From 516e920cd96730cf470357aa250636d9d42a849c Mon Sep 17 00:00:00 2001
From: Freya Murphy <freya@freyacat.org>
Date: Thu, 3 Apr 2025 16:53:51 -0400
Subject: [PATCH] memory allocator/pager, plus other stuff

---
 build.zig                             |  10 +
 include/stdlib.h                      |  57 +++
 kernel/include/comus/asm.h            |  64 +++
 kernel/include/comus/memory.h         |  76 +++-
 kernel/include/comus/memory/mapping.h |  20 -
 kernel/io/io.c                        |   9 +
 kernel/io/panic.c                     |  16 +
 kernel/kernel.c                       |   7 +-
 kernel/kernel.ld                      |   4 +
 kernel/memory/memory.c                |  15 +
 kernel/memory/paging.c                | 591 ++++++++++++++++++++++++++
 kernel/memory/paging.h                |  24 ++
 kernel/memory/physalloc.c             | 242 +++++++++++
 kernel/memory/physalloc.h             |  44 ++
 kernel/memory/virtalloc.c             | 200 +++++++++
 kernel/memory/virtalloc.h             |  31 ++
 kernel/old/include/offsets.h          |  83 ++++
 lib/alloc.c                           | 211 +++++++++
 18 files changed, 1681 insertions(+), 23 deletions(-)
 create mode 100644 kernel/include/comus/asm.h
 delete mode 100644 kernel/include/comus/memory/mapping.h
 create mode 100644 kernel/io/io.c
 create mode 100644 kernel/io/panic.c
 create mode 100644 kernel/memory/memory.c
 create mode 100644 kernel/memory/paging.c
 create mode 100644 kernel/memory/paging.h
 create mode 100644 kernel/memory/physalloc.c
 create mode 100644 kernel/memory/physalloc.h
 create mode 100644 kernel/memory/virtalloc.c
 create mode 100644 kernel/memory/virtalloc.h
 create mode 100644 kernel/old/include/offsets.h
 create mode 100644 lib/alloc.c

diff --git a/build.zig b/build.zig
index 61dba0e..f7e0e87 100644
--- a/build.zig
+++ b/build.zig
@@ -25,9 +25,16 @@ const boot_src = &[_][]const u8{"boot/boot.S"};
 const kernel_src = &[_][]const u8{
     "kernel/entry.S", // must be first
     "kernel/kernel.c",
+    "kernel/io/io.c",
+    "kernel/io/panic.c",
+    "kernel/memory/memory.c",
+    "kernel/memory/paging.c",
+    "kernel/memory/physalloc.c",
+    "kernel/memory/virtalloc.c",
 };
 
 const lib_src = &[_][]const u8{
+    "lib/alloc.c",
     "lib/atox.c",
     "lib/bound.c",
     "lib/btoa.c",
@@ -38,8 +45,11 @@ const lib_src = &[_][]const u8{
     "lib/itoc.c",
     "lib/memcmp.c",
     "lib/memcpy.c",
+    "lib/memcpyv.c",
     "lib/memmove.c",
+    "lib/memmovev.c",
     "lib/memset.c",
+    "lib/memsetv.c",
     "lib/printf.c",
     "lib/stpcpy.c",
     "lib/stpncpy.c",
diff --git a/include/stdlib.h b/include/stdlib.h
index 6a2051d..1455a1f 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -11,6 +11,8 @@
 
 #include <stddef.h>
 
+#define PAGE_SIZE 4096
+
 /**
  * converts single digit int to base 36
  * @param i - int
@@ -194,4 +196,59 @@ extern unsigned int bound(unsigned int min, unsigned int value,
  */
 extern void delay(int count);
 
+/**
+ * Allocates size_t bytes in memory
+ *
+ * @param size - the amount of bytes to allocate
+ * @returns the address allocated or NULL on failure
+ */
+extern void *malloc(size_t size);
+
+/**
+ * Rellocates a given allocated ptr to a new size of bytes in memory.
+ * If ptr is NULL it will allocate new memory.
+ *
+ * @param ptr - the pointer to reallocate
+ * @param size - the amount of bytes to reallocate to
+ * @returns the address allocated or NULL on failure
+ */
+extern void *realloc(void *ptr, size_t size);
+
+/**
+ * Frees an allocated pointer in memory
+ *
+ * @param ptr - the pointer to free
+ */
+extern void free(void *ptr);
+
+/**
+ * Allocate a single page of memory
+ *
+ * @returns the address allocated or NULL on failure
+ */
+extern void *alloc_page(void);
+
+/**
+ * Allocate size_t amount of contiguous virtual pages
+ *
+ * @param count - the number of pages to allocate
+ * @returns the address allocated or NULL on failure
+ */
+extern void *alloc_pages(size_t count);
+
+/**
+ * Free allocated pages.
+ *
+ * @param ptr - the pointer provided by alloc_page or alloc_pages
+ */
+extern void free_pages(void *ptr);
+
+/**
+ * Abort the current process with a given message.
+ *
+ * @param format - the format string
+ * @param ... - variable args for the format
+ */
+__attribute__((noreturn)) extern void panic(const char *format, ...);
+
 #endif /* stlib.h */
diff --git a/kernel/include/comus/asm.h b/kernel/include/comus/asm.h
new file mode 100644
index 0000000..5e1dce7
--- /dev/null
+++ b/kernel/include/comus/asm.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include <stdint.h>
+
+static inline uint8_t inb(uint16_t port)
+{
+	uint8_t ret;
+	__asm__ volatile("inb %1, %0" : "=a"(ret) : "Nd"(port));
+	return ret;
+}
+
+static inline void outb(uint16_t port, uint8_t val)
+{
+	__asm__ volatile("outb %0, %1" : : "a"(val), "Nd"(port));
+}
+
+static inline uint16_t inw(uint16_t port)
+{
+	uint16_t ret;
+	__asm__ volatile("inw %1, %0" : "=a"(ret) : "Nd"(port));
+	return ret;
+}
+
+static inline void outw(uint16_t port, uint16_t val)
+{
+	__asm__ volatile("outw %0, %1" : : "a"(val), "Nd"(port));
+}
+
+static inline uint32_t inl(uint16_t port)
+{
+	uint32_t ret;
+	__asm__ volatile("inl %1, %0" : "=a"(ret) : "Nd"(port));
+	return ret;
+}
+
+static inline void outl(uint16_t port, uint32_t val)
+{
+	__asm__ volatile("outl %0, %1" : : "a"(val), "Nd"(port));
+}
+
+static inline void io_wait(void)
+{
+	outb(0x80, 0);
+}
+
+static inline void sti(void)
+{
+	__asm__ volatile("sti");
+}
+
+static inline void cli(void)
+{
+	__asm__ volatile("cli");
+}
+
+static inline void int_wait(void)
+{
+	__asm__ volatile("sti; hlt");
+}
+
+static inline void halt(void)
+{
+	__asm__ volatile("cli; hlt");
+}
diff --git a/kernel/include/comus/memory.h b/kernel/include/comus/memory.h
index 938bc6b..411c039 100644
--- a/kernel/include/comus/memory.h
+++ b/kernel/include/comus/memory.h
@@ -1 +1,75 @@
-#include <memory/mapping.h>
+/**
+ * @file memory.h
+ *
+ * @author Freya Murphy <freya@freyacat.org>
+ *
+ * Kernel memory functions
+ */
+
+#ifndef _MEMORY_H
+#define _MEMORY_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define MMAP_MAX_ENTRY 64
+
+struct memory_segment {
+	uint64_t addr;
+	uint64_t len;
+};
+
+struct memory_map {
+	uint32_t entry_count;
+	struct memory_segment entries[MMAP_MAX_ENTRY];
+};
+
+/**
+ * Initalize system memory allocator
+ */
+void memory_init(struct memory_map *map);
+
+/**
+ * @returns how much memory the system has
+ */
+uint64_t memory_total(void);
+
+/**
+ * @returns how much memory is free
+ */
+uint64_t memory_free(void);
+
+/**
+ * @returns how much memory is used
+ */
+uint64_t memory_used(void);
+
+/**
+ * Allocates at least len bytes of memory starting at
+ * physical address addr. Returned address can be
+ * any virtural address.
