1 files changed, 111 insertions, 2 deletions

diff --git a/na/drivers/uart.cc b/na/drivers/uart.cc
index 264ec6a..467b496 100644
--- a/na/drivers/uart.cc
+++ b/na/drivers/uart.cc
@@ -2,9 +2,18 @@
 /* Copyright (C) 2026 Richard Qin */
 
 /*
- * uart.cc — 16550a UART driver (early console)
+ * uart.cc — 16550a UART driver + console registry
  *
- * Implements the early UART output mapping required by panic and kernel_main.
+ * Two roles:
+ *   1. Early console: early_putc() for pre-init output (panic, kprintf)
+ *   2. Runtime console: struct console registered with register_console().
+ *      klog/printk route through console_write_all() → uart_console_write().
+ *
+ * The console registry is a simple linked list of struct console.
+ * console_write_all() iterates the list and calls each console's write().
+ * If no console is registered, it falls back to early_putc().
+ *
+ * Reference: Linux kernel/printk/printk.c, drivers/tty/serial/8250/
  */
 
 #include <lume/console.h>
@@ -13,11 +22,19 @@
 #include <lume/addr.h>
 #include <arch/config.h>
 
+/* ================================================================== */
+/*  UART state                                                        */
+/* ================================================================== */
+
 static uint64 g_uart_pa = 0;
 static uint64 g_uart_size = 0;
 static bool g_runtime_mapping_ready = false;
 static bool g_mmu_enabled = false;
 
+/* ================================================================== */
+/*  Early console (Phase 1)                                           */
+/* ================================================================== */
+
 extern "C" void console_set_mmu_enabled() {
     g_mmu_enabled = true;
 }
@@ -70,3 +87,95 @@ void console_init() {
 void console_use_runtime_mapping() {
     g_runtime_mapping_ready = true;
 }
+
+/* ================================================================== */
+/*  Console registry (Phase 2) — linked list of struct console        */
+/* ================================================================== */
+
+static list_node g_console_list;
+static bool g_console_list_init = false;
+
+void register_console(console* con)
+{
+    if (!con) return;
+
+    if (!g_console_list_init) {
+        g_console_list.init();
+        g_console_list_init = true;
+    }
+
+    con->flags |= CON_ENABLED;
+    con->list.init();
+
+    /* Insert at tail */
+    list_add_tail(&con->list, &g_console_list);
+}
+
+void unregister_console(console* con)
+{
+    if (!con) return;
+
+    list_del_init(&con->list);
+    con->flags &= ~CON_ENABLED;
+}
+
+bool console_drivers_registered()
+{
+    if (!g_console_list_init) return false;
+    return !list_empty(&g_console_list);
+}
+
+void console_write_all(const char* s, int count)
+{
+    if (g_console_list_init && !list_empty(&g_console_list)) {
+        list_node* pos;
+        list_for_each(pos, &g_console_list) {
+            auto* con = container_of(pos, console, list);
+            if ((con->flags & CON_ENABLED) && con->write) {
+                con->write(con, s, static_cast<unsigned int>(count));
+            }
+        }
+    } else {
+        /* Fallback: direct early_putc (pre-registration) */
+        for (int i = 0; i < count; i++) {
+            early_putc(s[i]);
+        }
+    }
+}
+
+/* ================================================================== */
+/*  UART console driver                                               */
+/* ================================================================== */
+
+static void uart_console_write(console* /*con*/, const char* s, unsigned int count)
+{
+    for (unsigned int i = 0; i < count; i++) {
+        if (s[i] == '\n') {
+            early_putc('\r');
+        }
+        early_putc(s[i]);
+    }
+}
+
+/*
+ * uart_console must be initialized at RUNTIME, not with static
+ * aggregate initializers. Reason: KASLR self-relocation processes
+ * .rela.dyn entries for simple pointer variables, but may not cover
+ * function pointer fields inside static aggregate initializers.
+ * A static `{ .write = uart_console_write }` would store the
+ * pre-relocation address, causing a crash when called.
+ */
+static console uart_console;
+
+void uart_register_console()
+{
+    uart_console.name  = "ttyS";
+    uart_console.write = uart_console_write;
+    uart_console.setup = nullptr;
+    uart_console.flags = CON_ENABLED | CON_BOOT;
+    uart_console.index = 0;
+    uart_console.data  = nullptr;
+    uart_console.list.init();
+    register_console(&uart_console);
+}
+