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