4lDO2
934 lines
34 KiB
Rust
934 lines
34 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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BumpAllocator, FrameAllocator, FrameCount, FrameUsage, TableKind, VirtualAddress
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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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total_frames() - used_frames()
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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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// TODO: Include bump allocator static pages?
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FREELIST.lock().used_frames
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}
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pub fn total_frames() -> usize {
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// TODO: Include bump allocator static pages?
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sections().iter().map(|section| section.frames.len()).sum()
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}
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/// Allocate a range of frames
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pub fn allocate_p2frame(order: u32) -> Option<Frame> {
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allocate_p2frame_complex(order, (), None, order).map(|(f, _)| f)
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}
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pub fn allocate_frame() -> Option<Frame> {
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allocate_p2frame(0)
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}
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// TODO: Flags, strategy
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pub fn allocate_p2frame_complex(_req_order: u32, _flags: (), _strategy: Option<()>, min_order: u32) -> Option<(Frame, usize)> {
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let mut freelist = FREELIST.lock();
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let Some((frame_order, frame)) = freelist.for_orders.iter().enumerate().skip(min_order as usize).find_map(|(i, f)| f.map(|f| (i as u32, f))) else {
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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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debug_assert_eq!(next_free.order(), frame_order, "{frame:?}->next {next_free:?}.order != {frame_order}");
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if let Some(next) = next_free.frame() {
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let f = get_free_alloc_page_info(next);
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debug_assert_eq!(f.prev().frame(), Some(frame));
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debug_assert_ne!(next, frame);
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debug_assert!(next.is_aligned_to_order(frame_order), "NEXT {next:?} UNALIGNED");
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f.set_prev(P2Frame::new(None, frame_order));
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}
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debug_assert!(frame.is_aligned_to_order(frame_order));
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debug_assert_eq!(next_free.order(), frame_order);
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freelist.for_orders[frame_order as usize] = next_free.frame();
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// TODO: Is this LIFO cache optimal?
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//log::info!("MIN{min_order}FRAMEORD{frame_order}");
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for order in (min_order..frame_order).rev() {
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//log::info!("SPLIT ORDER {order}");
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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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debug_assert_eq!(freelist.for_orders[order as usize], None);
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let hi_info = get_page_info(hi).expect("sub-p2frame of split p2flame lacked PageInfo").make_free(order);
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debug_assert!(!hi.is_aligned_to_order(frame_order));
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debug_assert!(hi.is_aligned_to_order(order));
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hi_info.set_next(P2Frame::new(None, order));
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hi_info.set_prev(P2Frame::new(None, order));
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freelist.for_orders[order as usize] = Some(hi);
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}
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freelist.used_frames += 1 << min_order;
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info.mark_used();
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drop(freelist);
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unsafe {
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(RmmA::phys_to_virt(frame.start_address()).data() as *mut u8).write_bytes(0, PAGE_SIZE << min_order);
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}
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debug_assert!(frame.start_address().data() >= unsafe { ALLOCATOR_DATA.abs_off });
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Some((frame, PAGE_SIZE << min_order))
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}
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pub unsafe fn deallocate_p2frame(orig_frame: Frame, order: u32) {
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let mut freelist = FREELIST.lock();
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let mut largest_order = order;
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let mut current = orig_frame;
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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 sibling = Frame::containing_address(PhysicalAddress::new(current.start_address().data() ^ (PAGE_SIZE << merge_order)));
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let Some(_) = get_page_info(current) else {
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unreachable!("attempting to free non-allocator-owned page");
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};
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let Some(sib_info) = get_page_info(sibling) else {
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// The frame that was deallocated, was at the unaligned start or end of its section
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// (i.e. there aren't 1 << merge_order additional pages).
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break;
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};
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let PageInfoKind::Free(sib_info) = sib_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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// If the sibling p2frame has lower order than merge_order, it cannot be merged into
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// current.
