diff --git a/Makefile.am b/Makefile.am
index ba92d35..0fcdcae 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,4 +1,4 @@
-SUBDIRS = src
+SUBDIRS = src include
 
 quark.iso: src/quark-kernel rootfs/boot/grub/grub.cfg
 	mkdir -p rootfs/apps
diff --git a/README.md b/README.md
index 8ccfaed..e8288a2 100755
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ You will need:
 
 To build the kernel for the x86 platform, run:
 - `autoreconf -i`
-- `./configure --host=i686-elf CFLAGS=-ffreestanding LDFLAGS=-nostdlib`
+- `./configure --host=i686-elf --prefix=<your_desired_prefix> --bindir=$(prefix)/apps CFLAGS=-ffreestanding LDFLAGS=-nostdlib`
 - `make`
 
 To generate a bootable disk image, run:
diff --git a/configure.ac b/configure.ac
index 4cd90c7..92890ab 100644
--- a/configure.ac
+++ b/configure.ac
@@ -27,5 +27,5 @@ AC_TYPE_UINT8_T
 
 AM_CONDITIONAL([x86], [test $host = i686-elf])
 
-AC_CONFIG_FILES([Makefile src/Makefile])
+AC_CONFIG_FILES([Makefile src/Makefile include/Makefile])
 AC_OUTPUT
diff --git a/include/Makefile.am b/include/Makefile.am
new file mode 100644
index 0000000..eb82e4f
--- /dev/null
+++ b/include/Makefile.am
@@ -0,0 +1 @@
+nobase_include_HEADERS = types/status.h types/syscallid.h types/physaddr.h types/syscallarg.h
\ No newline at end of file
diff --git a/include/kernel.h b/include/kernel.h
index 6908394..e2922ec 100644
--- a/include/kernel.h
+++ b/include/kernel.h
@@ -22,6 +22,8 @@
 #define IO_PORT 1 << 1
 #define IO_MAILBOX 2 << 1
 
+typedef unsigned long (*signal_handler_t)(void*, void*);
+
 struct process_context_t;
 
 struct module_t
@@ -73,10 +75,24 @@ struct port_t
     unsigned long owner_pid;
 };
 
+struct signal_action_t
+{
+    unsigned long pid;
+    signal_handler_t func_ptr;
+    void (*trampoline_ptr)();
+    void *userdata;
+};
+
+struct signal_context_t
+{
+    unsigned long signal_id;
+};
+
 struct kernel_t
 {
     struct syscall_t syscall_table[MAX_SYSCALL_ID];
     struct priority_queue_t priority_queue;
+    struct avltree_t *interrupt_handlers;
     struct avltree_t *port_table;
     struct avltree_t *process_table;
     struct process_t *active_process;
@@ -85,35 +101,41 @@ struct kernel_t
 
 void kernel_initialize(struct boot_info_t *boot_info);
 
-enum error_t set_syscall(int id, int arg_count, int pid, void *func_ptr);
+error_t set_syscall(int id, int arg_count, int pid, void *func_ptr);
 
-size_t do_syscall(enum syscall_id_t id, syscall_arg_t arg1, syscall_arg_t arg2, syscall_arg_t arg3, void *pc, void *stack, unsigned long flags);
+size_t do_syscall(syscall_id_t id, syscall_arg_t arg1, syscall_arg_t arg2, syscall_arg_t arg3, void *pc, void *stack, unsigned long flags);
 
-enum error_t kernel_load_module(struct module_t *module);
+error_t kernel_load_module(struct module_t *module);
 
 unsigned long kernel_current_pid();
 
 struct process_context_t *kernel_current_context();
 
-enum error_t kernel_store_active_context(struct process_context_t *context);
+error_t kernel_store_active_context(struct process_context_t *context);
 
 unsigned long kernel_spawn_process(void *program_entry, int priority, physaddr_t address_space);
 
 struct process_context_t *kernel_advance_scheduler();
 
-enum error_t kernel_terminate_process(size_t process_id);
+error_t kernel_terminate_process(size_t process_id);
 
-enum error_t kernel_create_port(unsigned long id);
+error_t kernel_create_port(unsigned long id);
 
-enum error_t kernel_remove_port(unsigned long id);
+error_t kernel_remove_port(unsigned long id);
 
 unsigned long kernel_get_port_owner(unsigned long id);
 
-enum error_t kernel_send_message(unsigned long recipient, struct message_t *message);
+error_t kernel_send_message(unsigned long recipient, struct message_t *message);
 
-enum error_t kernel_queue_sender(unsigned long recipient);
+error_t kernel_queue_message(unsigned long recipient, struct message_t *message);
 
-enum error_t kernel_queue_message(unsigned long recipient, struct message_t *message);
+error_t kernel_register_interrupt_handler(unsigned long interrupt, signal_handler_t handler, void *userdata);
+
+error_t kernel_remove_interrupt_handler(unsigned long interrupt);
+
+error_t kernel_execute_interrupt_handler(unsigned long interrupt);
+
+error_t kernel_signal_return();
 
 int receive_message(struct message_t *buffer, int flags);
 
diff --git a/include/mmgr.h b/include/mmgr.h
index 731afb9..8af38d8 100644
--- a/include/mmgr.h
+++ b/include/mmgr.h
@@ -3,6 +3,7 @@
 #include "memmap.h"
 #include "platform/paging.h"
 #include "types/physaddr.h"
+#include "types/status.h"
 #include <stddef.h>
 
 extern const size_t page_size;
@@ -71,7 +72,7 @@ void *page_map_end();
  * @param block_size 
  * @return enum error_t 
  */
-enum error_t initialize_page_map(struct memory_map_t *map, void *base, size_t memory_size, unsigned long block_size);
+error_t initialize_page_map(struct memory_map_t *map, void *base, size_t memory_size, unsigned long block_size);
 
 /**
  * @brief Create a new top-level page table and map the kernel in it.
diff --git a/include/platform/context.h b/include/platform/context.h
index 2152655..92b7a03 100644
--- a/include/platform/context.h
+++ b/include/platform/context.h
@@ -33,12 +33,28 @@ struct process_context_t
 
 void load_context(struct process_context_t *context);
 
