Implement Serial Console messaging.

Intended to be used for debugging, but it's useful.

include/kernel/serial.h

@@ -0,0 +1,19 @@
+#pragma once
+
+extern void init_serial();
+
+extern void serial_set_baud_rate(uint16_t, uint16_t);
+
+extern void serial_configure_line(uint16_t);
+
+extern void serial_configure_buffers(uint16_t);
+
+extern void serial_write(uint16_t, const char);
+
+extern void serial_configure_modem(uint16_t);
+
+extern int serial_check_tqueue(uint16_t);
+
+extern void serial_print(uint16_t, const char*);
+
+extern void serial_printf(const char*, ...);

include/kernel/tty.h

@@ -25,8 +25,5 @@ void puts(const char*);
 void handleControlSequence(struct csi_sequence);
 void set_cursor(int, int);
 void term_scroll(bool);
-void int_to_ascii(int, char*);
-void int_to_hex(int, char*);
-void empty_string(char*);
 
 bool isDigit(char c);

include/kernel/utils.h

@@ -12,4 +12,10 @@ void outb(unsigned short, unsigned char);
 
 void memcpy(void*, void*, size_t);
 
-void memset(void*, int, size_t);
+void memset(void*, int, size_t);
+
+void int_to_ascii(int, char*);
+
+void int_to_hex(int, char*);
+
+void empty_string(char*);

kernel/gdt.c

@@ -30,13 +30,13 @@ void gdt_set_gate(int num, unsigned long base,
 		gdt[num].low_limit = (limit & 0xFFFF);
 		gdt[num].granular = ((limit >> 16) & 0x0F);
 		
-		gdt[num].granular != (gran & 0xF0);
+		gdt[num].granular = (gran & 0xF0);
 		gdt[num].access = access;
 }
 
 void gdt_install() {
 	gp.limit = (sizeof(struct gdt_item) * 3) - 1;
-	gp.base = &gdt;
+	gp.base = (unsigned int)&gdt;
 	
 	gdt_set_gate(0, 0, 0, 0, 0); //NULL item
 	

kernel/kernel.c

@@ -2,15 +2,20 @@
 //#include <stdio.h>
 
 #include <kernel/tty.h>
-#include <kernel/gdt.h>
+#include <kernel/gdt.h>
+#include <kernel/serial.h>
 
-int kernel_main(void) {
-	//Prepare the GDT
-	gdt_install();
-	//Prepare interrupts
+int kernel_main(void) {
+	// Prepare the screen, and blank it out.
+	screen_initialize();
+	
+	// Prepare the serial console.
+	init_serial();
+	serial_print(0x3F8, "[INFO] Serial ready.");
+	// Prepare the GDT
+	//gdt_install();
+	// Prepare interrupts
 	//idt_install();
-	//Prepare the screen, and blank it out.
-	screen_initialize();
 	
 	//Print a copyright message.
 	term_writes("(c)");