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if sib_info.next().order() < merge_order {
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break;
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}
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debug_assert!(!(sib_info.next().order() > merge_order), "sibling page has unaligned order or contains current page");
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//log::info!("MERGED {lo:?} WITH {hi:?} ORDER {order}");
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if let Some(sib_prev) = sib_info.prev().frame() {
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get_free_alloc_page_info(sib_prev).set_next(sib_info.next());
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} else {
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debug_assert_eq!(freelist.for_orders[merge_order as usize], Some(sibling));
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debug_assert!(sib_info.next().frame().map_or(true, |f| f.is_aligned_to_order(merge_order)));
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debug_assert_eq!(sib_info.next().order(), merge_order);
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freelist.for_orders[merge_order as usize] = sib_info.next().frame();
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}
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if let Some(sib_next) = sib_info.next().frame() {
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get_free_alloc_page_info(sib_next).set_prev(sib_info.prev());
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}
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current = Frame::containing_address(PhysicalAddress::new(current.start_address().data() & !(PAGE_SIZE << merge_order)));
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largest_order = merge_order + 1;
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}
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get_page_info(current)
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.expect("freeing frame without PageInfo")
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.make_free(largest_order);
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let new_head = current;
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debug_assert!(new_head.is_aligned_to_order(largest_order));
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if let Some(old_head) = freelist.for_orders[largest_order as usize].replace(new_head) {
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//log::info!("HEAD {:p} FREED {:p} BARRIER {:p}", get_page_info(old_head).unwrap(), get_page_info(frame).unwrap(), unsafe { ALLOCATOR_DATA.abs_off as *const u8 });
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let old_head_info = get_free_alloc_page_info(old_head);
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let new_head_info = get_free_alloc_page_info(new_head);
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new_head_info.set_next(P2Frame::new(Some(old_head), largest_order));
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new_head_info.set_prev(P2Frame::new(None, largest_order));
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old_head_info.set_prev(P2Frame::new(Some(new_head), largest_order));
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}
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//log::info!("FREED {frame:?}+2^{order}");
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freelist.used_frames -= 1 << 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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#[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 & !RC_USED_NOT_FREE).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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self.base()
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}
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/// Create a frame containing `address`
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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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/// 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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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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#[track_caller]
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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 or null in Frame::next_by")
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}
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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 unsafe fn new_unchecked(inner: Frame) -> Self {
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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() == None
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{
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unsafe {
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deallocate_frame(self.inner);
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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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}
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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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const RC_COUNT_MASK: usize = !(RC_USED_NOT_FREE | RC_SHARED_NOT_COW);
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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: &[], abs_off: 0 };
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struct AllocatorData {
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// TODO: Memory hotplugging?
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sections: &'static [Section],
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abs_off: usize,
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}
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#[derive(Debug)]
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struct FreeList {
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for_orders: [Option<Frame>; ORDER_COUNT as usize],
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used_frames: usize,
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}
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static FREELIST: Mutex<FreeList> = Mutex::new(FreeList { for_orders: [None; ORDER_COUNT as usize], used_frames: 0 });
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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 (free_areas, offset_into_first_free_area) = allocator.free_areas();
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let free_areas_iter = || free_areas.iter().copied().enumerate().map(|(i, area)| if i == 0 {
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rmm::MemoryArea {
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base: area.base.add(offset_into_first_free_area),
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size: area.size - offset_into_first_free_area,
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}
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} else {
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area
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});
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let sections: &'static mut [Section] = {
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let max_section_count: usize = free_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 = free_areas_iter().peekable();
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let mut i = 0;
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while let Some(mut memory_map_area) = iter.next() {
|
|
// TODO: NonZeroUsize
|
|
|
|
// TODO: x86_32 fails without this check
|
|
if memory_map_area.size == 0 {
|
|
continue;
|
|
}
|
|
|
|
assert_ne!(
|
|
memory_map_area.size, 0,
|
|
"RMM should enforce areas are not zeroed"
|
|
);
|
|
|
|
// TODO: Should RMM do this?
