rCore/kernel/src/syscall/mem.rs

use rcore_memory::memory_set::handler::{ByFrame, Delay};
use rcore_memory::memory_set::MemoryAttr;
use rcore_memory::paging::PageTable;
use rcore_memory::Page;
use rcore_memory::PAGE_SIZE;

use crate::memory::GlobalFrameAlloc;

use super::*;

pub fn sys_mmap(
    mut addr: usize,
    len: usize,
    prot: usize,
    flags: usize,
    fd: usize,
    offset: usize,
) -> SysResult {
    let prot = MmapProt::from_bits_truncate(prot);
    let flags = MmapFlags::from_bits_truncate(flags);
    info!(
        "mmap: addr={:#x}, size={:#x}, prot={:?}, flags={:?}, fd={}, offset={:#x}",
        addr, len, prot, flags, fd, offset
    );

    let mut proc = process();
    if addr == 0 {
        // although NULL can be a valid address
        // but in C, NULL is regarded as allocation failure
        // so just skip it
        addr = PAGE_SIZE;
    }

    if flags.contains(MmapFlags::FIXED) {
        // we have to map it to addr, so remove the old mapping first
        proc.vm.pop_with_split(addr, addr + len);
    } else {
        addr = proc.vm.find_free_area(addr, len);
    }

    if flags.contains(MmapFlags::ANONYMOUS) {
        if flags.contains(MmapFlags::SHARED) {
            return Err(SysError::EINVAL);
        }
        proc.vm.push(
            addr,
            addr + len,
            prot.to_attr(),
            Delay::new(GlobalFrameAlloc),
            "mmap_anon",
        );
        return Ok(addr);
    } else {
        // only check
        let _ = proc.get_file(fd)?;

        // TODO: delay mmap file
        proc.vm.push(
            addr,
            addr + len,
            prot.to_attr(),
            ByFrame::new(GlobalFrameAlloc),
            "mmap_file",
        );
        let data = unsafe { slice::from_raw_parts_mut(addr as *mut u8, len) };
        let file = proc.get_file(fd)?;
        let read_len = file.read_at(offset, data)?;
        if read_len != data.len() {
            // use count() to consume the iterator
            data[read_len..].iter_mut().map(|x| *x = 0).count();
        }
        return Ok(addr);
    }
}

pub fn sys_mprotect(addr: usize, len: usize, prot: usize) -> SysResult {
    let prot = MmapProt::from_bits_truncate(prot);
    info!(
        "mprotect: addr={:#x}, size={:#x}, prot={:?}",
        addr, len, prot
    );

    let mut proc = process();
    let attr = prot.to_attr();

    // FIXME: properly set the attribute of the area
    //        now some mut ptr check is fault
    let memory_area = proc
        .vm
        .iter()
        .find(|area| area.is_overlap_with(addr, addr + len));
    if memory_area.is_none() {
        return Err(SysError::ENOMEM);
    }
    proc.vm.edit(|pt| {
        for page in Page::range_of(addr, addr + len) {
            let entry = pt
                .get_entry(page.start_address())
                .expect("failed to get entry");
            attr.apply(entry);
        }
    });
    Ok(0)
}

pub fn sys_munmap(addr: usize, len: usize) -> SysResult {
    info!("munmap addr={:#x}, size={:#x}", addr, len);
    let mut proc = process();
    proc.vm.pop_with_split(addr, addr + len);
    Ok(0)
}

bitflags! {
    pub struct MmapProt: usize {
        /// Data cannot be accessed
        const NONE = 0;
        /// Data can be read
        const READ = 1 << 0;
        /// Data can be written
        const WRITE = 1 << 1;
        /// Data can be executed
        const EXEC = 1 << 2;
    }
}

bitflags! {
    pub struct MmapFlags: usize {
        /// Changes are shared.
        const SHARED = 1 << 0;
        /// Changes are private.
        const PRIVATE = 1 << 1;
        /// Place the mapping at the exact address
        const FIXED = 1 << 4;
        /// The mapping is not backed by any file. (non-POSIX)
        const ANONYMOUS = 1 << 5;
    }
}

impl MmapProt {
    fn to_attr(self) -> MemoryAttr {
        let mut attr = MemoryAttr::default().user();
        if self.contains(MmapProt::EXEC) {
            attr = attr.execute();
        }
        // FIXME: see sys_mprotect
        //        if !self.contains(MmapProt::WRITE) { attr = attr.readonly(); }
        attr
    }
}