1 files changed, 68 insertions, 0 deletions
diff --git a/Source/Kernel/MemoryManager/PageAlloc.ns.cpp b/Source/Kernel/MemoryManager/PageAlloc.ns.cpp
new file mode 100644
index 0000000..ac2969e
--- /dev/null
+++ b/Source/Kernel/MemoryManager/PageAlloc.ns.cpp
@@ -0,0 +1,68 @@
+#include "PageAlloc.ns.h"
+#include <MemoryManager/PhysMem.ns.h>
+
+#define CACHED_PAGES 3
+
+// This mechanism is supposed to make it impossible to run out of free pages to use as a page table
+
+namespace PageAlloc {
+
+void* freePage[CACHED_PAGES];
+int freec = 0;
+bool usable = false, locked = false;
+
+void init() {
+	freec = CACHED_PAGES;
+	for (u32int i = 0; i < CACHED_PAGES; i++) {
+		freePage[i] = Mem::kalloc(0x1000, true);
+	}
+	usable = true;
+}
+
+void* alloc(u32int* phys) {
+	if (!usable) init();
+
+	while (freec < CACHED_PAGES && (!locked)) {
+		locked = true;
+		void* next = 0;
+		if (!Mem::pagingEnabled) {
+			next = Mem::kalloc(0x1000, true);
+		} else {
+			u32int i = 0xFFFFF000;
+			page_t *p;
+			while (1) {
+				p = kernelPageDirectory->getPage(i, true);
+				if (p->frame == 0) break;
+				i -= 0x1000;
+			}
+			PhysMem::allocFrame(p, true, false);
+			next = (void*)i;
+		}
+		freePage[freec] = next;
+		freec++;
+		locked = false;
+	}
+
+	freec--;
+	void* ret = freePage[freec];
+	if (!Mem::pagingEnabled) {
+		*phys = (u32int)ret - 0xC0000000;
+	} else {
+		page_t* p = kernelPageDirectory->getPage((u32int)ret, false);
+		if (p == 0) {	//THIS SHOULD NEVER HAPPEN
+			PANIC("Cached free page does not exist.");
+		} else if (p->frame == 0) {
+			PANIC("Cached free page is not mapped to a frame.");
+		} else {
+			*phys = (p->frame * 0x1000);
+		}
+	}
+	return ret;
+}
+
+void free(void *ptr) {
+	kernelPageDirectory->freeFrame((u32int)ptr);
+	return;
+}
+
+}