|
|
|
|
while let Some(next_area) = iter.peek() && next_area.base == memory_map_area.base.add(memory_map_area.size) {
|
|
memory_map_area.size += next_area.size;
|
|
let _ = iter.next();
|
|
}
|
|
|
|
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)
|
|
};
|
|
for p in &*page_info_array {
|
|
assert_eq!(p.next.load(Ordering::Relaxed), 0);
|
|
assert_eq!(p.refcount.load(Ordering::Relaxed), 0);
|
|
}
|
|
|
|
sections[i] = Section {
|
|
base,
|
|
frames: page_info_array,
|
|
};
|
|
i += 1;
|
|
|
|
pages_left -= page_info_count;
|
|
base = base.next_by(page_info_count);
|
|
}
|
|
}
|
|
let sections = &mut sections[..i];
|
|
|
|
sections.sort_unstable_by_key(|s| s.base);
|
|
|
|
// The bump allocator has been used during the section array and page info array allocation
|
|
// phases, which means some of the PageInfos will be pointing to those arrays themselves.
|
|
// Mark those pages as used!
|
|
'sections: for section in &*sections {
|
|
for (off, page_info) in section.frames.iter().enumerate() {
|
|
let frame = section.base.next_by(off);
|
|
if frame.start_address() >= allocator.abs_offset() {
|
|
break 'sections;
|
|
}
|
|
//log::info!("MARKING {frame:?} AS USED");
|
|
page_info.refcount.store(RC_USED_NOT_FREE, Ordering::Relaxed);
|
|
page_info.next.store(0, Ordering::Relaxed);
|
|
}
|
|
}
|
|
|
|
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: Frame, info: &'static PageInfo, order| {
|
|
let this_page = (page, info);
|
|
|
|
if page.start_address() < allocator.abs_offset() {
|
|
return;
|
|
}
|
|
debug_assert!(info.as_free().is_some());
|
|
debug_assert!(this_page.0.is_aligned_to_order(order));
|
|
debug_assert_eq!(info.next.load(Ordering::Relaxed), order as usize);
|
|
debug_assert_eq!(info.refcount.load(Ordering::Relaxed), 0);
|
|
|
|
let last_page = last_pages[order as usize].replace(this_page);
|
|
|
|
if let Some((last_frame, last_page_info)) = last_page {
|
|
let last_info = last_page_info.as_free().unwrap();
|
|
|
|
debug_assert_eq!(last_info.next().order(), order);
|
|
debug_assert_eq!(last_info.next().frame(), None);
|
|
|
|
last_info.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);
|
|
info.as_free().unwrap().set_prev(P2Frame::new(None, order));
|
|
info.as_free().unwrap().set_next(P2Frame::new(None, order));
|
|
}
|
|
};
|
|
unsafe {
|
|
ALLOCATOR_DATA = AllocatorData { sections, abs_off: allocator.abs_offset().data() };
|
|
}
|
|
|
|
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) {
|
|
frames[0].next.store(order as usize, Ordering::Relaxed);
|
|
// 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);
|
|
frames = &frames[pages_for_current_order..];
|
|
} else {
|
|
//log::info!("ORDER {order}: FIRST SKIP");
|
|
}
|
|
|
|
if !frames.is_empty() && order != MAX_ORDER && !base.next_by(frames.len()).is_aligned_to_order(order + 1) {
|
|
// The last section page is not aligned to the next order size.
