diff --git a/library/std/src/os/yggdrasil/debug.rs b/library/std/src/os/yggdrasil/debug.rs
new file mode 100644
index 00000000000..689a9d3f49c
--- /dev/null
+++ b/library/std/src/os/yggdrasil/debug.rs
@@ -0,0 +1,20 @@
+#![unstable(feature = "yggdrasil_os", issue = "none")]
+
+use crate::fmt;
+use yggdrasil_rt::sys as syscall;
+
+// This is a safer version of debug_trace! from yggdrasil_rt that uses heap-allocated buffer
+// instead of a fixed-size chunk.
+#[macro_export]
+macro_rules! debug_trace {
+    ($($arg:tt)+) => {
+        $crate::os::yggdrasil::debug::_debug_trace(format_args!($($arg)+))
+    };
+}
+
+pub fn _debug_trace(args: fmt::Arguments<'_>) {
+    let string = format!("{}", args);
+    unsafe {
+        syscall::debug_trace(string.as_str());
+    }
+}
diff --git a/library/std/src/os/yggdrasil/fs.rs b/library/std/src/os/yggdrasil/fs.rs
new file mode 100644
index 00000000000..1aaa4d4dc6a
--- /dev/null
+++ b/library/std/src/os/yggdrasil/fs.rs
@@ -0,0 +1,16 @@
+#![unstable(feature = "yggdrasil_os", issue = "none")]
+
+use crate::fs::Metadata;
+use crate::sys_common::AsInner;
+use yggdrasil_rt::io::FileMode;
+
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+pub trait MetadataExt {
+    fn mode_ext(&self) -> FileMode;
+}
+
+impl MetadataExt for Metadata {
+    fn mode_ext(&self) -> FileMode {
+        self.as_inner().mode_ext()
+    }
+}
diff --git a/library/std/src/os/yggdrasil/io/mod.rs b/library/std/src/os/yggdrasil/io/mod.rs
index bdc3b7310d8..8658f8faab9 100644
--- a/library/std/src/os/yggdrasil/io/mod.rs
+++ b/library/std/src/os/yggdrasil/io/mod.rs
@@ -8,14 +8,18 @@ pub(crate) mod raw;
 use crate::io::StdinLock;
 
 use crate::mem::MaybeUninit;
+use crate::path::Path;
 use crate::sys::cvt_io;
-use yggdrasil_rt::sys as syscall;
+use yggdrasil_rt::{
+    io::{FileMode, OpenOptions},
+    sys as syscall,
+};
 
 // Public exports
 
 #[unstable(feature = "yggdrasil_os", issue = "none")]
 pub use yggdrasil_rt::io::{
-    DeviceRequest, TerminalInputOptions, TerminalLineOptions, TerminalOptions,
+    DeviceRequest, MountOptions, TerminalInputOptions, TerminalLineOptions, TerminalOptions,
     TerminalOutputOptions,
 };
 
@@ -64,6 +68,26 @@ pub unsafe fn get_terminal_options<F: raw::AsRawFd>(fd: F) -> crate::io::Result<
     Ok(opt.assume_init())
 }
 
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+pub unsafe fn start_terminal_session<P: AsRef<Path>>(terminal: P) -> crate::io::Result<()> {
+    let terminal = terminal.as_ref().to_str().unwrap();
+
+    cvt_io(syscall::start_session())?;
+
+    // TODO implement open flags to explicitly set stdin/stdout/stderr
+
+    cvt_io(syscall::open(None, terminal, OpenOptions::READ, FileMode::empty()))?;
+    cvt_io(syscall::open(None, terminal, OpenOptions::WRITE, FileMode::empty()))?;
+    cvt_io(syscall::open(None, terminal, OpenOptions::WRITE, FileMode::empty()))?;
+
+    Ok(())
+}
+
+#[unstable(feature = "yggdrasil_os", issue = "none")]
+pub unsafe fn mount_raw(options: &MountOptions<'_>) -> crate::io::Result<()> {
+    cvt_io(syscall::mount(options))
+}
+
 #[unstable(feature = "yggdrasil_os", issue = "none")]
 pub unsafe fn update_terminal_options<
     F: raw::AsRawFd,
diff --git a/library/std/src/os/yggdrasil/mod.rs b/library/std/src/os/yggdrasil/mod.rs
index 4fd27ad26e7..1557d44fd22 100644
--- a/library/std/src/os/yggdrasil/mod.rs
+++ b/library/std/src/os/yggdrasil/mod.rs
@@ -1,5 +1,7 @@
 #![stable(feature = "os", since = "1.0.0")]
 
+pub mod debug;
+pub mod fs;
 pub mod io;
 pub mod process;
 
diff --git a/library/std/src/sys/yggdrasil/fs/mod.rs b/library/std/src/sys/yggdrasil/fs/mod.rs
index 74a652fd831..99530cbde4c 100644
--- a/library/std/src/sys/yggdrasil/fs/mod.rs
+++ b/library/std/src/sys/yggdrasil/fs/mod.rs
@@ -40,6 +40,10 @@ impl FileAttr {
         FileType(self.0.ty)
     }
 
+    pub fn mode_ext(&self) -> OsFileMode {
+        self.0.mode
+    }
+
     pub fn modified(&self) -> io::Result<SystemTime> {
         Err(crate::io::const_io_error!(
             crate::io::ErrorKind::Unsupported,