Rust: Fs: Ramfs in rust

This is still in a early stage. The ultimate goal is to write a
complete ram fs in rust.

Current status:
We can register and mount the fs,
and read write some predefined files in the root folder.

Signed-off-by: Fox Chen <[email protected]>

Author: foxhlchen

Makefile

@@ -524,7 +524,7 @@ KBUILD_RUSTCFLAGS := --emit=dep-info,obj,metadata --edition=2018 \
 		     -Cpanic=abort -Cembed-bitcode=n -Clto=n -Crpath=n \
 		     -Cforce-unwind-tables=n -Ccodegen-units=1 \
 		     -Zbinary_dep_depinfo=y -Zsymbol-mangling-version=v0 \
-		     -D unsafe_op_in_unsafe_fn
+		     -D unsafe_op_in_unsafe_fn -Zmacro-backtrace
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
 KBUILD_RUSTCFLAGS_KERNEL :=

rust/kernel/fs.rs

@@ -0,0 +1,345 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! File System Interfaces.
+
+use super::file_operations::{FileOpenAdapter, FileOpener, FileOperationsVtable};
+use crate::bindings::{
+    dentry, file, file_operations, file_system_type, inode, mount_bdev, mount_nodev, mount_single,
+    register_filesystem, super_block, unregister_filesystem,
+};
+use crate::str::*;
+use crate::{c_str, c_types, error::Error, Result, ThisModule};
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::ptr;
+
+pub const S_IRWXU: i32 = crate::bindings::S_IRWXU as i32;
+pub const S_IRUSR: i32 = crate::bindings::S_IRUSR as i32;
+pub const S_IWUSR: i32 = crate::bindings::S_IWUSR as i32;
+pub const S_IXUSR: i32 = crate::bindings::S_IXUSR as i32;
+pub const S_IRWXG: i32 = crate::bindings::S_IRWXG as i32;
+pub const S_IRGRP: i32 = crate::bindings::S_IRGRP as i32;
+pub const S_IWGRP: i32 = crate::bindings::S_IWGRP as i32;
+pub const S_IXGRP: i32 = crate::bindings::S_IXGRP as i32;
+pub const S_IRWXO: i32 = crate::bindings::S_IRWXO as i32;
+pub const S_IROTH: i32 = crate::bindings::S_IROTH as i32;
+pub const S_IWOTH: i32 = crate::bindings::S_IWOTH as i32;
+pub const S_IXOTH: i32 = crate::bindings::S_IXOTH as i32;
+
+unsafe extern "C" fn mount_callback<T: FileSystem>(
+    fs_type: *mut file_system_type,
+    flags: c_types::c_int,
+    dev_name: *const c_types::c_char,
+    data: *mut c_types::c_void,
+) -> *mut dentry {
+    let r_fs_type = FSType::from_c_fs_type(fs_type).unwrap();
+    let r_dev_name = if dev_name.is_null() {
+        c_str!("")
+    } else {
+        unsafe { CStr::from_char_ptr(dev_name) }
+    };
+    let r_data = if data.is_null() {
+        c_str!("")
+    } else {
+        unsafe { CStr::from_char_ptr(data as *const c_types::c_char) }
+    };
+
+    let rt: Result<Dentry> = match T::MOUNT_TYPE {
+        MountType::Custom => T::mount(&r_fs_type, flags, r_dev_name, r_data),
+        MountType::Single => Dentry::from_c_dentry(unsafe {
+            mount_single(fs_type, flags, data, Some(fill_super_callback::<T>))
+        }),
+        MountType::BDev => Dentry::from_c_dentry(unsafe {
+            mount_bdev(
+                fs_type,
+                flags,
+                dev_name,
+                data,
+                Some(fill_super_callback::<T>),
+            )
+        }),
+        MountType::NoDev => Dentry::from_c_dentry(unsafe {
+            mount_nodev(fs_type, flags, data, Some(fill_super_callback::<T>))
+        }),
+    };
+
+    if let Err(e) = rt {
+        //TODO wrap ETR_PTR
+        return e.to_kernel_errno() as *mut dentry;
+    }
+
+    rt.unwrap().to_c_dentry()
+}
+
+unsafe extern "C" fn fill_super_callback<T: FileSystem>(
+    sb: *mut super_block,
+    data: *mut c_types::c_void,
