4lDO2
844 lines
30 KiB
Rust
844 lines
30 KiB
Rust
//! # Memory management
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//! Some code was borrowed from [Phil Opp's Blog](http://os.phil-opp.com/allocating-frames.html)
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use core::{
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cell::SyncUnsafeCell,
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mem,
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num::NonZeroUsize,
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sync::atomic::{AtomicUsize, Ordering},
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};
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use spin::Mutex;
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use crate::context::{self, memory::{AccessMode, PfError}};
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use crate::kernel_executable_offsets::{__usercopy_start, __usercopy_end};
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use crate::paging::Page;
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pub use crate::paging::{PAGE_SIZE, PAGE_MASK, PhysicalAddress, RmmA, RmmArch};
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use rmm::{
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FrameAllocator,
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FrameCount, VirtualAddress, TableKind, BumpAllocator,
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};
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use crate::syscall::error::{ENOMEM, Error};
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/// A memory map area
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#[derive(Copy, Clone, Debug, Default)]
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#[repr(packed)]
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pub struct MemoryArea {
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pub base_addr: u64,
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pub length: u64,
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pub _type: u32,
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pub acpi: u32,
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}
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/// Get the number of frames available
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pub fn free_frames() -> usize {
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0
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}
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/// Get the number of frames used
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pub fn used_frames() -> usize {
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0
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}
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/// Allocate a range of frames
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pub fn allocate_frames(count: usize) -> Option<Frame> {
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allocate_frames_complex(count, (), None, count).map(|(f, _)| f)
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}
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pub fn allocate_frame() -> Option<Frame> {
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allocate_frames(1)
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}
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pub fn allocate_frames_complex(count: usize, flags: (), strategy: Option<()>, min: usize) -> Option<(Frame, usize)> {
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// TODO: Split into sub-power of two allocations.
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let min_order = min.next_power_of_two().trailing_zeros();
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let _req_order = count.next_power_of_two().trailing_zeros();
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let mut freelist = FREELIST.lock();
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let Some((frame_order, frame)) = freelist[min_order as usize..].iter().enumerate().find_map(|(i, f)| f.map(|f| (i, f))) else {
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// TODO: For larger sizes than the max order, split into power of two allocations.
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return None
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};
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let info = get_page_info(frame)
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.unwrap_or_else(|| panic!("no page info for allocated frame {frame:?}"))
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.as_free().expect("freelist frames must not be marked used!");
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let next_free = info.next();
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log::info!("FREE {frame:?} ORDER {frame_order} NEXT_FREE {next_free:?}");
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freelist[frame_order] = next_free.frame();
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// TODO: Is this LIFO cache optimal?
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for order in (min..frame_order).rev() {
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let order_page_count = 1 << order;
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let hi = frame.next_by(order_page_count);
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log::info!("SPLIT INTO {frame:?}:{hi:?} ORDER {order}");
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if let Some(old_head) = freelist[order].replace(hi) {
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let hi_info = get_page_info(hi)
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.expect("no page info for allocated frame")
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.as_free().expect("freelist cannot contain used pages!");
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hi_info.set_next(P2Frame::new(Some(old_head), order as u32));
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get_page_info(old_head).expect("freelist head needs page info")
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.as_free().expect("freelist head cannot be in use")
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.set_prev(P2Frame::new(Some(hi), order as u32));
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}
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}
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log::info!("ALLOCATED {frame:?}+2^{min_order}");
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Some((frame, PAGE_SIZE << min_order))
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}
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/// Deallocate a range of frames
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pub unsafe fn deallocate_frames(frame: Frame, count: usize) {
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let max_order = core::cmp::min(MAX_ORDER, count.next_power_of_two().trailing_zeros());
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let (first_aligned, chunk_order, number_of_chunks) = (0..=max_order).rev().find_map(|order| {
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let bytes_for_order = PAGE_SIZE << order;
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let first_aligned = frame.start_address().data().next_multiple_of(bytes_for_order);
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let last_aligned = (frame.start_address().data() + count * PAGE_SIZE) / bytes_for_order * bytes_for_order;
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let chunks = (last_aligned - first_aligned) / bytes_for_order;
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(first_aligned < last_aligned).then_some((first_aligned, order, chunks))
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}).expect("must succeed at least for order=0");
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for i in 0..number_of_chunks {
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deallocate_p2frame(Frame::containing_address(PhysicalAddress::new(first_aligned + i * (PAGE_SIZE << chunk_order))), chunk_order);
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}
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let first_aligned_frame = Frame::containing_address(PhysicalAddress::new(first_aligned));
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let lo_subblock_page_count = first_aligned_frame.offset_from(frame);
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let hi_subblock_page_count = count - (number_of_chunks << chunk_order) - lo_subblock_page_count;
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deallocate_frames(frame, lo_subblock_page_count);
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deallocate_frames(first_aligned_frame.next_by(number_of_chunks << chunk_order), hi_subblock_page_count);
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}
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unsafe fn deallocate_p2frame(mut frame: Frame, order: u32) {
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let mut freelist = FREELIST.lock();
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let mut largest_order = 0;
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for merge_order in order..=MAX_ORDER {
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// Because there's a PageInfo, this frame must be allocator-owned. We need to be very
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// careful with who owns this page, as the refcount can be anything from 0 (undefined) to
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// 2^addrwidth - 1. However, allocation and deallocation must be synchronized (the "next"
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// word of the PageInfo).
