1 files changed, 52 insertions, 59 deletions

diff --git a/kernel/vm/shadow.c b/kernel/vm/shadow.c
index 06cf20d..4883160 100644
--- a/kernel/vm/shadow.c
+++ b/kernel/vm/shadow.c
@@ -43,6 +43,7 @@ void shadow_init()
 {
     // NOT_YET_IMPLEMENTED("VM: shadow_init");
     shadow_allocator = slab_allocator_create("shadow", sizeof(mobj_shadow_t));
+    KASSERT(shadow_allocator);
 }
 
 /*
@@ -55,7 +56,7 @@ void shadow_init()
  *  2) Set up the bottom object of the shadow chain, which could have two cases:
  *     a) Either shadowed is a shadow object, and you can use its bottom_mobj
  *     b) Or shadowed is not a shadow object, in which case it is the bottom 
- *        object of this chain.
+ *        object of this chain.shadow_create
  * 
  *  Make sure to manage the refcounts correctly.
  */
@@ -63,6 +64,11 @@ mobj_t *shadow_create(mobj_t *shadowed)
 {
     // NOT_YET_IMPLEMENTED("VM: shadow_create");
 
+    if (!shadowed)
+    {
+        return NULL;
+    }
+
     // create a new shadow object
     mobj_shadow_t *so = (mobj_shadow_t *)slab_obj_alloc(shadow_allocator);
     if (!so)
@@ -142,46 +148,41 @@ static long shadow_get_pframe(mobj_t *o, size_t pagenum, long forwrite,
                               pframe_t **pfp)
 {
     // NOT_YET_IMPLEMENTED("VM: shadow_get_pframe");
-
-    // if forwrite is set, use mobj_default_get_pframe
+    // return 0;
     if (forwrite)
     {
         return mobj_default_get_pframe(o, pagenum, forwrite, pfp);
     }
-
-    // else, check if the object already contains the desired frame
+    // check if o already contains the desired frame.
     pframe_t *pf = NULL;
     mobj_find_pframe(o, pagenum, &pf);
     if (pf)
     {
-        // if it does, return the pframe
         *pfp = pf;
         return 0;
     }
 
-    // iterate through the shadow chain to find the nearest shadow mobj that has the frame
-    mobj_shadow_t *so = MOBJ_TO_SO(o);
-    mobj_t *iter = so->shadowed;
-    while (iter && iter->mo_type == MOBJ_SHADOW)
+    mobj_shadow_t *shadow = MOBJ_TO_SO(o);
+    mobj_t *current = shadow->shadowed; 
+
+    while (current && current->mo_type == MOBJ_SHADOW)
     {
-        mobj_lock(iter);
-        mobj_find_pframe(iter, pagenum, &pf);
-        mobj_unlock(iter);
+        mobj_lock(current);
+        mobj_find_pframe(current, pagenum, &pf);
+        mobj_unlock(current);
+        
         if (pf)
         {
             *pfp = pf;
             return 0;
         }
-        // update the iterator
-        so = MOBJ_TO_SO(iter);
-        iter = so->shadowed;
-    }
 
-    // if no shadow objects have the page, call mobj_get_pframe() to get the page from the bottom object
-    // at this point, iter is the bottom object
-    mobj_lock(so->bottom_mobj);
-    long ret = mobj_get_pframe(so->bottom_mobj, pagenum, forwrite, pfp);
-    mobj_unlock(so->bottom_mobj);
+        shadow = MOBJ_TO_SO(current);
+        current = shadow->shadowed;
+    }
+    mobj_lock(shadow->bottom_mobj);
+    long ret = mobj_get_pframe(shadow->bottom_mobj, pagenum, forwrite, pfp);
+    mobj_unlock(shadow->bottom_mobj);
     return ret;
 }
 
@@ -208,48 +209,39 @@ static long shadow_get_pframe(mobj_t *o, size_t pagenum, long forwrite,
  */
 static long shadow_fill_pframe(mobj_t *o, pframe_t *pf)
 {
-    // NOT_YET_IMPLEMENTEDshadow_fill_pframe");
+    // NOT_YET_IMPLEMENTED("VM: shadow_fill_pframe");
+    // return -1;
+    pframe_t *pf_shadow = NULL;
+    long ret = 0;
+
 
