Fix a bug with freeing kernel stacks.

proc.c was using kfree, which places the two page stacks on the single page free lists.

Fix a bug with freeing kernel stacks.
e65d0098 · Silas Boyd-Wickizer · bfae3e6a · e65d0098 · e65d0098 · e65d0098
--- a/kalloc.c
+++ b/kalloc.c
@@ -395,3 +395,9 @@ kfree(void *v)
 {
  kfree_pool(mykmem(), v);
 }
+
+void
+ksfree(slab_t slab, void *v)
+{
+  kfree_pool(slabmem[slab], v);
+}
--- a/kernel.h
+++ b/kernel.h
@@ -142,8 +142,9 @@ typedef enum {
  slab_perf,
 } slab_t;
 char*           kalloc(void);
+void            kfree(void*);
 void*           ksalloc(slab_t);
-void            kfree(void *);
+void            ksfree(slab_t, void*);
 void*           kmalloc(u64);
 void            kmfree(void*);


--- a/proc.c
+++ b/proc.c
@@ -563,8 +563,8 @@ fork(int flags)
  if(flags == 0) {
    // Copy process state from p.
    if((np->vmap = vmap_copy(myproc()->vmap, cow)) == 0){
-      kfree(np->kstack);
-      np->kstack = 0;
+      ksfree(slab_stack, np->kstack);
+      np->kstack = NULL;
      np->state = UNUSED;
      if (ns_remove(nspid, KI(np->pid), np) == 0)
 	panic("fork: ns_remove");
@@ -624,8 +624,8 @@ wait(void)
 	  pid = p->pid;
 	  SLIST_REMOVE(&myproc()->childq, p, proc, child_next);
 	  release(&myproc()->lock);
-	  kfree(p->kstack);
-	  p->kstack = 0;
+	  ksfree(slab_stack, p->kstack);
+	  p->kstack = NULL;
 	  vmap_decref(p->vmap);
 	  p->state = UNUSED;
 	  if (ns_remove(nspid, KI(p->pid), p) == 0)