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let frame_info = get_page_info(frame)
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.expect("deallocating frame without PageInfo")
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.as_free().expect("deallocating used page!");
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let Some(neighbor) = frame.neighbor(merge_order) else {
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break;
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};
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let Some(neighbor_info) = get_page_info(neighbor) else {
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// The frame that was deallocated, was the end of a contiguous allocator memory range.
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break;
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};
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let PageInfoKind::Free(neighbor_info) = neighbor_info.kind() else {
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// The frame is currently in use (refcounted). It cannot be merged!
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break;
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};
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// Whether or not there's a linked frame, the order is nevertheless stored.
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if neighbor_info.next().order() != merge_order {
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break;
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}
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// Link frame->prev->next to neighbor->next
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if let Some(prev_info) = frame_info.prev().frame() {
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get_page_info(prev_info).expect("linked frame lacks PageInfo")
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.as_free().expect("frame->prev pointing to used frame!")
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.set_next(neighbor_info.next())
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}
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// Link neighbor->next->prev to frame->prev
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if let Some(next_info) = neighbor_info.next().frame() {
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get_page_info(next_info).expect("linked frame lacks PageInfo")
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.as_free().expect("neighbor->next pointing to used frame!")
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.set_prev(frame_info.prev())
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}
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// Pick either frame or neighbor depending on which is aligned to the next power of two.
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frame = frame.align_down_to_order(order)
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.expect("must succeed since the neighbor p2frame existed");
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largest_order = merge_order;
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}
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if let Some(old_head) = freelist[largest_order as usize].replace(frame) {
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let head_info = get_page_info(old_head).expect("failed to get page info for old head")
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.as_free().expect("freelist head is currently in use!");
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head_info.set_next(P2Frame::new(Some(frame), largest_order));
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get_page_info(frame).expect("failed to get page info for possibly merged frame")
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.as_free().expect("page was used but should be free")
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.set_prev(P2Frame::new(Some(old_head), largest_order));
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}
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log::info!("FREED {frame:?}+2^{order}");
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}
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pub unsafe fn deallocate_frame(frame: Frame) {
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deallocate_p2frame(frame, 0)
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}
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const ORDER_COUNT: u32 = 11;
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const MAX_ORDER: u32 = ORDER_COUNT - 1;
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pub struct FreeList {
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for_orders: [Option<Frame>; ORDER_COUNT as usize],
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}
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#[derive(Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
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pub struct Frame {
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// On x86/x86_64, all memory below 1 MiB is reserved, and although some frames in that range
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// may end up in the paging code, it's very unlikely that frame 0x0 would.
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physaddr: NonZeroUsize,
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}
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/// Option<Frame> combined with power-of-two size.
