Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753237AbcDKOjN (ORCPT ); Mon, 11 Apr 2016 10:39:13 -0400 Received: from mail-wm0-f50.google.com ([74.125.82.50]:38681 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750928AbcDKOjK convert rfc822-to-8bit (ORCPT ); Mon, 11 Apr 2016 10:39:10 -0400 MIME-Version: 1.0 In-Reply-To: <20160411074452.GC26116@js1304-P5Q-DELUXE> References: <4f6880ee0c1545b3ae9c25cfe86a879d724c4e7b.1457949315.git.glider@google.com> <20160411074452.GC26116@js1304-P5Q-DELUXE> Date: Mon, 11 Apr 2016 16:39:08 +0200 Message-ID: Subject: Re: [PATCH v7 5/7] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB From: Alexander Potapenko To: Joonsoo Kim Cc: Andrey Konovalov , Christoph Lameter , Dmitriy Vyukov , Andrew Morton , Andrey Ryabinin , Steven Rostedt , Kostya Serebryany , kasan-dev , LKML , Linux Memory Management List Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1429 Lines: 48 On Mon, Apr 11, 2016 at 9:44 AM, Joonsoo Kim wrote: > On Mon, Mar 14, 2016 at 11:43:43AM +0100, Alexander Potapenko wrote: >> +depot_stack_handle_t depot_save_stack(struct stack_trace *trace, >> + gfp_t alloc_flags) >> +{ >> + u32 hash; >> + depot_stack_handle_t retval = 0; >> + struct stack_record *found = NULL, **bucket; >> + unsigned long flags; >> + struct page *page = NULL; >> + void *prealloc = NULL; >> + bool *rec; >> + >> + if (unlikely(trace->nr_entries == 0)) >> + goto fast_exit; >> + >> + rec = this_cpu_ptr(&depot_recursion); >> + /* Don't store the stack if we've been called recursively. */ >> + if (unlikely(*rec)) >> + goto fast_exit; >> + *rec = true; >> + >> + hash = hash_stack(trace->entries, trace->nr_entries); >> + /* Bad luck, we won't store this stack. */ >> + if (hash == 0) >> + goto exit; > > Hello, > > why is hash == 0 skipped? > > Thanks. We have to keep a special value to distinguish allocations for which we don't have the stack trace for some reason. Making 0 such a value seems natural. -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg