diff --git a/kernel.ld b/kernel.ld
index e78fd38..11dc98f 100644
--- a/kernel.ld
+++ b/kernel.ld
@@ -41,9 +41,10 @@ SECTIONS
 	.data : {
 		*(.data)
 	}
-	PROVIDE(edata = .);
-	.bss : {
+	bss : {
+		PROVIDE(edata = .);
 		*(.bss)
+		*(COMMON)
+		PROVIDE(end = .);
 	}
-	PROVIDE(end = .);
 }
diff --git a/proc.c b/proc.c
index 58ae948..3ab23f4 100644
--- a/proc.c
+++ b/proc.c
@@ -6,7 +6,6 @@
 #include "x86.h"
 #include "proc.h"
 #include "spinlock.h"
-#include "msr.h"
 
 struct {
   struct spinlock lock;
@@ -17,7 +16,11 @@ static struct proc *initproc;
 
 int nextpid = 1;
 extern void forkret(void);
+
+// we can return two ways out of the kernel and
+// for new processes we can choose either way
 extern void sysexit(void);
+extern void trapret(void);
 
 static void wakeup1(void *chan);
 
@@ -101,6 +104,10 @@ found:
 
   // Leave room for trap frame.
   sp -= sizeof *p->tf;
+
+  if ((uint64) sp % 16)
+    panic("misaligned sp");
+
   p->tf = (struct trapframe*)sp;
 
   // Set up new context to start executing at forkret,
@@ -132,6 +139,8 @@ userinit(void)
   inituvm(p->pgdir, _binary_initcode_start, (uint64)_binary_initcode_size);
   p->sz = PGSIZE;
   memset(p->tf, 0, sizeof(*p->tf));
+  p->tf->cs = UCSEG | 0x3;
+  p->tf->ss = UDSEG | 0x3;
   p->tf->r11 = FL_IF;
   p->tf->rsp = PGSIZE;
   p->tf->rcx = 0;  // beginning of initcode.S
@@ -321,12 +330,12 @@ scheduler(void)
 {
   struct proc *p;
   struct cpu *c = mycpu();
+   
   c->proc = 0;
-  
   for(;;){
     // Enable interrupts on this processor.
     sti();
-
+    
     // Loop over process table looking for process to run.
     acquire(&ptable.lock);
     for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
@@ -336,7 +345,6 @@ scheduler(void)
       // Switch to chosen process.  It is the process's job
       // to release ptable.lock and then reacquire it
       // before jumping back to us.
-
       c->proc = p;
       switchuvm(p);
       p->state = RUNNING;
diff --git a/trapasm.S b/trapasm.S
index b6dbb1a..d160ff2 100644
--- a/trapasm.S
+++ b/trapasm.S
@@ -22,7 +22,7 @@ alltraps:
   push %rbx
   push %rax
 
-  cmpw $KCSEG, 32(%rsp)   # compare to saved cs
+  cmpw $KCSEG, 144(%rsp)   # compare to saved cs
   jz 1f 
   swapgs
   
@@ -33,7 +33,7 @@ alltraps:
 .globl trapret
 trapret:
   cli
-  cmpw $KCSEG, 32(%rsp)  # compare to saved cs
+  cmpw $KCSEG, 144(%rsp)  # compare to saved cs
   jz 1f
   swapgs
 
@@ -72,12 +72,12 @@ sysentry:  # Build trap frame.
   movq  %rax, %rsp
   movq  %gs:0, %rax  // restore rax
 
-  // push usp
-  push $0
+  // push usp to make a valid trapframe
+  push $(UDSEG|0x3)
   push %gs:8
   // safe eflags and eip
   push %r11
-  push $UCSEG
+  push $(UCSEG|0x3)
   push %rcx
   // push errno and trapno to make stack look like a trap
   push $0
@@ -130,6 +130,7 @@ sysexit:
 
   add $(5*8), %rsp  # discard trapnum, errorcode, rip, cs and rflags
   mov (%rsp),%rsp  # switch to the user stack
+  # there are two more values on the stack, but we don't care about them	
   swapgs	
 
   sysretq