started work on pmm

kernel/memory/mm.c

@@ -0,0 +1,37 @@
+#include "multiboot.h"
+
+static uint32_t max_address = 0;
+static uint32_t total_available_memory = 0;
+
+void parse_mmap(void* base, uint32_t limit) {
+    multiboot_mmap_entry* entry = (multiboot_mmap_entry*)base;
+    void* end = (void*)((uint32_t)base + limit);
+
+    while ((void*)entry < end) {
+        if (entry->type == 1) {
+            uint32_t region_start = (uint32_t)(entry->addr);
+            uint32_t region_end = (uint32_t)(entry->addr + entry->len);
+            if (region_end > max_address) {
+                max_address = region_end;
+            }
+
+            total_available_memory += entry->len;
+
+            // start breaking up the address range
+            // if it's safe (not kernel, not BIOS structures, etc..), find the corresponding page in our PMM, mark it free
+            // need to align start and end to 4kb
+            if (entry->len < 4096) {
+                continue;
+            }
+
+            for (uint32_t addr = region_start; addr < region_end; addr += 4096) {
+                // check for physical kernel address range 
+
+                // check if this address range contains our multiboot structure
+
+                // don't allow pages under 1MB
+            }
+        }
+        entry = (multiboot_mmap_entry*)((uint32_t)entry + entry->size + sizeof(entry->size));
+    }
+}