feat: userspace faults

src/arch/x86_64/interrupts/exceptions.rs

@@ -1,7 +1,10 @@
 use core::arch::asm;
 
 use super::idt::{self, InterruptFrame, InterruptStackFrame, stub_err, stub_no_err};
-use crate::{hcf, println};
+use crate::{
+    hcf, println,
+    task::tcb::{ExitReason, Fault},
+};
 
 stub_no_err!(stub_divide_error, 0);
 stub_no_err!(stub_debug, 1);
@@ -22,45 +25,32 @@ stub_no_err!(stub_simd_floating_point, 19);
 stub_no_err!(stub_user_test_exit, 0x80);
 
 pub(super) fn handle(frame: &mut InterruptFrame) {
-    match frame.vector as u8 {
-        0 => fatal_exception("DIVIDE ERROR", &frame.stack_frame, None),
-        1 => fatal_exception("DEBUG EXCEPTION", &frame.stack_frame, None),
-        2 => fatal_exception("NON-MASKABLE INTERRUPT", &frame.stack_frame, None),
-        3 => report_exception("BREAKPOINT", &frame.stack_frame, None),
-        6 => fatal_exception("INVALID OPCODE", &frame.stack_frame, None),
-        7 => fatal_exception("DEVICE NOT AVAILABLE", &frame.stack_frame, None),
-        8 => fatal_exception("DOUBLE FAULT", &frame.stack_frame, Some(frame.error_code)),
-        10 => fatal_exception("INVALID TSS", &frame.stack_frame, Some(frame.error_code)),
-        11 => fatal_exception("SEGMENT NOT PRESENT", &frame.stack_frame, Some(frame.error_code)),
-        12 => fatal_exception("STACK-SEGMENT FAULT", &frame.stack_frame, Some(frame.error_code)),
-        13 => fatal_exception(
-            "GENERAL PROTECTION FAULT",
-            &frame.stack_frame,
-            Some(frame.error_code),
-        ),
-        14 => {
-            report_exception("PAGE FAULT", &frame.stack_frame, Some(frame.error_code));
-            println!("Faulting address: {:#X}", read_cr2());
-            print_page_fault_error(frame.error_code);
-            hcf();
-        }
-        16 => fatal_exception("X87 FLOATING-POINT EXCEPTION", &frame.stack_frame, None),
-        17 => fatal_exception("ALIGNMENT CHECK", &frame.stack_frame, Some(frame.error_code)),
-        18 => fatal_exception("MACHINE CHECK", &frame.stack_frame, None),
-        19 => fatal_exception("SIMD FLOATING-POINT EXCEPTION", &frame.stack_frame, None),
-        0x80 => {
-            if frame.stack_frame.code_segment & 0b11 != 3 {
-                panic!("user_test_exit_handler called from kernel");
-            }
+    let is_user = frame.stack_frame.code_segment & 0b11 == 3;
 
-            println!("User test exit");
-            hcf();
-        }
-        _ => {
-            println!("Unhandled exception vector: {:#X}", frame.vector);
-            hcf();
+    if !is_user {
+        match frame.vector as u8 {
+            8 => fatal_exception("DOUBLE FAULT", &frame.stack_frame, Some(frame.error_code)),
+            14 => {
+                report_exception("PAGE FAULT", &frame.stack_frame, Some(frame.error_code));
+                println!("Faulting address: {:#X}", read_cr2());
+                print_page_fault_error(frame.error_code);
+                hcf();
+            }
+            _ => fatal_exception("KERNEL FAULT", &frame.stack_frame, Some(frame.error_code)),
         }
     }
+
+    let fault = match frame.vector as u8 {
+        // Page fault, GPF, Stack/Segment faults -> SegmentationFault
+        11 | 12 | 13 | 14 => Fault::SegmentationFault,
+        // Invalid Opcode -> IllegalInstruction
+        6 => Fault::IllegalInstruction,
+        // Divide by zero, Alignment check, SIMD/x87 -> Abort
+        0 | 16 | 17 | 19 => Fault::Abort,
+        _ => Fault::Abort,
+    };
+
+    crate::task::scheduler::exit_current(ExitReason::Fault(fault));
 }
 
 pub(super) fn install(idt: &mut idt::Idt) {

src/syscall/mod.rs

@@ -2,6 +2,8 @@ mod table;
 
 use table::*;
 
+use crate::task::tcb::{ExitReason, Fault};
+
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 #[repr(u64)]
 pub enum Status {
@@ -31,7 +33,7 @@ pub enum SyscallNumber {
 }
 
 impl TryFrom<u64> for SyscallNumber {
-    type Error = Status;
+    type Error = ();
     fn try_from(val: u64) -> Result<Self, Self::Error> {
         match val {
             1 => Ok(Self::Yield),
@@ -45,14 +47,17 @@ impl TryFrom<u64> for SyscallNumber {
             9 => Ok(Self::Map),
             10 => Ok(Self::Unmap),
             11 => Ok(Self::TaskCreate),
-            _ => Err(Status::InvalidArgument),
+            _ => Err(()),
         }
     }
 }
 
 pub fn handle(num: u64, arg0: u64, arg1: u64, arg2: u64, arg3: u64, arg4: u64, _arg5: u64) -> u64 {
     let result = (|| -> Result<(), Status> {
-        let syscall = SyscallNumber::try_from(num)?;
+        let syscall = SyscallNumber::try_from(num).unwrap_or_else(|_| {
+            crate::task::scheduler::exit_current(ExitReason::Fault(Fault::BadSystemCall))
+        });
+
         match syscall {
             SyscallNumber::Yield => sys_yield(),
             SyscallNumber::Exit => sys_exit(arg0 as usize),

src/syscall/table.rs

@@ -6,7 +6,7 @@ use crate::{
     println,
     task::{
         scheduler::TaskId,
-        tcb::{BlockReason, Handle, KernelObject, MAX_MSG_SIZE, Message, Rights},
+        tcb::{BlockReason, ExitReason, Handle, KernelObject, MAX_MSG_SIZE, Message, Rights},
     },
 };
 
@@ -18,7 +18,7 @@ pub fn sys_yield() -> Result<(), Status> {
 }
 
 pub fn sys_exit(exit_code: usize) -> ! {
-    crate::task::scheduler::exit_current(exit_code);
+    crate::task::scheduler::exit_current(ExitReason::Exited(exit_code));
 }
 
 pub fn sys_write(fd: usize, buf_ptr: usize, len: usize, out_ptr: usize) -> Result<(), Status> {

src/task/scheduler.rs

@@ -344,7 +344,7 @@ pub fn yield_current() {
     crate::arch::restore_interrupts(interrupt_state);
 }
 
-pub fn exit_current(exit_code: usize) -> ! {
+pub fn exit_current(reason: ExitReason) -> ! {
     crate::arch::disable_interrupts();
 
     let switch = {
@@ -356,7 +356,7 @@ pub fn exit_current(exit_code: usize) -> ! {
         };
 
         let current = scheduler.tasks[current_id.0].as_mut().unwrap();
-        current.state = ThreadState::Dead(ExitReason::Exited(exit_code));
+        current.state = ThreadState::Dead(reason);
 
         scheduler.tasks[next_id.0].as_mut().unwrap().state = ThreadState::Running;
         scheduler.current = Some(next_id);

userspace/omega3/src/main.rs

@@ -40,9 +40,9 @@ pub extern "C" fn _start() -> ! {
     map_stack(client_as, STACK_TOP, STACK_PAGES);
     let _ = sys_task_create(client_as, client_entry, STACK_TOP).unwrap();
 
-    let ptr = 0xDEAD_BEEF as *mut u32;
+    // call a bogus system call
     unsafe {
-        core::ptr::write_volatile(&mut *ptr, 0xDEAD_BEEF);
+        core::arch::asm!("syscall", in("rax") 134);
     }
 
     sys_exit(0);