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#[derive(Clone, Copy)]
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struct P2Frame(usize);
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impl P2Frame {
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fn new(frame: Option<Frame>, order: u32) -> Self {
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Self(
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frame.map_or(0, |f| f.physaddr.get()) | (order as usize),
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)
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}
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fn get(self) -> (Option<Frame>, u32) {
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let page_off_mask = PAGE_SIZE - 1;
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(NonZeroUsize::new(self.0 & !page_off_mask).map(|physaddr| Frame { physaddr }), (self.0 & page_off_mask) as u32)
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}
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fn frame(self) -> Option<Frame> {
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self.get().0
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}
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fn order(self) -> u32 {
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self.get().1
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}
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}
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impl core::fmt::Debug for P2Frame {
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fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
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let (frame, order) = self.get();
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write!(f, "[frame at {frame:?}] order {order}")
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}
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}
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impl core::fmt::Debug for Frame {
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fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
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write!(
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f,
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"[frame at {:p}]",
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self.start_address().data() as *const u8
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)
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}
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}
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impl Frame {
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/// Get the address of this frame
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// TODO: Remove
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pub fn start_address(&self) -> PhysicalAddress {
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PhysicalAddress::new(self.physaddr.get())
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}
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/// Create a frame containing `address`
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pub fn containing(address: PhysicalAddress) -> Frame {
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Frame {
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physaddr: NonZeroUsize::new(address.data() & !PAGE_MASK).expect("frame 0x0 is reserved"),
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}
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}
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// TODO: Remove
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pub fn containing_address(address: PhysicalAddress) -> Frame {
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Self::containing(address)
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}
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pub fn base(self) -> PhysicalAddress {
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PhysicalAddress::new(self.physaddr.get())
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}
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//TODO: Set private
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pub fn range_inclusive(start: Frame, end: Frame) -> impl Iterator<Item = Frame> {
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(start.physaddr.get()..=end.physaddr.get()).step_by(PAGE_SIZE).map(|number| Frame { physaddr: NonZeroUsize::new(number).unwrap() })
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}
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pub fn next_by(self, n: usize) -> Self {
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Self {
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physaddr: self
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.physaddr
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.get()
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.checked_add(n * PAGE_SIZE)
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.and_then(NonZeroUsize::new)
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.expect("overflow in Frame::next_by"),
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}
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}
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pub fn prev_by(self, n: usize) -> Self {
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Self {
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physaddr: self.physaddr.get().checked_sub(n.checked_mul(PAGE_SIZE).expect("unreasonable n")).and_then(NonZeroUsize::new).expect("overflow in Frame::prev_by"),
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}
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}
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pub fn neighbor(self, order: u32) -> Option<Self> {
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if self.is_aligned_to_order(order) {
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Some(self.next_by(1 << order))
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} else {
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self.align_down_to_order(order)
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}
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}
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pub fn align_down_to_order(self, order: u32) -> Option<Self> {
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Some(Self { physaddr: NonZeroUsize::new(self.physaddr.get() / (PAGE_SIZE << order) * (PAGE_SIZE << order))? })
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}
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pub fn offset_from(self, from: Self) -> usize {
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self.physaddr
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.get()
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.checked_sub(from.physaddr.get())
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.expect("overflow in Frame::offset_from") / PAGE_SIZE
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}
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pub fn is_aligned_to_order(self, order: u32) -> bool {
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self.start_address().data() % (PAGE_SIZE << order) == 0
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}
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}
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#[derive(Debug)]
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pub struct Enomem;
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impl From<Enomem> for Error {
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fn from(_: Enomem) -> Self {
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Self::new(ENOMEM)
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}
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}
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#[derive(Debug)]
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pub struct RaiiFrame {
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inner: Frame,
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}
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impl RaiiFrame {
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pub fn allocate() -> Result<Self, Enomem> {
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init_frame(RefCount::One)
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.map_err(|_| Enomem)
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.map(|inner| Self { inner })
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}
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pub fn get(&self) -> Frame {
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self.inner
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}
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}
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impl Drop for RaiiFrame {
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fn drop(&mut self) {
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if get_page_info(self.inner)
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.expect("RaiiFrame lacking PageInfo")
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.remove_ref()
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== RefCount::Zero
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{
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unsafe {
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crate::memory::deallocate_frames(self.inner, 1);
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}
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}
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}
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}
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// TODO: Make PageInfo a union, since *every* allocated page will have an associated PageInfo.
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// Pages that aren't AddrSpace data pages, such as paging-structure pages, might use the memory
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// occupied by a PageInfo for something else, potentially allowing paging structure-level CoW too.
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//
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// TODO: Another interesting possibility would be to use a slab allocator for (ideally
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// power-of-two) allocations smaller than a page, in which case this PageInfo might store a bitmap
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// of used sub-allocations.
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//
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// TODO: Alternatively or in conjunction, the PageInfo can store the number of used entries for
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// each page table, possibly even recursively (total number of mapped pages).
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// NOTE: init_sections depends on the default initialized value consisting of all zero bytes.
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#[derive(Debug)]
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pub struct PageInfo {
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/// Stores the reference count to this page, i.e. the number of present page table entries that
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/// point to this particular frame.
