os/trap/
mod.rs

1//! Trap handling functionality
2//!
3//! For rCore, we have a single trap entry point, namely `__alltraps`. At
4//! initialization in [`init()`], we set the `stvec` CSR to point to it.
5//!
6//! All traps go through `__alltraps`, which is defined in `trap.S`. The
7//! assembly language code does just enough work restore the kernel space
8//! context, ensuring that Rust code safely runs, and transfers control to
9//! [`trap_handler()`].
10//!
11//! It then calls different functionality based on what exactly the exception
12//! was. For example, timer interrupts trigger task preemption, and syscalls go
13//! to [`syscall()`].
14
15mod context;
16
17use crate::syscall::syscall;
18use crate::task::{exit_current_and_run_next, suspend_current_and_run_next};
19use crate::timer::set_next_trigger;
20use core::arch::global_asm;
21use riscv::interrupt::{Exception, Interrupt, Trap};
22use riscv::register::{mtvec::TrapMode, scause, sie, stval, stvec};
23
24global_asm!(include_str!("trap.S"));
25
26/// initialize CSR `stvec` as the entry of `__alltraps`
27pub fn init() {
28    unsafe extern "C" {
29        safe fn __alltraps();
30    }
31    unsafe {
32        stvec::write(stvec::Stvec::new(
33            linker_symbol_addr!(__alltraps),
34            TrapMode::Direct,
35        ));
36    }
37}
38
39/// timer interrupt enabled
40pub fn enable_timer_interrupt() {
41    unsafe {
42        sie::set_stimer();
43    }
44}
45
46#[unsafe(no_mangle)]
47/// handle an interrupt, exception, or system call from user space
48pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
49    let scause = scause::read(); // get trap cause
50    let stval = stval::read(); // get extra value
51    let trap: Trap<Interrupt, Exception> = match scause.cause().try_into() {
52        Ok(trap) => trap,
53        Err(_) => panic!(
54            "Unsupported trap {:?}, stval = {:#x}!",
55            scause.cause(),
56            stval
57        ),
58    };
59    match trap {
60        Trap::Exception(Exception::UserEnvCall) => {
61            cx.sepc += 4;
62            cx.x[10] = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]) as usize;
63        }
64        Trap::Exception(Exception::StoreFault) | Trap::Exception(Exception::StorePageFault) => {
65            println!(
66                "[kernel] PageFault in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
67                stval, cx.sepc
68            );
69            exit_current_and_run_next();
70        }
71        Trap::Exception(Exception::IllegalInstruction) => {
72            println!("[kernel] IllegalInstruction in application, kernel killed it.");
73            exit_current_and_run_next();
74        }
75        Trap::Interrupt(Interrupt::SupervisorTimer) => {
76            set_next_trigger();
77            suspend_current_and_run_next();
78        }
79        _ => {
80            panic!("Unsupported trap {:?}, stval = {:#x}!", trap, stval);
81        }
82    }
83    cx
84}
85
86pub use context::TrapContext;
os/trap/mod.rs

os/trap/
mod.rs
