diff --git a/Makefile b/Makefile
index b03527c..2ba72ee 100644
--- a/Makefile
+++ b/Makefile
@@ -129,13 +129,13 @@ QEMUOPTS += -global virtio-mmio.force-legacy=false
 QEMUOPTS += -drive file=fs.img,if=none,format=raw,id=x0
 QEMUOPTS += -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0
 
-qemu: kernel/kernel fs.img
+qemu: kernel fs.img
 	$(QEMU) $(QEMUOPTS)
 
 .gdbinit: .gdbinit.tmpl-riscv
 	sed "s/:1234/:$(GDBPORT)/" < $^ > $@
 
-qemu-gdb: kernel/kernel .gdbinit fs.img
+qemu-gdb: kernel .gdbinit fs.img
 	@echo "*** Now run 'gdb' in another window." 1>&2
 	$(QEMU) $(QEMUOPTS) -S $(QEMUGDB)
 
diff --git a/kernel/rustkernel/Cargo.lock b/kernel/rustkernel/Cargo.lock
index 9bafc96..516fd1e 100644
--- a/kernel/rustkernel/Cargo.lock
+++ b/kernel/rustkernel/Cargo.lock
@@ -2,29 +2,6 @@
 # It is not intended for manual editing.
 version = 3
 
-[[package]]
-name = "arrayvec"
-version = "0.7.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96d30a06541fbafbc7f82ed10c06164cfbd2c401138f6addd8404629c4b16711"
-
-[[package]]
-name = "format_no_std"
-version = "1.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0f6ab8bf81c8fc5032d2d3e651eb5fda8e225e278f1bc7abeda0a258b7ab5eff"
-
-[[package]]
-name = "libc"
-version = "0.2.149"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a08173bc88b7955d1b3145aa561539096c421ac8debde8cbc3612ec635fee29b"
-
 [[package]]
 name = "rustkernel"
 version = "0.1.0"
-dependencies = [
- "arrayvec",
- "format_no_std",
- "libc",
-]
diff --git a/kernel/rustkernel/Cargo.toml b/kernel/rustkernel/Cargo.toml
index d7718bc..25087f9 100644
--- a/kernel/rustkernel/Cargo.toml
+++ b/kernel/rustkernel/Cargo.toml
@@ -4,9 +4,6 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
-arrayvec = { version = "0.7.4", default-features = false }
-format_no_std = "1.0.0"
-libc = { version = "0.2.149", default-features = false }
 
 [lib]
 crate-type = ["staticlib"]
diff --git a/kernel/rustkernel/src/console/mod.rs b/kernel/rustkernel/src/console/mod.rs
index 4e79259..65314b6 100644
--- a/kernel/rustkernel/src/console/mod.rs
+++ b/kernel/rustkernel/src/console/mod.rs
@@ -46,6 +46,14 @@ impl Console {
         &mut self.buffer[i]
     }
 }
+impl core::fmt::Write for Console {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        for b in s.as_bytes() {
+            Uart::write_byte_sync(*b);
+        }
+        core::fmt::Result::Ok(())
+    }
+}
 
 #[no_mangle]
 pub static cons: SpinMutex<Console> = SpinMutex::new(Console {
diff --git a/kernel/rustkernel/src/console/printf.rs b/kernel/rustkernel/src/console/printf.rs
index 1a17c51..cbd6d69 100644
--- a/kernel/rustkernel/src/console/printf.rs
+++ b/kernel/rustkernel/src/console/printf.rs
@@ -14,22 +14,13 @@ pub struct PrintLock {
 
 macro_rules! print {
     ($($arg:tt)*) => {{
+        use core::fmt::Write;
+
         // Still unsafe because static mut.
         let _guard = unsafe { $crate::console::printf::PRINT_LOCK.lock() };
 
-        // Allocate a page of memory as the buffer and release it when we're done.
-        let buf = unsafe { $crate::mem::kalloc::kalloc() as *mut [u8; 4096] };
-
-        let s: &str = format_no_std::show(
-            unsafe { buf.as_mut() }.unwrap(),
-            format_args!($($arg)*),
-        ).unwrap();
-
-        for c in s.as_bytes() {
-            $crate::console::consputc(*c);
-        }
-
-        unsafe { $crate::mem::kalloc::kfree(buf.cast()) };
+        let mut cons = $crate::console::cons.lock();
+        let _ = core::write!(cons.as_mut(), $($arg)*);
     }};
 }
 pub(crate) use print;
diff --git a/kernel/rustkernel/src/lib.rs b/kernel/rustkernel/src/lib.rs
index 6ad6d00..574a2d0 100644
--- a/kernel/rustkernel/src/lib.rs
+++ b/kernel/rustkernel/src/lib.rs
@@ -3,6 +3,7 @@
 #![allow(dead_code)]
 #![allow(clippy::missing_safety_doc)]
 #![feature(negative_impls)]
+#![feature(panic_info_message)]
 
 extern crate alloc;
 extern crate core;
@@ -88,20 +89,21 @@ pub unsafe extern "C" fn main() -> ! {
 
