From 9536ddd3d3ff39b919e248f4c6168089cf6747b1 Mon Sep 17 00:00:00 2001
From: Robbe Van Herck <robbevanherck1@gmail.com>
Date: Fri, 10 Jan 2020 10:05:19 +0100
Subject: [PATCH] Made getgdt more descriptive

---
 bootloader/main.asm |  4 ++--
 docs/bootloader.md  |  4 ++--
 kernel/shell.c      | 42 ++++++++++++++++++++++++++++++++++--------
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/bootloader/main.asm b/bootloader/main.asm
index 7e613ae..877456a 100644
--- a/bootloader/main.asm
+++ b/bootloader/main.asm
@@ -327,14 +327,14 @@ dd 0x00000000
 dw 0xffff
 dw 0x0000
 db 0x00
-db 0b10011010
+db 0b10011110
 db 0b11001111
 db 0x00
 
 dw 0xffff
 dw 0x0000
 db 0x00
-db 0b10010010
+db 0b10010110
 db 0b11001111
 db 0x00
 .gdt_end:
diff --git a/docs/bootloader.md b/docs/bootloader.md
index ac4dc75..af71b18 100644
--- a/docs/bootloader.md
+++ b/docs/bootloader.md
@@ -50,8 +50,8 @@
 | Entry | Base        | Limit   | Flags  | Access     | Purpose      |
 |-------|-------------|---------|--------|------------|--------------|
 | 0x0   | 0x00000000  | 0x00000 | 0b0000 | 0b00000000 | Null Segment |
-| 0x8   | 0x00000000  | 0xfffff | 0b1100 | 0b10011010 | Code Segment |
-| 0x10  | 0x00000000  | 0xfffff | 0b1100 | 0b10010010 | Data Segment |
+| 0x8   | 0x00000000  | 0xfffff | 0b1100 | 0b10011110 | Code Segment |
+| 0x10  | 0x00000000  | 0xfffff | 0b1100 | 0b10010110 | Data Segment |
 
 ## Known issues
 
diff --git a/kernel/shell.c b/kernel/shell.c
index 82b0bb1..956754e 100644
--- a/kernel/shell.c
+++ b/kernel/shell.c
@@ -44,6 +44,7 @@ int get_gdt(char* unused) {
         uint32_t base = entry.base_lower | entry.base_middle << 16 | entry.base_higher << 24;
         uint32_t limit = entry.limit_lower | (entry.flags_limit_higher & 0x0f) << 16;
         uint8_t flags = (entry.flags_limit_higher >> 4);
+        bool is_data = ((entry.access_byte & 0b00001000) >> 3) == 0;
         
         //terminal_writestring("\nEntry ");
         //terminal_writeint(entry_num, 10);
@@ -70,14 +71,39 @@ int get_gdt(char* unused) {
         terminal_writeint(entry.access_byte, 2);
         terminal_writestring(" (ring ");
         terminal_writeint((entry.access_byte & 0b01100000) >> 5, 10);
-        terminal_writestring(", S = ");
-        terminal_writeint((entry.access_byte & 0b00010000) >> 4, 2);
-        terminal_writestring(", EX = ");
-        terminal_writeint((entry.access_byte & 0b00001000) >> 3, 2);
-        terminal_writestring(", DC = ");
-        terminal_writeint((entry.access_byte & 0b00000100) >> 2, 2);
-        terminal_writestring(", RW = ");
-        terminal_writeint((entry.access_byte & 0b00000010) >> 1, 2);
+        if ((entry.access_byte & 0b00010000) == 0) {
+            terminal_writestring(", System");
+        }
+        if (is_data) {
+            terminal_writestring(", Data");
+
+            if((entry.access_byte & 0b00000100) == 0) {
+                terminal_writestring(" (growing up, ");
+            } else {
+                terminal_writestring(" (growing down, ");
+            }
+
+            if((entry.access_byte & 0b00000010) == 0) {
+                terminal_writestring("r--)");
+            } else {
+                terminal_writestring("rw-)");
+            }
+        } else {
+            terminal_writestring(", Code");
+
+            if((entry.access_byte & 0b00000100) == 0) {
+                terminal_writestring(" (non-conforming, ");
+            } else {
+                terminal_writestring(" (conforming, ");
+            }
+
+            if((entry.access_byte & 0b00000010) == 0) {
+                terminal_writestring("--x)");
+            } else {
+                terminal_writestring("r-x)");
+            }
+        }
+
         terminal_writestring(")\n");
     }
     return 0;