1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129

mod context;

use crate::config::{TRAMPOLINE, TRAP_CONTEXT};
use crate::syscall::syscall;
use crate::task::{
    check_signals_error_of_current, current_add_signal, current_trap_cx, current_user_token,
    exit_current_and_run_next, suspend_current_and_run_next, SignalFlags, handle_signals,
};
use crate::timer::set_next_trigger;
use core::arch::{asm, global_asm};
use riscv::register::{
    mtvec::TrapMode,
    scause::{self, Exception, Interrupt, Trap},
    sie, stval, stvec,
};

global_asm!(include_str!("trap.S"));

pub fn init() {
    set_kernel_trap_entry();
}

fn set_kernel_trap_entry() {
    unsafe {
        stvec::write(trap_from_kernel as usize, TrapMode::Direct);
    }
}

fn set_user_trap_entry() {
    unsafe {
        stvec::write(TRAMPOLINE as usize, TrapMode::Direct);
    }
}

pub fn enable_timer_interrupt() {
    unsafe {
        sie::set_stimer();
    }
}

#[no_mangle]
pub fn trap_handler() -> ! {
    set_kernel_trap_entry();
    let scause = scause::read();
    let stval = stval::read();
    match scause.cause() {
        Trap::Exception(Exception::UserEnvCall) => {
            // jump to next instruction anyway
            let mut cx = current_trap_cx();
            cx.sepc += 4;
            // get system call return value
            let result = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]);
            // cx is changed during sys_exec, so we have to call it again
            cx = current_trap_cx();
            cx.x[10] = result as usize;
        }
        Trap::Exception(Exception::StoreFault)
        | Trap::Exception(Exception::StorePageFault)
        | Trap::Exception(Exception::InstructionFault)
        | Trap::Exception(Exception::InstructionPageFault)
        | Trap::Exception(Exception::LoadFault)
        | Trap::Exception(Exception::LoadPageFault) => {
            /*
            println!(
                "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
                scause.cause(),
                stval,
                current_trap_cx().sepc,
            );
            */
            current_add_signal(SignalFlags::SIGSEGV);
        }
        Trap::Exception(Exception::IllegalInstruction) => {
            current_add_signal(SignalFlags::SIGILL);
        }
        Trap::Interrupt(Interrupt::SupervisorTimer) => {
            set_next_trigger();
            suspend_current_and_run_next();
        }
        _ => {
            panic!(
                "Unsupported trap {:?}, stval = {:#x}!",
                scause.cause(),
                stval
            );
        }
    }
    // handle signals (handle the sent signal)
    //println!("[K] trap_handler:: handle_signals");
    handle_signals();

    // check error signals (if error then exit)
    if let Some((errno, msg)) = check_signals_error_of_current() {
        println!("[kernel] {}", msg);
        exit_current_and_run_next(errno);
    }
    trap_return();
}

#[no_mangle]
pub fn trap_return() -> ! {
    set_user_trap_entry();
    let trap_cx_ptr = TRAP_CONTEXT;
    let user_satp = current_user_token();
    extern "C" {
        fn __alltraps();
        fn __restore();
    }
    let restore_va = __restore as usize - __alltraps as usize + TRAMPOLINE;
    unsafe {
        asm!(
            "fence.i",
            "jr {restore_va}",
            restore_va = in(reg) restore_va,
            in("a0") trap_cx_ptr,
            in("a1") user_satp,
            options(noreturn)
        );
    }
}

#[no_mangle]
pub fn trap_from_kernel() -> ! {
    use riscv::register::sepc;
    println!("stval = {:#x}, sepc = {:#x}", stval::read(), sepc::read());
    panic!("a trap {:?} from kernel!", scause::read().cause());
}

pub use context::TrapContext;