95 lines
3.7 KiB
Rust
95 lines
3.7 KiB
Rust
pub use super::PAGE_SIZE;
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use multiboot2::{MemoryArea, MemoryAreaIter};
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pub use x86_64::structures::paging::{
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frame::PhysFrame as Frame, FrameAllocator, FrameDeallocator, Size4KiB,
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};
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use x86_64::PhysAddr;
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pub struct AreaFrameAllocator {
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next_free_frame: Frame,
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current_area: Option<&'static MemoryArea>,
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areas: MemoryAreaIter,
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kernel_start: Frame,
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kernel_end: Frame,
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multiboot_start: Frame,
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multiboot_end: Frame,
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}
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impl AreaFrameAllocator {
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pub fn new(kernel_start: u64, kernel_end: u64, multiboot_start: u64, multiboot_end: u64, memory_areas: MemoryAreaIter) -> AreaFrameAllocator {
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let mut allocator = AreaFrameAllocator {
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next_free_frame: Frame::containing_address(PhysAddr::new(0)),
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current_area: None,
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areas: memory_areas,
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kernel_start: Frame::containing_address(PhysAddr::new(kernel_start)),
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kernel_end: Frame::containing_address(PhysAddr::new(kernel_end)),
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multiboot_start: Frame::containing_address(PhysAddr::new(multiboot_start)),
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multiboot_end: Frame::containing_address(PhysAddr::new(multiboot_end)),
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};
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allocator.choose_next_area();
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allocator
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}
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fn choose_next_area(&mut self) {
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self.current_area = self
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.areas
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.clone()
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.filter(|area| {
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let address = area.base_addr + area.length - 1;
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Frame::containing_address(PhysAddr::new(address)) >= self.next_free_frame
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})
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.min_by_key(|area| area.base_addr);
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if let Some(area) = self.current_area {
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let start_frame = Frame::containing_address(PhysAddr::new(area.base_addr));
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if self.next_free_frame < start_frame {
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self.next_free_frame = start_frame;
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}
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}
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}
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}
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unsafe impl FrameAllocator<Size4KiB> for AreaFrameAllocator {
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fn allocate_frame(&mut self) -> Option<Frame> {
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if let Some(area) = self.current_area {
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// "Clone" the frame to return it if it's free. Frame doesn't
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// implement Clone, but we can construct an identical frame.
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let frame = Frame::containing_address(self.next_free_frame.start_address());
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// the last frame of the current area
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let current_area_last_frame = {
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let address = area.base_addr + area.length - 1;
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Frame::containing_address(PhysAddr::new(address))
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};
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if frame > current_area_last_frame {
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// all frames of current area are used, switch to next area
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self.choose_next_area();
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} else if frame >= self.kernel_start && frame <= self.kernel_end {
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// `frame` is used by the kernel
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self.next_free_frame =
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Frame::containing_address(self.kernel_end.start_address() + PAGE_SIZE);
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} else if frame >= self.multiboot_start && frame <= self.multiboot_end {
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// `frame` is used by the multiboot information structure
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self.next_free_frame =
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Frame::containing_address(self.multiboot_end.start_address() + PAGE_SIZE);
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} else {
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// frame is unused, increment `next_free_frame` and return it
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self.next_free_frame =
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Frame::containing_address(self.next_free_frame.start_address() + PAGE_SIZE);
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return Some(frame);
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}
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// `frame` was not valid, try it again with the updated `next_free_frame`
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self.allocate_frame()
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} else {
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None // no free frames left
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}
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}
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}
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impl FrameDeallocator<Size4KiB> for AreaFrameAllocator {
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unsafe fn deallocate_frame(&mut self, _frame: Frame) {
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unimplemented!()
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}
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}
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