kernel: Fix ELF hashtable iterator handling.

As a result of the refactoring for OpenHashTable, the iterator semantics
have changed a bit, such that the end of the table is no longer signalled
by the iterator returning NULL. This wasn't taken into account during
refactoring, which would lead to various places returning the last item
in the list in the case where no matching item was found, causing e.g.
drivers not to be loaded properly. This fixes the boot hang regressions
introduced in hrev48640.

src/system/kernel/elf.cpp

@@ -165,8 +165,6 @@ register_elf_image(struct elf_image_info *image)
 static struct elf_image_info *
 find_image_at_address(addr_t address)
 {
-	struct elf_image_info *image = NULL;
-
 #if KDEBUG
 	if (!debug_debugger_running())
 		ASSERT_LOCKED_MUTEX(&sImageMutex);
@@ -177,16 +175,16 @@ find_image_at_address(addr_t address)
 	// get image that may contain the address
 
 	while (iterator.HasNext()) {
-		image = iterator.Next();
+		struct elf_image_info* image = iterator.Next();
 		if ((address >= image->text_region.start && address
 				<= (image->text_region.start + image->text_region.size))
 			|| (address >= image->data_region.start
 				&& address
 					<= (image->data_region.start + image->data_region.size)))
-			break;
+			return image;
 	}
 
-	return image;
+	return NULL;
 }
 
 
@@ -235,20 +233,16 @@ find_image(image_id id)
 static struct elf_image_info *
 find_image_by_vnode(void *vnode)
 {
-	struct elf_image_info *image = NULL;
+	MutexLocker locker(sImageMutex);
 
-	mutex_lock(&sImageMutex);
 	ImageHash::Iterator iterator(sImagesHash);
-
 	while (iterator.HasNext()) {
-		image = iterator.Next();
+		struct elf_image_info* image = iterator.Next();
 		if (image->vnode == vnode)
-			break;
+			return image;
 	}
 
-	mutex_unlock(&sImageMutex);
+	return NULL;
-
-	return image;
 }
 
 
@@ -411,12 +405,14 @@ dump_symbols(int argc, char **argv)
 
 				ImageHash::Iterator iterator(sImagesHash);
 				while (iterator.HasNext()) {
-					image = iterator.Next();
+					elf_image_info* current = iterator.Next();
-					if (image->text_region.start <= num
+					if (current->text_region.start <= num
-						&& image->text_region.start + image->text_region.size
+						&& current->text_region.start + current->text_region.size
-							>= num)
+							>= num) {
+						image = current;
 						break;
 					}
+				}
 
 				if (image == NULL) {
 					kprintf("No image covers %#" B_PRIxADDR " in the kernel!\n",
@@ -433,10 +429,12 @@ dump_symbols(int argc, char **argv)
 			// look for image by name
 			ImageHash::Iterator iterator(sImagesHash);
 			while (iterator.HasNext()) {
-				image = iterator.Next();
+				elf_image_info* current = iterator.Next();
-				if (!strcmp(image->name, argv[1]))
+				if (!strcmp(current->name, argv[1])) {
+					image = current;
 					break;
 				}
+			}
 
 			if (image == NULL)
 				kprintf("No image \"%s\" found in kernel!\n", argv[1]);