feature: thread::current() using tpidr_el0

kernel/src/arch/aarch64/context.S

@@ -32,27 +32,6 @@ __aa64_ctx_enter_kernel:
     eret
 
 __aa64_ctx_enter_from_fork:
-    // stack.push(frame.x[18]);
-    // stack.push(frame.x[17]);
-    // stack.push(frame.x[16]);
-    // stack.push(frame.x[15]);
-    // stack.push(frame.x[14]);
-    // stack.push(frame.x[13]);
-    // stack.push(frame.x[12]);
-    // stack.push(frame.x[11]);
-    // stack.push(frame.x[10]);
-    // stack.push(frame.x[9]);
-    // stack.push(frame.x[8]);
-    // stack.push(frame.x[7]);
-    // stack.push(frame.x[6]);
-    // stack.push(frame.x[5]);
-    // stack.push(frame.x[4]);
-    // stack.push(frame.x[3]);
-    // stack.push(frame.x[2]);
-    // stack.push(frame.x[1]);
-
-    // stack.push(frame.elr_el1 as usize);
-    // stack.push(frame.sp_el0 as usize);
     ldp x0,  x1,  [sp, #16 * 0]
     msr sp_el0, x0
     msr elr_el1, x1
@@ -82,7 +61,8 @@ __aa64_ctx_switch:
     stp x27, x28, [sp, #16 * 4]
     stp x29, x30, [sp, #16 * 5]
     mrs x19, TTBR0_EL1
-    stp x19, xzr, [sp, #16 * 6]
+    mrs x20, TPIDR_EL0
+    stp x19, x20, [sp, #16 * 6]
 
     mov x19, sp
     str x19, [x1]
@@ -90,8 +70,9 @@ __aa64_ctx_switch_to:
     ldr x0, [x0]
     mov sp, x0
 
-    ldp x19, xzr, [sp, #16 * 6]
+    ldp x19, x20, [sp, #16 * 6]
     msr TTBR0_EL1, x19
+    msr TPIDR_EL0, x20
     ldp x19, x20, [sp, #16 * 0]
     ldp x21, x22, [sp, #16 * 1]
     ldp x23, x24, [sp, #16 * 2]

kernel/src/arch/aarch64/context.rs

@@ -67,7 +67,7 @@ impl Context {
         stack.push(frame.sp_el0 as usize);
 
         // Setup common
-        stack.push(0);
+        stack.push(0);          // tpidr_el0
         stack.push(ttbr0);
         stack.push(__aa64_ctx_enter_from_fork as usize); // x30/lr
         stack.push(frame.x[29]); // x29
@@ -96,7 +96,7 @@ impl Context {
 
         stack.push(entry);
         stack.push(arg);
-        stack.push(/* ttbr0 */ 0);
+        stack.push(0);
         stack.push(ustack);
 
         stack.setup_common(__aa64_ctx_enter_user as usize, ttbr0);
@@ -176,7 +176,7 @@ impl Stack {
     }
 
     pub fn setup_common(&mut self, entry: usize, ttbr: usize) {
-        self.push(0);
+        self.push(0);       // tpidr_el0
         self.push(ttbr);
         self.push(entry);   // x30/lr
         self.push(0);       // x29

kernel/src/proc/process.rs

@@ -197,11 +197,10 @@ impl Process {
 
     // TODO a way to terminate a single thread?
     /// Terminates a process.
-    pub fn exit<I: Into<ExitCode>>(status: I) {
+    pub fn exit(status: ExitCode) {
         unsafe {
             asm!("msr daifclr, #0xF");
         }
-        let status = status.into();
         let thread = Thread::current();
         let process = thread.owner().unwrap();
         let mut lock = process.inner.lock();
@@ -213,7 +212,7 @@ impl Process {
 
         for &tid in lock.threads.iter() {
             debugln!("Dequeue {:?}", tid);
-            Thread::get(tid).unwrap().terminate();
+            Thread::get(tid).unwrap().terminate(status);
             SCHED.dequeue(tid);
         }
         SCHED.debug();
@@ -234,7 +233,7 @@ impl Process {
         panic!("This code should never run");
     }
 