kernel/serial.c

@@ -0,0 +1,184 @@
+#include <kernel/utils.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stddef.h>
+
+#define SERIAL_DATA_PORT(base)           (base)
+#define SERIAL_FIFO_COMMAND_PORT(base)   (base + 2)
+#define SERIAL_LINE_COMMAND_PORT(base)   (base + 3)
+#define SERIAL_MODEM_COMMAND_PORT(base)  (base + 4)
+#define SERIAL_LINE_STATUS_PORT(base)    (base + 5)
+#define SERIAL_COM1_BASE                 0x3F8
+
+#define SERIAL_LINE_ENABLE_DLAB          0x80
+
+/**   serial_set_baud_rate:
+  *   Sets the speed that data is sent via the serial port.
+  *   The default speed is 115200 bits/s.
+  *   The argument given is the divisor of the number.
+  *   Hence, the new speed becomes (115200/divisor) bits/s.
+  *
+  *   @param com      The COM port to configure.
+  *   @param divisor  The new divisor for the baud rate.
+  */
+
+void serial_set_baud_rate(uint16_t com, uint16_t divisor) {
+	outb(SERIAL_LINE_COMMAND_PORT(com),
+		 SERIAL_LINE_ENABLE_DLAB);
+		 
+	outb(SERIAL_DATA_PORT(com),
+		 (divisor >> 8) & 0x00FF);
+	
+	outb(SERIAL_DATA_PORT(com),
+		 divisor & 0x00FF);
+		
+}
+
+/**   serial_configure_line:
+  *   Sets a specific data byteset in the Serial hardware.
+  *   Required for expected operation.
+  *
+  *   @param com  The COM port to configure.
+  */
+
+void serial_configure_line(uint16_t com) {
+   /* Bit:        | 7 | 6 | 5 4 3 | 2 | 1 0 |
+    * Content:    | d | b | parity| s | dl  |
+	* Value:      | 0 | 0 | 0 0 0 | 0 | 1 1 | = 0x03
+	*/
+	 
+	outb(SERIAL_LINE_COMMAND_PORT(com), 0x0B);
+}
+
+/**   serial_configure_buffers:
+  *   Enables FIFO (First In First Out) on the Serial line.
+  *   It clears both the receive and transmit queues.
+  *   It uses a 14 byte wide queue.
+  *
+  *  @param com   The COM port to configure.
+  */
+  
+void serial_configure_buffers(uint16_t com) {
+   /* Bit:        | 7 6 | 5  | 4 |  3  |  2  |  1  | 0 |
+	* Content:    | 1v1 | bs | r | dma | clt | clr | e |
+	* Value:      | 1 1 | 0  | 0 |  0  |  1  |  1  | 1 | = 0xC7
+	*/
+	
+	outb(SERIAL_FIFO_COMMAND_PORT(com), 0xC7);
+}
+
+/**   serial_configure_modem
+  *   @param com  The COM port to configure.
+  */
+  
+void serial_configure_modem(uint16_t com) {
+   /* Bit:        | 7 | 6 | 5  | 4  |  3  |  2  |  1  |  0  |
+    * Content:    | r | r | af | lb | ao2 | ao1 | rts | dtr |
+	* Value:      | 0 | 0 | 0  | 0  |  0  |  0  |  1  |  1  | = 0x03
+	*/
+	
+	outb(SERIAL_MODEM_COMMAND_PORT(com), 0x3);
+}
+
+/**   serial_check_tqueue:
+  *   Checks whether the Transmit FIFO Queue is empty on the given port.
+  *
+  *   @param com  The COM port to check.
+  *   @return  0  If the queue is not empty.
+  *            1  If the queue is empty.
+  */
+  
+int serial_check_tqueue(uint16_t com) {
+	return inb(SERIAL_LINE_STATUS_PORT(com)) & 0x20;
+}
+
+/**   serial_write:
+  *   Prints a single character to the serial port.
+  *   Does nothing fancy.
+  *   @param com  The COM port to write to.
+  *   @param data The character to write.
+  */
+
+void serial_write(uint16_t com, const char chr) {
+	//Hang until we have access to the COM port.
+	while(serial_check_tqueue(com) == 0);
+	outb(com, chr);
+}
+
+/**   serial_print:
+  *   Prints a string to the serial port.
+  *   Does not support ANSI codes, or color.
+  *
+  *   @param com  The COM port to write to.
+  *   @param data The string to write.
+  */
+ 
+void serial_print(uint16_t com, const char* data) {
+	for(size_t i = 0; i < strlen(data); i++) {
+		serial_write(com, data[i]);
+	}
+}
+
+/**   serial_printf:
+  *   A printf-style function for the serial port.
+  *   
+  *   @param format  The base string - used to substitute the succeding values.
+  *   @param ...     The substitutions.
+  */
+  
+void serial_printf(uint16_t com, const char* format, ...) {
+	uint32_t storage; //To hold temporary variables
+	char stringstore[10] = {0}; //To convert ints to strings.
+	va_list list;
+	va_start(list, format);
+	
+	for(size_t i = 0; i < strlen(format); i++) {
+		//Check for the format specifier
+		if(format[i] == '%') {
+			//Check for the other specs
+			if(format[i+1] == 'd') {
+				
+				storage = va_arg(list, int);
+				int_to_ascii(storage, stringstore);
+				serial_print(com, stringstore);
+				empty_string(stringstore);
+				i += 2;
+				
+			} else if(format[i+1] == 'x') {
+				
+				storage = va_arg(list, int);
+				int_to_hex(storage, stringstore);
+				serial_print(com, stringstore);
+				empty_string(stringstore);
+				i += 2;
+				
+			} else if(format[i+1] == 's') {
+				
+				serial_print(com, va_arg(list, char*));
+				i += 2;
+				
+			} else {
+				serial_print(com, "ERROR: Attempting to parse unknown format string.");
+				return;
+			}
+		} else {
+			serial_write(com, format[i]);
+			i++;
+		}
+	}
+	va_end(list); //Free the list
+}
+
+void init_serial() {
+	// Disable interrupts
+	outb(SERIAL_COM1_BASE + 1, 0x00);
+	
+	// Set baud rate divisor.
+	serial_set_baud_rate(SERIAL_COM1_BASE, 3);
+	// 8 bits, no parity, one stop bit.
+	serial_configure_line(SERIAL_COM1_BASE);
+	// Enable FIFO and clear buffers.
+	serial_configure_buffers(SERIAL_COM1_BASE);
+	// Enable IRQs, RTS/DSR set.
+	serial_configure_modem(SERIAL_COM1_BASE);
+}

