From af3a28aa9087d291e146884644937a2a913e615c Mon Sep 17 00:00:00 2001
From: Eggert Jung <eggert.s.jung@wischhof13.de>
Date: Sat, 10 Jan 2026 22:29:28 +0100
Subject: [PATCH] add bitmap

---
 kernel/memory/pageframealloc.cc | 28 ++++++++++++++++++++++++----
 kernel/memory/pageframealloc.h  |  2 ++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/kernel/memory/pageframealloc.cc b/kernel/memory/pageframealloc.cc
index 82c87d0..9b38975 100644
--- a/kernel/memory/pageframealloc.cc
+++ b/kernel/memory/pageframealloc.cc
@@ -5,16 +5,36 @@
 
 #include "../memory/config.h"
 
+uint8_t PageFrameAllocator::bitmap[4294967296 / 4096 / 8];
 
 void PageFrameAllocator::init(){
-    Multiboot::Memory* memory_map_start = Multiboot::getMemoryMap();
+    Multiboot::Memory* memory_map_entry = Multiboot::getMemoryMap();
 
     dout << "kernel start: " << ___KERNEL_START___;
     dout << " kernel end: " << ___KERNEL_END___ << endl;
-    while(memory_map_start != 0){
-        dout << "Memory: " << hex << memory_map_start->getStartAddress() << " to " << memory_map_start->getEndAddress() << " is available: " << memory_map_start->isAvailable() << ".\n";
-        memory_map_start = memory_map_start->getNext();
+    while(memory_map_entry != 0){
+        void* start =  memory_map_entry->getStartAddress();
+        void* end =  memory_map_entry->getEndAddress();
+        bool available = memory_map_entry->isAvailable();
+        dout << "Memory: " << hex << start << " to " << end << " is available: " << available << "." << endl;
+
+        //TODO priotity for conflicting regions
+        for(uint64_t i = (uint64_t)start; i < (uint64_t)end; i += 4096){
+            uint64_t pg = i/4096;
+            if(available)
+                bitmap[pg/8] |= 1 << pg%8;
+            else
+                bitmap[pg/8] &= ~(1 << pg%8);
+        }
+
+        memory_map_entry = memory_map_entry->getNext();
     }
+
+    for(uint64_t i = (uint64_t)&___KERNEL_START___; i < (uint64_t)&___KERNEL_END___; i += 4096){
+        uint64_t pg = i/4096;
+        bitmap[pg/8] &= ~(1 << pg%8);
+    }
+
 }
 
 void PageFrameAllocator::stats(){
diff --git a/kernel/memory/pageframealloc.h b/kernel/memory/pageframealloc.h
index 8f9a2e6..22534b2 100644
--- a/kernel/memory/pageframealloc.h
+++ b/kernel/memory/pageframealloc.h
@@ -5,6 +5,8 @@
 #include "../memory/pageframe.h"
 
 namespace PageFrameAllocator {
+    extern uint8_t bitmap[4294967296 / 4096 / 8];
+
     void init ();
     void stats ();
     PageFrame* alloc(bool kernel);