+    silent: c_types::c_int,
+) -> c_types::c_int {
+    let r_sb_rs = SuperBlock::from_c_super_block(sb);
+    if let Err(e) = r_sb_rs {
+        return e.to_kernel_errno();
+    }
+
+    let mut r_sb = r_sb_rs.unwrap();
+    let r_data = if data.is_null() {
+        c_str!("")
+    } else {
+        unsafe { CStr::from_char_ptr(data as *const c_types::c_char) }
+    };
+
+    let rs = T::fill_super(&mut r_sb, r_data, silent as i32);
+    if let Err(e) = rs {
+        return e.to_kernel_errno();
+    }
+
+    0
+}
+
+unsafe extern "C" fn kill_sb_callback<T: FileSystem>(sb: *mut super_block) {
+    let r_sb_rs = SuperBlock::from_c_super_block(sb);
+
+    if let Ok(r_sb) = r_sb_rs {
+        T::kill_sb(&r_sb);
+    }
+}
+
+pub struct Dentry {
+    c_dentry: *mut dentry,
+}
+
+impl Dentry {
+    pub fn default() -> Dentry {
+        Dentry {
+            c_dentry: ptr::null_mut(),
+        }
+    }
+
+    pub fn from_c_dentry(c_dentry: *mut dentry) -> Result<Self> {
+        if c_dentry.is_null() {
+            return Err(Error::EINVAL);
+        }
+
+        //TODO inc refcnt, and dec in dtor
+        let mut d = Dentry::default();
+        d.c_dentry = c_dentry;
+
+        Ok(d)
+    }
+
+    pub fn to_c_dentry(&self) -> *mut dentry {
+        return self.c_dentry;
+    }
+}
+
+pub struct Inode {
+    c_inode: *mut inode,
+}
+
+impl Inode {
+    pub fn default() -> Inode {
+        Inode {
+            c_inode: ptr::null_mut(),
+        }
+    }
+
+    pub fn from_c_inode(c_inode: *mut inode) -> Result<Self> {
+        if c_inode.is_null() {
+            return Err(Error::EINVAL);
+        }
+
+        //TODO inc refcnt, and dec in dtor
+        let mut i = Inode::default();
+        i.c_inode = c_inode;
+
+        Ok(i)
+    }
+
+    pub fn to_c_inode(&self) -> *mut inode {
+        return self.c_inode;
+    }
+}
+
+pub struct SuperBlock {
+    c_sb: *mut super_block,
+}
+
+impl SuperBlock {
+    pub fn default() -> SuperBlock {
+        SuperBlock {
+            c_sb: ptr::null_mut(),
+        }
+    }
+
+    pub fn from_c_super_block(c_sb: *mut super_block) -> Result<Self> {
+        if c_sb.is_null() {
+            return Err(Error::EINVAL);
+        }
+
+        let mut sb = SuperBlock::default();
+        sb.c_sb = c_sb;
+
+        Ok(sb)
+    }
+
+    pub fn to_c_super_block(&mut self) -> *mut super_block {
+        self.c_sb
+    }
+}
+
+pub struct FSType {
+    c_fs_type: *mut file_system_type,
+}
+
+impl FSType {
+    pub fn default() -> FSType {
+        FSType {
+            c_fs_type: ptr::null_mut(),
+        }
+    }
+
+    pub fn from_c_fs_type(c_fs_type: *mut file_system_type) -> Result<Self> {
+        if c_fs_type.is_null() {
+            return Err(Error::EINVAL);
+        }
+
+        let mut fs_type = FSType::default();
+        fs_type.c_fs_type = c_fs_type;
+
+        Ok(fs_type)
+    }
+
+    pub fn to_c_fs_type(&mut self) -> *mut file_system_type {
+        self.c_fs_type
+    }
+}
+
+pub enum MountType {
+    // Call user provided mount function instead of [`fill_super()`]
+    Custom,
+
+    // Mount a filesystem residing on a block device
+    BDev,
+
+    // Mount a filesystem that is not backed by a device
+    NoDev,
+
+    // Mount a filesystem which shares the instance between all mounts
+    Single,
+}
+
+impl<T: FileOpener<()>> FileOpenAdapter for T {
+    type Arg = ();
+
+    unsafe fn convert(_inode: *mut inode, _file: *mut file) -> *const Self::Arg {
+        &()
+    }
+}
+
