From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luc Van Oostenryck Subject: Re: [PATCH] perf: enum overflow in uapi/linux/perf_event.h Date: Fri, 7 Sep 2018 20:43:59 +0200 Message-ID: <20180907184358.pg2ho4m4tc3dpwlw@ltop.local> References: <20180907134246.GC24106@hirez.programming.kicks-ass.net> <20180907135817.GF24106@hirez.programming.kicks-ass.net> <7a086a56-a896-9513-7315-9d0d21b61a44@c-s.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <7a086a56-a896-9513-7315-9d0d21b61a44@c-s.fr> Sender: linux-kernel-owner@vger.kernel.org To: Christophe LEROY Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sparse@vger.kernel.org List-Id: linux-sparse@vger.kernel.org On Fri, Sep 07, 2018 at 04:15:33PM +0200, Christophe LEROY wrote: > Le 07/09/2018 à 15:58, Peter Zijlstra a écrit : > > On Fri, Sep 07, 2018 at 01:50:18PM +0000, Christophe Leroy wrote: > > > > > > > > > On 09/07/2018 01:42 PM, Peter Zijlstra wrote: > > > > On Fri, Sep 07, 2018 at 01:27:19PM +0000, Christophe Leroy wrote: > > > > > On PPC32, enums are 32 bits, so __PERF_SAMPLE_CALLCHAIN_EARLY is > > > > > out of scope. The following sparse warning is encountered: > > > > > > > > > > CHECK arch/powerpc/kernel/process.c > > > > > ./include/uapi/linux/perf_event.h:147:56: warning: cast truncates bits from constant value (8000000000000000 becomes 0) > > > > > > > > Urgh... what compiler is that? I've not seen anything like that from the > > > > build bots. > > > > > > > > > > [root@pc16082vm linux-powerpc]# sparse --version > > > 0.5.2 > > > > > > [root@pc16082vm linux-powerpc]# ppc-linux-gcc --version > > > ppc-linux-gcc (GCC) 5.4.0 > > > > Ah, that's a sparse warning. But does your GCC agree? The thing is, > > sparse uses the C enum spec, but I suspect GCC uses the C++ enum spec > > and it all works fine. Sparse is a bit weird about the exact underlying type used for enums. > Ah yes, it seems that GCC is happy. So sparse should be fixed instead ? I'll investigate (I suppose the same is given on x86-32). -- Luc