From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga05.intel.com ([192.55.52.43]:26588 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753590AbeFGH5O (ORCPT ); Thu, 7 Jun 2018 03:57:14 -0400 Date: Thu, 7 Jun 2018 15:46:29 +0800 From: "Du, Changbin" Subject: Re: [PATCH v5 2/4] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations Message-ID: <20180607074628.kd3iyxevwj3ypzbr@intel.com> References: <1528186420-6615-3-git-send-email-changbin.du@intel.com> <201806060501.btF3aJMZ%fengguang.wu@intel.com> <20180606095714.1d3c2def@vmware.local.home> <20180606142600.GN13775@localhost> <20180606142622.2338abf6@vmware.local.home> <20180607041718.qpqucjzlvcm5h3gn@vireshk-i7> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180607041718.qpqucjzlvcm5h3gn@vireshk-i7> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Viresh Kumar Cc: Steven Rostedt , gregkh@linuxfoundation.org, alex.elder@linaro.org, Johan Hovold , kbuild test robot , linux-arch@vger.kernel.org, michal.lkml@markovi.net, linux-kernel@vger.kernel.org, arnd@arndb.de, yamada.masahiro@socionext.com, lgirdwood@gmail.com, broonie@kernel.org, rdunlap@infradead.org, x86@kernel.org, linux@armlinux.org.uk, changbin.du@intel.com, linux-sparse@vger.kernel.org, mingo@redhat.com, kbuild-all@01.org, akpm@linux-foundation.org, changbin.du@gmail.com, tglx@linutronix.de, linux-kbuild@vger.kernel.org, linux-arm-kernel@lists.infradead.org Hi, On Thu, Jun 07, 2018 at 09:47:18AM +0530, Viresh Kumar wrote: > +Greg/Alex, > > @Fegguang/build-bot: I do see mention of Greg and /me in your initial email's > body saying TO: Viresh, CC: Greg, but I don't see any of us getting cc'd in your > email. Bug ? > > On 06-06-18, 14:26, Steven Rostedt wrote: > > On Wed, 6 Jun 2018 16:26:00 +0200 > > Johan Hovold wrote: > > > > > Looks like the greybus code above is working as intended by checking for > > > unterminated string after the strncpy, even if this does now triggers > > > the truncation warning. > > So why exactly are we generating a warning here ? Is it because it is possible > that the first n bytes of src may not have the null terminating byte and the > dest may not be null terminated eventually ? > > Maybe I should just use memcpy here then ? > I think if the destination is not a null terminated string (If I understand your description below), memcpy can be used to get rid of such warning. The warning makes sense in general as explained in mannual. Thanks! > But AFAIR, I used strncpy() specifically because it also sets all the remaining > bytes after the null terminating byte with the null terminating byte. And so it > is pretty easy for me to check if the final string is null terminated by > checking [max - 1] byte against '\0', which the code is doing right now. > > I am not sure what would the best way to get around this incorrect-warning. > > And I am wondering on why buildbot reported the warning only for two instances > in that file, while I have done the same thing at 4 places. > > > Ah, yes I now see that. Thanks for pointing it out. But perhaps it > > should also add the "- 1" to the strncpy() so that gcc doesn't think > > it's a mistake. > > The src string is passed on from a firmware entity and we need to make sure the > protocol (greybus) is implemented properly by the other end. For example, in the > current case if the firmware sends "HELLOWORLD", its an error as it should have > sent "HELLWORLD\0". But with what you are saying we will forcefully make dest as > "HELLWORLD\0", which wouldn't be the right thing to do as we will miss the bug > present in firmware. > > -- > viresh -- Thanks, Changbin Du