+void *get_context_pc(struct process_context_t *context);
+
 void set_context_pc(struct process_context_t *context, void *pc);
 
+void *get_context_stack(struct process_context_t *context);
+
 void set_context_stack(struct process_context_t *context, void *stack);
 
 void set_context_flags(struct process_context_t *context, unsigned long flags);
 
 void set_context_return(struct process_context_t *context, unsigned long value);
 
+void *context_stack_push(struct process_context_t *context, unsigned long value);
+
+void *context_stack_push_struct(struct process_context_t *context, void *data, unsigned long size);
+
+void *context_stack_pop(struct process_context_t *context, void *value);
+
+void *context_stack_pop_struct(struct process_context_t *context, void *value, unsigned long size);
+
+void context_call_func(struct process_context_t *context, void *func_ptr, void *ret_ptr, int argc, ...);
+
+void context_cleanup_func(struct process_context_t *context, int argc);
+
 #endif
diff --git a/include/queue.h b/include/queue.h
index 6b8368a..7e77e15 100644
--- a/include/queue.h
+++ b/include/queue.h
@@ -43,7 +43,7 @@ void queue_construct(struct queue_t *queue);
  * @param ptr A pointer to some user-defined data to store on the queue.
  * @return enum error_t
  */
-enum error_t queue_insert(struct queue_t *queue, void *ptr);
+error_t queue_insert(struct queue_t *queue, void *ptr);
 
 /**
  * @brief Removes the next item from the queue and returns it.
diff --git a/include/syscalls.h b/include/syscalls.h
index 7787fce..efd1e8b 100644
--- a/include/syscalls.h
+++ b/include/syscalls.h
@@ -1,15 +1,9 @@
 #pragma once
 
+#include "types/syscallarg.h"
 #include <stdbool.h>
 #include <stddef.h>
 
-typedef union
-{
-    long signed_int;
-    unsigned long unsigned_int;
-    void *ptr;
-} syscall_arg_t;
-
 typedef size_t (*syscall_ptr_0_t)();
 
 typedef size_t (*syscall_ptr_1_t)(syscall_arg_t);
diff --git a/include/types/physaddr.h b/include/types/physaddr.h
index 6631873..3e12471 100644
--- a/include/types/physaddr.h
+++ b/include/types/physaddr.h
@@ -1,14 +1,6 @@
 #ifndef _QUARK_PHYSADDR_H
 #define _QUARK_PHYSADDR_H
 
-#include <stdint.h>
-
-#if defined __i386__ || __arm__
-typedef uint32_t physaddr_t;
-#elif defined __x86_64__ || __aarch64__
-typedef uint64_t physaddr_t;
-#else
-typedef uint64_t physaddr_t;
-#endif
+typedef unsigned long int physaddr_t;
 
 #endif
\ No newline at end of file
diff --git a/include/types/status.h b/include/types/status.h
index 60eec73..ed04ac2 100644
--- a/include/types/status.h
+++ b/include/types/status.h
@@ -1,7 +1,7 @@
 #ifndef _QUARK_ERROR_H
 #define _QUARK_ERROR_H
 
-enum error_t
+typedef enum
 {
     ENONE = 0,
     ENULLPTR,
@@ -15,6 +15,6 @@ enum error_t
     EPERM,
     EBUSY,
     EEXITED
-};
+} error_t;
 
 #endif
\ No newline at end of file
diff --git a/include/types/syscallarg.h b/include/types/syscallarg.h
new file mode 100644
index 0000000..b1a49c8
--- /dev/null
+++ b/include/types/syscallarg.h
@@ -0,0 +1,11 @@
+#ifndef _QUARK_SYSCALLARG_H
+#define _QUARK_SYSCALLARG_H
+
+typedef union
+{
+    long int signed_int;
+    unsigned long int unsigned_int;
+    void *ptr;
+} syscall_arg_t;
+
+#endif
\ No newline at end of file
diff --git a/include/types/syscallid.h b/include/types/syscallid.h
index fe95a5b..b04b0e3 100644
--- a/include/types/syscallid.h
+++ b/include/types/syscallid.h
@@ -1,7 +1,7 @@
 #ifndef QUARK_SYSCALLID_H
 #define QUARK_SYSCALLID_H
 
-enum syscall_id_t
+typedef enum
 {
     SYSCALL_TEST = 1,
     SYSCALL_MMAP,
@@ -12,6 +12,6 @@ enum syscall_id_t
     SYSCALL_RECEIVE,
     SYSCALL_OPEN_PORT,
     SYSCALL_CLOSE_PORT
-};
+} syscall_id_t;
 
 #endif
\ No newline at end of file
diff --git a/include/x86/idt.h b/include/x86/idt.h
index 3b78343..0e018dc 100644
--- a/include/x86/idt.h
+++ b/include/x86/idt.h
@@ -32,11 +32,11 @@ enum interrupt_code_t
 
 enum isr_type_t
 {
-    INTERRPUT_TASK32 = 5,
-    INTERRPUT_TRAP32 = 15,
-    INTERRPUT_INT32 = 14,
-    INTERRPUT_TRAP16 = 7,
-    INTERRPUT_INT16 = 6
+    INTERRUPT_TASK32 = 5,
+    INTERRUPT_TRAP32 = 15,
+    INTERRUPT_INT32 = 14,
+    INTERRUPT_TRAP16 = 7,
+    INTERRUPT_INT16 = 6
 };
 
 void initialize_gdt();
diff --git a/src/Makefile.am b/src/Makefile.am
index 9bd5478..5954e6f 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,4 +1,4 @@
-noinst_PROGRAMS = quark-kernel
+bin_PROGRAMS = quark-kernel
 quark_kernel_SOURCES = kernel.c mmgr.c priorityqueue.c stdio.c string.c elf.c syscalls.c heap.c memmap.c avltree.c queue.c math.c
 quark_kernel_LDADD = -lgcc
 quark_kernel_CFLAGS = -I$(top_srcdir)/include -ffreestanding -mgeneral-regs-only -O0 -Wall -ggdb
diff --git a/src/avltree.c b/src/avltree.c
index 41ae7c9..8902d54 100644
--- a/src/avltree.c
+++ b/src/avltree.c
@@ -179,20 +179,20 @@ struct avltree_t *avl_remove(struct avltree_t *tree, int key)
 
