refactor(ke): remove console abstraction

src/kern/log.zig

@@ -5,48 +5,25 @@ const pl = b.pl;
 const ke = b.ke;
 const ki = ke.private;
 
-var console_lock = ke.SpinLock.init();
+const DebugWriter = struct {
-var console_list: rtl.List = .{ .head = .{ .next = &console_list.head, .prev = &console_list.head } };
-
-/// Represents a console device.
-/// This is used as an output device.
-pub const Console = struct {
-    last_seq: u64,
-    write: WriteFn,
-    link: rtl.List.Entry,
-    pub const WriteFn = *const fn (self: *Console, data: []const u8) void;
-};
-
-/// Register a console.
-pub fn register_console(console: *Console) void {
-    const ipl = console_lock.acquire();
-    console_list.insert_tail(&console.link);
-    console_lock.release(ipl);
-
-    flush();
-}
-
-const ConsoleWriter = struct {
     interface: std.Io.Writer,
-    console: *Console,
 
-    pub fn init(console: *Console) ConsoleWriter {
+    pub fn init() DebugWriter {
         return .{
             .interface = .{
                 .vtable = &.{ .drain = drain },
                 .buffer = &.{},
                 .end = 0,
             },
-            .console = console,
         };
     }
 
-    fn drain(w: *std.Io.Writer, data: []const []const u8, _: usize) std.Io.Writer.Error!usize {
+    fn drain(_: *std.Io.Writer, data: []const []const u8, _: usize) std.Io.Writer.Error!usize {
-        const self: *ConsoleWriter = @fieldParentPtr("interface", w);
-
         var total_written: usize = 0;
         for (data) |slice| {
-            self.console.write(self.console, slice);
+            for (slice) |byte| {
+                pl.impl.debug_write(byte);
+            }
             total_written += slice.len;
         }
 
@@ -56,32 +33,6 @@ const ConsoleWriter = struct {
 
 var ringbuffer = ki.log_ring.RingBuffer(14, 5).init();
 
-fn flush() void {
-    var buf: [512]u8 = undefined;
-
-    // Note: we trylock here because if the lock is already held, that means
-    // someone else is already flushing the logs.
-    if (console_lock.try_acquire()) |ipl| {
-        var it = console_list.iterator();
-
-        while (it.next()) : (it.advance()) {
-            const console: *Console = @fieldParentPtr("link", it.get());
-            var writer = ConsoleWriter.init(console);
-
-            while (true) {
-                const info = ringbuffer.read(console.last_seq, &buf) catch break;
-
-                writer.interface.print("[{:>5}.{:06}] ", .{ info.timestamp / std.time.ns_per_s, info.timestamp / std.time.ns_per_us }) catch break;
-                console.write(console, buf[0..info.length]);
-
-                console.last_seq = info.sequence + 1;
-            }
-        }
-
-        console_lock.release(ipl);
-    }
-}
-
 pub fn log(
     comptime level: std.log.Level,
     comptime scope: @EnumLiteral(),
@@ -91,17 +42,25 @@ pub fn log(
     _ = level;
     _ = scope;
 
-    var discarder: std.Io.Writer.Discarding = .init(&.{});
+    // Calculate the length required.
-    discarder.writer.print(fmt ++ "\n", args) catch return;
+    const required_len = std.fmt.count(fmt ++ "\n", args);
 
-    var res = ringbuffer.reserve(discarder.fullCount()) catch return;
+    // Reserve space in the ring buffer.
+    var res = ringbuffer.reserve(required_len) catch return;
 
     res.info.timestamp = ke.time.read_time_nano();
-    res.info.length = @truncate(discarder.fullCount());
+    res.info.length = @truncate(required_len);
 
+    // Format the log message into the reserved buffer.
     res.buf = std.fmt.bufPrint(res.buf, fmt ++ "\n", args) catch return;
 
     ringbuffer.publish(res);
 
-    flush();
+    // TODO: for now, we print to the platform's debug output immediately.
+    // In the future, we should instead set an event that would get triggered in Ex,
+    // which would consume the ringbuffer from multiple consoles in a separate thread.
+    var writer = DebugWriter.init();
+
+    writer.interface.print("[{:>5}.{:06}] ", .{ res.info.timestamp / std.time.ns_per_s, res.info.timestamp / std.time.ns_per_us }) catch return;
+    _ = writer.interface.writeAll(res.buf[0..res.info.length]) catch return;
 }

src/platform/um/impl.zig

@@ -39,8 +39,8 @@ pub threadlocal var my_cpu: *ke.Cpu = undefined;
 
 pub fn devices_init() void {}
 
-fn debug_write(_: *ke.Console, buf: []const u8) void {
+pub fn debug_write(char: u8) void {
-    _ = linux.write(1, buf.ptr, @intCast(buf.len));
+    _ = linux.write(linux.STDERR_FILENO, @ptrCast(&char), 1);
 }
 
 pub const arm_timer = timer.arm_timer;
@@ -60,12 +60,6 @@ const bootstrap_offsets = [1]usize{0};
 
 pub var cpu_offsets: []usize = undefined;
 
-var early_console: ke.Console = .{
-    .write = debug_write,
-    .last_seq = 0,
-    .link = undefined,
-};
-
 pub fn early_init() linksection(b.init) void {
     // Ensure we can use per-cpu data.
     cpu_offsets = @constCast(&bootstrap_offsets);
@@ -106,8 +100,6 @@ pub fn early_init() linksection(b.init) void {
     b.kernel_heap_base = heap_base;
 
     std.log.info("um: kernel heap lives at {X}", .{heap_base});
-
-    ke.log.register_console(&early_console);
 }
 
 fn sigusr1_handler(_: posix.SIG, _: *const posix.siginfo_t, _: ?*anyopaque) callconv(.c) void {