 #[panic_handler]
 fn panic_wrapper(panic_info: &core::panic::PanicInfo) -> ! {
-    if let Some(s) = panic_info.payload().downcast_ref::<&str>() {
-        print!("kernel panic: {}\n", s);
+    if let Some(location) = panic_info.location() {
+        print!("kernel panic ({}): ", location.file());
     } else {
-        print!("kernel panic\n");
+        print!("kernel panic: ");
     }
 
-    // crate::printf::print!("  ______\n");
-    // crate::printf::print!("< fuck!! >\n");
-    // crate::printf::print!("  ------\n");
-    // crate::printf::print!("         \\   ^__^ \n");
-    // crate::printf::print!("          \\  (oo)\\_______\n");
-    // crate::printf::print!("             (__)\\       )\\/\\\\\n");
-    // crate::printf::print!("                 ||----w |\n");
-    // crate::printf::print!("                 ||     ||\n");
+    if let Some(s) = panic_info.message() {
+        print!("{}\n", s);
+    } else if let Some(s) = panic_info.payload().downcast_ref::<&str>() {
+        print!("{}\n", s);
+    } else if let Some(s) = panic_info.payload().downcast_ref::<&CStr>() {
+        print!("{:?}\n", s);
+    } else {
+        print!("could not recover error message\n");
+    }
 
     print!("███████╗██╗   ██╗ ██████╗██╗  ██╗██╗██╗\n");
     print!("██╔════╝██║   ██║██╔════╝██║ ██╔╝██║██║\n");
@@ -110,7 +112,11 @@ fn panic_wrapper(panic_info: &core::panic::PanicInfo) -> ! {
     print!("██║     ╚██████╔╝╚██████╗██║  ██╗██╗██╗\n");
     print!("╚═╝      ╚═════╝  ╚═════╝╚═╝  ╚═╝╚═╝╚═╝\n");
 
-    unsafe { crate::PANICKED = true };
+    unsafe {
+        crate::PANICKED = true;
+        // Quit QEMU for convenience.
+        crate::syscall::Syscall::Shutdown.call();
+    }
 
     loop {
         core::hint::spin_loop();
@@ -118,7 +124,8 @@ fn panic_wrapper(panic_info: &core::panic::PanicInfo) -> ! {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn panic(s: *const c_char) -> ! {
-    let s = CStr::from_ptr(s).to_str().unwrap_or("panic from c");
-    panic!("{}", s);
+pub unsafe extern "C" fn panic(_: *const c_char) -> ! {
+    panic!("panic from c");
+    // let s = CStr::from_ptr(s).to_str().unwrap_or("panic from c");
+    // panic!("{:?}", CStr::from_ptr(s));
 }
diff --git a/kernel/rustkernel/src/sync/spinmutex.rs b/kernel/rustkernel/src/sync/spinmutex.rs
index fe99ec4..890546b 100644
--- a/kernel/rustkernel/src/sync/spinmutex.rs
+++ b/kernel/rustkernel/src/sync/spinmutex.rs
@@ -1,5 +1,6 @@
 use core::{
     cell::UnsafeCell,
+    convert::{AsMut, AsRef},
     ops::{Deref, DerefMut, Drop},
     sync::atomic::{AtomicBool, Ordering},
 };
@@ -42,6 +43,16 @@ impl<'m, T> DerefMut for SpinMutexGuard<'m, T> {
         unsafe { &mut *self.mutex.inner.get() }
     }
 }
+impl<'m, T> AsRef<T> for SpinMutexGuard<'m, T> {
+    fn as_ref(&self) -> &T {
+        self.deref()
+    }
+}
+impl<'m, T> AsMut<T> for SpinMutexGuard<'m, T> {
+    fn as_mut(&mut self) -> &mut T {
+        self.deref_mut()
+    }
+}
 impl<'m, T> Drop for SpinMutexGuard<'m, T> {
     fn drop(&mut self) {
         unsafe { self.mutex.unlock() }
diff --git a/kernel/rustkernel/src/syscall.rs b/kernel/rustkernel/src/syscall.rs
index d11c5e0..0c4e10f 100644
--- a/kernel/rustkernel/src/syscall.rs
+++ b/kernel/rustkernel/src/syscall.rs
@@ -1,7 +1,7 @@
 use crate::{
     console::printf::print,
     proc::{self, myproc, sleep_lock},
-    riscv::{Pagetable, memlayout::QEMU_POWER},
+    riscv::{memlayout::QEMU_POWER, Pagetable},
     string::strlen,
 };
 use core::{mem::size_of, ptr::addr_of_mut};