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///
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/// Bits 0..=N-1 are used for the actual reference count, whereas bit N-1 indicates the page is
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/// shared if set, and CoW if unset. The flag is not meaningful when the refcount is 0 or 1.
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pub refcount: AtomicUsize,
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// TODO: Add one flag indicating whether the page contents is zeroed? Or should this primarily
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// be managed by the memory allocator first?
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pub next: AtomicUsize,
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}
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enum PageInfoKind<'info> {
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Used(PageInfoUsed<'info>),
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Free(PageInfoFree<'info>),
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}
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struct PageInfoUsed<'info> {
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refcount: &'info AtomicUsize,
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_misc: &'info AtomicUsize,
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}
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struct PageInfoFree<'info> {
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prev: &'info AtomicUsize,
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next: &'info AtomicUsize,
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last_next: usize,
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}
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// There should be at least 2 bits available; even with a 4k page size on a 32-bit system (where a
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// paging structure node is itself a 4k page size, i.e. on i386 with 1024 32-bit entries), there
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// simply cannot be more than 2^30 entries pointing to the same page. However, to be able to use
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// fetch_add safely, we reserve another bit (which makes fetch_add safe if properly reverted, and
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// there aren't more than 2^(BITS-2) CPUs on the system).
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// Indicates whether the page is free (and thus managed by the allocator), or owned (and thus
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// managed by the kernel heap, or most commonly, the virtual memory system). The refcount may
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// increase or decrease with fetch_add, but must never flip this bit.
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const RC_USED_NOT_FREE: usize = 1 << (usize::BITS - 1);
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// Only valid if RC_USED. Controls whether the page is CoW (map readonly, on page fault, copy and
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// remap writable) or shared (mapped writable in the first place).
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const RC_SHARED_NOT_COW: usize = 1 << (usize::BITS - 2);
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// The page refcount limit. This acts as a buffer zone allowing subsequent fetch_sub to correct
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// overflow, which works as long as there's fewer CPUs than RC_MAX itself (and interrupts are
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// disabled).
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const RC_MAX: usize = 1 << (usize::BITS - 3);
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// TODO: Use some of the flag bits as a tag, indicating the type of page (e.g. paging structure,
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// userspace data page, or kernel heap page). This could be done only when debug assertions are
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// enabled.
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bitflags::bitflags! {
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#[derive(Debug)]
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pub struct FrameFlags: usize {
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const NONE = 0;
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}
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}
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static mut ALLOCATOR_DATA: AllocatorData = AllocatorData { sections: &[] };
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struct AllocatorData {
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// TODO: Memory hotplugging?
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sections: &'static [Section],
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}
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static FREELIST: Mutex<[Option<Frame>; ORDER_COUNT as usize]> = Mutex::new([None; ORDER_COUNT as usize]);
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pub struct Section {
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base: Frame,
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frames: &'static [PageInfo],
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}
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pub const MAX_SECTION_SIZE_BITS: u32 = 27;
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pub const MAX_SECTION_SIZE: usize = 1 << MAX_SECTION_SIZE_BITS;
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pub const MAX_SECTION_PAGE_COUNT: usize = MAX_SECTION_SIZE / PAGE_SIZE;
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const _: () = {
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assert!(mem::size_of::<PageInfo>().is_power_of_two());
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};
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#[cold]
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fn init_sections(mut allocator: BumpAllocator<RmmA>) {
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let sections: &'static mut [Section] = {
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let max_section_count: usize = allocator.areas().iter().map(|area| {
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let aligned_end = area.base.add(area.size).data().next_multiple_of(MAX_SECTION_SIZE);
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let aligned_start = area.base.data() / MAX_SECTION_SIZE * MAX_SECTION_SIZE;
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(aligned_end - aligned_start) / MAX_SECTION_SIZE
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}).sum();
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let section_array_page_count = (max_section_count * mem::size_of::<Section>()).div_ceil(PAGE_SIZE);
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unsafe {
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let base = allocator.allocate(FrameCount::new(section_array_page_count)).expect("failed to allocate sections array");
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core::slice::from_raw_parts_mut(RmmA::phys_to_virt(base).data() as *mut Section, max_section_count)
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}
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};
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let mut iter = allocator.areas().iter().copied().peekable();
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let mut i = 0;
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while let Some(mut memory_map_area) = iter.next() {
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// TODO: NonZeroUsize
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assert_ne!(
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memory_map_area.size, 0,
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"RMM should enforce areas are not zeroed"
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);
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// TODO: Would it make sense to naturally align the sections?