+ *
+ * @param addr - the physical address to map
+ * @param len - the minimum length to map
+ * @param writable - if this memory should be writable
+ * @param user - if this memory should be user writable
+ */
+void *mapaddr(void *addr, size_t len);
+
+/**
+ * Unmaps mapped address from the mmap function
+ * @param addr - the address returned from mmap
+ * @param len - the length allocated
+ */
+void unmapaddr(void *addr);
+
+/**
+ * Attemps to load a mapped but not yet allocated page.
+ *
+ * @param virt_addr - the virtural address from either page allocation function
+ *
+ * @returns 0 on success and a negative error code on failure.
+ */
+int load_page(void *virt_addr);
+
+#endif /* memory.h */
diff --git a/kernel/include/comus/memory/mapping.h b/kernel/include/comus/memory/mapping.h
deleted file mode 100644
index e1b7102..0000000
--- a/kernel/include/comus/memory/mapping.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/**
- * @file memory.h
- *
- * @author Freya Murphy
- *
- * Kernel memory declarations
- */
-
-#ifndef _MEMORY_MAPPING_H
-#define _MEMORY_MAPPING_H
-
-// paging
-#define PAGE_SIZE 4096
-#define PAGE_PRESENT 0x1
-#define PAGE_WRITE 0x2
-#define PAGE_USER 0x4
-#define PAGE_HUGE 0x80
-#define PAGE_GLOBAL 0x100
-
-#endif
diff --git a/kernel/io/io.c b/kernel/io/io.c
new file mode 100644
index 0000000..a68114d
--- /dev/null
+++ b/kernel/io/io.c
@@ -0,0 +1,9 @@
+#include <lib.h>
+#include <stdio.h>
+
+void fputc(FILE *stream, char c) {
+	(void) stream;
+	(void) c;
+
+	// FIXME: !!!
+}
diff --git a/kernel/io/panic.c b/kernel/io/panic.c
new file mode 100644
index 0000000..948542e
--- /dev/null
+++ b/kernel/io/panic.c
@@ -0,0 +1,16 @@
+#include <lib.h>
+#include <stdarg.h>
+#include <comus/asm.h>
+
+__attribute__((noreturn))
+void panic(const char *format, ...) {
+	cli();
+	va_list list;
+	va_start(list, format);
+	printf("\n\n!!! PANIC !!!\n");
+	vprintf(format, list);
+	printf("\n\n");
+
+	while (1)
+		halt();
+}
diff --git a/kernel/kernel.c b/kernel/kernel.c
index 075c878..ac0546c 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,5 +1,8 @@
+#include <comus/memory.h>
 
+void main(void)
+{
 
-void main(void) {
-	while (1) ;
+	while (1)
+		;
 }
diff --git a/kernel/kernel.ld b/kernel/kernel.ld
index b31cbf0..8ee6a5b 100644
--- a/kernel/kernel.ld
+++ b/kernel/kernel.ld
@@ -4,6 +4,8 @@ SECTIONS
 {
 	. = 1M;
 
+	kernel_start = .;
+
 	. = ALIGN(0x1000);
 
 	.boot : {
@@ -40,4 +42,6 @@ SECTIONS
 		*(.eh_frame .eh_frame_hdr)
 		*(.note.GNU-stack .note.gnu.property .comment)
 	}
+
+	kernel_end = .;
 }
diff --git a/kernel/memory/memory.c b/kernel/memory/memory.c
new file mode 100644
index 0000000..1334051
--- /dev/null
+++ b/kernel/memory/memory.c
@@ -0,0 +1,15 @@
+#include <comus/memory.h>
+#include <comus/asm.h>
+
+#include "paging.h"
+#include "virtalloc.h"
+#include "physalloc.h"
+
+void memory_init(struct memory_map *map)
+{
+	cli();
+	paging_init();
+	virtaddr_init();
+	physalloc_init(map);
+	sti();
+}
diff --git a/kernel/memory/paging.c b/kernel/memory/paging.c
new file mode 100644
index 0000000..045afc7
--- /dev/null
+++ b/kernel/memory/paging.c
@@ -0,0 +1,591 @@
+#include <lib.h>
+#include <comus/memory.h>
+
+#include "virtalloc.h"
+#include "physalloc.h"
+#include "paging.h"
+
+// PAGE MAP LEVEL 4 ENTRY
+struct pml4e {
+	uint64_t flags : 6;
+	uint64_t : 6;
+	uint64_t address : 40;
+	uint64_t : 11;
+	uint64_t execute_disable : 1;
+};
+
+// PAGE DIRECTORY POINTER TABLE ENTRY
+struct pdpte {
+	uint64_t flags : 6;
+	uint64_t : 1;
+	uint64_t page_size : 1;
+	uint64_t : 4;
+	uint64_t address : 40;
+	uint64_t : 11;
+	uint64_t execute_disable : 1;
+};
+
+// PAGE DIRECTORY ENTRY
+struct pde {
+	uint64_t flags : 6;
+	uint64_t : 1;
+	uint64_t page_size : 1;
+	uint64_t : 4;
+	uint64_t address : 40;
+	uint64_t : 11;
+	uint64_t execute_disable : 1;
+};
+
+// PAGE TABLE ENTRY
+struct pte {
+	uint64_t flags : 9;
+	uint64_t loaded : 1;
+	uint64_t : 2;
+	uint64_t address : 40;
+	uint64_t : 7;
+	uint64_t protection_key : 4;
+	uint64_t execute_disable : 1;
+};
+
+// bss segment, can write to
+extern volatile struct pml4e kernel_pml4[512];
+extern volatile struct pdpte kernel_pdpt_0[512];
+extern volatile struct pde kernel_pd_0[512];
+extern volatile struct pte bootstrap_pt[512];
+extern volatile struct pte
+	paging_pt[512]; // paging_pt should NEVER be outside of this file, NEVER i say
+
+// paged address to read page tables
+// the structures are not gurenteed to be ident mapped
+// map them here with map_<type>(phys_addr) before useing structures
+void volatile *addr_mapped = (void *)(uintptr_t)0x204000;
+static volatile struct pml4e *pml4_mapped = (void *)(uintptr_t)0x200000;
+static volatile struct pdpte *pdpt_mapped = (void *)(uintptr_t)0x201000;
+static volatile struct pde *pd_mapped = (void *)(uintptr_t)0x202000;
+static volatile struct pte *pt_mapped = (void *)(uintptr_t)0x203000;
+
+static inline void invlpg(volatile void *addr)
+{
+	__asm__ volatile("invlpg (%0)" ::"r"(addr) : "memory");
+}
+
