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=-5.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B7E3FC433E6 for ; Fri, 26 Feb 2021 16:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A1EC64F13 for ; Fri, 26 Feb 2021 16:42:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230222AbhBZQml (ORCPT ); Fri, 26 Feb 2021 11:42:41 -0500 Received: from mail.efficios.com ([167.114.26.124]:36424 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229698AbhBZQmh (ORCPT ); Fri, 26 Feb 2021 11:42:37 -0500 Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id AFBCA30FFD5; Fri, 26 Feb 2021 11:41:54 -0500 (EST) Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id CpPO6ujUHOK6; Fri, 26 Feb 2021 11:41:54 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 5644330FFD4; Fri, 26 Feb 2021 11:41:54 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 5644330FFD4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1614357714; bh=9EqQ5l+XNXPd5I1zSOvJAP0xTZ+Swb445kGkcyrpk8U=; h=Date:From:To:Message-ID:MIME-Version; b=Z0WEmsDshbewOVhb0LWdVoVeUqkFM6z29cy7WbqIfMl0OkeZEbtRIeihwDZ+1oNER 3kWTdFN0yvkhrEEpFtsQ3Dc2IchPGFg9yUGZgWnhX7sjh1xigATUc0RF5dUhUw08DO yD/Esss/cvDaG2ufKqtHe3tT+ZX5NvSPzksMk18mlpj9S5WAazLyQPDmAIia1j5cAF WuWkAVRmRBFqh7kBdLoT2ibTFVMMUvyjGE/TuHNdDj9Hcbs4MJQ9LQVwDcu+PKzuWF bvyjeLyW+DnMphE2XU4rKWBlfvUkGBHEU8tPpiFC0lh3AQR4pH7zZ7sKTAoLykFH2d CkCqg8nEHARsw== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([127.0.0.1]) by localhost (mail03.efficios.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id gQj5kSzTepm5; Fri, 26 Feb 2021 11:41:54 -0500 (EST) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 419EA30FFCF; Fri, 26 Feb 2021 11:41:54 -0500 (EST) Date: Fri, 26 Feb 2021 11:41:54 -0500 (EST) From: Mathieu Desnoyers To: emmir Cc: Piotr Figiel , Andrew Morton , Peter Zijlstra , paulmck , Boqun Feng , Oleg Nesterov , "Dmitry V. Levin" , Florian Weimer , Alexey Dobriyan , Andrei Vagin , linux-kernel , Peter Oskolkov , Kamil Yurtsever , Chris Kennelly , Paul Turner , linux-man , linux-api Message-ID: <1701013445.8323.1614357714148.JavaMail.zimbra@efficios.com> In-Reply-To: References: <20210226135156.1081606-1-figiel@google.com> <192824546.8190.1614353555831.JavaMail.zimbra@efficios.com> Subject: Re: [PATCH v2] ptrace: add PTRACE_GET_RSEQ_CONFIGURATION request MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_3996 (ZimbraWebClient - FF86 (Linux)/8.8.15_GA_4007) Thread-Topic: ptrace: add PTRACE_GET_RSEQ_CONFIGURATION request Thread-Index: fQP+S8uPXpOVtfpNg34/mjrGX16yEg== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Feb 26, 2021, at 11:04 AM, emmir emmir@google.com wrote: > On Fri, 26 Feb 2021 at 16:32, Mathieu Desnoyers > wrote: >> >> ----- On Feb 26, 2021, at 8:51 AM, Piotr Figiel figiel@google.com wrote: >> [...] >> > --- >> > v2: >> > Applied review comments: >> > - changed return value from the ptrace request to the size of the >> > configuration structure >> > - expanded configuration structure with the flags field and >> > the rseq abi structure size >> > >> [...] >> > +#define PTRACE_GET_RSEQ_CONFIGURATION 0x420f >> > + >> > +struct ptrace_rseq_configuration { >> > + __u64 rseq_abi_pointer; >> > + __u32 rseq_abi_size; >> > + __u32 signature; >> > + __u32 flags; >> > + __u32 pad; >> > +}; >> > + >> [...] >> > +#ifdef CONFIG_RSEQ >> > +static long ptrace_get_rseq_configuration(struct task_struct *task, >> > + unsigned long size, void __user *data) >> > +{ >> > + struct ptrace_rseq_configuration conf = { >> > + .rseq_abi_pointer = (u64)(uintptr_t)task->rseq, >> > + .rseq_abi_size = sizeof(*task->rseq), >> > + .signature = task->rseq_sig, >> > + .flags = 0, >> > + }; >> > + >> > + size = min_t(unsigned long, size, sizeof(conf)); >> > + if (copy_to_user(data, &conf, size)) >> > + return -EFAULT; >> > + return sizeof(conf); >> > +} >> >> I think what Florian was after would be: >> >> struct ptrace_rseq_configuration { >> __u32 size; /* size of struct ptrace_rseq_configuration */ >> __u32 flags; >> __u64 rseq_abi_pointer; >> __u32 signature; >> __u32 pad; >> }; >> >> where: >> >> .size = sizeof(struct ptrace_rseq_configuration), >> >> This way, the configuration structure can be expanded in the future. The >> rseq ABI structure is by definition fixed-size, so there is no point in >> having its size here. >> >> Florian, did I understand your request correctly, or am I missing your point ? > > In this case returning sizeof(conf) would serve the same purpose, wouldn't it? If the size is received as input from user-space as well, this can be used to make sure the kernel detects what size is expected by user-space and act accordingly. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com