redox/kernel/context/memory.rs

use alloc::arc::{Arc, Weak};
use collections::VecDeque;
use core::intrinsics;
use spin::Mutex;

use arch::memory::Frame;
use arch::paging::{ActivePageTable, InactivePageTable, Page, PageIter, PhysicalAddress, VirtualAddress};
use arch::paging::entry::{self, EntryFlags};
use arch::paging::temporary_page::TemporaryPage;

#[derive(Debug)]
pub struct Grant {
    start: VirtualAddress,
    size: usize,
    flags: EntryFlags
}

impl Grant {
    pub fn physmap(from: PhysicalAddress, to: VirtualAddress, size: usize, flags: EntryFlags) -> Grant {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut flush_all = false;

        let start_page = Page::containing_address(to);
        let end_page = Page::containing_address(VirtualAddress::new(to.get() + size - 1));
        for page in Page::range_inclusive(start_page, end_page) {
            let frame = Frame::containing_address(PhysicalAddress::new(page.start_address().get() - to.get() + from.get()));
            active_table.map_to(page, frame, flags);
            flush_all = true;
        }

        if flush_all {
            active_table.flush_all();
        }

        Grant {
            start: to,
            size: size,
            flags: flags
        }
    }

    pub fn map_inactive(from: VirtualAddress, to: VirtualAddress, size: usize, flags: EntryFlags, new_table: &mut InactivePageTable, temporary_page: &mut TemporaryPage) -> Grant {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut frames = VecDeque::new();

        let start_page = Page::containing_address(from);
        let end_page = Page::containing_address(VirtualAddress::new(from.get() + size - 1));
        for page in Page::range_inclusive(start_page, end_page) {
            let frame = active_table.translate_page(page).expect("grant references unmapped memory");
            frames.push_back(frame);
        }

        active_table.with(new_table, temporary_page, |mapper| {
            let start_page = Page::containing_address(to);
            let end_page = Page::containing_address(VirtualAddress::new(to.get() + size - 1));
            for page in Page::range_inclusive(start_page, end_page) {
                let frame = frames.pop_front().expect("grant did not find enough frames");
                mapper.map_to(page, frame, flags);
            }
        });

        Grant {
            start: to,
            size: size,
            flags: flags
        }
    }

    pub fn start_address(&self) -> VirtualAddress {
        self.start
    }

    pub fn size(&self) -> usize {
        self.size
    }

    pub fn flags(&self) -> EntryFlags {
        self.flags
    }

    pub fn unmap(self) {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut flush_all = false;

        let start_page = Page::containing_address(self.start);
        let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size - 1));
        for page in Page::range_inclusive(start_page, end_page) {
            active_table.unmap_return(page);
            flush_all = true;
        }

        if flush_all {
            active_table.flush_all();
        }
    }

    pub fn unmap_inactive(self, new_table: &mut InactivePageTable, temporary_page: &mut TemporaryPage) {
        let mut active_table = unsafe { ActivePageTable::new() };

        active_table.with(new_table, temporary_page, |mapper| {
            let start_page = Page::containing_address(self.start);
            let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size - 1));
            for page in Page::range_inclusive(start_page, end_page) {
                mapper.unmap_return(page);
            }
        });
    }
}

#[derive(Clone, Debug)]
pub enum SharedMemory {
    Owned(Arc<Mutex<Memory>>),
    Borrowed(Weak<Mutex<Memory>>)
}

impl SharedMemory {
    pub fn with<F, T>(&self, f: F) -> T where F: FnOnce(&mut Memory) -> T {
        match *self {
            SharedMemory::Owned(ref memory_lock) => {
                let mut memory = memory_lock.lock();
                f(&mut *memory)
            },
            SharedMemory::Borrowed(ref memory_weak) => {
                let memory_lock = memory_weak.upgrade().expect("SharedMemory::Borrowed no longer valid");
                let mut memory = memory_lock.lock();
                f(&mut *memory)
            }
        }
    }

    pub fn borrow(&self) -> SharedMemory {
        match *self {
            SharedMemory::Owned(ref memory_lock) => SharedMemory::Borrowed(Arc::downgrade(memory_lock)),
            SharedMemory::Borrowed(ref memory_lock) => SharedMemory::Borrowed(memory_lock.clone())
        }
    }
}