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// TODO: Should RMM do this?
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while let Some(next_area) = iter.peek() && next_area.base == memory_map_area.base.add(memory_map_area.size) {
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memory_map_area.size += next_area.size;
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let _ = iter.next();
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}
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assert_eq!(
|
|
memory_map_area.base.data() % PAGE_SIZE,
|
|
0,
|
|
"RMM should enforce area alignment"
|
|
);
|
|
assert_eq!(
|
|
memory_map_area.size % PAGE_SIZE,
|
|
0,
|
|
"RMM should enforce area length alignment"
|
|
);
|
|
|
|
let mut pages_left = memory_map_area.size.div_floor(PAGE_SIZE);
|
|
let mut base = Frame::containing_address(memory_map_area.base);
|
|
|
|
while pages_left > 0 {
|
|
let page_info_max_count = core::cmp::min(pages_left, MAX_SECTION_PAGE_COUNT);
|
|
let pages_to_next_section = (MAX_SECTION_SIZE - (base.start_address().data() % MAX_SECTION_SIZE)) / PAGE_SIZE;
|
|
let page_info_count = core::cmp::min(page_info_max_count, pages_to_next_section);
|
|
|
|
let page_info_array_size_pages = (page_info_count * mem::size_of::<PageInfo>()).div_ceil(PAGE_SIZE);
|
|
let page_info_array = unsafe {
|
|
let base = allocator.allocate(FrameCount::new(page_info_array_size_pages)).expect("failed to allocate page info array");
|
|
core::slice::from_raw_parts_mut(RmmA::phys_to_virt(base).data() as *mut PageInfo, page_info_count)
|
|
};
|
|
|
|
sections[i] = Section {
|
|
base,
|
|
frames: page_info_array,
|
|
};
|
|
i += 1;
|
|
|
|
pages_left -= page_info_count;
|
|
base = base.next_by(page_info_count);
|
|
}
|
|
}
|
|
|
|
let mut first_pages: [Option<(Frame, &'static PageInfo)>; ORDER_COUNT as usize] = [None; ORDER_COUNT as usize];
|
|
let mut last_pages = first_pages;
|
|
|
|
let mut append_page = |page, info, order| {
|
|
let this_page = (page, info);
|
|
let last_page = last_pages[order as usize].replace(this_page);
|
|
|
|
if let Some((last_frame, last_page_info)) = last_page {
|
|
last_page_info.as_free().unwrap().set_next(P2Frame::new(Some(page), order));
|
|
info.as_free().unwrap().set_prev(P2Frame::new(Some(last_frame), order));
|
|
} else {
|
|
first_pages[order as usize] = Some(this_page);
|
|
}
|
|
};
|
|
|
|
for section in &*sections {
|
|
let mut base = section.base;
|
|
let mut frames = section.frames;
|
|
|
|
for order in 0..=MAX_ORDER {
|
|
let pages_for_current_order = 1 << order;
|
|
|
|
if !frames.is_empty() && (order == MAX_ORDER || !base.is_aligned_to_order(order + 1)) {
|
|
// The first section page is not aligned to the next order size.
|
|
|
|
log::info!("ORDER {order}: FIRST {base:?}");
|
|
append_page(base, &frames[0], order);
|
|
|
|
base = base.next_by(pages_for_current_order << order);
|
|
frames = &frames[pages_for_current_order..];
|
|
} else {
|
|
log::info!("ORDER {order}: FIRST SKIP");
|
|
}
|
|
|
|
if let Some(off2) = frames.len().checked_sub(2 * pages_for_current_order) && (order == MAX_ORDER || !base.next_by(off2).is_aligned_to_order(order + 1)) {
|
|
let off = frames.len() - pages_for_current_order;
|
|
|
|
log::info!("ORDER {order}: LAST {base:?}");
|
|
append_page(base.next_by(off), &frames[off], order);
|
|
|
|
// The last section page is not aligned to the next order size.
