Implemented serial driver

kernel/src/entry.s

@@ -17,11 +17,12 @@ multiboot:
 	dd FLAGS
 	dd CHECK
 
-; Initialize stack
 section .bss
 align 16
+
+; Initialize stack
 stack_bottom:
-resb 16384	; 16kB
+	resb 16384	; 16kB
 stack_top:
 
 ; Entry point
@@ -29,9 +30,8 @@ section .text
 global _start
 extern kmain
 _start:
-	mov esp, stack_top
-
-	call kmain	; Call kernel main
+	mov esp, stack_top	; Setup stack
+	call kmain		; Call kernel main
 
 	; Hang if kernel returns
 	cli

kernel/src/kernel.c

@@ -1,13 +1,25 @@
 #include <kernel.h>
+#include <serial.h>
 #include <tty.h>
 
 #define _hlt()	while (1) __asm__ volatile ("cli; hlt");
 
 __noreturn
 void kmain(void) {
+	serial_init(COM1);
+	serial_print(COM1, "kern.\n\n");
+	while (1) {
+		char c = serial_recv(COM1);
+		serial_send(COM1, c);
+		if (c == '\r') {
+			serial_send(COM1, '\n');
+			break;
+		}
+	}
+
 	tty_init();
 	tty_puts("Hello, World!\n");
 
-	_hlt();
+	panic("kmain() reached end!");
 }
 

kernel/src/serial.c

@@ -0,0 +1,53 @@
+#include <kernel.h>
+#include <system.h>
+#include <serial.h>
+
+int serial_init(int dev) {
+	outb(dev + 1, 0x00);	// Disable serial interrupts
+	outb(dev + 3, 0x80);	// Enable DLAB (set baud rate divisor)
+	outb(dev + 0, 0x03);	// Set divisor to 3 (low byte) 38400 baud
+	outb(dev + 1, 0x00);	//                  (high byte)
+	outb(dev + 3, 0x03);	// 8 bits, no parity, one stop bit
+	outb(dev + 2, 0xC7);	// Enable FIFO, clear them, with 14 byte threshold
+	outb(dev + 4, 0x0B);	// IRQs enabled, RTS/DSR set
+	outb(dev + 4, 0x1E);	// Set in loopback mode, test the serial chip
+	outb(dev + 0, 0xAE);	// Test serial chip (send byte 0xAE and check if it returns)
+	
+	if (inb(dev + 0) != 0xAE) return 1;
+	outb(dev + 4, 0x0F);	// non-loopback, IRQs enabled, OUT#1 and OUT#2 bits enabled
+	
+	return 0;
+}
+
+int serial_txem(int dev) { 
+	return inb(dev + 5) & 0x20;
+}
+
+void serial_send(int dev, char data) {
+	while (serial_txem(dev) == 0);
+	outb(dev, data);
+}
+
+int serial_rcvd(int dev) {
+	return inb(dev + 5) & 1;
+}
+
+char serial_recv(int dev) {
+	while (serial_rcvd(dev) == 0);
+	return inb(dev);
+}
+
+void serial_write(int dev, char* buf, size_t len) {
+	for (size_t i = 0; i < len; i++) {
+		if (buf[i] == '\n') serial_send(dev, '\r');
+		serial_send(dev, buf[i]);
+	}
+}
+
+void serial_print(int dev, char* s) {
+	size_t len = 0;
+	char* p = s;
+	while (*p++ != '\0') len++;
+	serial_write(dev, s, len);
+}
+

kernel/src/system.c

@@ -0,0 +1,39 @@
+#include <kernel.h>
+
+void cpuid(uint32_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx) {
+	__asm__ volatile ("cpuid"
+		: "=a"(*eax), "=b"(*ebx), "=c"(*ecx), "=d"(*edx)
+		: "a"(*eax)
+		: "memory");
+}
+
+uint8_t inb(uint16_t port) {
+	uint8_t r;
+	__asm__ volatile ("inb %1, %0" : "=a"(r) : "dN"(port));
+	return r;
+}
+
+void outb(uint16_t port, uint8_t data) {
+	__asm__ volatile ("outb %1, %0" :: "dN"(port), "a"(data));
+}
+
+uint16_t inw(uint16_t port) {
+	uint16_t r;
+	__asm__ volatile ("inw %1, %0" : "=a"(r) : "dN"(port));
+	return r;
+}
+
+void outw(uint16_t port, uint16_t data) {
+	__asm__ volatile ("outw %1, %0" :: "dN"(port), "a"(data));
+}
+
+uint32_t inl(uint16_t port) {
+	uint32_t r;
+	__asm__ volatile ("inl %1, %0" : "=a"(r) : "dN"(port));
+	return r;
+}
+
+void outl(uint16_t port, uint32_t data) {
+	__asm__ volatile ("outl %1, %0" :: "dN"(port), "a"(data));
+}
+