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Kernel: Support loading the kernel at almost arbitrary virtual addresses

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This enables further work on implementing KASLR by adding relocation
support to the pre-kernel and updating the kernel to be less dependent
on specific virtual memory layouts.
This commit is contained in:
Gunnar Beutner 2021-07-26 15:10:51 +02:00 • committed by Andreas Kling
parent e3d2ca6bd2
commit 57417a3d6e
20 changed files with 123 additions and 87 deletions
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6
Kernel/VM/PageDirectory.cpp
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@ -51,7 +51,7 @@ UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
dmesgln("MM: boot_pd_kernel @ {}", boot_pd_kernel);
m_directory_table = PhysicalPage::create(boot_pdpt, MayReturnToFreeList::No);
m_directory_pages[0] = PhysicalPage::create(boot_pd0, MayReturnToFreeList::No);
m_directory_pages[(kernel_base >> 30) & 0x1ff] = PhysicalPage::create(boot_pd_kernel, MayReturnToFreeList::No);
m_directory_pages[(kernel_mapping_base >> 30) & 0x1ff] = PhysicalPage::create(boot_pd_kernel, MayReturnToFreeList::No);
}
PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
@ -77,13 +77,13 @@ PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
m_directory_table = MM.allocate_user_physical_page();
if (!m_directory_table)
return;
auto kernel_pd_index = (kernel_base >> 30) & 0x1ffu;
auto kernel_pd_index = (kernel_mapping_base >> 30) & 0x1ffu;
for (size_t i = 0; i < kernel_pd_index; i++) {
m_directory_pages[i] = MM.allocate_user_physical_page();
if (!m_directory_pages[i])
return;
}
// Share the top 1 GiB of kernel-only mappings (>=kernel_base)
// Share the top 1 GiB of kernel-only mappings (>=kernel_mapping_base)
m_directory_pages[kernel_pd_index] = MM.kernel_page_directory().m_directory_pages[kernel_pd_index];
#if ARCH(X86_64)