userlib: Add print! and println! support

Implement console access and provide the the print! and println!
macros. Use the new macros to print a message in the panic handler.

Signed-off-by: Joerg Roedel <[email protected]>

user/lib/src/console.rs

@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright (c) 2024 SUSE LLC
+//
+// Author: Joerg Roedel <[email protected]>
+
+use crate::SpinLock;
+use core::fmt;
+use syscall::write_console;
+
+#[derive(Debug, Default)]
+struct ConsoleWriter {}
+
+impl ConsoleWriter {
+    const fn new() -> Self {
+        Self {}
+    }
+}
+
+impl fmt::Write for ConsoleWriter {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        // Ignore any errors from console writing.
+        let _ = write_console(s.as_bytes());
+        Ok(())
+    }
+}
+
+static CONSOLE_WRITER: SpinLock<ConsoleWriter> = SpinLock::new(ConsoleWriter::new());
+
+#[doc(hidden)]
+pub fn console_print(args: fmt::Arguments<'_>) {
+    use core::fmt::Write;
+    CONSOLE_WRITER.lock().write_fmt(args).unwrap()
+}
+
+#[macro_export]
+macro_rules! print {
+        ($($arg:tt)*) => (console_print(format_args!($($arg)*)))
+}
+
+#[macro_export]
+macro_rules! println {
+    () => (print!("\n"));
+    ($($arg:tt)*) => (print!("{}\n", format_args!($($arg)*)));
+}

user/lib/src/lib.rs

@@ -6,8 +6,10 @@
 
 #![no_std]
 
+pub mod console;
 pub mod locking;
 
+pub use console::*;
 use core::panic::PanicInfo;
 pub use locking::*;
 pub use syscall::*;
@@ -27,6 +29,7 @@ macro_rules! declare_main {
 }
 
 #[panic_handler]
-fn panic(_info: &PanicInfo<'_>) -> ! {
+fn panic(info: &PanicInfo<'_>) -> ! {
+    println!("Panic: {}", info);
     exit(!0);
 }