Module os::trap

Trap handling functionality

For rCore, we have a single trap entry point, namely __alltraps. At initialization in init(), we set the stvec CSR to point to it.

All traps go through __alltraps, which is defined in trap.S. The assembly language code does just enough work restore the kernel space context, ensuring that Rust code safely runs, and transfers control to trap_handler().

It then calls different functionality based on what exactly the exception was. For example, timer interrupts trigger task preemption, and syscalls go to syscall().

Modules

context

Implementation of TrapContext

Structs

TrapContext

trap context structure containing sstatus, sepc and registers

Functions

enable_timer_interrupt

enable timer interrupt in sie CSR

init

initialize CSR stvec as the entry of __alltraps

set_kernel_trap_entry

set_user_trap_entry

trap_from_kernel

Unimplement: traps/interrupts/exceptions from kernel mode Todo: Chapter 9: I/O device

trap_handler

handle an interrupt, exception, or system call from user space

trap_return

set the new addr of __restore asm function in TRAMPOLINE page, set the reg a0 = trap_cx_ptr, reg a1 = phy addr of usr page table, finally, jump to new addr of __restore asm function