[MEMORY] Memory pages and paging management

kernel/mem/pmm.c

@@ -0,0 +1,53 @@
+#include <mem.h>
+#include <multiboot.h>
+#include <debug.h>
+
+
+int pmm_running = 0;
+void *pmm_pos = &kernel_end;
+void **pmm_stack = 0;
+
+uintptr_t pmm_alloc()
+{
+  void **p;
+  if(!pmm_running)
+  {
+    p = (void **)pmm_pos;
+    pmm_pos = incptr(pmm_pos, PAGE_SIZE);
+  } else {
+    p = pmm_stack;
+    pmm_stack = *p;
+  }
+  return (uintptr_t)V2P(p);
+}
+
+void pmm_free(uintptr_t page)
+{
+  void **p  = (void **)P2V(page & ~PAGE_FLAGS_MASK);
+  *p = pmm_stack;
+  pmm_stack = p;
+  pmm_running = 1;
+}
+
+
+void pmm_init()
+{
+  uintptr_t start, end;
+  uint32_t type;
+
+  while(multiboot_get_memory_area(&start, &end, &type))
+  {
+    debug_info("PMM - %x->%x%s\n", start, end, (type==MBOOT_MMAP_FREE)?" (free)":" (reserved)");
+    for(uintptr_t p = start; (p+PAGE_SIZE) < end; p += PAGE_SIZE)
+    {
+      vmm_set_page(0, (uintptr_t)P2V(p), p, PAGE_PRESENT | PAGE_WRITE);
+      if((p >= (uintptr_t)V2P(&kernel_start)) && (p < (uintptr_t)V2P(pmm_pos)))
+        continue;
+      if(multiboot_page_used(p))
+        continue;
+      if(type == MBOOT_MMAP_FREE)
+        pmm_free(p);
+    }
+  }
+
+}