34 lines
1.4 KiB
Rust
34 lines
1.4 KiB
Rust
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use x86_64::{structures::paging::{PageTable,OffsetPageTable}, VirtAddr, PhysAddr};
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/// Initialize a new OffsetPageTable.
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///
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/// This function is unsafe because the caller must guarantee that the
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/// complete physical memory is mapped to virtual memory at the passed
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/// `physical_memory_offset`. Also, this function must be only called once
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/// to avoid aliasing `&mut` references (which is undefined behavior).
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pub unsafe fn init(physical_memory_offset: VirtAddr) -> OffsetPageTable<'static> {
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let level_4_table = active_level_4_table(physical_memory_offset);
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OffsetPageTable::new(level_4_table, physical_memory_offset)
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}
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/// Returns a mutable reference to the active level 4 table.
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///
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/// This function is unsafe because the caller must guarantee that the
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/// complete physical memory is mapped to virtual memory at the passed
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/// `physical_memory_offset`. Also, this function must be only called once
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/// to avoid aliasing `&mut` references (which is undefined behavior).
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unsafe fn active_level_4_table(physical_memory_offset: VirtAddr)
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-> &'static mut PageTable
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{
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use x86_64::registers::control::Cr3;
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let (level_4_table_frame, _) = Cr3::read();
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let phys = level_4_table_frame.start_address();
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let virt = physical_memory_offset + phys.as_u64();
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let page_table_ptr: *mut PageTable = virt.as_mut_ptr();
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&mut *page_table_ptr // unsafe
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}
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