kernel/slab: Add checks to object_cache_alloc for 0xdeadbeef.

We should always find it if PARANOID_KERNEL_FREE is enabled
and the object size is at least 2 pointers.

src/system/kernel/slab/ObjectCache.cpp

@@ -159,6 +159,7 @@ ObjectCache::InitSlab(slab* slab, void* pages, size_t byteCount, uint32 flags)
 			return NULL;
 		}
 
+		fill_freed_block(data, object_size);
 		slab->free.Push(object_to_link(data, object_size));
 
 		ADD_PARANOIA_CHECK(PARANOIA_SUSPICIOUS, slab,

src/system/kernel/slab/Slab.cpp

@@ -1240,14 +1240,11 @@ object_cache_set_minimum_reserve(object_cache* cache, size_t objectCount)
 void*
 object_cache_alloc(object_cache* cache, uint32 flags)
 {
-	if (!(cache->flags & CACHE_NO_DEPOT)) {
+	void* object = NULL;
-		void* object = object_depot_obtain(&cache->depot);
+	if ((cache->flags & CACHE_NO_DEPOT) == 0)
-		if (object) {
+		object = object_depot_obtain(&cache->depot);
-			add_alloc_tracing_entry(cache, flags, object);
-			return fill_allocated_block(object, cache->object_size);
-		}
-	}
 
+	if (object == NULL) {
 		MutexLocker locker(cache->lock);
 		slab* source = NULL;
 
@@ -1291,8 +1288,15 @@ object_cache_alloc(object_cache* cache, uint32 flags)
 			cache->full.Add(source);
 		}
 
-	void* object = link_to_object(link, cache->object_size);
+		object = link_to_object(link, cache->object_size);
 		locker.Unlock();
+	}
+
+#if PARANOID_KERNEL_FREE
+	if (cache->object_size >= (sizeof(void*) * 2)) {
+		ASSERT_ALWAYS(*(uint32*)object == 0xdeadbeef);
+	}
+#endif
 
 	add_alloc_tracing_entry(cache, flags, object);
 	return fill_allocated_block(object, cache->object_size);