kernel/utils.c

@@ -1,4 +1,7 @@
-
+#include <kernel/utils.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
 #include <stddef.h>
 
 size_t strlen(const char* string) {
@@ -33,3 +36,69 @@ void memset(void* src, int chr, size_t n) {
 		*ptr++ = (unsigned char) chr;
 	}
 }
+
+void int_to_ascii(int num, char* string) {
+	size_t i = 0; //Counter.
+	//TODO: Convert this to a for-loop?
+	int32_t calc = 0;
+	bool negative = false;
+	
+	if(num == 0) {
+		string[0] = '0';
+		string[1] = '\0';
+		return;
+	}
+	
+	if(num < 0) {
+		negative = true;
+		num = -num;
+	}
+	
+	while(num != 0) {
+		calc = num % 10;
+		num = num / 10;
+		calc += 48;
+		
+		string[i] = calc;
+		i++;
+	}
+	
+	if(negative) {
+		string[i] = '-';
+		i++;
+	}
+	
+	for(size_t j = 0; j < i/2; j++) {
+		calc = string[j];
+		string[j] = string[i-j-1];
+		string[j-i-1] = calc;
+	}
+}
+
+void int_to_hex(int num, char* string) {
+	empty_string(string);
+	
+	uint8_t i = 8;
+	uint8_t temp = 0;
+	
+	while(i != 0) {
+		i--;
+		temp = num & 0xF;
+		num = num >> 4;
+		
+		if(temp >= 10) {
+			temp += 7;
+		}
+		
+		temp += 48;
+		string[i] = temp;
+	}
+}
+
+void empty_string(char* string) {
+	size_t len = strlen(string);
+	
+	for(size_t i = 0; i < len + 1; i++) {
+		string[i] = '\0';
+	}
+}

makefile

@@ -30,6 +30,7 @@ LIBS:=$(LIBS) $(KERNEL_ARCH_LIBS)
 KERNEL_OBJS=           \
 $(KERNEL_ARCH_OBJS)    \
 kernel/utils.o         \
+kernel/serial.o        \
 kernel/gdt.o           \
 kernel/idt.o           \
 kernel/kernel.o