Add /proc/filesystems support

kernel/aster-nix/src/fs/procfs/filesystems.rs

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use alloc::format;
+
+use crate::{
+    fs::{
+        procfs::template::{FileOps, ProcFileBuilder},
+        utils::Inode,
+    },
+    prelude::*,
+};
+
+/// Represents the inode at /proc/filesystems.
+pub struct FileSystemsFileOps;
+
+impl FileSystemsFileOps {
+    pub fn new_inode(parent: Weak<dyn Inode>) -> Arc<dyn Inode> {
+        ProcFileBuilder::new(Self).parent(parent).build().unwrap()
+    }
+}
+
+impl FileOps for FileSystemsFileOps {
+    fn data(&self) -> Result<Vec<u8>> {
+        let mut result = String::new();
+        for fs in FILESYSTEM_TYPES.iter() {
+            if fs.is_nodev {
+                result.push_str(&format!("nodev\t{}\n", fs.name));
+            } else {
+                result.push_str(&format!("\t{}\n", fs.name));
+            }
+        }
+        Ok(result.into_bytes())
+    }
+}
+
+lazy_static! {
+    static ref FILESYSTEM_TYPES: Vec<FileSystemType> = {
+        vec![
+            FileSystemType::new("proc", true),
+            FileSystemType::new("ramfs", true),
+            FileSystemType::new("devpts", true),
+            FileSystemType::new("ext2", false),
+            FileSystemType::new("exfat", false),
+        ]
+    };
+}
+
+struct FileSystemType {
+    name: String,
+    is_nodev: bool,
+}
+
+impl FileSystemType {
+    fn new(name: &str, is_nodev: bool) -> Self {
+        FileSystemType {
+            name: name.to_string(),
+            is_nodev,
+        }
+    }
+}

kernel/aster-nix/src/fs/procfs/mod.rs

@@ -11,11 +11,15 @@ use self::{
 };
 use crate::{
     events::Observer,
-    fs::utils::{DirEntryVecExt, FileSystem, FsFlags, Inode, SuperBlock, NAME_MAX},
+    fs::{
+        procfs::filesystems::FileSystemsFileOps,
+        utils::{DirEntryVecExt, FileSystem, FsFlags, Inode, SuperBlock, NAME_MAX},
+    },
     prelude::*,
     process::{process_table, process_table::PidEvent, Pid},
 };
 
+mod filesystems;
 mod pid;
 mod self_;
 mod sys;
@@ -96,6 +100,8 @@ impl DirOps for RootDirOps {
             SelfSymOps::new_inode(this_ptr.clone())
         } else if name == "sys" {
             SysDirOps::new_inode(this_ptr.clone())
+        } else if name == "filesystems" {
+            FileSystemsFileOps::new_inode(this_ptr.clone())
         } else if let Ok(pid) = name.parse::<Pid>() {
             let process_ref =
                 process_table::get_process(pid).ok_or_else(|| Error::new(Errno::ENOENT))?;
@@ -114,6 +120,9 @@ impl DirOps for RootDirOps {
         let mut cached_children = this.cached_children().write();
         cached_children.put_entry_if_not_found("self", || SelfSymOps::new_inode(this_ptr.clone()));
         cached_children.put_entry_if_not_found("sys", || SysDirOps::new_inode(this_ptr.clone()));
+        cached_children.put_entry_if_not_found("filesystems", || {
+            FileSystemsFileOps::new_inode(this_ptr.clone())
+        });
 
         for process in process_table::process_table().iter() {
             let pid = process.pid().to_string();