set up a userspace page directory
m_directory_table = MM.allocate_supervisor_physical_page();
m_directory_pages[0] = MM.allocate_supervisor_physical_page();
m_directory_pages[1] = MM.allocate_supervisor_physical_page();
@ -58,10 +58,11 @@ PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_rang
table().raw[3] = (u64)m_directory_pages[3]->paddr().as_ptr() | 1;
// Clone bottom 8 MB of mappings from kernel_page_directory
table().directory(0)[0].copy_from({}, MM.kernel_page_directory().table().directory(0)[0]);
table().directory(0)[1].copy_from({}, MM.kernel_page_directory().table().directory(0)[1]);
table().directory(0)[2].copy_from({}, MM.kernel_page_directory().table().directory(0)[2]);
table().directory(0)[3].copy_from({}, MM.kernel_page_directory().table().directory(0)[3]);
PageDirectoryEntry buffer[4];
auto* kernel_pd = MM.quickmap_pd(MM.kernel_page_directory(), 0);
memcpy(buffer, kernel_pd, sizeof(PageDirectoryEntry) * 4);
auto* new_pd = MM.quickmap_pd(*this, 0);
memcpy(new_pd, buffer, sizeof(PageDirectoryEntry) * 4);
InterruptDisabler disabler;
cr3_map().set(cr3(), this);
@ -74,4 +75,4 @@ PageDirectory::~PageDirectory()
#endif
InterruptDisabler disabler;
cr3_map().remove(cr3());
}
}