From 245d09b056304aa0cb50e70bc4427ba220960ea4 Mon Sep 17 00:00:00 2001
From: Jenny Curle <thecurle12@gmail.com>
Date: Sun, 7 Apr 2019 13:16:53 +0100
Subject: [PATCH] Implemented IDT But something's wrong with the GDT Next up is
 a Serial Console

---
 arch/i386/boot.s                   |  9 ++++++-
 include/kernel/descriptor_tables.h |  7 +++++
 include/kernel/idt.h               | 19 ++++++++++++++
 include/kernel/utils.h             |  4 +++
 kernel/idt.c                       | 42 ++++++++++++++++++++++++++++++
 kernel/kernel.c                    |  4 ++-
 kernel/utils.c                     | 18 ++++++++++++-
 makefile                           |  1 +
 8 files changed, 101 insertions(+), 3 deletions(-)
 create mode 100755 include/kernel/descriptor_tables.h
 create mode 100755 include/kernel/idt.h
 create mode 100755 kernel/idt.c

diff --git a/arch/i386/boot.s b/arch/i386/boot.s
index 76b5444..a00dde8 100755
--- a/arch/i386/boot.s
+++ b/arch/i386/boot.s
@@ -52,4 +52,11 @@ gdt_flush:
 	push $flush2
 	ljmp *(%esp) #long jump
 flush2:
-	ret           #return to c code
\ No newline at end of file
+	ret           #return to c code
+	
+.global idt_load
+.extern idtp
+idt_load:
+	lidt (idtp)
+	ret
+	
\ No newline at end of file
diff --git a/include/kernel/descriptor_tables.h b/include/kernel/descriptor_tables.h
new file mode 100755
index 0000000..1d71852
--- /dev/null
+++ b/include/kernel/descriptor_tables.h
@@ -0,0 +1,7 @@
+#pragma once
+
+void gdt_set_gate(int, unsigned long, unsigned long, unsigned char, unsigned char);
+void gdt_install();
+
+void idt_set_gate(unsigned char, unsigned long, unsigned short, unsigned char);
+void idt_install();
\ No newline at end of file
diff --git a/include/kernel/idt.h b/include/kernel/idt.h
new file mode 100755
index 0000000..c3f9aa7
--- /dev/null
+++ b/include/kernel/idt.h
@@ -0,0 +1,19 @@
+#include <kernel/utils.h>
+
+struct idt_entry {
+	unsigned short base_low;
+	unsigned short selector;
+	unsigned char always0;
+	unsigned char flags;
+	unsigned short base_high;
+} __attribute__((packed));
+
+struct idt_ptr {
+	unsigned short limit;
+	unsigned int base;
+}__attribute__((packed));
+
+struct idt_entry idt[256]; //interrupt table of 256 entries
+struct idt_ptr idtp; //pointer to idt table
+
+extern void idt_load();
diff --git a/include/kernel/utils.h b/include/kernel/utils.h
index 22b3469..ba8debb 100755
--- a/include/kernel/utils.h
+++ b/include/kernel/utils.h
@@ -9,3 +9,7 @@ size_t strlen(const char*);
 unsigned char inb(unsigned short);
 
 void outb(unsigned short, unsigned char);
+
+void memcpy(void*, void*, size_t);
+
+void memset(void*, int, size_t);
\ No newline at end of file
diff --git a/kernel/idt.c b/kernel/idt.c
new file mode 100755
index 0000000..ef73559
--- /dev/null
+++ b/kernel/idt.c
@@ -0,0 +1,42 @@
+#include <kernel/utils.h>
+
+struct idt_entry {
+	unsigned short base_low;
+	unsigned short selector;
+	unsigned char always0;
+	unsigned char flags;
+	unsigned short base_high;
+} __attribute__((packed));
+
+struct idt_ptr {
+	unsigned short limit;
+	unsigned int base;
+}__attribute__((packed));
+
+struct idt_entry idt[256]; // Interrupt table of 256 entries
+struct idt_ptr idtp; // Pointer to idt table
+
+extern void idt_load();
+
+void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel, unsigned char flags) {
+	idt[num].base_low = base & 0xFFFF;
+	idt[num].base_high = (base >> 16) & 0xFFFF;
+	
+	idt[num].selector = sel;
+	idt[num].always0 = 0;
+	
+	// Must be uncommented when we get to usermode - it sets the permission
+	// level to 3
+	idt[num].flags = flags; // | 0x60;
+}
+
+void idt_install() {
+	idtp.limit = (sizeof (struct idt_entry) * 256) - 1;
+	idtp.base = &idt;
+	
+	memset(&idt, 0, sizeof(struct idt_entry) * 256);
+	
+	// All ISRs go here
+	
+	idt_load();
+}
\ No newline at end of file
diff --git a/kernel/kernel.c b/kernel/kernel.c
index 2edb848..5b67615 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -6,7 +6,9 @@
 
 int kernel_main(void) {
 	//Prepare the GDT
-	gdt_install();
+	gdt_install();
+	//Prepare interrupts
+	//idt_install();
 	//Prepare the screen, and blank it out.
 	screen_initialize();
 	
diff --git a/kernel/utils.c b/kernel/utils.c
index b868fc9..279cb89 100644
--- a/kernel/utils.c
+++ b/kernel/utils.c
@@ -16,4 +16,20 @@ unsigned char inb(unsigned short port) {
 
 void outb(unsigned short port, unsigned char data) {
 	asm volatile("outb %1, %0" : : "dN" (port), "a" (data));
-}
+}
+
+void memcpy(void* dest, void* src, size_t n) {
+	char* src_c  = (char*)src;
+	char* dest_c = (char*)dest;
+	
+	for(size_t i = 0; i < n; i++) {
+		dest_c[i] = src_c[i];
+	}
+}
+
+void memset(void* src, int chr, size_t n) {
+	unsigned char* ptr = src;
+	while(n--) {
+		*ptr++ = (unsigned char) chr;
+	}
+}
diff --git a/makefile b/makefile
index 060d5ca..ffe3c36 100755
--- a/makefile
+++ b/makefile
@@ -31,6 +31,7 @@ KERNEL_OBJS=           \
 $(KERNEL_ARCH_OBJS)    \
 kernel/utils.o         \
 kernel/gdt.o           \
+kernel/idt.o           \
 kernel/kernel.o        
 
 OBJS=\