|
|
|
|
let off = frames.len() - pages_for_current_order;
|
|
let final_page = base.next_by(off);
|
|
|
|
frames[off].next.store(order as usize, Ordering::Relaxed);
|
|
|
|
//log::info!("ORDER {order}: LAST {final_page:?}");
|
|
append_page(final_page, &frames[off], order);
|
|
|
|
frames = &frames[..frames.len() - pages_for_current_order];
|
|
} else {
|
|
//log::info!("ORDER {order}: LAST SKIP");
|
|
}
|
|
|
|
if order == MAX_ORDER {
|
|
debug_assert_eq!(frames.len() % pages_for_current_order, 0);
|
|
debug_assert!(base.is_aligned_to_order(MAX_ORDER));
|
|
|
|
for (off, info) in frames.iter().enumerate().step_by(pages_for_current_order) {
|
|
info.next.store(MAX_ORDER as usize, Ordering::Relaxed);
|
|
append_page(base.next_by(off), info, MAX_ORDER);
|
|
}
|
|
}
|
|
}
|
|
|
|
//log::info!("SECTION from {:?}, {} pages, array at {:p}", section.base, section.frames.len(), section.frames);
|
|
}
|
|
for (order, tuple_opt) in last_pages.iter().enumerate() {
|
|
let Some((frame, info)) = tuple_opt else { continue; };
|
|
debug_assert!(frame.is_aligned_to_order(order as u32));
|
|
let free = info.as_free().unwrap();
|
|
debug_assert_eq!(free.prev().order(), order as u32);
|
|
free.set_next(P2Frame::new(None, order as u32));
|
|
}
|
|
|
|
FREELIST.lock().for_orders = first_pages.map(|pair| pair.map(|(frame, _)| frame));
|
|
|
|
//debug_freelist();
|
|
log::info!("Initial freelist consistent");
|
|
|
|
}
|
|
|
|
#[cold]
|
|
pub fn init_mm(allocator: BumpAllocator<RmmA>) {
|
|
init_sections(allocator);
|
|
|
|
unsafe {
|
|
let the_frame = allocate_frame().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, PartialEq)]
|
|
pub enum AddRefError {
|
|
CowToShared,
|
|
SharedToCow,
|
|
RcOverflow,
|
|
}
|
|
impl PageInfo {
|
|
fn kind(&self) -> PageInfoKind<'_> {
|
|
let prev = self.refcount.load(Ordering::Relaxed);
|
|
|
|
if prev & 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 })
|
|
}
|
|
}
|
|
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().expect("cannot add_ref to free frame"), kind) {
|
|
(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_COUNT_MASK) >= 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 None"]
|
|
pub fn remove_ref(&self) -> Option<RefCount> {
|
|
match self.refcount() {
|
|
None => panic!("refcount was already zero when calling remove_ref!"),
|
|
Some(RefCount::One) => {
|
|
// Used to be RC_USED_NOT_FREE | ?RC_SHARED_NOT_COW | 0, now becomes 0
|
|
//self.refcount.store(0, Ordering::Relaxed);
|
|
|
|
None
|
|
}
|
|
Some(RefCount::Cow(_) | RefCount::Shared(_)) => RefCount::from_raw({
|
|
// Used to be 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) | RC_USED_NOT_FREE
|
|
}),
|
|
}
|
|
}
|
|
#[track_caller]
|
|
pub fn allows_writable(&self) -> bool {
|
|
match self.refcount().expect("using allows_writable on free page!") {
|
|
RefCount::One => true,
|
|
RefCount::Cow(_) => false,
|
|
RefCount::Shared(_) => true,
|
|
}
|
|
}
|
|
|
|
pub fn refcount(&self) -> Option<RefCount> {
|
|
let refcount = self.refcount.load(Ordering::Relaxed);
|
|
|
|
RefCount::from_raw(refcount)
|
|
}
|
|
fn make_free(&self, order: u32) -> PageInfoFree<'_> {
|
|
// Order needs to be known so we don't for example merge A: [A] A A A B: [B] U U U into a
|
|
// 2^3 page (if U indicates "used").
