os/trap/
mod.rs

1mod context;
2
3use crate::config::TRAMPOLINE;
4use crate::syscall::syscall;
5use crate::task::{
6    SignalFlags, check_signals_of_current, current_add_signal, current_trap_cx,
7    current_trap_cx_user_va, current_user_token, exit_current_and_run_next,
8    suspend_current_and_run_next,
9};
10use crate::timer::{check_timer, set_next_trigger};
11use core::arch::{asm, global_asm};
12use riscv::interrupt::{Exception, Interrupt, Trap};
13use riscv::register::{mtvec::TrapMode, scause, sie, sscratch, sstatus, stval, stvec};
14
15global_asm!(include_str!("trap.S"));
16
17pub fn init() {
18    set_kernel_trap_entry();
19}
20
21fn set_kernel_trap_entry() {
22    unsafe extern "C" {
23        unsafe fn __alltraps();
24        unsafe fn __alltraps_k();
25    }
26    let __alltraps_k_va =
27        linker_symbol_addr!(__alltraps_k) - linker_symbol_addr!(__alltraps) + TRAMPOLINE;
28    unsafe {
29        stvec::write(stvec::Stvec::new(__alltraps_k_va, TrapMode::Direct));
30        sscratch::write(linker_symbol_addr!(trap_from_kernel));
31    }
32}
33
34fn set_user_trap_entry() {
35    unsafe {
36        stvec::write(stvec::Stvec::new(TRAMPOLINE as usize, TrapMode::Direct));
37    }
38}
39
40pub fn enable_timer_interrupt() {
41    unsafe {
42        sie::set_stimer();
43    }
44}
45
46fn enable_supervisor_interrupt() {
47    unsafe {
48        sstatus::set_sie();
49    }
50}
51
52fn disable_supervisor_interrupt() {
53    unsafe {
54        sstatus::clear_sie();
55    }
56}
57
58#[unsafe(no_mangle)]
59pub fn trap_handler() -> ! {
60    set_kernel_trap_entry();
61    let scause = scause::read();
62    let stval = stval::read();
63    let trap: Trap<Interrupt, Exception> = match scause.cause().try_into() {
64        Ok(trap) => trap,
65        Err(_) => panic!(
66            "Unsupported trap {:?}, stval = {:#x}!",
67            scause.cause(),
68            stval
69        ),
70    };
71    match trap {
72        Trap::Exception(Exception::UserEnvCall) => {
73            // jump to next instruction anyway
74            let mut cx = current_trap_cx();
75            cx.sepc += 4;
76
77            enable_supervisor_interrupt();
78
79            // get system call return value
80            let result = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]);
81            // cx is changed during sys_exec, so we have to call it again
82            cx = current_trap_cx();
83            cx.x[10] = result as usize;
84        }
85        Trap::Exception(Exception::StoreFault)
86        | Trap::Exception(Exception::StorePageFault)
87        | Trap::Exception(Exception::InstructionFault)
88        | Trap::Exception(Exception::InstructionPageFault)
89        | Trap::Exception(Exception::LoadFault)
90        | Trap::Exception(Exception::LoadPageFault) => {
91            /*
92            println!(
93                "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
94                scause.cause(),
95                stval,
96                current_trap_cx().sepc,
97            );
98            */
99            current_add_signal(SignalFlags::SIGSEGV);
100        }
101        Trap::Exception(Exception::IllegalInstruction) => {
102            current_add_signal(SignalFlags::SIGILL);
103        }
104        Trap::Interrupt(Interrupt::SupervisorTimer) => {
105            set_next_trigger();
106            check_timer();
107            suspend_current_and_run_next();
108        }
109        Trap::Interrupt(Interrupt::SupervisorExternal) => {
110            crate::board::irq_handler();
111        }
112        _ => {
113            panic!(
114                "Unsupported trap {:?}, stval = {:#x}!",
115                scause.cause(),
116                stval
117            );
118        }
119    }
120    // check signals
121    if let Some((errno, msg)) = check_signals_of_current() {
122        println!("[kernel] {}", msg);
123        exit_current_and_run_next(errno);
124    }
125    trap_return();
126}
127
128#[unsafe(no_mangle)]
129/// set the new addr of __restore asm function in TRAMPOLINE page,
130/// set the reg a0 = trap_cx_ptr, reg a1 = phy addr of usr page table,
131/// finally, jump to new addr of __restore asm function
132pub fn trap_return() -> ! {
133    disable_supervisor_interrupt();
134    set_user_trap_entry();
135    let trap_cx_user_va = current_trap_cx_user_va();
136    let user_satp = current_user_token();
137    unsafe extern "C" {
138        unsafe fn __alltraps();
139        unsafe fn __restore();
140    }
141    let restore_va = linker_symbol_addr!(__restore) - linker_symbol_addr!(__alltraps) + TRAMPOLINE;
142    //println!("before return");
143    unsafe {
144        asm!(
145            "fence.i",
146            "jr {restore_va}",
147            restore_va = in(reg) restore_va,
148            in("a0") trap_cx_user_va,
149            in("a1") user_satp,
150            options(noreturn)
151        );
152    }
153}
154
155#[unsafe(no_mangle)]
156pub fn trap_from_kernel(_trap_cx: &TrapContext) {
157    let scause = scause::read();
158    let stval = stval::read();
159    let trap: Trap<Interrupt, Exception> = match scause.cause().try_into() {
160        Ok(trap) => trap,
161        Err(_) => panic!(
162            "Unsupported trap from kernel: {:?}, stval = {:#x}!",
163            scause.cause(),
164            stval
165        ),
166    };
167    match trap {
168        Trap::Interrupt(Interrupt::SupervisorExternal) => {
169            crate::board::irq_handler();
170        }
171        Trap::Interrupt(Interrupt::SupervisorTimer) => {
172            set_next_trigger();
173            check_timer();
174            // do not schedule now
175        }
176        _ => {
177            panic!(
178                "Unsupported trap from kernel: {:?}, stval = {:#x}!",
179                scause.cause(),
180                stval
181            );
182        }
183    }
184}
185
186pub use context::TrapContext;
os/trap/mod.rs

os/trap/
mod.rs