 void *avl_get(struct avltree_t *tree, int key)
 {
-    if(tree == NULL)
+    while(tree != NULL)
     {
-        return NULL;
-    }
-    else if(key < tree->key)
-    {
-        return avl_get(tree->left, key);
-    }
-    else if(key > tree->key)
-    {
-        return avl_get(tree->right, key);
-    }
-    else
-    {
-        return tree->value;
+        if(key < tree->key)
+        {
+            tree = tree->left;
+        }
+        else if(key > tree->key)
+        {
+            tree = tree->right;
+        }
+        else
+        {
+            return tree->value;
+        }
     }
+    return NULL;
 }
\ No newline at end of file
diff --git a/src/heap.c b/src/heap.c
index 488fa5a..e194a60 100644
--- a/src/heap.c
+++ b/src/heap.c
@@ -19,9 +19,9 @@ struct heap_t
 
 struct heap_node_t
 {
-    size_t height : 5;
     size_t mapped : 1;
     size_t state : 2;
+    size_t height : 5;
 } __attribute__ ((packed));
 
 size_t find_free_block(struct heap_t *heap, size_t height)
diff --git a/src/kernel.c b/src/kernel.c
index dad6537..f778a08 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -17,18 +17,19 @@ struct kernel_t kernel;
 
 void kernel_initialize(struct boot_info_t *boot_info)
 {
-    insert_region(&boot_info->map, (physaddr_t)&_kernel_pstart, (physaddr_t)&_kernel_pend - (physaddr_t)&_kernel_pstart, M_UNAVAILABLE);
-    initialize_page_map(&boot_info->map, (physaddr_t*)&_kernel_end, boot_info->memory_size, page_size);
-    kminit(&_kernel_start, page_map_end(), 0xFFC00000 - (size_t)&_kernel_start, 64);
     initialize_screen();
     printf("***%s***\n", PACKAGE_STRING);
     printf("Total memory: %08x\n", boot_info->memory_size);
+    printf("kernel: %08x ... %08x\n", &_kernel_pstart, &_kernel_pend);
     printf("Type\t\tLocation\t\tSize\n");
     for (size_t i = 0; i < boot_info->map.size && boot_info->map.array[i].size > 0; i++)
     {
         printf("%i\t\t\t%08x\t\t%u\n", boot_info->map.array[i].type, boot_info->map.array[i].location, boot_info->map.array[i].size);
     }
 
+    insert_region(&boot_info->map, (physaddr_t)&_kernel_pstart, (physaddr_t)&_kernel_pend - (physaddr_t)&_kernel_pstart, M_UNAVAILABLE);
+    initialize_page_map(&boot_info->map, (physaddr_t*)&_kernel_end, boot_info->memory_size, page_size);
+    kminit(&_kernel_start, page_map_end(), 0xFFC00000 - (size_t)&_kernel_start, 64);
     kernel.active_process = NULL;
     kernel.next_pid = 1;
     kernel.process_table = NULL;
@@ -62,7 +63,7 @@ void kernel_initialize(struct boot_info_t *boot_info)
     load_context(kernel_advance_scheduler());
 }
 
-enum error_t set_syscall(int id, int arg_count, int pid, void *func_ptr)
+error_t set_syscall(int id, int arg_count, int pid, void *func_ptr)
 {
     if(id < 0 || id > MAX_SYSCALL_ID)
     {
@@ -91,7 +92,7 @@ enum error_t set_syscall(int id, int arg_count, int pid, void *func_ptr)
     return ENONE;
 }
 
-size_t do_syscall(enum syscall_id_t id, syscall_arg_t arg1, syscall_arg_t arg2, syscall_arg_t arg3, void *pc, void *stack, unsigned long flags)
+size_t do_syscall(syscall_id_t id, syscall_arg_t arg1, syscall_arg_t arg2, syscall_arg_t arg3, void *pc, void *stack, unsigned long flags)
 {
     if(id < 0 || id > MAX_SYSCALL_ID)
     {
@@ -139,7 +140,7 @@ size_t do_syscall(enum syscall_id_t id, syscall_arg_t arg1, syscall_arg_t arg2,
     return result;
 }
 
-enum error_t kernel_load_module(struct module_t *module)
+error_t kernel_load_module(struct module_t *module)
 {
     physaddr_t module_address_space = create_address_space();
     if(module_address_space == ENOMEM) {
@@ -264,13 +265,13 @@ struct process_context_t *kernel_advance_scheduler()
     if(kernel.active_process != NULL)
     {
         paging_load_address_space(kernel.active_process->page_table);
-        printf("entering process %08x cr3=%08x ctx=%08x.\n", kernel.active_process->pid, kernel.active_process->page_table, kernel.active_process->ctx);
+        printf("entering process %08x cr3=%08x ctx=%08x sched=%i.\n", kernel.active_process->pid, kernel.active_process->page_table, kernel.active_process->ctx, kernel.priority_queue.size);
         return kernel.active_process->ctx;
     }
     panic("no processes available to enter!");
 }
 
-enum error_t kernel_terminate_process(size_t process_id)
+error_t kernel_terminate_process(size_t process_id)
 {
     struct process_t *process = avl_get(kernel.process_table, process_id);
     if(process == NULL)
@@ -298,7 +299,7 @@ enum error_t kernel_terminate_process(size_t process_id)
     return ENONE;
 }
 
-enum error_t kernel_store_active_context(struct process_context_t *context)
+error_t kernel_store_active_context(struct process_context_t *context)
 {
     if(kernel.active_process != NULL && kernel.active_process->ctx != NULL)
     {
@@ -311,7 +312,7 @@ enum error_t kernel_store_active_context(struct process_context_t *context)
     }
 }
 
-enum error_t kernel_create_port(unsigned long id)
+error_t kernel_create_port(unsigned long id)
 {
     if(avl_get(kernel.port_table, id) != NULL)
     {
@@ -325,7 +326,7 @@ enum error_t kernel_create_port(unsigned long id)
     return ENONE;
 }
 