-    pub fn exit_thread(thread: ThreadRef) {
+    pub fn exit_thread(thread: ThreadRef, status: ExitCode) {
         let switch = {
             let switch = thread.state() == ThreadState::Running;
             let process = thread.owner().unwrap();
@@ -244,13 +243,13 @@ impl Process {
             if lock.threads.len() == 1 {
                 // TODO call Process::exit instead?
                 drop(lock);
-                Process::exit(ExitCode::from(0));
+                Process::exit(status);
                 panic!();
             }
 
             lock.threads.retain(|&e| e != tid);
 
-            thread.terminate();
+            thread.terminate(status);
             SCHED.dequeue(tid);
             debugln!("Thread {} terminated", tid);
 

kernel/src/proc/thread.rs

@@ -1,10 +1,11 @@
 use crate::arch::aarch64::exception::ExceptionFrame;
 use crate::proc::{wait::Wait, Process, ProcessRef, SCHED, THREADS};
 use crate::sync::IrqSafeSpinLock;
+use crate::util::InitOnce;
 use alloc::{rc::Rc, vec::Vec};
 use core::cell::UnsafeCell;
 use core::sync::atomic::{AtomicU32, Ordering};
-use libsys::{error::Errno, proc::Pid, signal::Signal};
+use libsys::{error::Errno, proc::{Pid, ExitCode}, signal::Signal};
 
 pub use crate::arch::platform::context::{self, Context};
 
@@ -36,6 +37,7 @@ struct ThreadInner {
 pub struct Thread {
     inner: IrqSafeSpinLock<ThreadInner>,
     exit_wait: Wait,
+    exit_status: InitOnce<ExitCode>,
     pub(super) ctx: UnsafeCell<Context>,
     signal_ctx: UnsafeCell<Context>,
     signal_pending: AtomicU32,
@@ -70,6 +72,7 @@ impl Thread {
             signal_ctx: UnsafeCell::new(Context::empty()),
             signal_pending: AtomicU32::new(0),
             exit_wait: Wait::new(),
+            exit_status: InitOnce::new(),
             inner: IrqSafeSpinLock::new(ThreadInner {
                 signal_entry: 0,
                 signal_stack: 0,
@@ -100,6 +103,7 @@ impl Thread {
             signal_ctx: UnsafeCell::new(Context::empty()),
             signal_pending: AtomicU32::new(0),
             exit_wait: Wait::new(),
+            exit_status: InitOnce::new(),
             inner: IrqSafeSpinLock::new(ThreadInner {
                 signal_entry: 0,
                 signal_stack: 0,
@@ -127,6 +131,7 @@ impl Thread {
             signal_ctx: UnsafeCell::new(Context::empty()),
             signal_pending: AtomicU32::new(0),
             exit_wait: Wait::new(),
+            exit_status: InitOnce::new(),
             inner: IrqSafeSpinLock::new(ThreadInner {
                 signal_entry: 0,
                 signal_stack: 0,
@@ -295,7 +300,7 @@ impl Thread {
         let mut lock = self.inner.lock();
         if lock.signal_entry == 0 || lock.signal_stack == 0 {
             drop(lock);
-            Process::exit_thread(self);
+            Process::exit_thread(self, ExitCode::from(-1));
             panic!();
         }
 
@@ -322,7 +327,7 @@ impl Thread {
         }
     }
 
-    pub fn terminate(&self) {
+    pub fn terminate(&self, status: ExitCode) {
         let mut lock = self.inner.lock();
         lock.state = State::Finished;
         let tid = lock.id;
@@ -331,6 +336,7 @@ impl Thread {
         if let Some(wait) = wait {
             wait.abort(tid);
         }
+        self.exit_status.init(status);
         self.exit_wait.wakeup_all();
     }
 }

kernel/src/syscall/mod.rs

@@ -10,7 +10,7 @@ use libsys::{
     abi,
     error::Errno,
     ioctl::IoctlCmd,
-    proc::Pid,
+    proc::{ExitCode, Pid},
     signal::{Signal, SignalDestination},
     stat::{FdSet, AccessMode, FileDescriptor, FileMode, OpenFlags, Stat, AT_EMPTY_PATH},
     traits::{Read, Write},
@@ -55,13 +55,16 @@ pub fn syscall(num: usize, args: &[usize]) -> Result<usize, Errno> {
     match num {
         // Process management system calls
         abi::SYS_EXIT => {
-            Process::exit(args[0] as i32);
+            Process::exit(ExitCode::from(args[0] as i32));
             unreachable!();
         }
         abi::SYS_EX_THREAD_EXIT => {
-            Process::exit_thread(Thread::current());
+            Process::exit_thread(Thread::current(), ExitCode::from(args[0] as i32));
             unreachable!();
         },
+        abi::SYS_EX_GETTID => {
+            Ok(Thread::current().id() as usize)
+        },
 
