fixes issue with exceptions (im dumb)

kernel/arch/boot.s

@@ -1,3 +1,7 @@
+; Here is our entry point to the kernel
+; A very simple assembly file
+; We set up some parameters and then pass the execution to our kmain
+
 global loader 				; entry symbol for ELF
 extern kmain
 
@@ -6,12 +10,17 @@ FLAGS		equ 0x3
 CHECKSUM	equ -(MAGIC_NUMBER + FLAGS)	; calculate the checksum
 KERNEL_STACK_SIZE equ 4096
 
+; The multiboot section is a semi requirement for grub
+; All this is doing is placing the required magic number, flags, and the checksum into the file first
+; This lets grub know if this is a valid multiboot kernel or not
 section .multiboot
 align 4 				; code must be 4 byte aligned
 	dd MAGIC_NUMBER
 	dd FLAGS
 	dd CHECKSUM
 
+; Here we're setting up the stack
+; Giving us 4096 bytes (resb)
 section .bss
 align 4
 kernel_stack:
@@ -19,10 +28,12 @@ kernel_stack:
 
 section .text
 loader:
-	mov esp, kernel_stack + KERNEL_STACK_SIZE
+	mov esp, kernel_stack + KERNEL_STACK_SIZE ; move the top of the stack into esp
 
-	call kmain
+	call kmain ; pass execution over to our kmain function, where all of the real stuff is done
 
-	;cli
+	; Should the system exit, we clear the interrupt flag
+	; and do an infinite loop of nothing
+	cli 
 loop:	hlt
 	jmp loop 

kernel/arch/gdt/gdt_entry.c

@@ -6,6 +6,25 @@
 #include <kernel/_kernel.h>
 #endif
 
+/**
+ * What is this file?
+ *
+ * Well, to properly set up a lot of the system, we need something called a GDT
+ * or, a Global Descriptor Table.
+ *
+ * This table, establishes a few things.
+ *
+ * Mainly it sets 4 segments,
+ * 	A kernel code segment, with RING 0 permissions
+ * 	A kernel data segment, with RING 0 permissions
+ * 	A user code segment, with RING 3 permissions
+ * 	A user data segment, with RING 3 permissions
+ *
+ * This allows for future userspace to properly segment code and data,
+ * anything in userspace shouldn't have access to hardware like the kernel does
+ * So by passing through this GDT, we can dish out authority to access certain data, functions,
+ * etc, by going through the CPU permission system (RING 0 - 3)
+ */
 
 uint64_t gdt[GDT_SIZE];
 
@@ -26,12 +45,14 @@ uint64_t create_descriptor(uint32_t base, uint32_t limit, uint16_t flag)
 	return descriptor;
 }
 
+#ifdef __TESTING__
 void dump_gdt(void)
 {
 	for (int i = 0; i < GDT_SIZE; i++) {
 		printf("GDT_ENTRY %d: %4 | %2\n", i, gdt[i], gdt[i]);
 	}
 }
+#endif
 
 
 void gdt_init(void)

kernel/arch/idt/idt.c

@@ -6,6 +6,7 @@
 #endif
 #include <kernel/x86/idt.h>
 #include <kernel/x86/pic.h>
+#include <kernel/x86/io.h>
 
 __attribute__((aligned(0x10)))
 static idt_entry_t idt[256];
@@ -20,7 +21,13 @@ void exception_handler(unsigned int i)
 	kerror("EXCEPTION");
 	printf("Exeption: %u\n", i);
 #endif
-	__asm__ volatile ("cli; hlt"); // hangs the computer
+	if (i <= 31)
+		__asm__ volatile ("cli; hlt"); // hangs the computer
+
+	if (i == PIC_PIT) {
+		printf("Sending EOI instruction to PIT\n");
+		PIC_sendEOI(0);
+	}
 }
 
 void idt_set_descriptor(uint8_t vector, void *isr, uint8_t flags)
@@ -52,7 +59,8 @@ void idt_init(void)
 	__asm__ volatile("lidt %0" : : "m"(idtr)); // load the new IDT
 						  
 	PIC_remap(0x20, 0x28);
-	IRQ_set_mask(0xfd); // unmask IRQ1
+	pic_disable(); // mask everything
+	IRQ_clear_mask(1);
 