|
|
frames = &frames[..frames.len() - pages_for_current_order];
|
|
} else {
|
|
log::info!("ORDER {order}: LAST SKIP");
|
|
}
|
|
}
|
|
|
|
log::info!("SECTION from {:?}, {} pages", section.base, section.frames.len());
|
|
}
|
|
|
|
*FREELIST.lock() = first_pages.map(|pair| pair.map(|(frame, _)| frame));
|
|
|
|
sections.sort_unstable_by_key(|s| s.base);
|
|
|
|
unsafe {
|
|
ALLOCATOR_DATA = AllocatorData { sections };
|
|
}
|
|
//loop {}
|
|
}
|
|
|
|
#[cold]
|
|
pub fn init_mm(allocator: BumpAllocator<RmmA>) {
|
|
init_sections(allocator);
|
|
|
|
unsafe {
|
|
let the_frame = allocate_frames(1).expect("failed to allocate static zeroed frame");
|
|
let the_info = get_page_info(the_frame).expect("static zeroed frame had no PageInfo");
|
|
the_info
|
|
.refcount
|
|
.store(RefCount::One.to_raw(), Ordering::Relaxed);
|
|
|
|
THE_ZEROED_FRAME.get().write(Some((the_frame, the_info)));
|
|
}
|
|
}
|
|
#[derive(Debug)]
|
|
pub enum AddRefError {
|
|
CowToShared,
|
|
SharedToCow,
|
|
RcOverflow,
|
|
}
|
|
impl PageInfo {
|
|
pub fn new() -> Self {
|
|
Self {
|
|
refcount: AtomicUsize::new(0),
|
|
next: AtomicUsize::new(0),
|
|
}
|
|
}
|
|
fn kind(&self) -> PageInfoKind<'_> {
|
|
let next = self.next.load(Ordering::Relaxed);
|
|
|
|
if next & RC_USED_NOT_FREE == RC_USED_NOT_FREE {
|
|
PageInfoKind::Used(PageInfoUsed { refcount: &self.refcount, _misc: &self.next })
|
|
} else {
|
|
PageInfoKind::Free(PageInfoFree { prev: &self.refcount, next: &self.next, last_next: next })
|
|
}
|
|
}
|
|
fn as_free(&self) -> Option<PageInfoFree<'_>> {
|
|
match self.kind() {
|
|
PageInfoKind::Free(f) => Some(f),
|
|
PageInfoKind::Used(_) => None,
|
|
}
|
|
}
|
|
pub fn add_ref(&self, kind: RefKind) -> Result<(), AddRefError> {
|
|
match (self.refcount(), kind) {
|
|
(RefCount::Zero, _) => self.refcount.store(RC_USED_NOT_FREE, Ordering::Relaxed),
|
|
(RefCount::One, RefKind::Cow) => self.refcount.store(RC_USED_NOT_FREE | 1, Ordering::Relaxed),
|
|
(RefCount::One, RefKind::Shared) => self.refcount.store(RC_USED_NOT_FREE | 1 | RC_SHARED_NOT_COW, Ordering::Relaxed),
|
|
(RefCount::Cow(_), RefKind::Cow) | (RefCount::Shared(_), RefKind::Shared) => {
|
|
let old = self.refcount.fetch_add(1, Ordering::Relaxed);
|
|
|
|
if old >= RC_MAX {
|
|
self.refcount.fetch_sub(1, Ordering::Relaxed);
|
|
return Err(AddRefError::RcOverflow);
|
|
}
|
|
}
|
|
(RefCount::Cow(_), RefKind::Shared) => return Err(AddRefError::CowToShared),
|
|
(RefCount::Shared(_), RefKind::Cow) => return Err(AddRefError::SharedToCow),
|
|
}
|
|
Ok(())
|
|
}
|
|
#[must_use = "must deallocate if refcount reaches zero"]
|
|
pub fn remove_ref(&self) -> RefCount {
|
|
RefCount::from_raw(match self.refcount() {
|
|
RefCount::Zero => panic!("refcount was already zero when calling remove_ref!"),
|
|
RefCount::One => {
|
|
// Used to be RC_USED_NOT_FREE | ?RC_SHARED_NOT_COW | 0, now becomes 0
|
|
self.refcount.store(0, Ordering::Relaxed);
|
|
|
|
0
|
|
}
|
|
RefCount::Cow(_) | RefCount::Shared(_) => {
|
|
// Was RC_USED_NOT_FREE | ?RC_SHARED_NOW_COW | n, now becomes RC_USED_NOT_FREE |
|
|
// ?RC_SHARED_NOW_COW | n - 1
|
|
self.refcount.fetch_sub(1, Ordering::Relaxed) - 1
|
|
},
|
|
})
|
|
}
|
|
pub fn allows_writable(&self) -> bool {
|
|
match self.refcount() {
|
|
RefCount::Zero | RefCount::One => true,
|
|
RefCount::Cow(_) => false,
|
|
RefCount::Shared(_) => true,
|
|
}
|
|
}
|
|
|
|
pub fn refcount(&self) -> RefCount {
|
|
let refcount = self.refcount.load(Ordering::Relaxed);
|
|
|
|
RefCount::from_raw(refcount)
|
|
}
|
|
}
|
|
impl PageInfoFree<'_> {
|
|
fn next(&self) -> P2Frame {
|
|
P2Frame(self.next.load(Ordering::Relaxed))
|
|
}
|
|
fn set_next(&self, next: P2Frame) {
|
|
self.next.store(next.0, Ordering::Relaxed)
|
|
}
|
|
fn prev(&self) -> P2Frame {
|
|
P2Frame(self.prev.load(Ordering::Relaxed))
|
|
}
|
|
fn set_prev(&self, prev: P2Frame) {
|
|
self.prev.store(prev.0, Ordering::Relaxed)
|
|
}
|
|
}
|
|
#[derive(Clone, Copy, Debug, PartialEq)]
|
|
pub enum RefKind {
|
|
Cow,
|
|
Shared,
|
|
// TODO: Observer?