         // I/O system calls
         abi::SYS_OPENAT => {

libsys/src/abi.rs

@@ -8,6 +8,7 @@ pub const SYS_EX_CLONE: usize = 133;
 pub const SYS_EX_YIELD: usize = 134;
 pub const SYS_EX_THREAD_EXIT: usize = 135;
 pub const SYS_EX_THREAD_WAIT: usize = 136;
+pub const SYS_EX_GETTID: usize = 137;
 
 pub const SYS_EXIT: usize = 1;
 pub const SYS_READ: usize = 2;
@@ -21,3 +22,4 @@ pub const SYS_WAITPID: usize = 9;
 pub const SYS_IOCTL: usize = 10;
 pub const SYS_SELECT: usize = 11;
 pub const SYS_FACCESSAT: usize = 12;
+// pub const SYS_GETPID: usize = 13;

libsys/src/calls.rs

@@ -188,7 +188,7 @@ pub fn sys_fstatat(
 ///
 /// System call
 #[inline(always)]
-pub fn sys_fork() -> Result<Option<Pid>, Errno> {
+pub unsafe fn sys_fork() -> Result<Option<Pid>, Errno> {
     Errno::from_syscall(unsafe { syscall!(abi::SYS_FORK) }).map(|res| {
         if res != 0 {
             Some(unsafe { Pid::from_raw(res as u32) })
@@ -344,3 +344,10 @@ pub fn sys_faccessat(
         )
     })
 }
+
+#[inline(always)]
+pub fn sys_ex_gettid() -> u32 {
+    unsafe {
+        syscall!(abi::SYS_EX_GETTID) as u32
+    }
+}

libusr/src/lib.rs

@@ -16,21 +16,8 @@ pub mod os;
 pub mod sys;
 pub mod sync;
 pub mod thread;
+pub mod signal;
 
-use sys::Signal;
-
-#[inline(never)]
-pub(crate) extern "C" fn _signal_handler(arg: Signal) -> ! {
-    trace!("Entered signal handler: arg={:?}", arg);
-    match arg {
-        Signal::Interrupt | Signal::SegmentationFault =>
-            loop {},
-        _ => todo!()
-    }
-    sys::sys_ex_sigreturn();
-}
-
-static mut SIGNAL_STACK: [u8; 4096] = [0; 4096];
 
 #[link_section = ".text._start"]
 #[no_mangle]
@@ -40,11 +27,7 @@ extern "C" fn _start(_arg: usize) -> ! {
     }
 
     unsafe {
-        sys::sys_ex_signal(
+        thread::init_main();
-            _signal_handler as usize,
-            SIGNAL_STACK.as_ptr() as usize + 4096,
-        )
-        .unwrap();
     }
 
     let res = unsafe { main() };
@@ -53,8 +36,9 @@ extern "C" fn _start(_arg: usize) -> ! {
 
 #[panic_handler]
 fn panic_handler(pi: &PanicInfo) -> ! {
-    // TODO handle non-main thread panics
+    // TODO unwind to send panic argument back to parent thread
     // TODO print to stdout/stderr (if available)
-    trace!("Panic ocurred: {}", pi);
+    let thread = thread::current();
+    trace!("{:?} panicked: {:?}", thread, pi);
     sys::sys_exit(ExitCode::from(-1));
 }

libusr/src/signal.rs

@@ -0,0 +1,13 @@
+use libsys::{calls::sys_ex_sigreturn, signal::Signal};
+use crate::trace;
+
+#[inline(never)]
+pub(crate) extern "C" fn signal_handler(arg: Signal) -> ! {
+    trace!("Entered signal handler: arg={:?}", arg);
+    match arg {
+        Signal::Interrupt | Signal::SegmentationFault =>
+            loop {},
+        _ => todo!()
+    }
+    sys_ex_sigreturn();
+}

