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[124.44.9.134]) by smtp.gmail.com with ESMTPSA id t134-v6sm57507773pgb.93.2018.06.11.14.19.55 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 11 Jun 2018 14:19:55 -0700 (PDT) Date: Tue, 12 Jun 2018 06:19:53 +0900 From: Stafford Horne To: Arnd Bergmann Cc: linux-kbuild@vger.kernel.org, Michal Marek , Masahiro Yamada , Douglas Anderson , Al Viro , Heiko Carstens , Mauro Carvalho Chehab , Matthew Wilcox , Matthias Kaehlcke , Deepa Dinamani , Thomas Gleixner , Frederic Weisbecker , Stephan Mueller , "David S. Miller" , Yonghong Song , Thomas Garnier , David Howells , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH 2/2] [RFC] disable -Wattribute-alias warning for SYSCALL_DEFINEx() Message-ID: <20180611211953.GJ3652@lianli.shorne-pla.net> References: <20171205153259.2522368-1-arnd@arndb.de> <20171205160651.2920270-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171205160651.2920270-1-arnd@arndb.de> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 05, 2017 at 05:06:31PM +0100, Arnd Bergmann wrote: > gcc-8 warns for every single definition of a system call entry > point, e.g.: > > include/linux/compat.h:56:18: error: 'compat_sys_rt_sigprocmask' alias between functions of incompatible types 'long int(int, compat_sigset_t *, compat_sigset_t *, compat_size_t)' {aka 'long int(int, struct *, struct *, unsigned int)'} and 'long int(long int, long int, long int, long int)' [-Werror=attribute-alias] > asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\ > ^~~~~~~~~~ > include/linux/compat.h:45:2: note: in expansion of macro 'COMPAT_SYSCALL_DEFINEx' > COMPAT_SYSCALL_DEFINEx(4, _##name, __VA_ARGS__) > ^~~~~~~~~~~~~~~~~~~~~~ > kernel/signal.c:2601:1: note: in expansion of macro 'COMPAT_SYSCALL_DEFINE4' > COMPAT_SYSCALL_DEFINE4(rt_sigprocmask, int, how, compat_sigset_t __user *, nset, > ^~~~~~~~~~~~~~~~~~~~~~ > include/linux/compat.h:60:18: note: aliased declaration here > asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\ > ^~~~~~~~~~ > > The new warning seems reasonable in principle, but it doesn't > help us here, since we rely on the type mismatch to sanitize the > system call arguments. After I reported this as GCC PR82435, a new > -Wno-attribute-alias option was added that could be used to turn the > warning off globally on the command line, but I'd prefer to do it a > little more fine-grained. > > Interestingly, turning a warning off and on again inside of > a single macro doesn't always work, in this case I had to add > an extra statement inbetween and decided to copy the __SC_TEST > one from the native syscall to the compat syscall macro. See > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83256 for more details > about this. > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82435 > Signed-off-by: Arnd Bergmann Hi Arnd, What ever happened to this patch? I am compiline the kernel with the new OpenRISC GCC backend port https://github.com/stffrdhrn/gcc/commits/or1k-port, which is based on gcc 9.0.0 and seeing similar 'alias between functions of incompatible types' warnings. I found this old patch which seems will fix the issue, but it seems to not have been merged. Did we find another solution? Case in point, when I build x86 64 on gcc 8.1.1, I am not seeing the warnings. Is this not an issue for x86? -Stafford