Fix last commit for exit_in_qemu

kernel/src/arch/aarch64/cpu.rs

@@ -7,6 +7,6 @@ pub fn id() -> usize {
     0
 }
 
-pub fn exit_in_qemu(error_code: u8) -> ! {
+pub unsafe fn exit_in_qemu(error_code: u8) -> ! {
     unimplemented!()
 }

kernel/src/arch/riscv32/cpu.rs

@@ -36,6 +36,6 @@ pub fn halt() {
     unsafe { riscv::asm::wfi() }
 }
 
-pub fn exit_in_qemu(error_code: u8) -> ! {
+pub unsafe fn exit_in_qemu(error_code: u8) -> ! {
     super::sbi::shutdown()
 }

kernel/src/syscall/misc.rs

@@ -117,7 +117,9 @@ const LINUX_REBOOT_CMD_HALT: u32 = 0xcdef0123;
 pub fn sys_reboot(magic: u32, magic2: u32, cmd: u32, arg: *const u8) -> SysResult {
     // we will skip verifying magic
     if cmd == LINUX_REBOOT_CMD_HALT {
-        cpu::exit_in_qemu(1);
+        unsafe {
+            cpu::exit_in_qemu(1);
+        }
     }
     Ok(0)
 }