+static void load_addr(volatile void *phys_addr)
+{
+	static volatile struct pte *pt = &paging_pt[4];
+	pt->address = (uint64_t)phys_addr >> 12;
+	pt->flags = F_PRESENT | F_WRITEABLE;
+	invlpg(addr_mapped);
+}
+
+static void load_pml4(volatile void *phys)
+{
+	static volatile struct pte *pt = &paging_pt[0];
+	if ((uint64_t)phys >> 12 == pt->address)
+		return;
+	pt->address = (uint64_t)phys >> 12;
+	pt->flags = F_PRESENT | F_WRITEABLE;
+	invlpg(pml4_mapped);
+}
+
+static void load_pdpt(volatile void *phys)
+{
+	static volatile struct pte *pt = &paging_pt[1];
+	if ((uint64_t)phys >> 12 == pt->address)
+		return;
+	pt->address = (uint64_t)phys >> 12;
+	pt->flags = F_PRESENT | F_WRITEABLE;
+	invlpg(pdpt_mapped);
+}
+
+static void load_pd(volatile void *phys)
+{
+	static volatile struct pte *pt = &paging_pt[2];
+	if ((uint64_t)phys >> 12 == pt->address)
+		return;
+	pt->address = (uint64_t)phys >> 12;
+	pt->flags = F_PRESENT | F_WRITEABLE;
+	invlpg(pd_mapped);
+}
+
+static void load_pt(volatile void *phys)
+{
+	static volatile struct pte *pt = &paging_pt[3];
+	if ((uint64_t)phys >> 12 == pt->address)
+		return;
+	pt->address = (uint64_t)phys >> 12;
+	pt->flags = F_PRESENT | F_WRITEABLE;
+	invlpg(pt_mapped);
+}
+
+#define PAG_SUCCESS 0
+#define PAG_CANNOT_ALLOC 1
+#define PAG_NOT_PRESENT 2
+
+static int select_pdpt(void *virt, unsigned int flags,
+					   volatile struct pml4e *root, volatile struct pdpte **res,
+					   bool create)
+{
+	load_pml4(root);
+	uint64_t offset = (uint64_t)virt >> 39;
+	volatile struct pml4e *pml4e = &pml4_mapped[offset];
+	if (!(pml4e->flags & F_PRESENT)) {
+		if (!create) {
+			return PAG_NOT_PRESENT;
+		}
+		void *new_page = alloc_phys_page();
+		if (new_page == NULL) {
+			return PAG_CANNOT_ALLOC;
+		}
+		load_addr(new_page);
+		memsetv(addr_mapped, 0, PAGE_SIZE);
+		pml4e->address = ((uint64_t)new_page) >> 12;
+		pml4e->flags = F_PRESENT;
+	}
+	if (flags)
+		pml4e->flags = F_PRESENT | flags;
+	*res = (volatile struct pdpte *)(uintptr_t)(pml4e->address << 12);
+	return PAG_SUCCESS;
+}
+
+static int select_pd(void *virt, unsigned int flags,
+					 volatile struct pdpte *pdpt, volatile struct pde **res,
+					 bool create)
+{
+	load_pdpt(pdpt);
+	uint64_t offset = ((uint64_t)virt >> 30) & 0x1ff;
+	volatile struct pdpte *pdpte = &pdpt_mapped[offset];
+	if (!(pdpte->flags & F_PRESENT)) {
+		if (!create) {
+			return PAG_NOT_PRESENT;
+		}
+		void *new_page = alloc_phys_page();
+		if (new_page == NULL) {
+			return PAG_CANNOT_ALLOC;
+		}
+		load_addr(new_page);
+		memsetv(addr_mapped, 0, PAGE_SIZE);
+		pdpte->address = ((uint64_t)new_page) >> 12;
+		pdpte->flags = F_PRESENT;
+	}
+	if (flags)
+		pdpte->flags = F_PRESENT | flags;
+	*res = (volatile struct pde *)(uintptr_t)(pdpte->address << 12);
+	return PAG_SUCCESS;
+}
+
+static int select_pt(void *virt, unsigned int flags, volatile struct pde *pd,
+					 volatile struct pte **res, bool create)
+{
+	load_pd(pd);
+	uint64_t offset = ((uint64_t)virt >> 21) & 0x1ff;
+	volatile struct pde *pde = &pd_mapped[offset];
+	if (!(pde->flags & F_PRESENT)) {
+		if (!create) {
+			return PAG_NOT_PRESENT;
+		}
+		void *new_page = alloc_phys_page();
+		if (new_page == NULL) {
+			return PAG_CANNOT_ALLOC;
+		}
+		load_addr(new_page);
+		memsetv(addr_mapped, 0, PAGE_SIZE);
+		pde->address = ((uint64_t)new_page) >> 12;
+		pde->flags = F_PRESENT;
+	}
+	if (flags)
+		pde->flags = F_PRESENT | flags;
+	*res = (volatile struct pte *)(uintptr_t)(pde->address << 12);
+	return PAG_SUCCESS;
+}
+
+static void select_page(void *virt, volatile struct pte *pt,
+						volatile struct pte **res)
+{
+	load_pt(pt);
+	uint64_t offset = ((uint64_t)virt >> 12) & 0x1ff;
+	volatile struct pte *page = &pt_mapped[offset];
+	*res = page;
+	return;
+}
+
+static inline void try_unmap_pml4(void)
+{
+	for (int i = 0; i < 512; i++) {
+		if (pml4_mapped[i].flags & F_PRESENT)
+			return;
+	}
+	for (int i = 0; i < 512; i++) {
+		if (pml4_mapped[i].address) {
+			void *addr = (void *)(uintptr_t)(pml4_mapped[i].address << 12);
+			free_phys_page(addr);
+		}
+	}
+}
+
+static inline void try_unmap_pdpt(void)
+{
+	for (int i = 0; i < 512; i++) {
+		if (pdpt_mapped[i].flags & F_PRESENT)
+			return;
+	}
+	for (int i = 0; i < 512; i++) {
+		if (pdpt_mapped[i].address) {
+			void *addr = (void *)(uintptr_t)(pdpt_mapped[i].address << 12);
+			free_phys_page(addr);
+		}
+	}
+	try_unmap_pml4();
+}
+
+static inline void try_unmap_pd(void)
+{
+	for (int i = 0; i < 512; i++) {
+		if (pd_mapped[i].flags & F_PRESENT)
+			return;
+	}
+	for (int i = 0; i < 512; i++) {
+		if (pd_mapped[i].address) {
+			void *addr = (void *)(uintptr_t)(pd_mapped[i].address << 12);
+			free_phys_page(addr);
+		}
+	}
+	try_unmap_pdpt();
+}
+
+static inline void try_unmap_pt(void)
+{
+	for (int i = 0; i < 512; i++) {
+		if (pt_mapped[i].flags & F_PRESENT)
+			return;
+	}
+	for (int i = 0; i < 512; i++) {
+		if (pt_mapped[i].address) {
+			void *addr = (void *)(uintptr_t)(pt_mapped[i].address << 12);
+			free_phys_page(addr);
+		}
+	}