-enum error_t kernel_remove_port(unsigned long id)
+error_t kernel_remove_port(unsigned long id)
 {
     struct port_t *port = avl_get(kernel.port_table, id);
     if(port == NULL)
@@ -355,14 +356,14 @@ unsigned long kernel_get_port_owner(unsigned long id)
     }
 }
 
-enum error_t kernel_send_message(unsigned long recipient, struct message_t *message)
+error_t kernel_send_message(unsigned long recipient, struct message_t *message)
 {
     struct process_t *dest = avl_get(kernel.process_table, recipient);
     if(dest == NULL)
     {
         return EDOESNTEXIST;
     }
-    else if(dest->message_buffer != NULL)
+    else if(dest->message_buffer != NULL && dest->state == PROCESS_REQUESTING)
     {
         printf("Sending message directly from %i to %i\n", kernel.active_process->pid, dest->pid);
         struct message_t kernel_buffer;
@@ -383,24 +384,7 @@ enum error_t kernel_send_message(unsigned long recipient, struct message_t *mess
     }
 }
 
-enum error_t kernel_queue_sender(unsigned long recipient)
-{
-    struct process_t *dest = avl_get(kernel.process_table, recipient);
-    if(dest != NULL)
-    {
-        printf("Queueing process %i to %i\n", kernel.active_process->pid, dest->pid);
-        queue_insert(&dest->sending_queue, kernel.active_process);
-        kernel.active_process->state = PROCESS_SENDING;
-        kernel.active_process = NULL;
-        return ENONE;
-    }
-    else
-    {
-        return EDOESNTEXIST;
-    }
-}
-
-enum error_t kernel_queue_message(unsigned long recipient, struct message_t *message)
+error_t kernel_queue_message(unsigned long recipient, struct message_t *message)
 {
     struct process_t *dest = avl_get(kernel.process_table, recipient);
     if(dest != NULL)
@@ -423,21 +407,7 @@ enum error_t kernel_queue_message(unsigned long recipient, struct message_t *mes
 
 int receive_message(struct message_t *buffer, int flags)
 {
-    if(kernel.active_process->sending_queue.count > 0)
-    {
-        struct message_t kernel_buffer;
-        struct process_t *sender = queue_get_next(&kernel.active_process->sending_queue);
-        paging_load_address_space(sender->page_table);
-        memcpy(&kernel_buffer, &sender->message_buffer, sizeof(struct message_t));
-        kernel_buffer.sender = sender->pid;
-        paging_load_address_space(kernel.active_process->page_table);
-        memcpy(buffer, &kernel_buffer, sizeof(struct message_t));
-        sender->state = PROCESS_ACTIVE;
-        set_context_return(sender->ctx, ENONE);
-        priorityqueue_insert(&kernel.priority_queue, sender, sender->priority);
-        return ENONE;
-    }
-    else if(kernel.active_process->message_queue.count > 0)
+    if(kernel.active_process->message_queue.count > 0)
     {
         struct message_t *queued_msg = queue_get_next(&kernel.active_process->message_queue);
         memcpy(buffer, queued_msg, sizeof(struct message_t));
@@ -457,6 +427,80 @@ int receive_message(struct message_t *buffer, int flags)
     }
 }
 
+error_t kernel_register_interrupt_handler(unsigned long interrupt, signal_handler_t handler, void *userdata)
+{
+    if(avl_get(kernel.interrupt_handlers, interrupt) != NULL)
+    {
+        return EEXISTS;
+    }
+    struct signal_action_t *action = kmalloc(sizeof(struct signal_action_t));
+    action->pid = kernel.active_process->pid;
+    action->func_ptr = handler;
+    action->userdata = userdata;
+    kernel.interrupt_handlers = avl_insert(kernel.interrupt_handlers, interrupt, action);
+    return ENONE;
+}
+
+error_t kernel_remove_interrupt_handler(unsigned long interrupt)
+{
+    struct signal_action_t *action = avl_get(kernel.interrupt_handlers, interrupt);
+    if(action == NULL)
+    {
+        return EDOESNTEXIST;
+    }
+    kfree(action);
+    kernel.interrupt_handlers = avl_remove(kernel.interrupt_handlers, interrupt);
+    return ENONE;
+}
+
+error_t kernel_execute_interrupt_handler(unsigned long interrupt)
+{
+    struct signal_action_t *action = avl_get(kernel.interrupt_handlers, interrupt);
+    if(action == NULL)
+    {
+        return EDOESNTEXIST;
+    }
+
+    struct process_t *process = avl_get(kernel.process_table, action->pid);
+    if(process == NULL)
+    {
+        kernel.interrupt_handlers = avl_remove(kernel.interrupt_handlers, interrupt);
+        return EDOESNTEXIST;
+    }
+
+    paging_load_address_space(process->page_table);
+
+    struct signal_context_t siginfo = {
+        .signal_id = interrupt
+    };
+    void *siginfo_ptr = context_stack_push_struct(process->ctx, &siginfo, sizeof(siginfo));
+    context_stack_push_struct(process->ctx, process->ctx, sizeof(*process->ctx));
+    context_stack_push(process->ctx, process->state);
+    context_call_func(process->ctx, action->func_ptr, action->trampoline_ptr, 2, action->userdata, siginfo_ptr);
+    if(process->state != PROCESS_ACTIVE)
+    {
+        process->state = PROCESS_ACTIVE;
+        priorityqueue_insert(&kernel.priority_queue, process, process->priority);
+    }
+
+    paging_load_address_space(kernel.active_process->page_table);
+
+    return ENONE;
+}
+
+error_t kernel_signal_return()
+{
+    context_cleanup_func(kernel.active_process->ctx, 2);
+    context_stack_pop(kernel.active_process->ctx, &kernel.active_process->state);
+    context_stack_pop_struct(kernel.active_process->ctx, kernel.active_process->ctx, sizeof(*kernel.active_process->ctx));
+    if(kernel.active_process->state == PROCESS_REQUESTING)
+    {
+        receive_message(kernel.active_process->message_buffer, 0);
+        load_context(kernel.active_process->ctx);
+    }
+    return ENONE;
+}
+
 void panic(const char *message)
 {
     printf("panic: %s", message);
diff --git a/src/mmgr.c b/src/mmgr.c
index 0caede0..c23c2e5 100644
--- a/src/mmgr.c
+++ b/src/mmgr.c
@@ -3,142 +3,152 @@
 #include "math.h"
 #include "platform/paging.h"
 #include "types/status.h"
+#include "stdio.h"
 #include <stdint.h>
 #include <stdbool.h>
 
