Merge pull request #203 from arihant2math/statfs

Implement `sys_statfs` and `sys_fstatfs`

etc/syscalls_linux_aarch64.md

@@ -43,8 +43,8 @@
 | 0x27 (39)   | umount                  | (char *name, int flags)                                                                                                                    | __arm64_sys_umount                  | false       |
 | 0x28 (40)   | mount                   | (char *dev_name, char *dir_name, char *type, unsigned long flags, void *data)                                                              | __arm64_sys_mount                   | false       |
 | 0x29 (41)   | pivot_root              | (const char *new_root, const char *put_old)                                                                                                | __arm64_sys_pivot_root              | false       |
-| 0x2b (43)   | statfs                  | (const char *pathname, struct statfs *buf)                                                                                                 | __arm64_sys_statfs                  | dummy       |
-| 0x2c (44)   | fstatfs                 | (unsigned int fd, struct statfs *buf)                                                                                                      | __arm64_sys_fstatfs                 | dummy       |
+| 0x2b (43)   | statfs                  | (const char *pathname, struct statfs *buf)                                                                                                 | __arm64_sys_statfs                  | partial     |
+| 0x2c (44)   | fstatfs                 | (unsigned int fd, struct statfs *buf)                                                                                                      | __arm64_sys_fstatfs                 | partial     |
 | 0x2d (45)   | truncate                | (const char *path, long length)                                                                                                            | __arm64_sys_truncate                | true        |
 | 0x2e (46)   | ftruncate               | (unsigned int fd, off_t length)                                                                                                            | __arm64_sys_ftruncate               | true        |
 | 0x2f (47)   | fallocate               | (int fd, int mode, loff_t offset, loff_t len)                                                                                              | __arm64_sys_fallocate               | false       |

libkernel/src/fs/filesystems/ext4/mod.rs

@@ -362,6 +362,11 @@ where
         self.id
     }
 
+    fn magic(&self) -> u64 {
+        // TODO: retrieve magic from superblock instead of hardcoding
+        0xef53 // EXT4 magic number
+    }
+
     /// Returns the root inode of the mounted EXT4 filesystem.
     async fn root_inode(&self) -> Result<Arc<dyn Inode>> {
         let root = self.inner.read_root_inode().await?;

libkernel/src/fs/filesystems/fat32/mod.rs

@@ -168,6 +168,10 @@ impl Filesystem for Fat32Filesystem {
         self.id
     }
 
+    fn magic(&self) -> u64 {
+        0x4D44 // MSDOS magic number
+    }
+
     /// Get the root inode of this filesystem.
     async fn root_inode(&self) -> Result<Arc<dyn Inode>> {
         Ok(Arc::new(Fat32DirNode::new(

libkernel/src/fs/filesystems/tmpfs.rs

@@ -821,6 +821,10 @@ where
     fn id(&self) -> u64 {
         self.id
     }
+
+    fn magic(&self) -> u64 {
+        0x01021994 // Tmpfs magic number
+    }
 }
 
 #[cfg(test)]

libkernel/src/fs/mod.rs

@@ -65,6 +65,9 @@ pub trait Filesystem: Send + Sync {
     /// Returns the instance ID for this FS.
     fn id(&self) -> u64;
 
+    /// Get magic
+    fn magic(&self) -> u64;
+
     /// Flushes all pending data to the underlying storage device(s).
     ///
     /// The default implementation is a no-op so that read-only filesystems do

src/arch/arm64/exceptions/syscall.rs

@@ -38,6 +38,7 @@ use crate::{
             setxattr::{sys_fsetxattr, sys_lsetxattr, sys_setxattr},
             splice::sys_sendfile,
             stat::sys_fstat,
+            statfs::{sys_fstatfs, sys_statfs},
             sync::{sys_fdatasync, sys_fsync, sys_sync, sys_syncfs},
             trunc::{sys_ftruncate, sys_truncate},
         },
@@ -227,7 +228,8 @@ pub async fn handle_syscall() {
             )
             .await
         }
-        0x2b | 0x2c => Err(KernelError::NotSupported),
+        0x2b => sys_statfs(TUA::from_value(arg1 as _), TUA::from_value(arg2 as _)).await,
+        0x2c => sys_fstatfs(arg1.into(), TUA::from_value(arg2 as _)).await,
         0x2d => sys_truncate(TUA::from_value(arg1 as _), arg2 as _).await,
         0x2e => sys_ftruncate(arg1.into(), arg2 as _).await,
         0x30 => sys_faccessat(arg1.into(), TUA::from_value(arg2 as _), arg3 as _).await,

src/drivers/fs/cgroup/mod.rs

@@ -127,6 +127,10 @@ impl Filesystem for CgroupFs {
     fn id(&self) -> u64 {
         CGROUPFS_ID
     }
+
+    fn magic(&self) -> u64 {
+        0x63677270 // v2 magic number
+    }
 }
 
 static SYSFS_INSTANCE: OnceLock<Arc<CgroupFs>> = OnceLock::new();

src/drivers/fs/dev.rs

@@ -88,6 +88,11 @@ impl Filesystem for DevFs {
     fn id(&self) -> u64 {
         DEVFS_ID
     }
+
+    fn magic(&self) -> u64 {
+        // TODO: Is this the right value
+        0x01021994 // TMPFS_MAGIC
+    }
 }
 