+	try_unmap_pd();
+}
+
+static void unmap_page(volatile struct pml4e *root, void *virt)
+{
+	volatile struct pdpte *pdpt;
+	volatile struct pde *pd;
+	volatile struct pte *pt;
+	volatile struct pte *page;
+
+	unsigned int df = 0;
+
+	if (select_pdpt(virt, df, root, &pdpt, false))
+		return;
+
+	if (select_pd(virt, df, pdpt, &pd, false))
+		return;
+
+	if (select_pt(virt, df, pd, &pt, false))
+		return;
+
+	select_page(virt, pt, &page);
+
+	page->address = 0;
+	page->flags = 0;
+	page->loaded = 0;
+
+	try_unmap_pt();
+
+	invlpg(virt);
+
+	return;
+}
+
+static void unmap_pages(volatile struct pml4e *root, void *virt_start,
+						long page_count)
+{
+	uint64_t pml4_o = -1, pdpt_o = -1, pd_o = -1;
+
+	uint64_t pml4_n, pdpt_n, pd_n;
+
+	volatile struct pdpte *pdpt = NULL;
+	volatile struct pde *pd = NULL;
+	volatile struct pte *pt = NULL;
+	volatile struct pte *page = NULL;
+
+	unsigned int df = 0;
+
+	void *virt;
+
+	for (long i = 0; i < page_count; i++) {
+		virt = (char *)virt_start + (i * PAGE_SIZE);
+
+		pml4_n = (uint64_t)virt >> 39;
+		pdpt_n = ((uint64_t)virt >> 30) & 0x1ff;
+		pd_n = ((uint64_t)virt >> 21) & 0x1ff;
+
+		if (pdpt == NULL || pml4_o != pml4_n) {
+			if (select_pdpt(virt, df, root, &pdpt, false))
+				continue;
+			pml4_o = pml4_n;
+		}
+
+		if (pd == NULL || pdpt_o != pdpt_n) {
+			if (select_pd(virt, df, pdpt, &pd, false))
+				continue;
+			pdpt_o = pdpt_n;
+		}
+
+		if (pt == NULL || pd_o != pd_n) {
+			if (pt) {
+				try_unmap_pt();
+			}
+			if (select_pt(virt, df, pd, &pt, false))
+				continue;
+			pd_o = pd_n;
+		}
+
+		select_page(virt, pt, &page);
+
+		page->address = 0;
+		page->flags = 0;
+		page->loaded = 0;
+	}
+
+	if (pt != NULL)
+		try_unmap_pt();
+
+	return;
+}
+
+static volatile struct pte *get_page(volatile struct pml4e *root, void *virt)
+{
+	volatile struct pdpte *pdpt;
+	volatile struct pde *pd;
+	volatile struct pte *pt;
+	volatile struct pte *page;
+
+	unsigned int df = 0;
+
+	if (select_pdpt(virt, df, root, &pdpt, false))
+		return NULL;
+
+	if (select_pd(virt, df, pdpt, &pd, false))
+		return NULL;
+
+	if (select_pt(virt, df, pd, &pt, false))
+		return NULL;
+
+	select_page(virt, pt, &page);
+
+	return page;
+}
+
+static int map_page(volatile struct pml4e *root, void *virt, void *phys,
+					unsigned int flags)
+{
+	volatile struct pdpte *pdpt;
+	volatile struct pde *pd;
+	volatile struct pte *pt;
+	volatile struct pte *page;
+
+	unsigned int df = F_WRITEABLE;
+
+	if (phys == NULL)
+		df = 0; // alloc page on fault
+
+	if (select_pdpt(virt, df, root, &pdpt, true))
+		return 1;
+
+	if (select_pd(virt, df, pdpt, &pd, true))
+		return 1;
+
+	if (select_pt(virt, df, pd, &pt, true))
+		return 1;
+
+	select_page(virt, pt, &page);
+
+	if (phys) {
+		page->flags = F_PRESENT | flags;
+		page->address = (uint64_t)phys >> 12;
+		page->loaded = 1;
+		invlpg(virt);
+	} else {
+		page->flags = flags;
+		page->address = 0;
+		page->loaded = 0;
+	}
+
+	return 0;
+}
+
+static int map_pages(volatile struct pml4e *root, void *virt_start,
+					 void *phys_start, unsigned int flags, long page_count)
+{
+	uint64_t pml4_o = -1, pdpt_o = -1, pd_o = -1;
+
+	uint64_t pml4_n, pdpt_n, pd_n;
+
+	volatile struct pdpte *pdpt = NULL;
+	volatile struct pde *pd = NULL;
+	volatile struct pte *pt = NULL;
+	volatile struct pte *page = NULL;
+
+	void *virt, *phys;
+
+	unsigned int df = F_WRITEABLE;
+
+	if (phys_start == NULL)
+		df = 0; // alloc page on fault
+
+	long i;
+	for (i = 0; i < page_count; i++) {
+		virt = (char *)virt_start + (i * PAGE_SIZE);
+		phys = (char *)phys_start + (i * PAGE_SIZE);
+
+		pml4_n = (uint64_t)virt >> 39;
+		pdpt_n = ((uint64_t)virt >> 30) & 0x1ff;
+		pd_n = ((uint64_t)virt >> 21) & 0x1ff;
+
+		if (pdpt == NULL || pml4_o != pml4_n) {
+			if (select_pdpt(virt, df, root, &pdpt, true))
+				goto failed;
+			pml4_o = pml4_n;
+		}
+
+		if (pd == NULL || pdpt_o != pdpt_n) {
+			if (select_pd(virt, df, pdpt, &pd, true))
+				goto failed;
+			pdpt_o = pdpt_n;
+		}
+
+		if (pt == NULL || pd_o != pd_n) {
+			if (select_pt(virt, df, pd, &pt, true))
+				goto failed;
+			pd_o = pd_n;
+		}
+
+		select_page(virt, pt, &page);
+
+		if (phys_start) {
+			page->flags = F_PRESENT | flags;
+			page->address = (uint64_t)phys >> 12;
+			page->loaded = 1;
+		} else {
+			page->flags = flags;
+			page->address = 0;
+			page->loaded = 0;
+		}
+
+		if (flags & F_GLOBAL)
+			invlpg(virt);
+	}
+
+	__asm__ volatile("mov %cr3, %rax; mov %rax, %cr3;");
+
+	return 0;
+
+failed:
+
+	unmap_pages(root, virt, i);
+
+	return 1;
+}
+
+void paging_init(void)
+{
+	kernel_pml4[0].flags = F_PRESENT | F_WRITEABLE;
+	kernel_pml4[0].address = (uint64_t)(&kernel_pdpt_0) >> 12;
+
+	kernel_pdpt_0[0].flags = F_PRESENT | F_WRITEABLE;
+	kernel_pdpt_0[0].address = (uint64_t)(&kernel_pd_0) >> 12;
+
+	kernel_pd_0[1].flags = F_PRESENT | F_WRITEABLE;
+	kernel_pd_0[1].address = (uint64_t)(&paging_pt) >> 12;
+	kernel_pd_0[2].flags = F_PRESENT | F_WRITEABLE;
+	kernel_pd_0[2].address = (uint64_t)(&bootstrap_pt) >> 12;
+
+	memsetv(&paging_pt, 0, 4096);