-/**
- * @brief Describes a stack containing the physical addresses of available page
- * frames.
- * 
- */
-struct page_stack_t
-{
-    
-    /**
-     * @brief The total number of physical pages managed by the system.
-     * 
-     */
-    unsigned long total_pages;
-
-    /**
-     * @brief Points to the topmost physical address on the stack.
-     * 
-     */
-    physaddr_t *stack_pointer;
-
-    /**
-     * @brief Points to the bottom of the stack.
-     * 
-     */
-    physaddr_t *base_pointer;
-
-    /**
-     * @brief Points to the limit of the stack. The stack cannot grow beyond
-     * this point.
-     * 
-     */
-    physaddr_t *limit_pointer;
-
-} page_stack;
+#define MAX_CACHE_SIZE 32
 
 struct page_map_t
 {
     /**
      * @brief The underlying bitmap representing the availability of chunks of
      * physical memory.
-     * 
+     *
      */
     unsigned long *bitmap;
 
     /**
-     * @brief The size of the bitmap in bytes.
+     * @brief Stores a list of available blocks of memory to speed up allocation.
      * 
      */
+    unsigned long *cache;
+
+    /**
+     * @brief The size of the bitmap in bytes.
+     *
+     */
     unsigned long bitmap_size;
 
     /**
      * @brief The size in bytes of the smallest unit of allocation.
-     * 
+     *
      * This value should either be the size of a page on the host system, or
      * possibly some number of pages.
-     * 
+     *
      */
     unsigned long block_size;
 
     /**
-     * @brief 
-     * 
+     * @brief
+     *
      */
     unsigned long height;
 
     /**
-     * @brief The number of available blocks of memory. 
-     * 
-     * Due to memory fragmentation, it may not be possible to allocate all 
+     * @brief The number of available blocks of memory.
+     *
+     * Due to memory fragmentation, it may not be possible to allocate all
      * available memory at once.
-     * 
+     *
      */
     unsigned long free_block_count;
 } page_map;
 
-const int bitmap_word_size = 8 * sizeof(*page_map.bitmap);
+static const int bitmap_word_size = 8 * sizeof(*page_map.bitmap);
+
+static void clear_cache()
+{
+    for(int i = 0; i < MAX_CACHE_SIZE; i++)
+    {
+        page_map.cache[i] = 0;
+    }
+}
+
+static void clear_bitmap()
+{
+    for(int i = 0; i < page_map.bitmap_size / sizeof(*page_map.bitmap); i++)
+    {
+        page_map.bitmap[i] = 0;
+    }
+}
 
 int split_block(int index)
 {
-    if(index)
+    if (index)
     {
-        int bitmap_index = index / bitmap_word_size;
-        int bitmap_offset = index % bitmap_word_size;
-        page_map.bitmap[bitmap_index] &= ~(1 << bitmap_offset);
+        unsigned long bitmap_index = index / bitmap_word_size;
+        unsigned long bitmap_offset = index % bitmap_word_size;
+        page_map.bitmap[bitmap_index] &= ~((unsigned long)1 << bitmap_offset);
         index *= 2;
         bitmap_index = index / bitmap_word_size;
-        bitmap_offset = index / bitmap_word_size;
-        page_map.bitmap[bitmap_index] |= 1 << bitmap_offset;
-        page_map.bitmap[bitmap_index] |= 1 << (bitmap_offset ^ 1);
+        bitmap_offset = index % bitmap_word_size;
+        page_map.bitmap[bitmap_index] |= (unsigned long)1 << bitmap_offset;
+        page_map.bitmap[bitmap_index] |= (unsigned long)1 << (bitmap_offset ^ 1);
+        unsigned long depth = llog2(index + 1) - 1;
+        unsigned long cache_start = llog2(bitmap_word_size);
+        if(depth >= cache_start && page_map.cache[depth - cache_start] == 0)
+        {
+            page_map.cache[depth - cache_start] = index + 1;
+        }
     }
     return index;
 }
 
 int find_free_region(int height)
 {
-    if(height > page_map.height || height < 0)
+    if (height > page_map.height || height < 0)
     {
         return 0;
     }
-    else if(height <= page_map.height - ilog2(bitmap_word_size))
+    else if (height <= page_map.height - ilog2(bitmap_word_size))
     {
-        for(int index = (1 << (page_map.height - height)) / bitmap_word_size; 
-            index < (1 << (page_map.height - height + 1)) / bitmap_word_size; 
-            index++)
+        if(page_map.cache[page_map.height - height - llog2(bitmap_word_size)])
         {
-            if(page_map.bitmap[index] != 0)
+            unsigned long index = page_map.cache[page_map.height - height - llog2(bitmap_word_size)];
+            page_map.cache[page_map.height - height - llog2(bitmap_word_size)] = 0;
+            return index;
+        }
+        unsigned long start = (1 << (page_map.height - height)) / bitmap_word_size;
+        unsigned long end = ((1 << (page_map.height - height + 1)) / bitmap_word_size);
+        for (int index = start; index < end; index++)
+        {
+            if (page_map.bitmap[index] != 0)
             {
-                return bitmap_word_size * index + __builtin_ctz(page_map.bitmap[index]);
+                return bitmap_word_size * index + __builtin_ctzl(page_map.bitmap[index]);
             }
         }
     }
     else
     {
-        static const int bitmasks[] = {0x00000002, 0x0000000C, 0x000000F0, 0x0000FF00, 0xFFFF0000};
+#if __SIZEOF_LONG__ == 8
+        static const unsigned long bitmasks[] = {0x00000002, 0x0000000C, 0x000000F0, 0x0000FF00, 0xFFFF0000, 0xFFFFFFFF00000000};
+#else
+        static const unsigned long bitmasks[] = {0x00000002, 0x0000000C, 0x000000F0, 0x0000FF00, 0xFFFF0000};
+#endif
         int depth = page_map.height - height;
-        if(page_map.bitmap[0] & bitmasks[depth])
+        if (page_map.bitmap[0] & bitmasks[depth])
         {
-            return __builtin_ctz(page_map.bitmap[0] & bitmasks[depth]);
+            return __builtin_ctzl(page_map.bitmap[0] & bitmasks[depth]);
         }
     }
     return split_block(find_free_region(height + 1));
 }
 