|
|
}
|
|
#[derive(Clone, Copy, Debug, PartialEq)]
|
|
pub enum RefCount {
|
|
Zero,
|
|
One,
|
|
Shared(NonZeroUsize),
|
|
Cow(NonZeroUsize),
|
|
}
|
|
impl RefCount {
|
|
pub fn from_raw(raw: usize) -> Self {
|
|
let refcount = raw & !RC_SHARED_NOT_COW;
|
|
|
|
if let Some(nz_refcount) = NonZeroUsize::new(refcount) {
|
|
if refcount == 1 {
|
|
RefCount::One
|
|
} else if raw & RC_SHARED_NOT_COW == RC_SHARED_NOT_COW {
|
|
RefCount::Shared(nz_refcount)
|
|
} else {
|
|
RefCount::Cow(nz_refcount)
|
|
}
|
|
} else {
|
|
RefCount::Zero
|
|
}
|
|
}
|
|
pub fn to_raw(self) -> usize {
|
|
match self {
|
|
Self::Zero => 0,
|
|
Self::One => 1,
|
|
Self::Shared(inner) => inner.get() | RC_SHARED_NOT_COW,
|
|
Self::Cow(inner) => inner.get(),
|
|
}
|
|
}
|
|
}
|
|
pub fn get_page_info(frame: Frame) -> Option<&'static PageInfo> {
|
|
let sections = unsafe { ALLOCATOR_DATA.sections };
|
|
|
|
let idx_res = sections.binary_search_by_key(&frame, |section| section.base);
|
|
|
|
if idx_res == Err(0) {
|
|
// The frame is before the first section
|
|
return None;
|
|
}
|
|
|
|
// binary_search_by_key returns either Ok(where it was found) or Err(where it would have been
|
|
// inserted). The base obviously cannot have been exactly matched from an entry at an
|
|
// out-of-bounds index, so the only Err(i) where i - 1 is out of bounds, is for i=0. That
|
|
// has already been checked.
|
|
let section = §ions[idx_res.unwrap_or_else(|e| e - 1)];
|
|
|
|
section.frames.get(frame.offset_from(section.base))
|
|
|
|
/*
|
|
sections
|
|
.range(..=frame)
|
|
.next_back()
|
|
.filter(|(base, section)| frame <= base.next_by(section.frames.len()))
|
|
.map(|(base, section)| PageInfoHandle { section, idx: frame.offset_from(*base) })
|
|
*/
|
|
}
|
|
pub struct Segv;
|
|
|
|
bitflags! {
|
|
/// Arch-generic page fault flags, modeled after x86's error code.
|
|
///
|
|
/// This may change when arch-specific features are utilized better.
