From a5ff8a6a9288e4386140fe6db934edc49264374d Mon Sep 17 00:00:00 2001
From: Julien CLEMENT <julien.clement@epita.fr>
Date: Tue, 13 Jul 2021 22:31:01 +0200
Subject: [PATCH] feat(gdt): add gdt kernel entries creation

Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>
---
 k/gdt.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 k/gdt.h |  5 ++++-
 k/k.c   |  1 +
 3 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/k/gdt.c b/k/gdt.c
index 7901109..7677c59 100644
--- a/k/gdt.c
+++ b/k/gdt.c
@@ -4,10 +4,58 @@ static struct gdt gdt = { 0 };
 
 static void create_kernel_ds()
 {
+    struct gdt_entry *entry = gdt.entries + KERNEL_DS_INDEX;
+
+    uint32_t limit = 0xffff;
+    uint32_t base = 0x0;
+
+    entry->granularity = 1;
+    entry->db = 1;
+    entry->l = 0;
+    entry->available = 0;
+
+    entry->present = 1;
+    entry->desc_priv = 0;
+    entry->desc_type = 1;
+    entry->ex = 0;
+    entry->dc = 0;
+    entry->rw = 1;
+    entry->accessed = 0;
+
+    entry->limit_1 = limit & 0xffff;
+    entry->limit_2 = (limit >> 16) & 0xf;
+
+    entry->base_1 = base & 0xffff;
+    entry->base_2 = (base >> 16) & 0xff;
+    entry->base_3 = (base >> 24) & 0xff;
 }
 
 static void create_kernel_cs()
 {
+    struct gdt_entry *entry = gdt.entries + KERNEL_CS_INDEX;
+
+    uint32_t limit = 0xffff;
+    uint32_t base = 0x0;
+
+    entry->granularity = 1;
+    entry->db = 1;
+    entry->l = 0;
+    entry->available = 0;
+
+    entry->present = 1;
+    entry->desc_priv = 0;
+    entry->desc_type = 1;
+    entry->ex = 1;
+    entry->dc = 0;
+    entry->rw = 1;
+    entry->accessed = 0;
+
+    entry->limit_1 = limit & 0xffff;
+    entry->limit_2 = (limit >> 16) & 0xf;
+
+    entry->base_1 = base & 0xffff;
+    entry->base_2 = (base >> 16) & 0xff;
+    entry->base_3 = (base >> 24) & 0xff;
 }
 
 static void create_gdt()
@@ -62,13 +110,18 @@ static void load_cs()
 
 static void reload_segment_selectors()
 {
+    printf("Before load_ds\r\n");
     load_ds();
     load_cs();
 }
 
 void init_gdt()
 {
+    printf("Before create_gdt\r\n");
     create_gdt();
+    printf("Before load_gdt\r\n");
     load_gdt();
+    printf("Before reload_segment_selectors\r\n");
     reload_segment_selectors();
+    printf("All good\r\n");
 }
diff --git a/k/gdt.h b/k/gdt.h
index 269fb60..9e1adbb 100644
--- a/k/gdt.h
+++ b/k/gdt.h
@@ -14,7 +14,10 @@ struct gdt_entry
     uint16_t limit_1    : 16;
     uint16_t base_1     : 16;
     uint8_t base_2      : 8;
-    uint8_t seg_type    : 4;
+    uint8_t accessed    : 1;
+    uint8_t rw          : 1;
+    uint8_t dc          : 1;
+    uint8_t ex          : 1;
     uint8_t desc_type   : 1;
     uint8_t desc_priv   : 2;
     uint8_t present     : 1;
diff --git a/k/k.c b/k/k.c
index 3fce470..a66b1e0 100644
--- a/k/k.c
+++ b/k/k.c
@@ -30,6 +30,7 @@
 static void k_init(void)
 {
     init_serial();
+    init_gdt();
 }
 
 void k_main(unsigned long magic, multiboot_info_t *info)