 enum InodeKind {

src/drivers/fs/proc.rs

@@ -51,6 +51,10 @@ impl Filesystem for ProcFs {
     fn id(&self) -> u64 {
         PROCFS_ID
     }
+
+    fn magic(&self) -> u64 {
+        0x9fa0 // procfs magic number
+    }
 }
 
 static PROCFS_INSTANCE: OnceLock<Arc<ProcFs>> = OnceLock::new();

src/drivers/fs/sys/mod.rs

@@ -176,6 +176,10 @@ impl Filesystem for SysFs {
     fn id(&self) -> u64 {
         SYSFS_ID
     }
+
+    fn magic(&self) -> u64 {
+        0x62656572 // sysfs magic number
+    }
 }
 
 static SYSFS_INSTANCE: OnceLock<Arc<SysFs>> = OnceLock::new();

src/fs/mod.rs

@@ -177,6 +177,13 @@ impl VFS {
         Ok(())
     }
 
+    pub async fn get_fs(&self, inode: Arc<dyn Inode>) -> Result<Arc<dyn Filesystem>> {
+        self.state
+            .lock_save_irq()
+            .get_fs(inode.id())
+            .ok_or(KernelError::from(FsError::NoDevice))
+    }
+
     /// Resolves a path string to an Inode, starting from a given root for
     /// relative paths.
     pub async fn resolve_path(

src/fs/syscalls/mod.rs

@@ -14,5 +14,6 @@ pub mod seek;
 pub mod setxattr;
 pub mod splice;
 pub mod stat;
+pub mod statfs;
 pub mod sync;
 pub mod trunc;

src/fs/syscalls/statfs.rs

@@ -0,0 +1,88 @@
+use crate::fs::VFS;
+use crate::memory::uaccess::cstr::UserCStr;
+use crate::memory::uaccess::{UserCopyable, copy_to_user};
+use crate::process::fd_table::Fd;
+use crate::sched::current::{current_task, current_task_shared};
+use alloc::sync::Arc;
+use core::ffi::c_char;
+use libkernel::error::KernelError;
+use libkernel::fs::Inode;
+use libkernel::fs::path::Path;
+use libkernel::memory::address::TUA;
+use libkernel::pod::Pod;
+
+type FswordT = u32;
+type FsBlockCntT = u64;
+
+#[repr(C)]
+#[derive(Debug, Clone, Copy)]
+pub struct StatFs {
+    /// Type of filesystem
+    f_type: FswordT,
+    /// Optimal transfer block size
+    f_bsize: FswordT,
+    /// Total data blocks in filesystem
+    f_blocks: FsBlockCntT,
+    /// Free blocks in filesystem
+    f_bfree: FsBlockCntT,
+    /// Free blocks available to unprivileged user
+    f_bavail: FsBlockCntT,
+    /// Total inodes in filesystem
+    f_files: FsBlockCntT,
+    /// Free inodes in filesystem
+    f_ffree: FsBlockCntT,
+    /// Filesystem ID
+    f_fsid: u64,
+    /// Maximum length of filenames
+    f_namelen: FswordT,
+    /// Fragment size (since Linux 2.6)
+    f_frsize: FswordT,
+    /// Mount flags of filesystem (since Linux 2.6.36)
+    f_flags: FswordT,
+    /// Padding bytes reserved for future use
+    f_spare: [FswordT; 6],
+}
+
+unsafe impl Pod for StatFs {}
+
+unsafe impl UserCopyable for StatFs {}
+
+async fn statfs_impl(inode: Arc<dyn Inode>) -> libkernel::error::Result<StatFs> {
+    let fs = VFS.get_fs(inode).await?;
+    Ok(StatFs {
+        f_type: fs.magic() as _,
+        f_bsize: 0,
+        f_blocks: 0,
+        f_bfree: 0,
+        f_bavail: 0,
+        f_files: 0,
+        f_ffree: 0,
+        f_fsid: fs.id(),
+        f_namelen: 0,
+        f_frsize: 0,
+        f_flags: 0,
+        f_spare: [0; 6],
+    })
+}
+
+pub async fn sys_statfs(path: TUA<c_char>, stat: TUA<StatFs>) -> libkernel::error::Result<usize> {
+    let mut buf = [0; 1024];
+    let path = Path::new(UserCStr::from_ptr(path).copy_from_user(&mut buf).await?);
+    let inode = VFS
+        .resolve_path(path, VFS.root_inode(), &current_task_shared())
+        .await?;
+    let statfs = statfs_impl(inode).await?;
+    copy_to_user(stat, statfs).await?;
+    Ok(0)
+}
+
+pub async fn sys_fstatfs(fd: Fd, stat: TUA<StatFs>) -> libkernel::error::Result<usize> {
+    let fd = current_task()
+        .fd_table
+        .lock_save_irq()
+        .get(fd)
+        .ok_or(KernelError::BadFd)?;
+    let statfs = statfs_impl(fd.inode().ok_or(KernelError::InvalidValue)?).await?;
+    copy_to_user(stat, statfs).await?;
+    Ok(0)
+}