Add syscall chroot

Signed-off-by: Zhenchen Wang <m202372036@hust.edu.cn>

Signed-off-by: Zhenchen Wang <m202372036@hust.edu.cn>

kernel/aster-nix/src/fs/fs_resolver.rs

@@ -57,6 +57,11 @@ impl FsResolver {
         self.cwd = dentry;
     }
 
+    /// Set the root directory
+    pub fn set_root(&mut self, dentry: Arc<Dentry>) {
+        self.root = dentry;
+    }
+
     /// Open or create a file inode handler.
     pub fn open(&self, path: &FsPath, flags: u32, mode: u16) -> Result<InodeHandle> {
         let creation_flags = CreationFlags::from_bits_truncate(flags);

kernel/aster-nix/src/syscall/chroot.rs

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use super::{SyscallReturn, SYS_CHROOT};
+use crate::{
+    fs::{fs_resolver::FsPath, utils::InodeType},
+    log_syscall_entry,
+    prelude::*,
+    syscall::constants::MAX_FILENAME_LEN,
+    util::read_cstring_from_user,
+};
+
+pub fn sys_chroot(pathname_addr: Vaddr) -> Result<SyscallReturn> {
+    log_syscall_entry!(SYS_CHROOT);
+    let pathname = read_cstring_from_user(pathname_addr, MAX_FILENAME_LEN)?;
+    debug!("pathname = {:?}", pathname);
+
+    let current = current!();
+    let mut fs = current.fs().write();
+    let dentry = {
+        let pathname = pathname.to_string_lossy();
+        if pathname.is_empty() {
+            return_errno_with_message!(Errno::ENOENT, "path is empty");
+        }
+        let fs_path = FsPath::try_from(pathname.as_ref())?;
+        fs.lookup(&fs_path)?
+    };
+    if dentry.type_() != InodeType::Dir {
+        return_errno_with_message!(Errno::ENOTDIR, "must be directory");
+    }
+    fs.set_root(dentry);
+    Ok(SyscallReturn::Return(0))
+}

kernel/aster-nix/src/syscall/mod.rs

@@ -25,6 +25,7 @@ use crate::{
         chdir::{sys_chdir, sys_fchdir},
         chmod::{sys_chmod, sys_fchmod, sys_fchmodat},
         chown::{sys_chown, sys_fchown, sys_fchownat, sys_lchown},
+        chroot::sys_chroot,
         clock_gettime::sys_clock_gettime,
         clock_nanosleep::sys_clock_nanosleep,
         clone::sys_clone,
@@ -104,6 +105,7 @@ mod brk;
 mod chdir;
 mod chmod;
 mod chown;
+mod chroot;
 mod clock_gettime;
 mod clock_nanosleep;
 mod clone;
@@ -330,6 +332,7 @@ define_syscall_nums!(
     SYS_SET_PRIORITY = 141,
     SYS_PRCTL = 157,
     SYS_ARCH_PRCTL = 158,
+    SYS_CHROOT = 161,
     SYS_SYNC = 162,
     SYS_GETTID = 186,
     SYS_TIME = 201,
@@ -517,6 +520,7 @@ pub fn syscall_dispatch(
         SYS_SET_PRIORITY => syscall_handler!(3, sys_set_priority, args),
         SYS_PRCTL => syscall_handler!(5, sys_prctl, args),
         SYS_ARCH_PRCTL => syscall_handler!(2, sys_arch_prctl, args, context),
+        SYS_CHROOT => syscall_handler!(1, sys_chroot, args),
         SYS_SYNC => syscall_handler!(0, sys_sync),
         SYS_GETTID => syscall_handler!(0, sys_gettid),
         SYS_TIME => syscall_handler!(1, sys_time, args),