get rid of magic exit codes in `tests/integration/test_kernel/src/lib.rs`

[wiktorwieclaw]

https://os.phil-opp.com/testing/#using-the-exit-device

[0xf4lc0n]

As mentioned in the article:

it causes QEMU to exit with exit status (value << 1) | 1. So when we write 0 to the port, QEMU will exit with exit status (0 << 1) | 1 = 1, and when we write 1 to the port, it will exit with exit status (1 << 1) | 1 = 3

So the exit code returned by QEMU is (value << 1) | 1, where value is a value passed to port.write().

cosmos/tests/integration/test_kernel/src/lib.rs

Lines 11 to 27 in 7cbc0f6

	#[derive(Debug, Clone, Copy, PartialEq, Eq)]
	#[repr(u32)]
	pub enum QemuExitCode {
	Success = 0x10,
	Failed = 0x11,
	}
	pub fn exit_qemu(exit_code: QemuExitCode) -> ! {
	use kernel::x86_64::instructions::port::Port;
	unsafe {
	let mut port = Port::new(0xf4);
	port.write(exit_code as u32);
	}
	unreachable!()
	}

In our case, we pass the values 0x10 and 0x11 to port.write() - these values are assigned to QemuExitCode variants.

To summarize in the following match statement:

• 33 corresponds to QemuExitCode::Success
• 35 corresponds to QemuExitCode::Failed
  

  cosmos/tests/integration/runner.rs

  Lines 59 to 63 in 7cbc0f6

  	match status.code() {
  	Some(33) => {}
  	Some(35) => panic!("Test failed"),
  	other => panic!("Test failed with unexpected exit code {other:?}"),
  	}