-    // get the mobj_shadow_t
     mobj_shadow_t *so = MOBJ_TO_SO(o);
-    // iterate over the shadow chain
-    mobj_t *iter = so->shadowed;
-    while (iter && iter->mo_type == MOBJ_SHADOW)
+    mobj_t *shadowed = so->shadowed;
+    while (shadowed && shadowed->mo_type == MOBJ_SHADOW)
     {
-        // get the pframe from the shadow object
-        pframe_t *spf = NULL;
-        mobj_lock(iter);
-        mobj_find_pframe(iter, pf->pf_pagenum, &spf);
-        mobj_unlock(iter);
+        mobj_lock(shadowed);
+        mobj_find_pframe(shadowed, pf->pf_pagenum, &pf_shadow);
+        mobj_unlock(shadowed);
 
-        // if the pframe is found, copy the contents into pf 
-        // then release the pframe
-        if (spf)
+        if (pf_shadow)
         {
-            memcpy(pf->pf_addr, spf->pf_addr, PAGE_SIZE);
-            pframe_release(&spf);
+            memcpy(pf->pf_addr, pf_shadow->pf_addr, PAGE_SIZE);
+            pframe_release(&pf_shadow);
             return 0;
         }
 
-        // update the iterator
-        so = MOBJ_TO_SO(iter);
-        iter = so->shadowed;
+        so = MOBJ_TO_SO(shadowed);
+        shadowed = so->shadowed;
     }
-
-    // if none of the shadow objects have a copy of the frame, use mobj_get_pframe on the bottom object
-    pframe_t *spf = NULL;
     mobj_lock(so->bottom_mobj);
-    long ret = mobj_get_pframe(so->bottom_mobj, pf->pf_pagenum, 0, &spf);
+    ret = mobj_get_pframe(so->bottom_mobj, pf->pf_pagenum, 0, &pf_shadow);
     mobj_unlock(so->bottom_mobj);
-    // check if the operation was sucessful, memcpy the contents into pf
-    // and release the pframe
-    if (ret >= 0)
-    {
-        memcpy(pf->pf_addr, spf->pf_addr, PAGE_SIZE);
-        pframe_release(&spf);
+    if (ret < 0) {
+        return ret;
     }
-
-    return ret;
+    memcpy(pf->pf_addr, pf_shadow->pf_addr, PAGE_SIZE);
+    pframe_release(&pf_shadow);
+    return 0;
 }
 
 /*
@@ -264,6 +256,7 @@ static long shadow_fill_pframe(mobj_t *o, pframe_t *pf)
 static long shadow_flush_pframe(mobj_t *o, pframe_t *pf)
 {
     // NOT_YET_IMPLEMENTED("VM: shadow_flush_pframe");
+    // return -1;
     return 0;
 }
 
@@ -280,17 +273,17 @@ static long shadow_flush_pframe(mobj_t *o, pframe_t *pf)
 static void shadow_destructor(mobj_t *o)
 {
     // NOT_YET_IMPLEMENTED("VM: shadow_destructor");
+    mobj_default_destructor(o);
 
-    // get the mobj_shadow_t
     mobj_shadow_t *so = MOBJ_TO_SO(o);
+    // dbg(DBG_PROC, "shadow_destructor: refcount bottom: %d\n", so->bottom_mobj->mo_refcount);
+    // dbg(DBG_PROC, "shadow_destructor: refcount: %d\n", so->shadowed->mo_refcount);
 
-    // call the default destructor
-    mobj_default_destructor(o);
-
-    // put the shadow and bottom_mobj
+    // put the shadow and bottom_mobj members of the shadow object
     mobj_put(&so->shadowed);
     mobj_put(&so->bottom_mobj);
 
-    // free the slab
     slab_obj_free(shadow_allocator, so);
-}
\ No newline at end of file
+
+    return;
+}