|
|
self.refcount.store(order as usize, Ordering::Relaxed);
|
|
self.next.store(order as usize, Ordering::Relaxed);
|
|
|
|
PageInfoFree {
|
|
next: &self.next,
|
|
prev: &self.refcount,
|
|
}
|
|
}
|
|
}
|
|
impl PageInfoFree<'_> {
|
|
fn next(&self) -> P2Frame {
|
|
P2Frame(self.next.load(Ordering::Relaxed))
|
|
}
|
|
#[track_caller]
|
|
fn set_next(&self, next: P2Frame) {
|
|
debug_assert!(next.frame().map_or(true, |f| f.is_aligned_to_order(next.order())));
|
|
self.next.store(next.0, Ordering::Relaxed)
|
|
}
|
|
fn prev(&self) -> P2Frame {
|
|
P2Frame(self.prev.load(Ordering::Relaxed))
|
|
}
|
|
fn set_prev(&self, prev: P2Frame) {
|
|
debug_assert!(prev.frame().map_or(true, |f| f.is_aligned_to_order(prev.order())));
|
|
self.prev.store(prev.0, Ordering::Relaxed)
|
|
}
|
|
fn mark_used(&self) {
|
|
// Order is irrelevant if marked "used"
|
|
self.prev.store(RC_USED_NOT_FREE, Ordering::Relaxed);
|
|
self.next.store(0, Ordering::Relaxed);
|
|
}
|
|
}
|
|
#[derive(Clone, Copy, Debug, PartialEq)]
|
|
pub enum RefKind {
|
|
Cow,
|
|
Shared,
|
|
// TODO: Observer?
|
|
}
|
|
#[derive(Clone, Copy, Debug, PartialEq)]
|
|
pub enum RefCount {
|
|
One,
|
|
Shared(NonZeroUsize),
|
|
Cow(NonZeroUsize),
|
|
}
|
|
impl RefCount {
|
|
pub fn from_raw(raw: usize) -> Option<Self> {
|
|
if raw & RC_USED_NOT_FREE != RC_USED_NOT_FREE {
|
|
return None;
|
|
}
|
|
let refcount_minus_one = raw & !(RC_SHARED_NOT_COW | RC_USED_NOT_FREE);
|
|
let nz_refcount = NonZeroUsize::new(refcount_minus_one + 1).unwrap();
|
|
|
|
Some(if nz_refcount.get() == 1 {
|
|
RefCount::One
|
|
} else if raw & RC_SHARED_NOT_COW == RC_SHARED_NOT_COW {
|
|
RefCount::Shared(nz_refcount)
|
|
} else {
|
|
RefCount::Cow(nz_refcount)
|
|
})
|
|
|
|
}
|
|
pub fn to_raw(self) -> usize {
|
|
match self {
|
|
Self::One => 0 | RC_USED_NOT_FREE,
|
|
Self::Shared(inner) => (inner.get() - 1) | RC_SHARED_NOT_COW | RC_USED_NOT_FREE,
|
|
Self::Cow(inner) => (inner.get() - 1) | RC_USED_NOT_FREE,
|
|
}
|
|
}
|
|
}
|
|
#[inline]
|
|
fn sections() -> &'static [Section] {
|
|
unsafe { ALLOCATOR_DATA.sections }
|
|
}
|
|
pub fn get_page_info(frame: Frame) -> Option<&'static PageInfo> {
|
|
let sections = 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) })
|
|
*/
|
|
}
|
|
|
|
#[track_caller]
|
|
fn get_free_alloc_page_info(frame: Frame) -> PageInfoFree<'static> {
|
|
let i = get_page_info(frame).unwrap_or_else(|| panic!("allocator-owned frames need a PageInfo, but none for {frame:?}"));
|
|
i.as_free().unwrap()//.unwrap_or_else(|| panic!("expected frame to be free, but {frame:?} wasn't, in {i:?}"))
|
|
}
|
|
|
|
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 = 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));
|
|
debug_assert_eq!(page_info.refcount(), Some(RefCount::One));
|
|
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> {
|
|
let order = count.data().next_power_of_two().trailing_zeros();
|
|
allocate_p2frame(order).map(|f| f.start_address())
|
|
}
|
|
unsafe fn free(&mut self, address: PhysicalAddress, count: FrameCount) {
|
|
let order = count.data().next_power_of_two().trailing_zeros();
|
|
deallocate_p2frame(Frame::containing_address(address), order)
|
|
}
|
|
unsafe fn usage(&self) -> FrameUsage {
|
|
FrameUsage::new(
|
|
FrameCount::new(used_frames()),
|
|
FrameCount::new(total_frames()),
|
|
)
|
|
}
|
|
}
|