From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6DEAC433E0 for ; Thu, 14 May 2020 10:19:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C07662065D for ; Thu, 14 May 2020 10:19:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726296AbgENKTU (ORCPT ); Thu, 14 May 2020 06:19:20 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:34210 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725925AbgENKTT (ORCPT ); Thu, 14 May 2020 06:19:19 -0400 Received: from ip5f5af183.dynamic.kabel-deutschland.de ([95.90.241.131] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jZAxP-00083T-Gs; Thu, 14 May 2020 10:19:15 +0000 Date: Thu, 14 May 2020 12:19:14 +0200 From: Christian Brauner To: John Paul Adrian Glaubitz Cc: "Luck, Tony" , "Yu, Fenghua" , "linux-ia64@vger.kernel.org" , Al Viro , Arnd Bergmann , Thomas Gleixner , Ingo Molnar , Sebastian Andrzej Siewior , "Peter Zijlstra (Intel)" , Qais Yousef , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] ia64: enable HAVE_COPY_THREAD_TLS, switch to kernel_clone_args Message-ID: <20200514101914.fu7xhgaxtb5fy2ky@wittgenstein> References: <20200513204848.1208864-1-christian.brauner@ubuntu.com> <3908561D78D1C84285E8C5FCA982C28F7F6266E0@ORSMSX115.amr.corp.intel.com> <79e58d9b-5a39-390c-2f0c-0d87b63442b4@physik.fu-berlin.de> <20200514074606.vkc35syhdep23rzh@wittgenstein> <6b298416-1e64-eee7-0bb4-3b1f7f67adc6@physik.fu-berlin.de> <20200514100459.pt7dxq2faghdds2c@wittgenstein> <2e22b0d2-b9ce-420d-48a0-0d9134108a5c@physik.fu-berlin.de> <20200514101540.25hvle74w63t66fs@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200514101540.25hvle74w63t66fs@wittgenstein> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 14, 2020 at 12:15:42PM +0200, Christian Brauner wrote: > On Thu, May 14, 2020 at 12:08:27PM +0200, John Paul Adrian Glaubitz wrote: > > On 5/14/20 12:04 PM, Christian Brauner wrote: > > > So that's interesting because systemd doesn't support itanium correctly afaict. > > > They have a raw_clone() function that they use which is not tailored to > > > ia64. __NR_clone should be defined as so to hit clone2() but they don't > > > pass a stack size argument down which is invalid on ia64: > > Ah, I wasn't aware of this limitation. I'm surprised the systemd testsuite passes > > then on ia64. > > > > On sparc64, Michael Karcher provided the hand-written assembly you quoted to > > fix the raw_clone() on this architecture. > > > > I assume we could do the same on ia64? > > I think the following should be correct: > > (Probably worth checking that __NR_clone and __NR_clone2 are the same > for ia64. Also note, that __NR_clone was _never_ supported by glibc on > ia64. They even have this comment: > > /* clone is not supported under Linux/ia64, use clone2. */ > ) > > static inline pid_t raw_clone(unsigned long flags) { > pid_t ret; > > assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID| > CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0); > #if defined(__s390x__) || defined(__s390__) || defined(__CRIS__) > /* On s390/s390x and cris the order of the first and second arguments > * of the raw clone() system call is reversed. */ > ret = (pid_t) syscall(__NR_clone, NULL, flags); > #elif defined(__sparc__) > { > /** > * sparc always returns the other process id in %o0, and > * a boolean flag whether this is the child or the parent in > * %o1. Inline assembly is needed to get the flag returned > * in %o1. > */ > int in_child, child_pid, error; > > asm volatile("mov %3, %%g1\n\t" > "mov %4, %%o0\n\t" > "mov 0 , %%o1\n\t" > #if defined(__arch64__) > "t 0x6d\n\t" > #else > "t 0x10\n\t" > #endif > "addx %%g0, 0, %2\n\t" > "mov %%o1, %0\n\t" > "mov %%o0, %1" : > "=r"(in_child), "=r"(child_pid), "=r"(error) : > "i"(__NR_clone), "r"(flags) : > "%o1", "%o0", "%g1", "cc" ); > > if (error) { > errno = child_pid; > ret = -1; > } else > ret = in_child ? 0 : child_pid; > } > +#elif defined(__ia64__) > + /* On ia64 the stack and stack size are passed as separate arguments. */ > + return (pid_t)syscall(__NR_clone, flags, NULL, 0); > +#else > + return (pid_t)syscall(__NR_clone, flags, NULL); > +#endif Scratch that. It's even worse. On ia64 it is _invalid_ to pass a NULL stack. That's at least what the glibc assembly assumes: cmp.eq p6,p0=0,in0 cmp.eq p7,p0=0,in1 mov r8=EINVAL mov out0=in3 /* Flags are first syscall argument. */ mov out1=in1 /* Stack address. */ (p6) br.cond.spnt.many __syscall_error /* no NULL function pointers */ (p7) br.cond.spnt.many __syscall_error /* no NULL stack pointers */ ;; mov out2=in2 /* Stack size. */ so newer systemd just works by accident on ia64 if at all correctly afaict.