feat: logging: parse loglevel from fdt

kernel/src/entry.rs

@@ -1,3 +1,4 @@
+use crate::logging::set_log_level;
 use crate::plat::console::{set_console, ConsoleDevice, ConsoleDriver, CONSOLE};
 use crate::plat::lowlevel::{Hardware, LowLevel};
 use crate::plat::timer::{Timer, TimerOps};
@@ -19,7 +20,9 @@ pub fn rust_main() -> ! {
 
     N_CPUS.store(fdt.cpus().count(), Ordering::Release);
 
+    set_log_level(&fdt);
     setup_console(&fdt);
+
     info!("Kernel Started");
 
     #[cfg(test)]

kernel/src/logging.rs

@@ -2,6 +2,7 @@ use crate::plat::console::CONSOLE;
 use crate::{entry::HART_ID, plat::timer::CURRENT_TICK};
 use core::fmt::Write;
 use core::sync::atomic::Ordering;
+use fdt::Fdt;
 use log::{LevelFilter, Log, Metadata, Record};
 
 #[macro_export]
@@ -59,6 +60,35 @@ impl Log for SimpleLogger {
 pub fn init() {
     log::set_logger(&SimpleLogger).unwrap();
 
-    // TODO: get log level from boot env
+    // Always log everything before the FDT is parsed
     log::set_max_level(LevelFilter::Trace);
 }
+
+pub fn set_log_level(fdt: &Fdt) {
+    const UNKNOWN_LEVEL: usize = 5;
+
+    let log_level = fdt
+        .chosen()
+        .bootargs()
+        .map(|args| args.split_ascii_whitespace())
+        .map(|args| args.filter(|arg| arg.starts_with("loglevel=")))
+        .map(|args| args.map(|arg| arg["loglevel=".len()..].parse::<usize>()))
+        .map(|args| args.last())
+        .flatten()
+        .map(|level| level.unwrap_or(UNKNOWN_LEVEL))
+        .unwrap_or(UNKNOWN_LEVEL);
+
+    let level = match log_level {
+        0 => LevelFilter::Error,
+        1 => LevelFilter::Warn,
+        2 => LevelFilter::Info,
+        3 => LevelFilter::Debug,
+        4 => LevelFilter::Trace,
+        #[cfg(debug_assertions)]
+        _ => LevelFilter::Trace,
+        #[cfg(not(debug_assertions))]
+        _ => LevelFilter::Error,
+    };
+
+    log::set_max_level(level);
+}