Added tons of documentation

Still need to document a lot of functions, but I cleaned up and
explained a lot of the code via comments.

include/idt.h

@@ -1,5 +1,11 @@
+/* IDT.h
+*   Interrupt Descriptor Table
+*   
+*   IDT related structures, globals and functions
+*/
 #ifndef IDT_H
 #define IDT_H
+
 #include <stdint.h>
 
 typedef struct InterruptDescriptor_s {

include/interrupt_handlers.h

@@ -1,3 +1,8 @@
+/*  interrupt_handlers.h
+*   Interrupt Handlers
+*   
+*   Functions and structs for the C side of handling interrupts.
+*/
 #ifndef INTERRUPTHANDLERS_H
 #define INTERRUPTHANDLERS_H
 #include <stdint.h>

include/kio.h

@@ -1,7 +1,7 @@
 /*  kio.h
  *  Kernel I/O
  *
- *  Handles any in/output
+ *  Responsible for kernel related in/output, such as VGA and serial
  */
 #ifndef KIO_H
 #define KIO_H

include/kmultiboot.h

@@ -1,3 +1,8 @@
+/*  kmultiboot.h
+*   Kernel Multiboot
+*   
+*   Data needed for multiboot compatibility.
+*/
 #ifndef KMULTIBOOT_H
 #define KMULTIBOOT_H
 

include/kttools.h

@@ -1,3 +1,8 @@
+/*  kttools.h
+*   Kernel Type Tools
+*   
+*   Library for converting types and transcribing data.
+*/
 #ifndef KTTOOLS_H
 #define KTTOOLS_H
 #include <stdint.h>

include/tss.h

@@ -1,8 +1,7 @@
-/*  kdtables.h
-*   Kernel Discriptor Tables
-*
-*   Contains GDT, IDT, and any relevant functions and structs pertaining to them
+/*  tss.h
+*   Task State Segment
 *
+*   Structure definitions for the TSS
 */
 #ifndef TSS_H
 #define TSS_H

src/gdt.s

@@ -52,6 +52,8 @@ section .gdt_sect
         dw 0
         gdt_end:
     gdtr:
+        ;size of the gdt
         dw gdt_end - gdt - 1
+        ;location of the gdt
         dd gdt    
 

src/idt.c

@@ -2,15 +2,18 @@
 #include "interrupt_handlers.h"
 
 void setup_idt() {
+    //IDT is pretty big. Lets make it 256 IDT entries large, 00-FF.
     idtr.size = (sizeof(InterruptDescriptor_t) * 256) - 1;
     idtr.IDT = &idt_start;
     write_descriptors();
+    //load_idt is in assembly, go find it in alloc_idt.s
     load_idt();
 }
 
 void write_descriptors() {
     
     for(int i = 0; i <= num_interrupts; i++) {
+        // Grab the location of the ISR we're working with and the location of the IDT entry to write it to.
         uint32_t current_isr = (uint32_t)isr_ptrs[i];
         InterruptDescriptor_t* current_idt_entry = idtr.IDT + i;
         

src/idt_asm.s

@@ -1,6 +1,10 @@
+;idt_asm.s
+;Memory allocation for the IDT and any assembly-required functions for it to work.
+
 %define NUM_INTERRUPTS 255
 global idtr, idt_start, num_interrupts, load_idt
 
+;Stub function that just loads the IDT.
 section .text
     load_idt:
        lidt [idtr]
@@ -10,10 +14,13 @@ section .idtr align=8
     num_interrupts:
         db NUM_INTERRUPTS
     idtr:
-        ;IDTR looks like the size (minus 1) and then the pointer to the start of it.
+        ;Word: size of idtr
         dw 0
+        ;DWord: location of IDTR
         dd 0
+
 section .idt nobits
+    ;Reserve some space for the IDT. Actually defined later in C.
     idt_start:
         resb (NUM_INTERRUPTS+1) * 8 
 

src/interrupts.s

@@ -21,23 +21,28 @@ isr_common:
     add esp,8 ;deallocate the error code from the stack before heading out
     iret
 
+;Macro for the isr: 1 argument for the interrupt ID
 %macro ISR_ENTRY 1
+;isr_int#
 isr_%1:
     cli
+    ;Small table of interrupts that don't have an error code associated, so we push a dummy for stack consistency.
     %if %1 = 8 || %1 = 10 || %1 = 11 || %1 = 12 || %1 = 13 || %1 = 14 || %1 = 17 || %1 = 21
     %else
         push dword 0
     %endif
-    push dword %1       ; saving our interrupt so C knows
+    ;This is us pushing the isr #, which is also just the interrupt ID. Useful later.
+    push dword %1
     jmp isr_common
 %endmacro
 
-
+;This is to trigger the above macro once for every ISR.
 %assign j 0
 %rep 255
       ISR_ENTRY j
 %assign j j+1
 %endrep
+
 ; Generate a table of pointers that point to each of our ISRs. This will be accessed from C to setup our IDT.
 isr_ptrs:
     %assign i 0

src/kio.c

@@ -73,6 +73,18 @@ void vga_printdec(uint32_t out) {
     vga_print(buff);
 }
 
+/**
+ * @brief Print a format string to the VGA output.
+ *
+ *  Print some format string to the vga output cleanly. Supports a few format strings in C format.
+ *  
+ *  @param  fmt:    The format string to print
+ *  @param  ...:    Values for the format specifiers
+ *
+ *  @return No return value
+ *
+ */
+
 void vga_printf(const char* fmt, ...) {
     va_list args;
     va_start(args, fmt);

src/kttools.c

@@ -11,8 +11,6 @@
  */
 
 
-//convert digits from int num to buffer buf. in hex. This is 32 bit only for now!
-//WARN: integer is written from right to left into the buffer, and will halt if the buffer is too small.
 
 /**
  * @brief Convert a hex int to string, up to 32 bits.

src/main.c

@@ -10,18 +10,9 @@ void kern_main(uint32_t multiboot_magic, mb_info_t* multiboot_info)
 {
     //Hello C! Let's get to work in cleaning up our environment a bit and creating some safety.
     //First interrupts.
-    vga_clear();
-    vga_printf("IDT base = %X", idtr.IDT);
-    
-
     setup_idt();
     
-    vga_printf("IDT test :)");
-    int x = 5;
-    int y = 1;
-    x = x / (y-1);
     
-    vga_printf("%d", x);
     //wipe the screen
 	vga_clear();
 	//We're going to use this buffer as our 8char hex representation for reading mem

src/start.s

@@ -1,4 +1,6 @@
-; Bootloader places us in 32 bit mode :)
+;start.s
+;Entrypoint for kernel, hello world!
+
 bits 32
 ;Some symbols we'll need from other files...
 extern kern_main