os/trap/
mod.rs

1mod context;
2
3use crate::config::{TRAMPOLINE, TRAP_CONTEXT};
4use crate::syscall::syscall;
5use crate::task::{
6    SignalFlags, check_signals_error_of_current, current_add_signal, current_trap_cx,
7    current_user_token, exit_current_and_run_next, handle_signals, suspend_current_and_run_next,
8};
9use crate::timer::set_next_trigger;
10use core::arch::{asm, global_asm};
11use riscv::interrupt::{Exception, Interrupt, Trap};
12use riscv::register::{mtvec::TrapMode, scause, sie, stval, stvec};
13
14global_asm!(include_str!("trap.S"));
15
16pub fn init() {
17    set_kernel_trap_entry();
18}
19
20fn set_kernel_trap_entry() {
21    unsafe {
22        stvec::write(stvec::Stvec::new(
23            linker_symbol_addr!(trap_from_kernel),
24            TrapMode::Direct,
25        ));
26    }
27}
28
29fn set_user_trap_entry() {
30    unsafe {
31        stvec::write(stvec::Stvec::new(TRAMPOLINE as usize, TrapMode::Direct));
32    }
33}
34
35pub fn enable_timer_interrupt() {
36    unsafe {
37        sie::set_stimer();
38    }
39}
40
41#[unsafe(no_mangle)]
42/// handle an interrupt, exception, or system call from user space
43pub fn trap_handler() -> ! {
44    set_kernel_trap_entry();
45    let scause = scause::read();
46    let stval = stval::read();
47    let trap: Trap<Interrupt, Exception> = match scause.cause().try_into() {
48        Ok(trap) => trap,
49        Err(_) => panic!(
50            "Unsupported trap {:?}, stval = {:#x}!",
51            scause.cause(),
52            stval
53        ),
54    };
55    match trap {
56        Trap::Exception(Exception::UserEnvCall) => {
57            // jump to next instruction anyway
58            let mut cx = current_trap_cx();
59            cx.sepc += 4;
60            // get system call return value
61            let result = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]);
62            // cx is changed during sys_exec, so we have to call it again
63            cx = current_trap_cx();
64            cx.x[10] = result as usize;
65        }
66        Trap::Exception(Exception::StoreFault)
67        | Trap::Exception(Exception::StorePageFault)
68        | Trap::Exception(Exception::InstructionFault)
69        | Trap::Exception(Exception::InstructionPageFault)
70        | Trap::Exception(Exception::LoadFault)
71        | Trap::Exception(Exception::LoadPageFault) => {
72            /*
73            println!(
74                "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
75                scause.cause(),
76                stval,
77                current_trap_cx().sepc,
78            );
79            */
80            current_add_signal(SignalFlags::SIGSEGV);
81        }
82        Trap::Exception(Exception::IllegalInstruction) => {
83            current_add_signal(SignalFlags::SIGILL);
84        }
85        Trap::Interrupt(Interrupt::SupervisorTimer) => {
86            set_next_trigger();
87            suspend_current_and_run_next();
88        }
89        _ => {
90            panic!(
91                "Unsupported trap {:?}, stval = {:#x}!",
92                scause.cause(),
93                stval
94            );
95        }
96    }
97    // handle signals (handle the sent signal)
98    //println!("[K] trap_handler:: handle_signals");
99    handle_signals();
100
101    // check error signals (if error then exit)
102    if let Some((errno, msg)) = check_signals_error_of_current() {
103        println!("[kernel] {}", msg);
104        exit_current_and_run_next(errno);
105    }
106    trap_return();
107}
108
109#[unsafe(no_mangle)]
110/// set the new addr of __restore asm function in TRAMPOLINE page,
111/// set the reg a0 = trap_cx_ptr, reg a1 = phy addr of usr page table,
112/// finally, jump to new addr of __restore asm function
113pub fn trap_return() -> ! {
114    set_user_trap_entry();
115    let trap_cx_ptr = TRAP_CONTEXT;
116    let user_satp = current_user_token();
117    unsafe extern "C" {
118        unsafe fn __alltraps();
119        unsafe fn __restore();
120    }
121    let restore_va = linker_symbol_addr!(__restore) - linker_symbol_addr!(__alltraps) + TRAMPOLINE;
122    unsafe {
123        asm!(
124            "fence.i",
125            "jr {restore_va}",
126            restore_va = in(reg) restore_va,
127            in("a0") trap_cx_ptr,
128            in("a1") user_satp,
129            options(noreturn)
130        );
131    }
132}
133
134#[unsafe(no_mangle)]
135/// Unimplement: traps/interrupts/exceptions from kernel mode
136/// Todo: Chapter 9: I/O device
137pub fn trap_from_kernel() -> ! {
138    use riscv::register::sepc;
139    let scause = scause::read();
140    let stval = stval::read();
141    let trap: Trap<Interrupt, Exception> = match scause.cause().try_into() {
142        Ok(trap) => trap,
143        Err(_) => panic!(
144            "Unsupported trap from kernel: {:?}, stval = {:#x}, sepc = {:#x}!",
145            scause.cause(),
146            stval,
147            sepc::read()
148        ),
149    };
150    println!("stval = {:#x}, sepc = {:#x}", stval, sepc::read());
151    panic!("a trap {:?} from kernel!", trap);
152}
153
154pub use context::TrapContext;
os/trap/mod.rs

os/trap/
mod.rs