|
|
pub struct GenericPfFlags: u32 {
|
|
const PRESENT = 1 << 0;
|
|
const INVOLVED_WRITE = 1 << 1;
|
|
const USER_NOT_SUPERVISOR = 1 << 2;
|
|
const INSTR_NOT_DATA = 1 << 3;
|
|
// "reserved bits" on x86
|
|
const INVL = 1 << 31;
|
|
}
|
|
}
|
|
|
|
pub trait ArchIntCtx {
|
|
fn ip(&self) -> usize;
|
|
fn recover_and_efault(&mut self);
|
|
}
|
|
|
|
pub fn page_fault_handler(
|
|
stack: &mut impl ArchIntCtx,
|
|
code: GenericPfFlags,
|
|
faulting_address: VirtualAddress,
|
|
) -> Result<(), Segv> {
|
|
let faulting_page = Page::containing_address(faulting_address);
|
|
|
|
let usercopy_region = __usercopy_start()..__usercopy_end();
|
|
|
|
// TODO: Most likely not necessary, but maybe also check that the faulting address is not too
|
|
// close to USER_END.
|
|
let address_is_user = faulting_address.kind() == TableKind::User;
|
|
|
|
let invalid_page_tables = code.contains(GenericPfFlags::INVL);
|
|
let caused_by_user = code.contains(GenericPfFlags::USER_NOT_SUPERVISOR);
|
|
let caused_by_kernel = !caused_by_user;
|
|
let caused_by_write = code.contains(GenericPfFlags::INVOLVED_WRITE);
|
|
let caused_by_instr_fetch = code.contains(GenericPfFlags::INSTR_NOT_DATA);
|
|
let is_usercopy = usercopy_region.contains(&stack.ip());
|
|
|
|
let mode = match (caused_by_write, caused_by_instr_fetch) {
|
|
(true, false) => AccessMode::Write,
|
|
(false, false) => AccessMode::Read,
|
|
(false, true) => AccessMode::InstrFetch,
|
|
(true, true) => {
|
|
unreachable!("page fault cannot be caused by both instruction fetch and write")
|
|
}
|
|
};
|
|
|
|
if invalid_page_tables {
|
|
// TODO: Better error code than Segv?
|
|
return Err(Segv);
|
|
}
|
|
|
|
if address_is_user && (caused_by_user || is_usercopy) {
|
|
match context::memory::try_correcting_page_tables(faulting_page, mode) {
|
|
Ok(()) => return Ok(()),
|
|
Err(PfError::Oom) => todo!("oom"),
|
|
Err(PfError::Segv | PfError::RecursionLimitExceeded) => (),
|
|
Err(PfError::NonfatalInternalError) => todo!(),
|
|
}
|
|
}
|
|
|
|
if address_is_user && caused_by_kernel && mode != AccessMode::InstrFetch && is_usercopy {
|
|
stack.recover_and_efault();
|
|
return Ok(());
|
|
}
|
|
|
|
Err(Segv)
|
|
}
|
|
static THE_ZEROED_FRAME: SyncUnsafeCell<Option<(Frame, &'static PageInfo)>> =
|
|
SyncUnsafeCell::new(None);
|
|
|
|
pub fn the_zeroed_frame() -> (Frame, &'static PageInfo) {
|
|
unsafe {
|
|
THE_ZEROED_FRAME
|
|
.get()
|
|
.read()
|
|
.expect("zeroed frame must be initialized")
|
|
}
|
|
}
|
|
|
|
pub fn init_frame(init_rc: RefCount) -> Result<Frame, PfError> {
|
|
let new_frame = crate::memory::allocate_frame().ok_or(PfError::Oom)?;
|
|
let page_info = get_page_info(new_frame).unwrap_or_else(|| panic!("all allocated frames need an associated page info, {:?} didn't", new_frame));
|
|
assert_eq!(page_info.refcount(), RefCount::Zero);
|
|
page_info
|
|
.refcount
|
|
.store(init_rc.to_raw(), Ordering::Relaxed);
|
|
|
|
Ok(new_frame)
|
|
}
|
|
#[derive(Debug)]
|
|
pub struct TheFrameAllocator;
|
|
|
|
impl FrameAllocator for TheFrameAllocator {
|
|
unsafe fn allocate(&mut self, count: FrameCount) -> Option<PhysicalAddress> {
|
|
allocate_frames(count.data()).map(|f| f.start_address())
|
|
}
|
|
unsafe fn free(&mut self, address: PhysicalAddress, count: FrameCount) {
|
|
deallocate_frames(Frame::containing_address(address), count.data())
|
|
}
|
|
unsafe fn usage(&self) -> rmm::FrameUsage {
|
|
todo!()
|
|
}
|
|
}
|
|
impl FreeList {
|
|
pub fn new() -> Self {
|
|
Self {
|
|
for_orders: [None; ORDER_COUNT as usize],
|
|
}
|
|
}
|
|
}
|