You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
55 lines
1.9 KiB
55 lines
1.9 KiB
/*
|
|
* Utility functions for trap handling in Supervisor mode.
|
|
*/
|
|
|
|
#include "riscv.h"
|
|
#include "process.h"
|
|
#include "strap.h"
|
|
#include "syscall.h"
|
|
|
|
#include "spike_interface/spike_utils.h"
|
|
|
|
//
|
|
// handling the syscalls. will call do_syscall() defined in kernel/syscall.c
|
|
//
|
|
static void handle_syscall(trapframe *tf) {
|
|
// tf->epc points to the address that our computer will jump to after the trap handling.
|
|
// for a syscall, we should return to the NEXT instruction after its handling.
|
|
// in RV64G, each instruction occupies exactly 32 bits (i.e., 4 Bytes)
|
|
tf->epc += 4;
|
|
|
|
// TODO (lab1_1): remove the panic call below, and call do_syscall (defined in
|
|
// kernel/syscall.c) to conduct real operations of the kernel side for a syscall.
|
|
// IMPORTANT: return value should be returned to user app, or else, you will encounter
|
|
// problems in later experiments!
|
|
panic( "call do_syscall to accomplish the syscall and lab1_1 here.\n" );
|
|
|
|
}
|
|
|
|
//
|
|
// kernel/smode_trap.S will pass control to smode_trap_handler, when a trap happens
|
|
// in S-mode.
|
|
//
|
|
void smode_trap_handler(void) {
|
|
// make sure we are in User mode before entering the trap handling.
|
|
// we will consider other previous case in lab1_3 (interrupt).
|
|
if ((read_csr(sstatus) & SSTATUS_SPP) != 0) panic("usertrap: not from user mode");
|
|
|
|
assert(current);
|
|
// save user process counter.
|
|
current->trapframe->epc = read_csr(sepc);
|
|
|
|
// if the cause of trap is syscall from user application.
|
|
// read_csr() and CAUSE_USER_ECALL are macros defined in kernel/riscv.h
|
|
if (read_csr(scause) == CAUSE_USER_ECALL) {
|
|
handle_syscall(current->trapframe);
|
|
} else {
|
|
sprint("smode_trap_handler(): unexpected scause %p\n", read_csr(scause));
|
|
sprint(" sepc=%p stval=%p\n", read_csr(sepc), read_csr(stval));
|
|
panic( "unexpected exception happened.\n" );
|
|
}
|
|
|
|
// continue (come back to) the execution of current process.
|
|
switch_to(current);
|
|
}
|