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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8F21C4332F for ; Wed, 28 Dec 2022 12:03:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232974AbiL1MDA (ORCPT ); Wed, 28 Dec 2022 07:03:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40988 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233112AbiL1MC3 (ORCPT ); Wed, 28 Dec 2022 07:02:29 -0500 Received: from gnuweeb.org (gnuweeb.org [51.81.211.47]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A492A2AEE; Wed, 28 Dec 2022 04:01:42 -0800 (PST) Received: from [10.7.7.5] (unknown [182.253.183.184]) by gnuweeb.org (Postfix) with ESMTPSA id E0E6A7E258; Wed, 28 Dec 2022 12:01:38 +0000 (UTC) X-GW-Data: lPqxHiMPbJw1wb7CM9QUryAGzr0yq5atzVDdxTR0iA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1672228902; bh=Yw3TuLngTSu3YPEHEdu5NGY2ZRCtBOIME+CW2blUEs8=; h=Date:To:Cc:References:From:Subject:In-Reply-To:From; b=MjNkG8lxgq2o1fPcIbFjRNB7VWK9krBeq3aNDYaLcqFQKPdejJx74tVrBb5T5s4au eTO2mkcJrwlA2NKG760KjK0uzSTTSCCXHnlSgHxFQtSGRD/s8tPnFTOchu/ZtFIGRK R1xXc3B7k09S33iZD5WoZjdWgCAdDy4zsH8h/5OYuMH21VXqgDtBQeXgREv0yG5dwL PO1PV0PUqkoTzNikbTKrlLOKFC47nkWAaYh1Rf5j3QsHru4h4e78sA8tm6ZfvkgVdT 7/+n+TudLNq68SljvWnDkPkVDulQz+wsCyEGJRPrV5fEHWkzpTmy1oL637AXb5w5Xb 5Mu8vAkMPnxCQ== Message-ID: <23e84c59-4f2c-01b4-5b8a-80af39a1d761@gnuweeb.org> Date: Wed, 28 Dec 2022 19:01:36 +0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 To: Willy Tarreau Cc: Shuah Khan , "Paul E. McKenney" , Gilang Fachrezy , VNLX Kernel Department , Alviro Iskandar Setiawan , Kanna Scarlet , Muhammad Rizki , GNU/Weeb Mailing List , Linux Kernel Mailing List , Linux Kselftest Mailing List References: <20221222035134.3467659-1-ammar.faizi@intel.com> <20221222043452.GB29086@1wt.eu> <20221222134615.3535422-1-ammar.faizi@intel.com> <20221227062640.GA5337@1wt.eu> <00eee75f-59fa-83b2-c7e1-f0da347b2dde@gnuweeb.org> <20221227184902.GA6287@1wt.eu> Content-Language: en-US From: Ammar Faizi Subject: Re: [RFC PATCH v1 0/8] nolibc signal handling support In-Reply-To: <20221227184902.GA6287@1wt.eu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 12/28/22 1:49 AM, Willy Tarreau wrote: > I'll try to do it but do not want to make you wait too long in case it > gets delayed. In the worst case we should only postpone the getauxval() > patch and not the other ones. I will split it into 2 patchset then. > BTW, do you think your arch-specific changes for sigaction() will be > easily portable to other architectures ? I feel a bit wary of starting > to have different features per architecture given the purpose of the > lib, so the more uniform the coverage the better. The 'rt_sigaction()' itself doesn't seem to be an arch specific, but the way it resumes the execution needs to call 'rt_sigreturn()' which is arch specific. I took a look at the kernel source code, most architectures read 'struct rt_sigframe' from the stack pointer. https://github.com/torvalds/linux/blob/631aa744423173bf921191ba695bbc7c1aabd9e0/arch/x86/kernel/signal_32.c#L145 https://github.com/torvalds/linux/blob/631aa744423173bf921191ba695bbc7c1aabd9e0/arch/x86/kernel/signal_64.c#L243-L271 https://github.com/torvalds/linux/blob/a6b450573b912316ad36262bfc70e7c3870c56d1/arch/arm64/kernel/signal.c#L668-L699 https://github.com/torvalds/linux/blob/a6b450573b912316ad36262bfc70e7c3870c56d1/arch/arm64/kernel/signal32.c#L259 https://github.com/torvalds/linux/blob/eb67d239f3aa1711afb0a42eab50459d9f3d672e/arch/riscv/kernel/signal.c#L101 On the x86-64 arch, the implementation is just like this: __arch_restore_rt: # # ((%rsp - sizeof(long)) must point to 'struct rt_sigframe') # # 'struct rt_sigframe' is automatically constructed by # the kernel when a signal is caught. # movl $0xf, %eax // __NR_rt_sigreturn == 0xf syscall I believe aarch64 and RISCV don't behave differently, but different registers. Not sure what PowerPC does here, it seems a bit different: https://github.com/torvalds/linux/blob/1612c382ffbdf1f673caec76502b1c00e6d35363/arch/powerpc/kernel/signal_64.c#L744 I haven't taken a look at other archs. What do you think? Is it affordable for nolibc to implement all of these? -- Ammar Faizi