+
 physaddr_t reserve_region(size_t size)
 {
     int height = llog2(size / page_map.block_size);
     int index = find_free_region(height);
-    if(index)
+    if (index)
     {
         int bitmap_index = index / bitmap_word_size;
         int bitmap_offset = index % bitmap_word_size;
-        page_map.bitmap[bitmap_index] &= ~(1 << bitmap_offset);
-        return (page_map.block_size << height) * (index - (1 << (page_map.height - height)));
+        page_map.bitmap[bitmap_index] &= ~((unsigned long)1 << bitmap_offset);
+        physaddr_t page = (page_map.block_size << height) * (index - ((unsigned long)1 << (page_map.height - height)));
+        if(page < 0x10000)
+            ;//printf("Reserved %08x\n", page);
+        return page;
     }
     else
     {
@@ -149,18 +159,29 @@ physaddr_t reserve_region(size_t size)
 int free_region(physaddr_t location, size_t size)
 {
     int height = llog2(size / page_map.block_size);
-    int index = (location / (page_map.block_size * (1 << height))) + (1 << (page_map.height - height));
+    int index = (location / (page_map.block_size * ((unsigned long)1 << height))) + (1 << (page_map.height - height));
     int bitmap_index = index / bitmap_word_size;
     int bitmap_offset = index % bitmap_word_size;
-    page_map.bitmap[bitmap_index] |= 1 << bitmap_offset;
-    while(page_map.bitmap[bitmap_index] & (1 << (bitmap_offset ^ 1)))
+    page_map.bitmap[bitmap_index] |= (unsigned long)1 << bitmap_offset;
+    unsigned long cache_start = llog2(bitmap_word_size);
+    while (page_map.bitmap[bitmap_index] & ((unsigned long)1 << (bitmap_offset ^ 1)))
     {
-        page_map.bitmap[bitmap_index] &= ~(1 << bitmap_offset);
-        page_map.bitmap[bitmap_index] &= ~(1 << (bitmap_offset ^ 1));
+        unsigned long depth = llog2(index + 1) - 1;
+        if(page_map.cache[depth - cache_start] == (index ^ 1))
+        {
+            page_map.cache[depth - cache_start] = 0;
+        }
+        page_map.bitmap[bitmap_index] &= ~((unsigned long)1 << bitmap_offset);
+        page_map.bitmap[bitmap_index] &= ~((unsigned long)1 << (bitmap_offset ^ 1));
         index /= 2;
         bitmap_index = index / bitmap_word_size;
         bitmap_offset = index % bitmap_word_size;
-        page_map.bitmap[bitmap_index] |= 1 << bitmap_offset;
+        page_map.bitmap[bitmap_index] |= (unsigned long)1 << bitmap_offset;
+    }
+    unsigned long depth = llog2(index + 1) - 1;
+    if (depth >= cache_start && page_map.cache[depth - cache_start] == 0)
+    {
+        page_map.cache[depth - cache_start] = index;
     }
     return ENONE;
 }
@@ -190,17 +211,21 @@ void *page_map_end()
     return (void*)page_map.bitmap + page_map.bitmap_size;
 }
 
-enum error_t initialize_page_map(struct memory_map_t *map, void *base, size_t memory_size, unsigned long block_size)
+error_t initialize_page_map(struct memory_map_t *map, void *base, size_t memory_size, unsigned long block_size)
 {
+    static unsigned long page_map_cache[MAX_CACHE_SIZE];
     // Round memory_size up to nearest power of 2
     memory_size = 1 << llog2(memory_size);
     page_map.bitmap = (unsigned long*) base;
+    page_map.cache = page_map_cache;
     page_map.bitmap_size = (memory_size / page_size) / 4;
     page_map.block_size = block_size;
     page_map.height = llog2(memory_size / block_size);
     page_map.free_block_count = 0;
     int block_log = llog2(block_size);
     int pages_mapped = 0;
+    bool initialized = false;
+    printf("bmpsz: %08x bmploc: %08x\n", page_map.bitmap_size, page_map.bitmap);
     for(int i = 0; i < map->size; i++)
     {
         if(map->array[i].type != M_AVAILABLE)
@@ -209,61 +234,84 @@ enum error_t initialize_page_map(struct memory_map_t *map, void *base, size_t me
         }
         physaddr_t location = (map->array[i].location + page_size - 1) & ~(page_size - 1);
         physaddr_t region_end = map->array[i].location + map->array[i].size;
-        while(location + block_size <= region_end)
+        while(location + block_size <= region_end && pages_mapped < (page_map.bitmap_size + page_size - 1) / page_size)
         {
-            if(pages_mapped < page_map.bitmap_size / page_size)
+            void *page = (void*)page_map.bitmap + pages_mapped * page_size;
+            for(int level = 0; level < page_table_levels; level++)
             {
-                void *page = (void*)page_map.bitmap + pages_mapped * page_size;
-                for(int level = 0; level < page_table_levels; level++)
+                if(!(get_pte_type(page, level) & PAGE_PRESENT))
                 {
-                    if(!(get_pte_type(page, level) & PAGE_PRESENT))
+                    if(set_pte(page, level, PAGE_PRESENT | PAGE_RW, location))
                     {
-                        if(set_pte(page, level, PAGE_PRESENT | PAGE_RW, location))
-                        {
-                            return ENOMEM;
-                        }
-                        else if(level == page_table_levels - 1)
-                        {
-                            pages_mapped++;
-                        }
-                        break;
+                        return ENOMEM;
                     }
                     else if(level == page_table_levels - 1)
                     {
                         pages_mapped++;
                     }
+                    break;
+                }
+                else if(level == page_table_levels - 1)
+                {
+                    pages_mapped++;
                 }
-                location += page_size;
-                continue;
             }
+            location += page_size;
+            continue;
+        }
+
+        if(!initialized)
+        {
+            clear_bitmap();
+            initialized = true;
+        }
+
+        while(location + block_size <= region_end)
+        {
             int bit_offset = (location / block_size) % bitmap_word_size;
-            int bitmap_index = (location / block_size) / bitmap_word_size;
+            int bitmap_index = ((1 << (page_map.height - 0)) / bitmap_word_size) + (location / block_size) / bitmap_word_size;
             size_t chunk_size = (bitmap_word_size - bit_offset) * block_size;
+            // BUG: bitmap entries are uninitialized at first, never zeroed out
+            if(location < 0x180000)
+                printf("%08x ", page_map.bitmap[bitmap_index]);
             if(bit_offset == 0 && (region_end - location) >= chunk_size)
             {
+                if(location < 0x180000)
+                printf("a ");
                 // Set all bits in the word
                 page_map.bitmap[bitmap_index] = ~0;
             }
             else if(bit_offset == 0)
             {
+                if(location < 0x180000)
+                printf("b ");
                 // Set the first 'count' bits
                 int count = (region_end - location) >> block_log;
                 page_map.bitmap[bitmap_index] |= (1 << count) - 1;
             }
             else if((region_end - location) >= chunk_size)
             {
+                if(location < 0x180000)
+                printf("c ");
                 // Set all bits starting at 'bit_offset'
                 page_map.bitmap[bitmap_index] |= ~((1 << bit_offset) - 1);
             }
             else
             {
+                if(location < 0x180000)
+                printf("d ");
                 // Set all bits starting at 'bit_offset' up to 'count'
                 int count = (region_end - location) >> block_log;
                 page_map.bitmap[bitmap_index] |= ((1 << count) - 1) & ~((1 << bit_offset) - 1);
             }
+            if(location < 0x180000) {
+                printf("bmp: %08x loc: %08x end: %08x off: %i idx: %i cnt: %i\n", page_map.bitmap[bitmap_index], location, region_end, bit_offset, bitmap_index, (region_end - location) >> block_log);
+            }
+            
             location += chunk_size;
         }
     }
+    clear_cache();
     return ENONE;
 }
 
