Add serial output to test framework

For printing error messages.

Author: phil-opp

Cargo.lock

@@ -17,5 +17,6 @@ fn run_test_binary(bin_name: &str) {
     cmd.arg("--bin").arg(bin_name);
     cmd.arg("--target").arg(" x86_64-example-kernel.json");
     cmd.arg("-Zbuild-std=core");
+    cmd.arg("-Zbuild-std-features=compiler-builtins-mem");
     assert!(cmd.status().unwrap().success());
 }

tests/default_settings.rs

@@ -7,3 +7,4 @@ edition = "2018"
 [dependencies]
 bootloader = { path = "../../.." }
 x86_64 = "0.12.2"
+uart_16550 = "0.2.10"

tests/test_kernels/default_settings/Cargo.toml

@@ -19,3 +19,9 @@ pub fn exit_qemu(exit_code: QemuExitCode) -> ! {
         nop();
     }
 }
+
+pub fn serial() -> uart_16550::SerialPort {
+    let mut port = unsafe { uart_16550::SerialPort::new(0x3F8) };
+    port.init();
+    port
+}