+	memsetv(&bootstrap_pt, 0, 4096);
+}
+
+static inline void *page_align(void *addr)
+{
+	uintptr_t a = (uintptr_t)addr;
+	a /= PAGE_SIZE;
+	a *= PAGE_SIZE;
+	return (void *)a;
+}
+
+void *mapaddr(void *addr, size_t len)
+{
+	void *phys = page_align(addr);
+	ptrdiff_t error = (char *)addr - (char *)phys;
+	len += error;
+	long pages = len / PAGE_SIZE + 1;
+	void *virt = virtaddr_alloc(pages);
+	if (virt == NULL) {
+		return NULL;
+	}
+	if (map_pages(kernel_pml4, virt, phys, F_WRITEABLE, pages)) {
+		virtaddr_free(virt);
+		return NULL;
+	}
+	return (char *)virt + error;
+}
+
+void unmapaddr(void *addr)
+{
+	long pages = virtaddr_free(addr);
+	if (pages < 1)
+		return;
+	unmap_pages(kernel_pml4, addr, pages);
+}
+
+void *alloc_pages(size_t count)
+{
+	void *virt = virtaddr_alloc(count);
+	if (virt == NULL)
+		return NULL;
+	//void *phys = alloc_phys_pages(count);
+	//if (phys == NULL) {
+	//	virtaddr_free(virt);
+	//	return NULL;
+	//}
+	if (map_pages(kernel_pml4, virt,
+				  //phys,
+				  //F_WRITEABLE,
+				  NULL, F_WRITEABLE, count)) {
+		virtaddr_free(virt);
+		return NULL;
+	}
+	return virt;
+}
+
+void free_page(void *virt)
+{
+	(void)virt;
+	panic("free_page is not yet implemented");
+}
+
+void free_pages(void *virt)
+{
+	long pages = virtaddr_free(virt);
+	if (pages < 1)
+		return;
+	unmap_pages(kernel_pml4, virt, pages);
+}
+
+int kload_page(void *virt_addr)
+{
+	volatile struct pte *page = get_page(kernel_pml4, virt_addr);
+	if (page == NULL)
+		return -1;
+	if (page->loaded)
+		return -1;
+	void *phys = alloc_phys_page();
+	if (phys == NULL)
+		return -2;
+	page->loaded = 1;
+	page->address = (uint64_t)phys >> 12;
+	page->flags |= F_PRESENT;
+	invlpg(virt_addr);
+	return 0;
+}
diff --git a/kernel/memory/paging.h b/kernel/memory/paging.h
new file mode 100644
index 0000000..be6fd06
--- /dev/null
+++ b/kernel/memory/paging.h
@@ -0,0 +1,24 @@
+/**
+ * @file paging.h
+ *
+ * @author Freya Murphy <freya@freyacat.org>
+ *
+ * 64-bit paging functions
+ */
+
+#ifndef PAGING_H_
+#define PAGING_H_
+
+#define F_PRESENT 0x001
+#define F_WRITEABLE 0x002
+#define F_UNPRIVILEGED 0x004
+#define F_WRITETHROUGH 0x008
+#define F_CACHEDISABLE 0x010
+#define F_ACCESSED 0x020
+#define F_DIRTY 0x040
+#define F_MEGABYTE 0x080
+#define F_GLOBAL 0x100
+
+void paging_init(void);
+
+#endif /* paging.h */
diff --git a/kernel/memory/physalloc.c b/kernel/memory/physalloc.c
new file mode 100644
index 0000000..de0e4a7
--- /dev/null
+++ b/kernel/memory/physalloc.c
@@ -0,0 +1,242 @@
+#include <lib.h>
+#include <comus/memory.h>
+#include <comus/asm.h>
+
+#include "physalloc.h"
+
+extern char kernel_start;
+extern char kernel_end;
+#define kaddr(addr) ((uintptr_t)(&addr))
+
+// between memory_start and kernel_start will be the bitmap
+static uintptr_t memory_start = 0;
+
+struct memory_area {
+	uint64_t len;
+	uintptr_t addr;
+};
+
+static uint64_t *bitmap;
+static uint64_t total_memory;
+static uint64_t free_memory;
+static uint64_t page_count;
+static uint64_t segment_count;
+struct memory_area *page_start;
+
+static int n_pages(const struct memory_area *m)
+{
+	return m->len / PAGE_SIZE;
+}
+
+static void *page_at(int i)
+{
+	int cur_page = 0;
+	for (uint64_t idx = 0; idx < segment_count; idx++) {
+		const struct memory_area *m = page_start;
+		int pages = n_pages(m);
+		if (i - cur_page < pages) {
+			return (void *)(m->addr + (PAGE_SIZE * (i - cur_page)));
+		}
+		cur_page += pages;
+	}
+	return NULL;
+}
+
+static long page_idx(void *page)
+{
+	uintptr_t addr = (uintptr_t)page;
+	int cur_page = 0;
+	for (uint64_t idx = 0; idx < segment_count; idx++) {
+		const struct memory_area *m = page_start;
+		if ((uintptr_t)m + m->len > addr) {
+			return cur_page + ((addr - m->addr) / PAGE_SIZE);
+		}
+		cur_page += n_pages(m);
+	}
+	return -1;
+}
+
+static inline bool bitmap_get(int i)
+{
+	return (bitmap[i / 64] >> i % 64) & 1;
+}
+
+static inline void bitmap_set(int i, bool v)
+{
+	if (v)
+		free_memory -= PAGE_SIZE;
+	else
+		free_memory += PAGE_SIZE;
+	int idx = i / 64;
+	bitmap[idx] &= ~(1 << i % 64);
+	bitmap[idx] |= (v << i % 64);
+}
+
+void *alloc_phys_page(void)
+{
+	return alloc_phys_pages(1);
+}
+
+void *alloc_phys_pages(int pages)
+{
+	if (pages < 1)
+		return NULL;
+
+	int n_contiguous = 0;
+	int free_region_start = 0;
+	for (uint64_t i = 0; i < page_count; i++) {
+		bool free = !bitmap_get(i);
+
+		if (free) {
+			if (n_contiguous == 0)
+				free_region_start = i;
+			n_contiguous++;
+			if (n_contiguous == pages) {
+				for (int j = 0; j < pages; j++)
+					bitmap_set(free_region_start + j, true);
+				return page_at(free_region_start);
+			}
+		} else
+			n_contiguous = 0;
+	}
+
+	return NULL;
+}
+
+void free_phys_page(void *ptr)
+{
+	free_phys_pages(ptr, 1);
+}
+
+void free_phys_pages(void *ptr, int pages)
+{
+	long idx = page_idx(ptr);
+	if (idx == -1)
+		return;
+
+	for (int i = 0; i < pages; i++)
+		bitmap_set(idx + pages, false);
+}
+
+static bool segment_invalid(const struct memory_segment *segment)
+{
+	if (segment->addr < kaddr(kernel_start))
+		return true;
+	if (segment->addr + segment->len < memory_start)
+		return true;
+	if (segment->addr + segment->len < kaddr(kernel_start))
+		return true;
+	return false;
+}
+
+static struct memory_area segment_to_area(const struct memory_segment *segment)
+{
+	uint64_t length = segment->len;
+	uintptr_t addr = segment->addr;
+
+	uintptr_t start;
+	if (memory_start)
+		start = memory_start;
+	else
+		start = kaddr(kernel_end);
+
+	if (segment->addr < start) {
+		addr = start;
+		length -= addr - segment->addr;
+	} else {
+		addr = segment->addr;
+	}
+
+	struct memory_area temp;
+	temp.len = length;
+	temp.addr = addr;
+
+	return temp;
+}
+
+static uintptr_t page_align(uintptr_t ptr)
+{
+	return (ptr + PAGE_SIZE - 1) / PAGE_SIZE * PAGE_SIZE;
+}
+
+void physalloc_init(struct memory_map *map)
+{
+	bitmap = NULL;
+	total_memory = 0;
+	free_memory = 0;
+	page_count = 0;
+	page_start = NULL;
+
+	segment_count = 0;
+
+	for (uint32_t i = 0; i < map->entry_count; i++) {
+		struct memory_segment *segment = &map->entries[i];
+
+		if (segment_invalid(segment))
+			continue;
+
+		struct memory_area temp = segment_to_area(segment);
+		page_count += n_pages(&temp);
+		segment_count++;
+	}
+
+	long bitmap_pages = (page_count / 64 / PAGE_SIZE) + 1;
+	long bitmap_size = bitmap_pages * PAGE_SIZE;
+	bitmap = (uint64_t *)page_align(kaddr(kernel_end));
+
+	long page_area_size = segment_count * sizeof(struct memory_area);
+	char *page_area_addr = (char *)bitmap + bitmap_size;
+	page_area_addr = (char *)page_align((uintptr_t)page_area_addr);
+
+	memory_start = page_align((uintptr_t)page_area_addr + page_area_size);
+
+	bitmap = mapaddr(bitmap, bitmap_size);
+	memset(bitmap, 0, bitmap_size);
+	page_area_addr = mapaddr(page_area_addr, page_area_size);
+	memset(page_area_addr, 0, page_area_size);
+
+	page_start = (struct memory_area *)page_area_addr;
+
+	struct memory_area *area = page_start;
+
+	for (uint32_t i = 0; i < map->entry_count; i++) {
+		struct memory_segment *segment = &map->entries[i];
+
+		if (segment_invalid(segment))
+			continue;
+
+		struct memory_area temp = segment_to_area(segment);
+		*area = temp;
+		area++;
+	}
+
+	total_memory = page_count * PAGE_SIZE;
+	page_count -= bitmap_pages;
+	free_memory = page_count * PAGE_SIZE;
+
+	char buf[20];
+	printf("\nMEMORY USAGE\n");
+	printf("mem total: %s\n", btoa(memory_total(), buf));
+	printf("mem free:  %s\n", btoa(memory_free(), buf));
+	printf("mem used:  %s\n\n", btoa(memory_used(), buf));
+}
+
+void *alloc_page(void)
+{
+	return alloc_pages(1);
+}
+
+uint64_t memory_total(void)
+{
+	return total_memory;
+}
+
+uint64_t memory_free(void)
+{
+	return free_memory;
+}
+
+uint64_t memory_used(void)
+{
+	return total_memory - free_memory;
+}
diff --git a/kernel/memory/physalloc.h b/kernel/memory/physalloc.h
new file mode 100644
index 0000000..7afe998
--- /dev/null
+++ b/kernel/memory/physalloc.h
@@ -0,0 +1,44 @@
+/**
+ * @file physalloc.h
+ *
+ * @author Freya Murphy <freya@freyacat.org>
+ *
+ * Physical page allocator functions
+ */
+
+#ifndef PHYSALLOC_H_
+#define PHYSALLOC_H_
+
+#include <comus/memory.h>
+
+/**
+ * Initalize the physical page allocator
+ */
+void physalloc_init(struct memory_map *map);
+
+/**
+ * Allocates a single physical page in memory
+ * @preturns the physical address of the page
+ */
+void *alloc_phys_page(void);
+
+/**
+ * Allocates count physical pages in memory
+ * @returns the physical address of the first page
+ */
+void *alloc_phys_pages(int count);
+
+/**
+* Frees a single physical page in memory
+ * @param ptr - the physical address of the page
+ */
+void free_phys_page(void *ptr);
+
+/**
+ * Frees count physical pages in memory
+ * @param ptr - the physical address of the first page
+ * @param count - the number of pages in the list
+ */
+void free_phys_pages(void *ptr, int count);
+
+#endif /* physalloc.h */
diff --git a/kernel/memory/virtalloc.c b/kernel/memory/virtalloc.c
new file mode 100644
index 0000000..a9f25af
--- /dev/null
+++ b/kernel/memory/virtalloc.c
@@ -0,0 +1,200 @@
+#include <lib.h>
+#include <comus/memory.h>
+
+#include "virtalloc.h"
+
+struct addr_node {
+	uintptr_t start;
+	uintptr_t end;
+	struct addr_node *next;
+	struct addr_node *prev;
+	uint8_t is_alloc; // if node is storing allocated data
+	uint8_t is_used; // if node is in use by virtalloc
+};
+
+#define BSS_NODES 64
+static struct addr_node bootstrap_nodes[BSS_NODES];
+static struct addr_node *alloc_nodes = NULL;
+static size_t free_node_start = 0;
+static size_t alloc_node_count = 0;
+static size_t used_node_count = 0;
+static bool is_allocating = false;
+
+static struct addr_node *start_node = NULL;
+
+static struct addr_node *get_node_idx(int idx)
+{
+	if (idx < BSS_NODES) {
+		return &bootstrap_nodes[idx];
+	} else {
+		return &alloc_nodes[idx - BSS_NODES];
+	}
+}
+
+static void update_node_ptrs(struct addr_node *old, struct addr_node *new,
+							 int old_len, int new_len)
+{
+	if (old == NULL)
+		return;
+	int idx = 0;
+	for (int i = 0; i < old_len; i++) {
+		struct addr_node *o = &old[i];
+		if (o && !o->is_used)
+			continue;
+		struct addr_node *n = &new[idx++];
+		*n = *o;
+		if (n->prev != NULL)
+			n->prev->next = n;
+		if (n->next != NULL)
+			n->next->prev = n;
+	}
+	for (int i = idx; i < new_len; i++) {
+		struct addr_node *n = &new[idx++];
+		n->is_used = false;
+	}
+}
+
+static struct addr_node *get_node(void)
+{
+	size_t count = BSS_NODES + alloc_node_count;
+
+	if (!is_allocating && used_node_count + 16 >= count) {
+		is_allocating = true;
+		int new_alloc = alloc_node_count * 2;
+		if (new_alloc < 8)
+			new_alloc = 8;
+		struct addr_node *new_nodes;
+		new_nodes = malloc(sizeof(struct addr_node) * new_alloc);
+		if (new_nodes == NULL)
+			panic("virt addr alloc nodes is null");
+		update_node_ptrs(alloc_nodes, new_nodes, alloc_node_count, new_alloc);
+		free(alloc_nodes);
+		alloc_nodes = new_nodes;
+		alloc_node_count = new_alloc;
+		is_allocating = false;
+		count = BSS_NODES + alloc_node_count;
+	}
+
+	size_t idx = free_node_start;
+	for (; idx < count; idx++) {
+		struct addr_node *node = get_node_idx(idx);
+		if (!node->is_used) {
+			used_node_count++;
+			return node;
+		}
+	}
+
+	panic("could not get virtaddr node");
+}
+
+static void free_node(struct addr_node *node)
+{
+	node->is_used = false;
+	used_node_count--;
+}
+
+void virtaddr_init(void)
+{
+	struct addr_node init = {
+		.start = 0x400000, // third page table
+		.end = 0x1000000000000, // 48bit memory address max
+		.next = NULL,
+		.prev = NULL,
+		.is_alloc = false,
+		.is_used = true,
+	};
+	memset(bootstrap_nodes, 0, sizeof(bootstrap_nodes));
+	bootstrap_nodes[0] = init;
+	start_node = &bootstrap_nodes[0];
+}
+
+static void merge_back(struct addr_node *node)
+{
+	while (node->prev) {
+		if (node->is_alloc != node->prev->is_alloc)
+			break;
+		struct addr_node *temp = node->prev;
+		node->start = temp->start;
+		node->prev = temp->prev;
+		if (temp->prev)
+			temp->prev->next = node;
+		free_node(temp);
+	}
+	if (node->prev == NULL) {
+		start_node = node;
+	}
+}
+
+static void merge_forward(struct addr_node *node)
+{
+	while (node->next) {
+		if (node->is_alloc != node->next->is_alloc)
+			break;
+		struct addr_node *temp = node->next;
+		node->end = temp->end;
+		node->next = temp->next;
+		if (temp->next)
+			temp->next->prev = node;
+		free_node(temp);
+	}
+}
+
+void *virtaddr_alloc(int n_pages)
+{
+	if (n_pages < 1)
+		return NULL;
+	long n_length = n_pages * PAGE_SIZE;
+	struct addr_node *node = start_node;
+
+	for (; node != NULL; node = node->next) {
+		long length = node->end - node->start;
+		if (node->is_alloc)
+			continue;
+
+		if (length >= n_length) {
+			struct addr_node *new = get_node();
+			if (node->prev != NULL) {
+				node->prev->next = new;
+			} else {
+				start_node = new;
+			}
+			new->next = node;
+			new->prev = node->prev;
+			node->prev = new;
+			new->start = node->start;
+			new->end = new->start + n_length;
+			node->start = new->end;
+			new->is_alloc = true;
+			new->is_used = true;
+			new->next = node;
+			void *mem = (void *)new->start;
+			merge_back(new);
+			merge_forward(new);
+			return mem;
+		}
+	}
+
+	return NULL;
+}
+
+long virtaddr_free(void *virtaddr)
+{
+	uintptr_t virt = (uintptr_t)virtaddr;
+
+	if (virt % PAGE_SIZE)
+		return -1; // not page aligned, we did not give this out!!!
+
+	struct addr_node *node = start_node;
+
+	for (; node != NULL; node = node->next) {
+		if (node->start == virt) {
+			int length = node->end - node->start;
+			int pages = length / PAGE_SIZE;
+			merge_back(node);
+			merge_forward(node);
+			return pages;
+		}
+	}
+
+	return -1;
+}
diff --git a/kernel/memory/virtalloc.h b/kernel/memory/virtalloc.h
new file mode 100644
index 0000000..a5ca840
--- /dev/null
+++ b/kernel/memory/virtalloc.h
@@ -0,0 +1,31 @@
+/**
+ * @file virtalloc.h
+ *
+ * @author Freya Murphy <freya@freyacat.org>
+ *
+ * Virtural address allocator functions
+ */
+
+#ifndef VIRTALLOC_H_
+#define VIRTALLOC_H_
+
+/**
+ * Initalizes the virtual address allocator
+ */
+void virtaddr_init(void);
+
+/**
+ * Allocate a virtual address of length x pages
+ * @param pages - x pages
+ * @returns virt addr
+ */
+void *virtaddr_alloc(int pages);
+
+/**
+ * Free the virtual address from virtaddr_alloc
+ * @param virtaddr - the addr to free
+ * @returns number of pages used for virtaddr
+ */
+long virtaddr_free(void *virtaddr);
+
+#endif /* virtalloc.h */
diff --git a/kernel/old/include/offsets.h b/kernel/old/include/offsets.h
new file mode 100644
index 0000000..bf19776
--- /dev/null
+++ b/kernel/old/include/offsets.h
@@ -0,0 +1,83 @@
+/**
+** @file	offsets.h
+**
+** GENERATED AUTOMATICALLY - DO NOT EDIT
+**
+** This header file contains C Preprocessor macros which expand
+** into the byte offsets needed to reach fields within structs
+** used in the baseline system.  Should those struct declarations
+** change, the Offsets program should be modified (if needed),
+** recompiled, and re-run to recreate this file.
