libos 0.1.2

Library OS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59

use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
use bootloader::BootInfo;
use x86_64::structures::paging::FrameAllocator;
use x86_64::structures::paging::PhysFrame;
use x86_64::structures::paging::Size4KiB;
use x86_64::PhysAddr;

static mut ALLOCATOR: Option<BootInfoFrameAllocator> = None;

/// A FrameAllocator that returns usable frames from the bootloader's memory map.
pub struct BootInfoFrameAllocator {
    memory_map: &'static MemoryMap,
    next: usize,
}

impl BootInfoFrameAllocator {
    /// Create a FrameAllocator from the passed memory map.
    ///
    /// This function is unsafe because the caller must guarantee that the passed
    /// memory map is valid. The main requirement is that all frames that are marked
    /// as `USABLE` in it are really unused.
    pub unsafe fn init(memory_map: &'static MemoryMap) -> Self {
        BootInfoFrameAllocator {
            memory_map,
            next: 0,
        }
    }

    /// Returns an iterator over the usable frames specified in the memory map.
    fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
        // get usable regions from memory map
        let regions = self.memory_map.iter();
        let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
        // map each region to its address range
        let addr_ranges = usable_regions.map(|r| r.range.start_addr()..r.range.end_addr());
        // transform to an iterator of frame start addresses
        let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096));
        // create `PhysFrame` types from the start addresses
        frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
    }
}

unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
    fn allocate_frame(&mut self) -> Option<PhysFrame> {
        let frame = self.usable_frames().nth(self.next);
        self.next += 1;
        frame
    }
}

pub fn page_alloc() -> &'static mut BootInfoFrameAllocator {
    unsafe { ALLOCATOR.as_mut().unwrap() }
}

pub fn page_alloc_init(boot_info: &'static BootInfo) {
    unsafe {
        ALLOCATOR.replace(BootInfoFrameAllocator::init(&boot_info.memory_map));
    }
}