#[derive(Debug)]
pub struct Memory {
    start: VirtualAddress,
    size: usize,
    flags: EntryFlags
}

impl Memory {
    pub fn new(start: VirtualAddress, size: usize, flags: EntryFlags, flush: bool, clear: bool) -> Self {
        let mut memory = Memory {
            start: start,
            size: size,
            flags: flags
        };

        memory.map(flush, clear);

        memory
    }

    pub fn to_shared(self) -> SharedMemory {
        SharedMemory::Owned(Arc::new(Mutex::new(self)))
    }

    pub fn start_address(&self) -> VirtualAddress {
        self.start
    }

    pub fn size(&self) -> usize {
        self.size
    }

    pub fn flags(&self) -> EntryFlags {
        self.flags
    }

    pub fn pages(&self) -> PageIter {
        let start_page = Page::containing_address(self.start);
        let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size - 1));
        Page::range_inclusive(start_page, end_page)
    }

    fn map(&mut self, flush: bool, clear: bool) {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut flush_all = false;

        //TODO: Clear pages?
        for page in self.pages() {
            active_table.map(page, self.flags);

            if flush {
                //active_table.flush(page);
                flush_all = true;
            }
        }

        if flush_all {
            active_table.flush_all();
        }

        if clear {
            assert!(flush && self.flags.contains(entry::WRITABLE));
            unsafe {
                intrinsics::write_bytes(self.start_address().get() as *mut u8, 0, self.size);
            }
        }
    }

    fn unmap(&mut self, flush: bool) {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut flush_all = false;

        for page in self.pages() {
            active_table.unmap(page);

            if flush {
                //active_table.flush(page);
                flush_all = true;
            }
        }

        if flush_all {
            active_table.flush_all();
        }
    }

    /// A complicated operation to move a piece of memory to a new page table
    /// It also allows for changing the address at the same time
    pub fn move_to(&mut self, new_start: VirtualAddress, new_table: &mut InactivePageTable, temporary_page: &mut TemporaryPage, flush: bool) {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut flush_all = false;

        for page in self.pages() {
            let frame = active_table.unmap_return(page);

            active_table.with(new_table, temporary_page, |mapper| {
                let new_page = Page::containing_address(VirtualAddress::new(page.start_address().get() - self.start.get() + new_start.get()));
                mapper.map_to(new_page, frame, self.flags);
            });

            if flush {
                //active_table.flush(page);
                flush_all = true;
            }
        }

        if flush_all {
            active_table.flush_all();
        }

        self.start = new_start;
    }

    pub fn remap(&mut self, new_flags: EntryFlags, flush: bool) {
        let mut active_table = unsafe { ActivePageTable::new() };

        let mut flush_all = false;

        for page in self.pages() {
            active_table.remap(page, new_flags);

            if flush {
                //active_table.flush(page);
                flush_all = true;
            }
        }

        if flush_all {
            active_table.flush_all();
        }

        self.flags = new_flags;
    }

    pub fn resize(&mut self, new_size: usize, flush: bool, clear: bool) {
        let mut active_table = unsafe { ActivePageTable::new() };

        //TODO: Calculate page changes to minimize operations
        if new_size > self.size {
            let mut flush_all = false;

            let start_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size));
            let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + new_size - 1));
            for page in Page::range_inclusive(start_page, end_page) {
                if active_table.translate_page(page).is_none() {
                    active_table.map(page, self.flags);

                    if flush {
                        //active_table.flush(page);
                        flush_all = true;
                    }
                }
            }

            if flush_all {
                active_table.flush_all();
            }

            if clear {
                assert!(flush);
                unsafe {
                    intrinsics::write_bytes((self.start.get() + self.size) as *mut u8, 0, new_size - self.size);
                }
            }
        } else if new_size < self.size {
            let mut flush_all = false;

            let start_page = Page::containing_address(VirtualAddress::new(self.start.get() + new_size));
            let end_page = Page::containing_address(VirtualAddress::new(self.start.get() + self.size - 1));
            for page in Page::range_inclusive(start_page, end_page) {
                if active_table.translate_page(page).is_some() {
                    active_table.unmap(page);

                    if flush {
                        //active_table.flush(page);
                        flush_all = true;
                    }
                }
            }

            if flush_all {
                active_table.flush_all();
            }
        }

        self.size = new_size;
    }
}

impl Drop for Memory {
    fn drop(&mut self) {
        self.unmap(true);
    }
}

#[derive(Debug)]
pub struct Tls {
    pub master: VirtualAddress,
    pub file_size: usize,
    pub mem: Memory
}