feat: add interrupt-driven PS/2 keyboard input

Co-authored-by: aider (openrouter/moonshotai/kimi-k2.6) <aider@aider.chat>

platform_kernel.c

@@ -36,6 +36,10 @@ static inline uint8_t inb(uint16_t port) {
     return ret;
 }
 
+static inline void io_wait(void) {
+    __asm__ volatile ("outb %0, %1" : : "a"((uint8_t)0), "Nd"((uint16_t)0x80));
+}
+
 static void serial_init(void) {
     outb(0x3F8 + 1, 0x00);
     outb(0x3F8 + 3, 0x80);
@@ -46,6 +50,83 @@ static void serial_init(void) {
     outb(0x3F8 + 4, 0x0B);
 }
 
+static uint64_t idt_entries[256][2];
+
+static void idt_set_gate(int vector, uint64_t offset, uint16_t selector, uint8_t type_attr) {
+    uint64_t low = (offset & 0xFFFFULL) |
+                   ((uint64_t)selector << 16) |
+                   ((uint64_t)(type_attr & 0xFF) << 40) |
+                   ((offset & 0xFFFF0000ULL) << 32);
+    uint64_t high = offset >> 32;
+    idt_entries[vector][0] = low;
+    idt_entries[vector][1] = high;
+}
+
+static struct {
+    uint16_t limit;
+    uint64_t base;
+} __attribute__((packed)) idt_ptr;
+
+static void pic_remap(void) {
+    uint8_t a1 = inb(0x21);
+    uint8_t a2 = inb(0xA1);
+
+    outb(0x20, 0x11);
+    io_wait();
+    outb(0xA0, 0x11);
+    io_wait();
+    outb(0x21, 0x20);
+    io_wait();
+    outb(0xA1, 0x28);
+    io_wait();
+    outb(0x21, 0x04);
+    io_wait();
+    outb(0xA1, 0x02);
+    io_wait();
+    outb(0x21, 0x01);
+    io_wait();
+    outb(0xA1, 0x01);
+    io_wait();
+
+    outb(0x21, a1);
+    outb(0xA1, a2);
+}
+
+static void pic_unmask_keyboard(void) {
+    uint8_t mask = inb(0x21);
+    mask &= ~(1 << 1);
+    outb(0x21, mask);
+}
+
+#define KEYBUF_SIZE 256
+static volatile char keybuf[KEYBUF_SIZE];
+static volatile int keybuf_head = 0;
+static volatile int keybuf_tail = 0;
+
+static const char scancode_map[] = {
+    0,  27, '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '-', '=', '\b',
+    '\t', 'q', 'w', 'e', 'r', 't', 'y', 'u', 'i', 'o', 'p', '[', ']', '\n',
+    0, 'a', 's', 'd', 'f', 'g', 'h', 'j', 'k', 'l', ';', '\'', '`',
+    0, '\\', 'z', 'x', 'c', 'v', 'b', 'n', 'm', ',', '.', '/', 0,
+    '*', 0, ' ', 0
+};
+
+void keyboard_handler(void) {
+    uint8_t scancode = inb(0x60);
+    if (scancode < sizeof(scancode_map)) {
+        char c = scancode_map[scancode];
+        if (c) {
+            int next = (keybuf_tail + 1) % KEYBUF_SIZE;
+            if (next != keybuf_head) {
+                keybuf[keybuf_tail] = c;
+                keybuf_tail = next;
+                forth_putchar(c);
+            }
+        }
+    }
+    outb(0x20, 0x20);
+}
+
 void forth_putchar(char c) {
     vga_putchar(c);
     while ((inb(0x3F8 + 5) & 0x20) == 0) { }
@@ -53,10 +134,12 @@ void forth_putchar(char c) {
 }
 
 int forth_getchar(void) {
-    if ((inb(0x3F8 + 5) & 1) == 0) {
-        return FORTH_EOF;
+    while (keybuf_head == keybuf_tail) {
+        __asm__ volatile ("pause");
     }
-    return inb(0x3F8);
+    char c = keybuf[keybuf_head];
+    keybuf_head = (keybuf_head + 1) % KEYBUF_SIZE;
+    return (int)c;
 }
 
 void forth_fflush(void) {
@@ -136,7 +219,20 @@ void forth_printf(const char* fmt, ...) {
 }
 
 void kernel_main(void) {
+    extern void isr_keyboard(void);
+
     serial_init();
+
+    idt_set_gate(0x21, (uint64_t)isr_keyboard, 0x08, 0x8E);
+    idt_ptr.limit = sizeof(idt_entries) - 1;
+    idt_ptr.base = (uint64_t)idt_entries;
+    __asm__ volatile ("lidt %0" : : "m"(idt_ptr));
+
+    pic_remap();
+    pic_unmask_keyboard();
+
+    __asm__ volatile ("sti");
+
     forth_printf("Kernel started\n");
     forth_run();
     forth_panic();