+pub fn build_fops<A: FileOpenAdapter, T: FileOpener<A::Arg>>() -> &'static file_operations {
+    return unsafe { FileOperationsVtable::<A, T>::build() };
+}
+
+// export tree_descr
+pub use crate::bindings::tree_descr;
+
+#[macro_export]
+macro_rules! treedescr {
+    (
+        $($name:literal,$ops:ident,$mode:expr;)+
+    ) => {
+        {
+            let mut v = Vec::<tree_descr>::new();
+
+            // Because the root inode is 1, the files array must not contain an
+	        // entry at index 1. We make them start at index 2.
+            v.push(tree_descr::default()); // index 0 skipped
+            v.push(tree_descr::default()); // index 1 skipped
+
+            $(
+                let mut tdesc = tree_descr::default();
+                tdesc.name = c_str!($name).as_char_ptr();
+                tdesc.ops = build_fops::<$ops, $ops>();
+                tdesc.mode = $mode;
+
+                v.push(tdesc);
+            )+
+
+            // Add ending mark
+            let mut tdesc = tree_descr::default();
+            tdesc.name = c_str!("").as_char_ptr();
+            v.push(tdesc);
+
+            v
+        }
+    };
+    () => {
+        {
+            let mut v = Vec::<tree_descr>::new();
+
+            let mut tdesc = tree_descr::default();
+            tdesc.name = c_str!("").as_char_ptr();
+
+            v.push(tdesc);
+            v
+        }
+    };
+}
+
+pub fn simple_fill_super(sb: &mut SuperBlock, magic: usize, vec: &Vec<tree_descr>) -> Result<()> {
+    let rt = unsafe {
+        crate::bindings::simple_fill_super(
+            sb.to_c_super_block(),
+            magic as c_types::c_ulong,
+            vec.as_ptr(),
+        )
+    };
+    if rt != 0 {
+        return Err(Error::from_kernel_errno(rt));
+    }
+
+    Ok(())
+}
+
+pub type FSHandle = Box<file_system_type>;
+
+pub trait FileSystem: Sized + Sync {
+    const MOUNT_TYPE: MountType;
+
+    fn mount(_fs_type: &FSType, _flags: i32, _dev_name: &CStr, _data: &CStr) -> Result<Dentry> {
+        Err(Error::EINVAL)
+    }
+
+    fn fill_super(_sb: &mut SuperBlock, _data: &CStr, _silent: i32) -> Result<()> {
+        Err(Error::EINVAL)
+    }
+
+    fn kill_sb(_sb: &SuperBlock) {}
+
+    fn register_self(name: &'static CStr, owner: &ThisModule) -> Result<FSHandle>
+    where
+        Self: Sized,
+    {
+        let mut c_fs_type = Box::new(file_system_type::default());
+        c_fs_type.mount = Some(mount_callback::<Self>);
+        c_fs_type.kill_sb = Some(kill_sb_callback::<Self>);
+        c_fs_type.owner = owner.0;
+        c_fs_type.name = name.as_char_ptr();
+
+        let err = unsafe { register_filesystem(c_fs_type.as_mut() as *mut _) };
+        if err != 0 {
+            return Err(Error::from_kernel_errno(err));
+        }
+
+        Ok(c_fs_type)
+    }
+
+    fn unregister_self(c_fs_type: &mut FSHandle) -> Result<()> {
+        let err = unsafe { unregister_filesystem(c_fs_type.as_mut() as *mut _) };
+        if err != 0 {
+            return Err(Error::from_kernel_errno(err));
+        }
+
+        Ok(())
+    }
+}

rust/kernel/lib.rs

@@ -48,6 +48,7 @@ pub mod chrdev;
 mod error;
 pub mod file;
 pub mod file_operations;
+pub mod fs;
 pub mod miscdev;
 pub mod pages;
 pub mod str;

rust/kernel/prelude.rs

@@ -15,7 +15,7 @@ pub use alloc::{borrow::ToOwned, string::String};
 
 pub use super::build_assert;
 
-pub use macros::{module, module_misc_device};
+pub use macros::{module, module_fs, module_misc_device};
 
 pub use super::{pr_alert, pr_crit, pr_emerg, pr_err, pr_info, pr_notice, pr_warn};