From 83f81b9a74e3f659ea51a8410c46c95492d8f732 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Sat, 18 Nov 2017 16:23:22 +0100
Subject: [PATCH] Cleaning up and commenting

---
 src/kernel/boot/boot.S      |  9 ++++++++-
 src/kernel/boot/kmain.c     |  4 ++--
 src/kernel/include/memory.h | 13 +++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/kernel/boot/boot.S b/src/kernel/boot/boot.S
index a3e2dc2..22b0399 100644
--- a/src/kernel/boot/boot.S
+++ b/src/kernel/boot/boot.S
@@ -54,17 +54,24 @@ _start:
   mov ds, eax
   mov es, eax
 
+  //; Jump to kernel address space
   movabs rax, offset upper_memory
   jmp rax
 
   upper_memory:
 
+  //; Move stack pointer to kernel space
   mov rax, KERNEL_OFFSET
   add rsp, rax
 
+  //; Remove identity mapping
   mov rax, 0
   movabs [BootP4], rax
 
+  //; Jump to kmain()
 .extern kmain
   movabs rax, offset kmain
-  jmp rax
+  call rax
+
+  hlt
+  jmp $
diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index e00461a..8dda4ce 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -2,14 +2,14 @@
 
 void clear_screen()
 {
-  unsigned char *vidmem = (void *)(0xB8000 + KERNEL_OFFSET);
+  unsigned char *vidmem = P2V(0xB8000);
   for(int i=0; i < 80*24*2; i++)
     *vidmem++ = 0;
 }
 
 void print_string(char *str)
 {
-  unsigned char *vidmem = (void *)(0xB8000 + KERNEL_OFFSET);
+  unsigned char *vidmem = P2V(0xB8000);
   while(*str)
   {
     *vidmem++ = *str++;
diff --git a/src/kernel/include/memory.h b/src/kernel/include/memory.h
index fee7398..c66d3ae 100644
--- a/src/kernel/include/memory.h
+++ b/src/kernel/include/memory.h
@@ -1,6 +1,19 @@
 #pragma once
 #define KERNEL_OFFSET 0xFFFFFF8000000000
+
+#ifdef __ASSEMBLER__
 #define V2P(a) ((a) - KERNEL_OFFSET)
+#define P2V(a) ((a) + KERNEL_OFFSET)
+#else
+#include <stdint.h>
+#define V2P(a) ((uintptr_t)(a) - KERNEL_OFFSET)
+#define P2V(a) ((void *)((uintptr_t)(a) + KERNEL_OFFSET))
+#endif
+
+#define P1_OFFSET(a) (((a)>>12) & 0x1FF)
+#define P2_OFFSET(a) (((a)>>21) & 0x1FF)
+#define P3_OFFSET(a) (((a)>>30) & 0x1FF)
+#define P4_OFFSET(a) (((a)>>39) & 0x1FF)
 
 #define PAGE_PRESENT      0x001
 #define PAGE_WRITE        0x002