diff --git a/src/queue.c b/src/queue.c
index 492f257..6cbefb7 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -23,7 +23,7 @@ void queue_construct(struct queue_t *queue)
     queue->count = 0;
 }
 
-enum error_t queue_insert(struct queue_t *queue, void *ptr)
+error_t queue_insert(struct queue_t *queue, void *ptr)
 {
     struct queue_node_t *node = kmalloc(sizeof(struct queue_node_t));
     if(node == NULL)
diff --git a/src/stdio.c b/src/stdio.c
index a487e3a..54a9f8c 100644
--- a/src/stdio.c
+++ b/src/stdio.c
@@ -27,6 +27,7 @@ char *itoa(unsigned int n, unsigned int base, unsigned int width)
     static const char *digits = "0123456789abcdef";
     static char buffer[65];
     char *s = &buffer[64];
+    *s = 0;
     unsigned int count = 0;
     do
     {
diff --git a/src/syscalls.c b/src/syscalls.c
index c36954c..297e871 100644
--- a/src/syscalls.c
+++ b/src/syscalls.c
@@ -110,20 +110,8 @@ size_t send(syscall_arg_t recipient, syscall_arg_t message, syscall_arg_t flags)
             return EDOESNTEXIST;
         }
     }
-    enum error_t status = kernel_send_message(recipient.unsigned_int, message.ptr);
-    if(status == EBUSY && op_type == IO_SYNC)
-    {
-        status = kernel_queue_sender(recipient.unsigned_int);
-        if(status)
-        {
-            return status;
-        }
-        else
-        {
-            load_context(kernel_advance_scheduler());
-        }
-    }
-    else if(status == EBUSY && op_type == IO_ASYNC)
+    error_t status = kernel_send_message(recipient.unsigned_int, message.ptr);
+    if(status == EBUSY/* && op_type == IO_ASYNC*/)
     {
         return kernel_queue_message(recipient.unsigned_int, message.ptr);
     }
diff --git a/src/x86/context.c b/src/x86/context.c
index 9e6b04c..bbc3107 100644
--- a/src/x86/context.c
+++ b/src/x86/context.c
@@ -4,16 +4,27 @@
 #include "heap.h"
 #include "string.h"
 #include "system.h"
+#include <stdarg.h>
+
+void *get_context_pc(struct process_context_t *context)
+{
+    return (void*) context->eip;
+}
 
 void set_context_pc(struct process_context_t *context, void *pc)
 {
-    context->eip = pc;
+    context->eip = (unsigned long) pc;
     context->cs = 0x1B;
 }
 
+void *get_context_stack(struct process_context_t *context)
+{
+    return (void*) context->gp_registers[7];
+}
+
 void set_context_stack(struct process_context_t *context, void *stack)
 {
-    context->gp_registers[7] = stack;
+    context->gp_registers[7] = (unsigned long)stack;
     context->ss = 0x23;
 }
 
@@ -25,4 +36,51 @@ void set_context_flags(struct process_context_t *context, unsigned long flags)
 void set_context_return(struct process_context_t *context, unsigned long value)
 {
     context->gp_registers[0] = value;
+}
+
+void *context_stack_push(struct process_context_t *context, unsigned long value)
+{
+    context->gp_registers[7] -= sizeof(long);
+    *((unsigned long*) context->gp_registers[7]) = value;
+    return (void*) context->gp_registers[7];
+}
+
+void *context_stack_push_struct(struct process_context_t *context, void *data, unsigned long size)
+{
+    context->gp_registers[7] -= size;
+    memcpy((void*) context->gp_registers[7], data, size);
+    return (void*) context->gp_registers[7];
+}
+
+void *context_stack_pop(struct process_context_t *context, void *value)
+{
+    unsigned long *prev_stack = ((unsigned long*) context->gp_registers[7]);
+    context->gp_registers[7] += sizeof(unsigned long);
+    *((unsigned long*) value) = *prev_stack;
+    return (void*) context->gp_registers[7];
+}
+
+void *context_stack_pop_struct(struct process_context_t *context, void *value, unsigned long size)
+{
+    void *prev_stack = ((void*) context->gp_registers[7]);
+    context->gp_registers[7] += size;
+    memcpy(value, prev_stack, size);
+    return (void*) context->gp_registers[7];
+}
+
+void context_call_func(struct process_context_t *context, void *func_ptr, void *ret_ptr, int argc, ...)
+{
+    context->eip = (uint32_t) func_ptr;
+    va_list valist;
+    va_start(valist, argc);
+    for(int i = 0; i < argc; i++)
+    {
+        context_stack_push(context, va_arg(valist, unsigned long));
+    }
+    context_stack_push(context, (unsigned long) ret_ptr);
+}
+
+void context_cleanup_func(struct process_context_t *context, int argc)
+{
+    context->gp_registers[7] -= sizeof(unsigned long) * argc;
 }
\ No newline at end of file
diff --git a/src/x86/idt.c b/src/x86/idt.c
index 6b9d1be..1bf0c51 100644
--- a/src/x86/idt.c
+++ b/src/x86/idt.c
@@ -125,7 +125,7 @@ void load_tr(uint16_t gdt_offset)
 
