From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id 07D736B000A for ; Wed, 24 Oct 2018 02:22:57 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id v15-v6so2304226edm.13 for ; Tue, 23 Oct 2018 23:22:56 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i5-v6si984285ejf.66.2018.10.23.23.22.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 23 Oct 2018 23:22:55 -0700 (PDT) Date: Wed, 24 Oct 2018 08:22:52 +0200 From: Michal Hocko Subject: Re: [RFC PATCH 0/2] improve vmalloc allocation Message-ID: <20181024062252.GA18839@dhcp22.suse.cz> References: <20181019173538.590-1-urezki@gmail.com> <20181022125142.GD18839@dhcp22.suse.cz> <20181022165253.uphv3xzqivh44o3d@pc636> <20181023072306.GN18839@dhcp22.suse.cz> <20181023152640.GD20085@bombadil.infradead.org> <20181023170532.GW18839@dhcp22.suse.cz> <98842edb-d462-96b1-311f-27c6ebfc108a@kernel.org> <20181023193044.GA139403@joelaf.mtv.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181023193044.GA139403@joelaf.mtv.corp.google.com> Sender: owner-linux-mm@kvack.org List-ID: To: Joel Fernandes Cc: Shuah Khan , Matthew Wilcox , Uladzislau Rezki , Kees Cook , Andrew Morton , linux-mm@kvack.org, LKML , Thomas Garnier , Oleksiy Avramchenko , Steven Rostedt , Joel Fernandes , Thomas Gleixner , Ingo Molnar , Tejun Heo , maco@android.com On Tue 23-10-18 12:30:44, Joel Fernandes wrote: > On Tue, Oct 23, 2018 at 11:13:36AM -0600, Shuah Khan wrote: > > On 10/23/2018 11:05 AM, Michal Hocko wrote: > > > On Tue 23-10-18 08:26:40, Matthew Wilcox wrote: > > >> On Tue, Oct 23, 2018 at 09:02:56AM -0600, Shuah Khan wrote: > > > [...] > > >>> The way it can be handled is by adding a test module under lib. test_kmod, > > >>> test_sysctl, test_user_copy etc. > > >> > > >> The problem is that said module can only invoke functions which are > > >> exported using EXPORT_SYMBOL. And there's a cost to exporting them, > > >> which I don't think we're willing to pay, purely to get test coverage. > > > > > > Yes, I think we do not want to export internal functionality which might > > > be still interesting for the testing coverage. Maybe we want something > > > like EXPORT_SYMBOL_KSELFTEST which would allow to link within the > > > kselftest machinery but it wouldn't allow the same for general modules > > > and will not give any API promisses. > > > > > > > I like this proposal. I think we will open up lot of test opportunities with > > this approach. > > > > Maybe we can use this stress test as a pilot and see where it takes us. > > I am a bit worried that such an EXPORT_SYMBOL_KSELFTEST mechanism can be abused by > out-of-tree module writers to call internal functionality. > > How would you prevent that? There is no way to prevent non-exported symbols abuse by 3rd party AFAIK. EXPORT_SYMBOL_* is not there to prohibid abuse. It is a mere signal of what is, well, an exported API. -- Michal Hocko SUSE Labs