+*/
+
+#ifndef OFFSETS_H_
+#define OFFSETS_H_
+
+// Sizes of basic types
+
+#define SZ_char 1
+#define SZ_short 2
+#define SZ_int 4
+#define SZ_long 4
+#define SZ_long_long 8
+#define SZ_pointer 4
+
+// Sizes of our types
+
+#define SZ_int8_t 1
+#define SZ_uint8_t 1
+#define SZ_int16_t 2
+#define SZ_uint16_t 2
+#define SZ_int32_t 4
+#define SZ_uint32_t 4
+#define SZ_int64_t 8
+#define SZ_uint64_t 8
+#define SZ_bool_t 1
+
+// context_t structure
+
+#define SZ_CTX 72
+
+#define CTX_ss 0
+#define CTX_gs 4
+#define CTX_fs 8
+#define CTX_es 12
+#define CTX_ds 16
+#define CTX_edi 20
+#define CTX_esi 24
+#define CTX_ebp 28
+#define CTX_esp 32
+#define CTX_ebx 36
+#define CTX_edx 40
+#define CTX_ecx 44
+#define CTX_eax 48
+#define CTX_vector 52
+#define CTX_code 56
+#define CTX_eip 60
+#define CTX_cs 64
+#define CTX_eflags 68
+
+// section_t structure
+
+#define SZ_SCT 8
+
+#define SCT_length 0
+#define SCT_addr 4
+
+// pcb_t structure
+
+#define SZ_PCB 72
+
+#define PCB_context 0
+#define PCB_pdir 4
+#define PCB_sects 8
+#define PCB_next 40
+#define PCB_parent 44
+#define PCB_wakeup 48
+#define PCB_exit_status 52
+#define PCB_pid 56
+#define PCB_state 60
+#define PCB_priority 64
+#define PCB_ticks 68
+
+#endif
diff --git a/lib/alloc.c b/lib/alloc.c
new file mode 100644
index 0000000..dfa2df5
--- /dev/null
+++ b/lib/alloc.c
@@ -0,0 +1,211 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define MAGIC 0xBEEFCAFE
+
+struct page_header {
+	struct page_header *next;
+	struct page_header *prev;
+	size_t
+		node_number; // all headers on the same page alloc have the same node number (so they can be merged)
+	size_t
+		free; // free space after the node (if its the last node in the alloc block)
+	size_t used; // how much space this allocation is using
+	uint64_t magic;
+};
+
+static const size_t header_len = sizeof(struct page_header);
+static struct page_header *start_header = NULL;
+static struct page_header *end_header = NULL;
+
+static struct page_header *get_header(void *ptr)
+{
+	struct page_header *header =
+		(struct page_header *)((uintptr_t)ptr - header_len);
+
+	// PERF: do we want to make sure this pointer is paged
+	// before reading it???
+	if (header->magic != MAGIC) {
+		return NULL; // invalid pointer
+	}
+
+	return header;
+}
+
+static void *alloc_new(size_t size)
+{
+	size_t pages = ((size + header_len) / PAGE_SIZE) + 1;
+
+	void *addr = alloc_pages(pages);
+	void *mem = (char *)addr + header_len;
+
+	size_t total = pages * PAGE_SIZE;
+	size_t free = total - (size + header_len);
+
+	if (addr == NULL) {
+		return NULL;
+	}
+
+	size_t node;
+	if (end_header != NULL) {
+		node = end_header->node_number + 1;
+	} else {
+		node = 0;
+	}
+
+	struct page_header *header = addr;
+	header->magic = 0xBEEFCAFE;
+	header->used = size;
+	header->free = free;
+	header->prev = end_header;
+	header->next = NULL;
+	header->node_number = node;
+
+	if (start_header == NULL) {
+		start_header = header;
+	}
+
+	if (end_header != NULL) {
+		end_header->next = header;
+	} else {
+		end_header = header;
+	}
+
+	return mem;
+}
+
+static void *alloc_block(size_t size, struct page_header *block)
+{
+	struct page_header *header =
+		(struct page_header *)((char *)block + block->used + header_len);
+
+	size_t free = block->free - (size + header_len);
+	block->free = 0;
+
+	header->magic = MAGIC;
+	header->used = size;
+	header->free = free;
+	header->prev = block;
+	header->next = block->next;
+	block->next = header;
+	header->node_number = block->node_number;
+
+	void *mem = (char *)header + header_len;
+
+	return mem;
+}
+
+void *malloc(size_t size)
+{
+	struct page_header *header = start_header;
+
+	for (; header != NULL; header = header->next) {
+		size_t free = header->free;
+		if (free < header_len)
+			continue;
+		if (size <=
+			(free - header_len)) { // we must be able to fit data + header
+			break;
+		}
+	}
+
+	if (header != NULL) {
+		return alloc_block(size, header);
+	} else {
+		return alloc_new(size);
+	}
+}
+
+void *realloc(void *src, size_t dst_len)
+{
+	struct page_header *header;
+	size_t src_len;
+	void *dst;
+
+	// realloc of 0 means free pointer
+	if (dst_len == 0) {
+		free(src);
+		return NULL;
+	}
+
+	// NULL src means allocate ptr
+	if (src == NULL) {
+		dst = malloc(dst_len);
+		return dst;
+	}
+
+	header = get_header(src);
+
+	if (header == NULL)
+		return NULL;
+
+	src_len = header->used;
+
+	if (src_len == 0)
+		return NULL;
+
+	dst = malloc(dst_len);
+
+	if (dst == NULL)
+		return NULL; // allocation failed
+
+	if (dst_len < src_len)
+		src_len = dst_len;
+
+	memcpy(dst, src, src_len);
+	free(src);
+
+	return dst;
+}
+
+void free(void *ptr)
+{
+	struct page_header *header;
+
+	if (ptr == NULL)
+		return;
+
+	header = get_header(ptr);
+
+	if (header == NULL)
+		return;
+
+	header->free += header->used;
+	header->used = 0;
+
+	struct page_header *neighbor;
+
+	// merge left
+	for (neighbor = header->prev; neighbor != NULL; neighbor = neighbor->prev) {
+		if (neighbor->node_number != header->node_number)
+			break;
+		if (neighbor->used && header->used)
+			break;
+		neighbor->free += header->free + header_len;
+		neighbor->next = header->next;
+		header = neighbor;
+	}
+
+	// merge right
+	for (neighbor = header->next; neighbor != NULL; neighbor = neighbor->next) {
+		if (neighbor->node_number != header->node_number)
+			break;
+		if (neighbor->used)
+			break;
+		header->free += neighbor->free + header_len;
+		header->next = neighbor->next;
+	}
+
+	if ((header->next == NULL ||
+		 header->next->node_number != header->node_number) &&
+		(header->prev == NULL ||
+		 header->prev->node_number != header->node_number) &&
+		header->used == 0) {
+		if (header->next)
+			header->next->prev = header->prev;
+		if (header->prev)
+			header->prev->next = header->next;
+		free_pages(header);
+	}
+}