From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 13202 invoked from network); 7 Sep 2020 22:12:07 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 7 Sep 2020 22:12:07 -0000 Received: (qmail 1319 invoked by uid 550); 7 Sep 2020 22:12:04 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 1301 invoked from network); 7 Sep 2020 22:12:03 -0000 Date: Mon, 7 Sep 2020 18:11:51 -0400 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20200907221151.GP3265@brightrain.aerifal.cx> References: <68b5e735-45be-413f-8153-cb97dd5967cd@www.fastmail.com> <20200907180636.GM3265@brightrain.aerifal.cx> <20200907214554.GO3265@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] riscv32 v2 On Mon, Sep 07, 2020 at 11:58:20PM +0200, Arnd Bergmann wrote: > On Mon, Sep 7, 2020 at 11:46 PM Rich Felker wrote: > > On Mon, Sep 07, 2020 at 11:35:45PM +0200, Arnd Bergmann wrote: > > > On Mon, Sep 7, 2020 at 8:06 PM Rich Felker wrote: > > > > On Mon, Sep 07, 2020 at 06:47:00AM -0400, Stefan O'Rear wrote: > > > > > > > > * Copy the IPC_TIME64 bits from arch/arm/bits to trigger the musl code > > > > > for fixing time64 IPC_STAT results. I'm not super happy with this, > > > > > maybe there should be a new mechanism in musl for fixing IPC_STAT for > > > > > unconditionally-time64 architectures. > > > > > > > > If the riscv32 IPC syscalls don't actually provide in-place time64 but > > > > require translation, I think it's fairly appropriate as-is. > > > > > > > > From the definitions in your patch, it looks like all the time fields > > > > are fixed-word-order (little endian) and possibly not aligned, so it > > > > seems like they can't be used in-place. Is this correct? > > > > > > Yes, rv32 uses the generic system call arguments, which are > > > unfortunately defined this way. In retrospect I wish I had > > > replaced the ipc syscalls with a sane version for time64, but at > > > the time time it seemed as easy way out to use the fields that > > > had been reserved for this purpose despite the broken > > > byte order and alignment. > > > > Thanks for clarifying. BTW does passing IPC_64 produce an error on > > rv32? If so, this is another advantage of keeping the IPC_TIME64 bit > > -- it would catch programs bypassing libc and making the syscalls > > directly. > > Yes, this is now the generic behavior for the split IPC syscalls Great! > (as opposed to sys_ipc on older architectures). The only architectures > that parse the version in the split ipc syscalls are the ones that > already had these and were interpreting IPC_64 before linux-5.1: > alpha, arm32, microblaze, mips-n32, mips-n64, and xtensa. > > There are additional architectures that require passing IPC_64 > in sys_ipc() but reject it in the split syscalls: m68k, mips-o32, > powerpc, s390, sh, sparc, and x86. Uhg, good to know. I just re-checked, and at present we don't use the new split syscalls unless SYS_ipc doesn't exist. musl's arch-specific IPC_64 definition (0 or 0x100) serves as the value needed for SYS_ipc if SYS_ipc is defined, and as the value needed for the split syscalls if SYS_ipc is not defined. So if in the future we want to use the new ones with fallback to SYS_ipc, we'd need the archs to define the needed IPC_64 flag separately for each... As an aside, I should probably cleanup the current definition framework where IPC_64==0x100 is the default and archs that want 0 have to define it explicitly. It looks like, for the most part, IPC_64 is needed iff SYS_ipc is defined. Of the archs we support, arm (32-bit) and mips{n32,64} seem to be the only ones that lack SYS_ipc but need the IPC_64 bit set. Does this agree with your assessment? Rich