From 29093837a33aa24449e4c398621d667e6bcab9d6 Mon Sep 17 00:00:00 2001
From: Arnau478 <arnauxabia@gmail.com>
Date: Sat, 18 Jun 2022 00:44:37 +0200
Subject: [PATCH] Implemented IDT

---
 src/kernel/arch/i686/idt.asm | 16 ++++++++++++++
 src/kernel/arch/i686/idt.c   | 41 ++++++++++++++++++++++++++++++++++++
 src/kernel/arch/i686/idt.h   | 23 ++++++++++++++++++++
 src/kernel/hal/hal.c         |  6 ++++++
 src/kernel/hal/hal.h         |  3 +++
 src/kernel/main.c            |  5 ++++-
 src/kernel/util/binary.h     |  4 ++++
 7 files changed, 97 insertions(+), 1 deletion(-)
 create mode 100644 src/kernel/arch/i686/idt.asm
 create mode 100644 src/kernel/arch/i686/idt.c
 create mode 100644 src/kernel/arch/i686/idt.h
 create mode 100644 src/kernel/hal/hal.c
 create mode 100644 src/kernel/hal/hal.h
 create mode 100644 src/kernel/util/binary.h

diff --git a/src/kernel/arch/i686/idt.asm b/src/kernel/arch/i686/idt.asm
new file mode 100644
index 0000000..d5c138b
--- /dev/null
+++ b/src/kernel/arch/i686/idt.asm
@@ -0,0 +1,16 @@
+[bits 32]
+
+global i686_idt_load
+i686_idt_load:
+    ; New call frame
+    push ebp
+    mov ebp, esp
+
+    ; Load IDT
+    mov eax, [ebp + 8]
+    lidt [eax]
+
+    ; Restore call frame
+    mov esp, ebp
+    pop ebp
+    ret
diff --git a/src/kernel/arch/i686/idt.c b/src/kernel/arch/i686/idt.c
new file mode 100644
index 0000000..78002a3
--- /dev/null
+++ b/src/kernel/arch/i686/idt.c
@@ -0,0 +1,41 @@
+#include "idt.h"
+#include "../../util/binary.h"
+
+typedef struct{
+    uint16_t base_low;
+    uint16_t segment_selector;
+    uint8_t reserved;
+    uint8_t flags;
+    uint16_t base_high;
+} idt_entry;
+
+typedef struct{
+    uint16_t limit;
+    idt_entry *ptr;
+} idt_descriptor;
+
+idt_entry g_idt[256];
+
+idt_descriptor g_idt_descriptor = {sizeof(g_idt) - 1, g_idt};
+
+void __attribute__((cdecl)) i686_idt_load(idt_descriptor *descriptor);
+
+void i686_idt_set_gate(int interrupt, void *base, uint16_t segment_descriptor, uint8_t flags){
+    g_idt[interrupt].base_low = ((uint32_t)base) & 0xFFFF;
+    g_idt[interrupt].segment_selector = segment_descriptor;
+    g_idt[interrupt].reserved = 0;
+    g_idt[interrupt].flags = flags;
+    g_idt[interrupt].base_high = ((uint32_t)base >> 16) & 0xFFFF;
+}
+
+void i686_idt_enable_gate(int interrupt){
+    FLAG_SET(g_idt[interrupt].flags, IDT_FLAG_PRESENT);
+}
+
+void i686_idt_disable_gate(int interrupt){
+    FLAG_UNSET(g_idt[interrupt].flags, IDT_FLAG_PRESENT);
+}
+
+void i686_idt_initialize(){
+    i686_idt_load(&g_idt_descriptor);
+}
diff --git a/src/kernel/arch/i686/idt.h b/src/kernel/arch/i686/idt.h
new file mode 100644
index 0000000..8d98362
--- /dev/null
+++ b/src/kernel/arch/i686/idt.h
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <stdint.h>
+
+typedef enum{
+    IDT_FLAG_GATE_TASK = 0x5,
+    IDT_FLAG_GATE_16BIT_INT = 0x6,
+    IDT_FLAG_GATE_16BIT_TRAP = 0x7,
+    IDT_FLAG_GATE_32BIT_INT = 0xE,
+    IDT_FLAG_GATE_32BIT_TRAP = 0xF,
+
+    IDT_FLAG_RING0 = (0 << 5),
+    IDT_FLAG_RING1 = (1 << 5),
+    IDT_FLAG_RING2 = (2 << 5),
+    IDT_FLAG_RING3 = (3 << 5),
+
+    IDT_FLAG_PRESENT = 0x80,
+} idt_flags;
+
+void i686_idt_initialize();
+void i686_idt_enable_gate(int interrupt);
+void i686_idt_disable_gate(int interrupt);
+void i686_idt_set_gate(int interrupt, void *base, uint16_t segment_descriptor, uint8_t flags);
diff --git a/src/kernel/hal/hal.c b/src/kernel/hal/hal.c
new file mode 100644
index 0000000..ab8602c
--- /dev/null
+++ b/src/kernel/hal/hal.c
@@ -0,0 +1,6 @@
+#include "hal.h"
+#include "../arch/i686/idt.h"
+
+void hal_initialize(){
+    i686_idt_initialize();
+}
diff --git a/src/kernel/hal/hal.h b/src/kernel/hal/hal.h
new file mode 100644
index 0000000..4fa1812
--- /dev/null
+++ b/src/kernel/hal/hal.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void hal_initialize();
diff --git a/src/kernel/main.c b/src/kernel/main.c
index f61db0d..44a9891 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -1,9 +1,12 @@
 #include <stdint.h>
 #include "stdio.h"
+#include "hal/hal.h"
 
 void __attribute__((cdecl)) kmain(uint64_t magic, uint64_t addr){
+    hal_initialize();
+    
     puts("\x1b[33mWARNING\x1b[0m");
     printf(": amazing %s ahead!\n", "math");
     printf("%i+%i=%i\n", 1, 1, 2);
-    for(;;); // Halt here 
+    for(;;); // Halt here
 }
diff --git a/src/kernel/util/binary.h b/src/kernel/util/binary.h
new file mode 100644
index 0000000..2d0ab9f
--- /dev/null
+++ b/src/kernel/util/binary.h
@@ -0,0 +1,4 @@
+#pragma once
+
+#define FLAG_SET(x, flag) (x) |= (flag)
+#define FLAG_UNSET(x, flag) (x) &= ~(flag)