Fix GDT subroutine

Also made some type changes in serial.h

arch/i386/boot.s

@@ -35,25 +35,6 @@ _start:
 	
 .size _start, . - _start
 
-
-# GDT segment register setup
-.global gdt_flush
-.extern gp
-gdt_flush:
-	lgdt (gp)    #load the GDT with the special pointer
-	mov %eax,0x10  #offset from GDT to data segment
-	mov %eax, %ds 
-	mov %eax, %es
-	mov %eax, %fs
-	mov %eax, %gs
-	mov %eax, %ss
-	
-	pushl 12(%esp)
-	push $flush2
-	ljmp *(%esp) #long jump
-flush2:
-	ret           #return to c code
-	
 .global idt_load
 .extern idtp
 idt_load:

arch/i386/gdt.s

@@ -0,0 +1,17 @@
+; This file is written with Intel ASM Syntax.
+
+[GLOBAL load_gdt]    ; Allows the C code to call gdt_flush().
+
+load_gdt:
+    mov eax, [esp+4]  ; Get the pointer to the GDT, passed as a parameter.
+    lgdt [eax]        ; Load the new GDT pointer
+
+    mov ax, 0x10      ; 0x10 is the offset in the GDT to our data segment
+    mov ds, ax        ; Load all data segment selectors
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    mov ss, ax
+    jmp 0x08:.flush   ; 0x08 is the offset to our code segment: Far jump!
+.flush:
+    ret

arch/i386/make.config

@@ -5,4 +5,5 @@ KERNEL_ARCH_LIBS=
 
 KERNEL_ARCH_OBJS= \
 $(ARCHDIR)/boot.o \
+$(ARCHDIR)/gdt.o  \
 $(ARCHDIR)/tty.o  

include/kernel/serial.h

@@ -1,4 +1,6 @@
 #pragma once
+#include <stdint.h>
+#include <stddef.h>
 
 extern void init_serial();
 

kernel/gdt.c

@@ -1,27 +1,31 @@
 #include <kernel/utils.h>
+#include <kernel/serial.h>
+#include <stddef.h>
+#include <stdint.h>
+
 
 struct gdt_item {
-	unsigned short low_limit;
-	unsigned short low_base;
-	unsigned char middle_base;
-	unsigned char access;
-	unsigned char granular;
-	unsigned char high_base;
+	uint16_t low_limit;
+	uint16_t low_base;
+	uint8_t middle_base;
+	uint8_t access;
+	uint8_t granular;
+	uint8_t high_base;
 } __attribute__((packed)); //Prevent compiler optimisation by packing
 
 struct gdt_ptr {
-	unsigned short limit;
+	uint16_t limit;
 	unsigned int base;
 } __attribute__((packed));
 
 struct gdt_item gdt[3]; //3-entry gdt
 struct gdt_ptr gp;
 
-extern void gdt_flush();
+extern void load_gdt(uint32_t);
 
-void gdt_set_gate(int num, unsigned long base,
-				unsigned long limit, unsigned char access,
-				unsigned char gran) {
+void gdt_set_gate(int num, uint32_t base,
+				uint32_t limit, uint8_t access,
+				uint8_t gran) {
 		//Implementation taken from osdever.net
 		gdt[num].low_base = (base & 0xFFFF);
 		gdt[num].middle_base = (base >> 16) & 0xFF;
@@ -38,6 +42,7 @@ void gdt_install() {
 	gp.limit = (sizeof(struct gdt_item) * 3) - 1;
 	gp.base = (unsigned int)&gdt;
 	
+	
 	gdt_set_gate(0, 0, 0, 0, 0); //NULL item
 	
 	//Code Segment - base 0, 4KiB granularity, 4GiB limit
@@ -47,5 +52,5 @@ void gdt_install() {
 	gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF);
 	
 	//Apply changes
-	gdt_flush();
+	load_gdt((uint32_t) &gp);
 }

kernel/kernel.c

@@ -11,9 +11,12 @@ int kernel_main(void) {
 	
 	// Prepare the serial console.
 	init_serial();
-	serial_print(0x3F8, "[INFO] Serial ready.");
-	// Prepare the GDT
-	//gdt_install();
+	serial_print(0x3F8, "[INFO] Serial ready.");
+	
+	// Prepare the GDT
+	serial_print(0x3F8, "[INFO] Beginning GDT subroutine.");
+	gdt_install();
+	
 	// Prepare interrupts
 	//idt_install();
 	

makefile

@@ -61,6 +61,9 @@ red.kernel: $(OBJS) $(ARCHDIR)/linker.ld
 
 $(ARCHDIR)/crtbegin.o $(ARCHDIR)/crtend.o:
 	OBJ=`$(CC) $(CFLAGS)  $(LDFLAGS) -print-file-name=$(@F)` && cp "$$OBJ" $@
+	
+$(ARCHDIR)/gdt.o:
+	nasm -f elf $(ARCHDIR)/gdt.s
 		
 .c.o:
 	$(CC) -MD -c $< -o $@ -std=gnu11 $(CFLAGS) $(CPPFLAGS)