 	__asm__ volatile("sti"); // set the interrupt flag
 #ifdef __TESTING__

kernel/arch/idt/idt_src.s

@@ -3,6 +3,7 @@ extern exception_handler
 %macro isr_err_stub 1
 isr_stub_%+%1:
 	pushad
+	cld
 	push dword %1
 	call exception_handler
 	popad
@@ -12,6 +13,7 @@ isr_stub_%+%1:
 %macro isr_no_err_stub 1
 isr_stub_%+%1:
 	pushad
+	cld
 	push dword %1
 	call exception_handler
 	popad

kernel/arch/link.ld

@@ -1,25 +1,41 @@
-ENTRY(loader)
+/**
+ * This is the linker file.
+ *
+ * This file tells the linker (ld) how we want to arrange the code into the output file.
+ */
+ENTRY(loader) /* This is the first entry point, defined in boot.s */
 
 SECTIONS
 {
-	. = 1M;
+	/* 
+	 * This is telling the linker that anything after here should be loaded at 2M onwards
+	 * The reason for 2M, is that we want to give room for the BIOS, (and UEFI), 2M is generally regarded as a safe spot
+	 * to place the memory offset 
+	 * */
+	. = 2M; 
 
-	.text BLOCK(4K) : ALIGN(4K)
+	/*
+	 *  BLOCK is an alias for ALIGN, we're telling the linker that we want each section to be aligned at 4K
+	 */
+	.text BLOCK(4K) : ALIGN(4K) /* The first section we want is the text section, this is where most code is */
 	{
-		*(.multiboot)
-		*(.text)
+		*(.multiboot) /* Multiboot needs to be early in the file, required by grub */
+		*(.text) /* The text section */
 	}
 
+	/* R/O data */
 	.rodata BLOCK(4K) : ALIGN(4K)
 	{
 		*(.rodata)
 	}
 
+	/* Data */
 	.data BLOCK(4K) : ALIGN(4K)
 	{
 		*(.data)
 	}
 
+	/* BSS */
 	.bss BLOCK(4K) : ALIGN(4K)
 	{
 		*(COMMON)

kernel/arch/pic/pic.c

@@ -1,5 +1,6 @@
 #ifdef __TESTING__
 #include <kernel/_kernel.h>
+#include <stdio.h>
 #endif
 #include <kernel/x86/io.h>
 #include <kernel/x86/pic.h>
@@ -71,6 +72,8 @@ void IRQ_set_mask(uint8_t IRQline) // Masked IRQlines are ignored by the PIC, ma
 		IRQline -= 8;
 	}
 	
+	printf("%x %x\n", port, IRQline);
+
 	value = inb(port) | (1 << IRQline);
 	outb(port, value);
 }

kernel/include/kernel/x86/pic.h

@@ -31,6 +31,23 @@
 #define PIC_READ_ISR	0x0b	/** OCW3 irq service next CMD read **/
 
 
+#define PIC_PIT 32
+#define PIC_KEYB 33
+#define PIC_CASCADE 34 // never raised 
+#define PIC_COM2 35
+#define PIC_COM1 36
+#define PIC_LPT2 37
+#define PIC_FLOPPY_DISK 38
+#define PIC_LPT1 39 // usually spurious interrupt
+#define PIC_CMOS 40
+#define PIC_FREE_ONE 41
+#define PIC_FREE_TWO 42
+#define PIC_FREE_THREE 43
+#define PIC_PS2_MOUSE 44
+#define PIC_FPU 45
+#define PIC_ATA_ONE 46
+#define PIC_ATA_TWO 47
+
 void PIC_sendEOI(uint8_t irq);
 
 /**

kernel/kmain.c

@@ -22,4 +22,23 @@ void kmain(void)
 	serial_initialize();
 #endif
 
+
+/**
+ * The computer is now hanging on INTERRUPT 32,
+ * this is good because that means the PIC is working, its the timer interrupt, except... the PIT is masked off...
+ * we need to now implement the ISR routines in exception_handler,
+ * first i want to implement all of the code for the basic exceptions..
+ * then i want to setup the PIC triggers
+ *
+ * now for keyboard stuff, i believe i need to start looking into setting up a ps/2 driver before the interrupts will even start arriving..
+ *
+ */
+
+	printf("Entering loop...\n");
+	while (1) {
+		
+		continue;
+	}
+	printf("Exiting loop...\n");
+
 }