libusr/src/thread.rs

@@ -2,12 +2,14 @@ use alloc::{boxed::Box, sync::Arc, vec};
 use core::cell::UnsafeCell;
 use core::mem::MaybeUninit;
 use libsys::{
-    calls::{sys_ex_clone, sys_ex_signal, sys_ex_thread_exit, sys_ex_thread_wait},
+    calls::{sys_ex_clone, sys_ex_signal, sys_ex_thread_exit, sys_ex_thread_wait, sys_ex_gettid},
     error::Errno,
     proc::ExitCode,
 };
-
+use core::sync::atomic::{AtomicU32, Ordering};
-use crate::trace;
+use core::any::Any;
+use crate::{trace, signal};
+use core::fmt;
 
 struct NativeData<F, T>
 where
@@ -16,24 +18,67 @@ where
     T: Send + 'static,
 {
     closure: F,
-    result: Arc<UnsafeCell<MaybeUninit<T>>>,
+    result: ThreadPacket<T>,
     stack: usize,
 }
 
+#[derive(Clone)]
+pub struct Thread {
+    id: u32
+}
+
+pub type ThreadResult<T> = Result<T, Box<dyn Any + Send + Sync>>;
+pub type ThreadPacket<T> = Arc<UnsafeCell<MaybeUninit<ThreadResult<T>>>>;
+
 pub struct JoinHandle<T> {
     native: u32,
-    result: Arc<UnsafeCell<MaybeUninit<T>>>,
+    result: ThreadPacket<T>
+}
+
+impl Thread {
+    pub const fn id(&self) -> u32 {
+        self.id
+    }
+}
+
+impl fmt::Debug for Thread {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Thread").field("id", &self.id).finish_non_exhaustive()
+    }
 }
 
 impl<T> JoinHandle<T> {
-    pub fn join(self) -> Result<T, ()> {
+    pub fn join(self) -> ThreadResult<T> {
         sys_ex_thread_wait(self.native).unwrap();
-        if let Ok(result) = Arc::try_unwrap(self.result) {
+        unsafe { Arc::try_unwrap(self.result).unwrap().into_inner().assume_init() }
-            Ok(unsafe { result.into_inner().assume_init() })
-        } else {
-            Err(())
     }
 }
+
+unsafe fn init_common(signal_stack_pointer: *mut u8) {
+    let tid = sys_ex_gettid();
+    asm!("msr tpidr_el0, {}", in(reg) tid);
+
+    // thread::current() should be valid at this point
+
+    sys_ex_signal(
+        signal::signal_handler as usize,
+        signal_stack_pointer as usize
+    )
+    .unwrap();
+}
+
+pub(crate) unsafe fn init_main() {
+    static mut SIGNAL_STACK: [u8; 4096] = [0; 4096];
+    init_common(SIGNAL_STACK.as_mut_ptr().add(SIGNAL_STACK.len()))
+}
+
+pub fn current() -> Thread {
+    let mut id: u32;
+    unsafe {
+        asm!("mrs {}, tpidr_el0", out(reg) id);
+    }
+
+    Thread { id }
 }
 
 pub fn spawn<F, T>(f: F) -> JoinHandle<T>
@@ -57,18 +102,14 @@ where
             let mut signal_stack = vec![0u8; 8192];
 
             unsafe {
-                sys_ex_signal(
+                init_common(signal_stack.as_mut_ptr().add(signal_stack.len()));
-                    crate::_signal_handler as usize,
-                    signal_stack.as_mut_ptr() as usize + signal_stack.len(),
-                )
-                .unwrap();
             }
 
             let data: Box<NativeData<F, T>> = unsafe { Box::from_raw(data) };
             let res = (data.closure)();
 
             unsafe {
-                (&mut *data.result.get()).write(res);
+                (&mut *data.result.get()).write(Ok(res));
             }
 
             (data.stack, 8192)

user/src/init/main.rs

@@ -7,7 +7,7 @@ extern crate libusr;
 
 #[no_mangle]
 fn main() -> i32 {
-    let pid = libusr::sys::sys_fork().unwrap();
+    let pid = unsafe { libusr::sys::sys_fork().unwrap() };
 
     if let Some(pid) = pid {
         let mut status = 0;

user/src/shell/main.rs

@@ -27,7 +27,7 @@ fn execute(line: &str) -> Result<ExitCode, Errno> {
     let mut words = line.split(' ');
     let cmd = words.next().unwrap();
 
-    if let Some(pid) = sys_fork()? {
+    if let Some(pid) = unsafe { sys_fork()? } {
         let mut status = 0;
         sys_waitpid(pid, &mut status)?;
         Ok(ExitCode::from(status))