Red Bear OS — microkernel OS in Rust, based on Redox

Derivative of Redox OS (https://www.redox-os.org) adding:
- AMD GPU driver (amdgpu) via LinuxKPI compat layer
- ext4 filesystem support (ext4d scheme daemon)
- ACPI fixes for AMD bare metal (x2APIC, DMAR, IVRS, MCFG)
- Custom branding (hostname, os-release, boot identity)

Build system is full upstream Redox with RBOS overlay in local/.
Patches for kernel, base, and relibc are symlinked from local/patches/
and protected from make clean/distclean. Custom recipes live in
local/recipes/ with symlinks into the recipes/ search path.

Build:  make all CONFIG_NAME=redbear-full
Sync:   ./local/scripts/sync-upstream.sh

local/recipes/system/udev-shim/source/src/main.rs

@@ -0,0 +1,82 @@
+mod device_db;
+mod scheme;
+
+use std::env;
+use std::process;
+
+use log::{error, info, LevelFilter, Metadata, Record};
+use redox_scheme::{SignalBehavior, Socket};
+
+use scheme::UdevScheme;
+
+struct StderrLogger {
+    level: LevelFilter,
+}
+
+impl log::Log for StderrLogger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        metadata.level() <= self.level
+    }
+    fn log(&self, record: &Record) {
+        if self.enabled(record.metadata()) {
+            eprintln!("[{}] {}", record.level(), record.args());
+        }
+    }
+    fn flush(&self) {}
+}
+
+fn run() -> Result<(), String> {
+    let mut scheme = UdevScheme::new();
+
+    match scheme.scan_pci_devices() {
+        Ok(n) => info!("udev-shim: enumerated {} PCI device(s)", n),
+        Err(e) => error!("udev-shim: PCI scan failed: {}", e),
+    }
+
+    let socket =
+        Socket::create("udev").map_err(|e| format!("failed to register udev scheme: {}", e))?;
+    info!("udev-shim: registered scheme:udev");
+
+    loop {
+        let request = match socket.next_request(SignalBehavior::Restart) {
+            Ok(Some(r)) => r,
+            Ok(None) => {
+                info!("udev-shim: scheme unmounted, exiting");
+                break;
+            }
+            Err(e) => {
+                error!("udev-shim: failed to read scheme request: {}", e);
+                continue;
+            }
+        };
+
+        let response = match request.handle_scheme_block_mut(&mut scheme) {
+            Ok(r) => r,
+            Err(_req) => {
+                error!("udev-shim: failed to handle request");
+                continue;
+            }
+        };
+
+        if let Err(e) = socket.write_response(response, SignalBehavior::Restart) {
+            error!("udev-shim: failed to write response: {}", e);
+        }
+    }
+
+    Ok(())
+}
+
+fn main() {
+    let log_level = match env::var("UDEV_SHIM_LOG").as_deref() {
+        Ok("debug") => LevelFilter::Debug,
+        Ok("trace") => LevelFilter::Trace,
+        _ => LevelFilter::Info,
+    };
+    let _ = log::set_boxed_logger(Box::new(StderrLogger { level: log_level }));
+    log::set_max_level(log_level);
+
+    if let Err(e) = run() {
+        error!("udev-shim: fatal error: {}", e);
+        process::exit(1);
+    }
+}