From b0e433fca25fa6d253cbb7db26171493c795a464 Mon Sep 17 00:00:00 2001
From: Quinten Kock <quintenkock@gmail.com>
Date: Mon, 7 Dec 2020 22:48:28 +0100
Subject: [PATCH] pretty-print GDT entries

---
 kernel/src/arch/x86/gdt.c               | 32 +++++++++++++++++++++++++
 kernel/src/arch/x86/gdt.h               |  3 +++
 kernel/src/arch/x86_64/entry-stivale2.c |  5 ++--
 kernel/src/arch/x86_64/gdt.h            |  2 +-
 kernel/src/print/print.c                | 14 +++++------
 5 files changed, 45 insertions(+), 11 deletions(-)
 create mode 100644 kernel/src/arch/x86/gdt.c
 create mode 100644 kernel/src/arch/x86/gdt.h

diff --git a/kernel/src/arch/x86/gdt.c b/kernel/src/arch/x86/gdt.c
new file mode 100644
index 0000000..e1c97db
--- /dev/null
+++ b/kernel/src/arch/x86/gdt.c
@@ -0,0 +1,32 @@
+#include <print/print.h>
+
+#include "gdt.h"
+
+void print_gdt_ent(uint64_t* ent) {
+    uint64_t e = *ent;
+    uint64_t base = ((e >> 16) & 0xFFFFFF) | ((e >> 32) & 0xFF000000);
+    uint64_t limit = (e & 0xFFFF) | ((e >> 32) & 0xF0000);
+    uint64_t flags = ((e >> 52) & 0xF);
+    uint64_t access = ((e >> 40) & 0xFF);
+
+    uint64_t code = (access & 0x8);
+
+    int bits = (flags&0x2) ? 64 : ((flags&0x4) ? 32 : 16);
+
+    uint64_t length = limit * ((flags & 0x8) ? 4096 : 1);
+    printf("%X (%h):  \t", base, length);
+    if(e == 0) {
+        puts("NULL");
+        return;
+    }
+    if(access & 0x80) putchar('P');
+    printf("%d", (access >> 5) & 0x3);
+    if(access & 0x10) putchar('S');
+    if(code) printf(" Code%d\t", bits); else puts(" Data\t");
+    if(access & 0x4) putchar(code ? 'C' : 'D');
+    if(access & 0x2) putchar(code ? 'R' : 'W');
+    if(access & 0x1) putchar('A');
+
+    if(flags & 0x8) putchar('G');
+    if(flags & 0x1) putchar('z');
+}
diff --git a/kernel/src/arch/x86/gdt.h b/kernel/src/arch/x86/gdt.h
new file mode 100644
index 0000000..9ca6416
--- /dev/null
+++ b/kernel/src/arch/x86/gdt.h
@@ -0,0 +1,3 @@
+#include <stdint.h>
+
+void print_gdt_ent(uint64_t* ent);
diff --git a/kernel/src/arch/x86_64/entry-stivale2.c b/kernel/src/arch/x86_64/entry-stivale2.c
index 214ca30..c609aad 100644
--- a/kernel/src/arch/x86_64/entry-stivale2.c
+++ b/kernel/src/arch/x86_64/entry-stivale2.c
@@ -3,11 +3,12 @@
 #include <stddef.h>
 
 #include <arch/x86/stivale2-parse.h>
+#include <arch/x86/gdt.h>
+#include <arch/x86_64/gdt.h>
 #include <print/print.h>
 
 #include <main.h>
 
-#include "gdt.h"
 
 static uint8_t stack[4096] = {0};
 void stivale2_main(struct stivale2_struct *info);
@@ -46,7 +47,7 @@ void stivale2_main(struct stivale2_struct *info) {
     printf("GDT: %x (%d)\n", pGDT.base, pGDT.limit);
     for(int i = 0; i < (pGDT.limit+1)/8; i++) {
         uint64_t *gdt_ent = pGDT.base + 8*i;
-        printf("GDTent(%d at %x): %x\n", i, gdt_ent, *gdt_ent);
+        printf("GDT %d: ", i); print_gdt_ent(gdt_ent); putchar('\n');
     }
 
 	char *argv[3] = {"stivale2", info->bootloader_brand, info->bootloader_version};
diff --git a/kernel/src/arch/x86_64/gdt.h b/kernel/src/arch/x86_64/gdt.h
index c759881..d908147 100644
--- a/kernel/src/arch/x86_64/gdt.h
+++ b/kernel/src/arch/x86_64/gdt.h
@@ -6,4 +6,4 @@ struct gdt_ptr
     uint64_t base;
 } __attribute__((packed));
 
-void loadgdt();
\ No newline at end of file
+void loadgdt();
diff --git a/kernel/src/print/print.c b/kernel/src/print/print.c
index fa06909..7044424 100644
--- a/kernel/src/print/print.c
+++ b/kernel/src/print/print.c
@@ -1,5 +1,6 @@
 #include <stddef.h>
 #include <stdarg.h>
+#include <stdbool.h>
 
 #include "print.h"
 
@@ -16,15 +17,10 @@ void print(const char* c) {
 static const char CONVERSION_TABLE[] = "0123456789abcdef";
 static const char UNITS[] = "bKM";
 
-static void printhex(size_t num) {
+static void printhex(size_t num, bool pad) {
     int i;
     char buf[17];
 
-    if (!num) {
-        puts("0x0");
-        return;
-    }
-
     buf[16] = 0;
 
     for (i = 15; num; i--) {
@@ -33,7 +29,7 @@ static void printhex(size_t num) {
     }
 
     puts("0x");
-    for(int j = i; j >= 0; j--) {
+    for(int j = i; pad && j >= 0; j--) {
         putchar('0');
     }
 
@@ -79,7 +75,9 @@ void printf(const char *format, ...) {
         if (*format == '%') {
             format++;
             if (*format == 'x') {
-                printhex(va_arg(argp, size_t));
+                printhex(va_arg(argp, size_t), false);
+            } else if (*format == 'X') {
+                printhex(va_arg(argp, size_t), true);
             } else if (*format == 'd') {
                 printdec(va_arg(argp, size_t));
             } else if (*format == 's') {