From ea7ebb942412c5452dbad060112b144aaf873062 Mon Sep 17 00:00:00 2001
From: Jonathan Klimt <jonathan.klimt@eonerc.rwth-aachen.de>
Date: Mon, 25 Nov 2024 22:19:33 +0100
Subject: [PATCH] Added uhyve buffered serial output for aarch64

---
 src/arch/aarch64/kernel/mod.rs    | 19 ++-----
 src/arch/aarch64/kernel/serial.rs | 94 +++++++++++++++++++++++--------
 2 files changed, 77 insertions(+), 36 deletions(-)

diff --git a/src/arch/aarch64/kernel/mod.rs b/src/arch/aarch64/kernel/mod.rs
index 723490ddb9..ae9313d675 100644
--- a/src/arch/aarch64/kernel/mod.rs
+++ b/src/arch/aarch64/kernel/mod.rs
@@ -25,7 +25,7 @@ use crate::env;
 
 const SERIAL_PORT_BAUDRATE: u32 = 115200;
 
-static COM1: SpinMutex<SerialPort> = SpinMutex::new(SerialPort::new(0x800));
+static COM1: SpinMutex<Option<SerialPort>> = SpinMutex::new(None);
 
 /// `CPU_ONLINE` is the count of CPUs that finished initialization.
 ///
@@ -81,9 +81,7 @@ pub fn args() -> Option<&'static str> {
 pub fn message_output_init() {
 	CoreLocal::install();
 
-	let mut com1 = COM1.lock();
-
-	com1.port_address = env::boot_info()
+	let com_port_address = env::boot_info()
 		.hardware_info
 		.serial_port_base
 		.map(|uartport| uartport.get())
@@ -93,18 +91,13 @@ pub fn message_output_init() {
 
 	// We can only initialize the serial port here, because VGA requires processor
 	// configuration first.
-	com1.init(SERIAL_PORT_BAUDRATE);
-}
-
-pub fn output_message_byte(byte: u8) {
-	// Output messages to the serial port.
-	COM1.lock().write_byte(byte);
+	let com = SerialPort::new(com_port_address);
+	com.init(SERIAL_PORT_BAUDRATE);
+	*COM1.lock() = Some(com);
 }
 
 pub fn output_message_buf(buf: &[u8]) {
-	for byte in buf {
-		output_message_byte(*byte);
-	}
+	COM1.lock().as_mut().unwrap().write_buf(buf);
 }
 
 /// Real Boot Processor initialization as soon as we have put the first Welcome message on the screen.
diff --git a/src/arch/aarch64/kernel/serial.rs b/src/arch/aarch64/kernel/serial.rs
index b061573564..8b29d637f7 100644
--- a/src/arch/aarch64/kernel/serial.rs
+++ b/src/arch/aarch64/kernel/serial.rs
@@ -1,36 +1,84 @@
 use core::arch::asm;
 
+use heapless::Vec;
+
+use crate::syscalls::interfaces::serial_buf_hypercall;
+
+const SERIAL_BUFFER_SIZE: usize = 256;
+
+#[allow(clippy::large_enum_variant)]
+enum SerialInner {
+	Uart(u32),
+	Uhyve(Vec<u8, SERIAL_BUFFER_SIZE>), // heapless vec to have print before allocators are initialized
+}
+
 pub struct SerialPort {
-	pub port_address: u32,
+	inner: SerialInner,
 }
 
 impl SerialPort {
-	pub const fn new(port_address: u32) -> Self {
-		Self { port_address }
+	pub fn new(port_address: u32) -> Self {
+		if crate::env::is_uhyve() {
+			Self {
+				inner: SerialInner::Uhyve(Vec::new()),
+			}
+		} else {
+			Self {
+				inner: SerialInner::Uart(port_address),
+			}
+		}
 	}
 
-	pub fn write_byte(&self, byte: u8) {
-		let port = core::ptr::with_exposed_provenance_mut::<u8>(self.port_address as usize);
-
-		// LF newline characters need to be extended to CRLF over a real serial port.
-		if byte == b'\n' {
-			unsafe {
-				asm!(
-					"strb w8, [{port}]",
-					port = in(reg) port,
-					in("x8") b'\r',
-					options(nostack),
-				);
+	pub fn write_buf(&mut self, buf: &[u8]) {
+		match &mut self.inner {
+			SerialInner::Uhyve(output_buf) => {
+				if SERIAL_BUFFER_SIZE - output_buf.len() >= buf.len() {
+					// unwrap: we checked that buf fits in output_buf
+					output_buf.extend_from_slice(buf).unwrap();
+					if buf.contains(&b'\n') {
+						serial_buf_hypercall(output_buf);
+						output_buf.clear();
+					}
+				} else {
+					serial_buf_hypercall(output_buf);
+					output_buf.clear();
+					if buf.len() >= SERIAL_BUFFER_SIZE {
+						serial_buf_hypercall(buf);
+					} else {
+						// unwrap: we checked that buf fits in output_buf
+						output_buf.extend_from_slice(buf).unwrap();
+						if buf.contains(&b'\n') {
+							serial_buf_hypercall(output_buf);
+							output_buf.clear();
+						}
+					}
+				}
 			}
-		}
+			SerialInner::Uart(port_address) => {
+				let port = core::ptr::with_exposed_provenance_mut::<u8>(*port_address as usize);
+				for &byte in buf {
+					// LF newline characters need to be extended to CRLF over a real serial port.
+					if byte == b'\n' {
+						unsafe {
+							asm!(
+								"strb w8, [{port}]",
+								port = in(reg) port,
+								in("x8") b'\r',
+								options(nostack),
+							);
+						}
+					}
 
-		unsafe {
-			asm!(
-				"strb w8, [{port}]",
-				port = in(reg) port,
-				in("x8") byte,
-				options(nostack),
-			);
+					unsafe {
+						asm!(
+							"strb w8, [{port}]",
+							port = in(reg) port,
+							in("x8") byte,
+							options(nostack),
+						);
+					}
+				}
+			}
 		}
 	}