feat(idt): add documentation

k/gdt.h

@@ -50,7 +50,7 @@ struct gdt
 struct gdt_r
 {
     uint16_t limit; // total size of the GDT - 1 in bytes
-    uint32_t addr;  // base address of the DGT
+    uint32_t addr;  // base address of the GDT
 } __attribute__ ((packed));
 
 struct segment_selector

k/idt.c

@@ -1,4 +1,5 @@
 #include "idt.h"
+#include "stdio.h"
 
 static struct idt idt = { 0 };
 
@@ -18,6 +19,7 @@ struct idt_entry_info infos[] = {
 
 void handle_interrupt(struct int_args args)
 {
+    (void)args;
     printf("INTERRUPT\r\n");
     return;
 }

k/idt.h

@@ -11,31 +11,19 @@
 #define INTERRUPT_TYPE 0x6
 #define TRAP_TYPE      0x7
 
-struct int_args
-{
-    uint32_t int_code;
-    uint32_t err;
-} __attribute__ ((packed));
-
-struct idt_entry_info
-{
-    void (*isr)(void);
-    uint32_t type;
-};
-
 struct idt_entry
 {
-    uint16_t offset_1   : 16;
+    uint16_t offset_1   : 16;   // 16 lsb of isr address
     struct segment_selector selector;
 
     uint8_t zero_1      : 8;    // unused, set to 0
     uint8_t type        : 3;    // gate type
-    uint8_t size        : 1;
+    uint8_t size        : 1;    // 0 => 16-bits     1 => 32-bits
     uint8_t zero_2      : 1;    // set to 0 for interrupt and trap gates
-    uint8_t desc_priv   : 2;    // Descriptor privilege
-    uint8_t present     : 1;
+    uint8_t desc_priv   : 2;    // descriptor privilege
+    uint8_t present     : 1;    // always 1
 
-    uint16_t offset_2   : 16;
+    uint16_t offset_2   : 16;   // 16 msb of isr address
 } __attribute__ ((packed));
 
 struct idt
@@ -45,10 +33,25 @@ struct idt
 
 struct idt_r
 {
-    uint16_t limit;
-    uint32_t addr;
+    uint16_t limit;  // total size of the IDT - 1 in bytes
+    uint32_t addr;   // base address of the IDT
 } __attribute__ ((packed));
 
+// FIXME: This struct is used to get int_code and err_code pushed to the stack
+// by the isr (but isn't working now)
+struct int_args
+{
+    uint32_t int_code;
+    uint32_t err_code;
+} __attribute__ ((packed));
+
+// This struct is used to know how to fill the idt entries
+struct idt_entry_info
+{
+    void (*isr)(void);  // function pointer on interrupt service routine (isr)
+    uint32_t type;      // gate type
+};
+
 void init_idt(void);
 void handle_interrupt(struct int_args args);
 

k/isr.h

@@ -1,6 +1,8 @@
 #ifndef ISR_H
 #define ISR_H
 
+// Every ISR for the 21 first intel-defined interrupts.
+
 void int_de(void);      // Divide Error
 void int_db(void);      // Debug Exception
 void int_nmi(void);     // NMI Interrupt