 void create_interrupt_descriptor(struct interrupt_descriptor_t *descriptor, void *isr, enum isr_type_t type, uint32_t privilage, uint32_t selector)
 {
-    if(type != INTERRPUT_TASK32)
+    if(type != INTERRUPT_TASK32)
     {
         descriptor->offset_1 = (uint32_t) isr & 0xFFFF;
         descriptor->offset_2 = (uint32_t) isr >> 16;
@@ -245,15 +245,15 @@ void initialize_idt()
     memset(idt, 0, sizeof(struct interrupt_descriptor_t) * idt_size);
     for(int i = 0; i < idt_size; i++)
     {
-        create_interrupt_descriptor(&idt[i], (void*)isr_generic, INTERRPUT_INT32, 0, 8);
+        create_interrupt_descriptor(&idt[i], (void*)isr_generic, INTERRUPT_INT32, 0, 8);
     }
-    create_interrupt_descriptor(&idt[EXCEPTION_DIV_BY_0], (void*)isr_division_by_zero, INTERRPUT_INT32, 0, 8);
-    create_interrupt_descriptor(&idt[EXCEPTION_SEGMENT_NOT_PRESENT], (void*)isr_segment_not_present, INTERRPUT_TRAP32, 0, 8);
-    create_interrupt_descriptor(&idt[EXCEPTION_GPF], (void*)isr_gp_fault, INTERRPUT_TRAP32, 0, 8);
-    create_interrupt_descriptor(&idt[EXCEPTION_PAGE_FAULT], (void*)isr_page_fault, INTERRPUT_TRAP32, 0, 8);
-    create_interrupt_descriptor(&idt[EXCEPTION_DOUBLE_FAULT], /*(void*)isr_double_fault*/NULL, INTERRPUT_TASK32, 0, 8 * 6);
-    create_interrupt_descriptor(&idt[ISR_PREEMPT], (void*)isr_preempt, INTERRPUT_INT32, 3, 8);
-    create_interrupt_descriptor(&idt[ISR_APIC_TIMER], (void*)isr_timer, INTERRPUT_INT32, 0, 8);
-    create_interrupt_descriptor(&idt[ISR_SYSCALL], (void*)isr_syscall, INTERRPUT_INT32, 3, 8);
+    create_interrupt_descriptor(&idt[EXCEPTION_DIV_BY_0], (void*)isr_division_by_zero, INTERRUPT_INT32, 0, 8);
+    create_interrupt_descriptor(&idt[EXCEPTION_SEGMENT_NOT_PRESENT], (void*)isr_segment_not_present, INTERRUPT_TRAP32, 0, 8);
+    create_interrupt_descriptor(&idt[EXCEPTION_GPF], (void*)isr_gp_fault, INTERRUPT_TRAP32, 0, 8);
+    create_interrupt_descriptor(&idt[EXCEPTION_PAGE_FAULT], (void*)isr_page_fault, INTERRUPT_TRAP32, 0, 8);
+    create_interrupt_descriptor(&idt[EXCEPTION_DOUBLE_FAULT], /*(void*)isr_double_fault*/NULL, INTERRUPT_TASK32, 0, 8 * 6);
+    create_interrupt_descriptor(&idt[ISR_PREEMPT], (void*)isr_preempt, INTERRUPT_INT32, 3, 8);
+    create_interrupt_descriptor(&idt[ISR_APIC_TIMER], (void*)isr_timer, INTERRUPT_INT32, 0, 8);
+    create_interrupt_descriptor(&idt[ISR_SYSCALL], (void*)isr_syscall, INTERRUPT_INT32, 3, 8);
     load_idt(idt);
 }
diff --git a/src/x86/multiboot2.c b/src/x86/multiboot2.c
index ed13e55..44aba57 100644
--- a/src/x86/multiboot2.c
+++ b/src/x86/multiboot2.c
@@ -107,9 +107,12 @@ void *read_multiboot_table_entry(struct boot_info_t *boot_info, void *table)
             boot_info->modules[boot_info->module_count].start = ((struct multiboot2_module_t*) table)->start;
             boot_info->modules[boot_info->module_count].end = ((struct multiboot2_module_t*) table)->end;
             strcpy(boot_info->modules[boot_info->module_count].str, &((struct multiboot2_module_t*) table)->str);
+            unsigned long size = ((struct multiboot2_module_t*) table)->end - ((struct multiboot2_module_t*) table)->start;
+            size += 4095;
+            size &= ~4095;
             insert_region(&boot_info->map, 
                 ((struct multiboot2_module_t*) table)->start, 
-                ((struct multiboot2_module_t*) table)->end - ((struct multiboot2_module_t*) table)->start, 
+                size, 
                 M_UNAVAILABLE);
             boot_info->module_count++;
         }
diff --git a/src/x86/paging.c b/src/x86/paging.c
index 4d4cdb5..630d89e 100644
--- a/src/x86/paging.c
+++ b/src/x86/paging.c
@@ -2,6 +2,7 @@
 #include "string.h"
 
 #include <stddef.h>
+#include <stdint.h>
 
 struct page_table_entry_t
 {