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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 2D156C43142 for ; Tue, 26 Jun 2018 17:38:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA2AF269F5 for ; Tue, 26 Jun 2018 17:38:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="Xbb9T4KQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AA2AF269F5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=efficios.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933968AbeFZRiK (ORCPT ); Tue, 26 Jun 2018 13:38:10 -0400 Received: from mail.efficios.com ([167.114.142.138]:55444 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933919AbeFZRiJ (ORCPT ); Tue, 26 Jun 2018 13:38:09 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 9999B22A833; Tue, 26 Jun 2018 13:38:08 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id eUAOqsexk4nw; Tue, 26 Jun 2018 13:38:08 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 1E05722A830; Tue, 26 Jun 2018 13:38:08 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 1E05722A830 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1530034688; bh=v6PnW4UX6KvghPW0ILK+Jy04kDUb5cB5okomDu7ZbnQ=; h=Date:From:To:Message-ID:MIME-Version; b=Xbb9T4KQzox73psHs6e981XbkLnm9wxG6OiMhzvOrAUjtaTC3SUYkVPNiaUptKv5o J8QTb5RHLHTMSskjRUi1i794j6lniYleaA6AVqtzZ2YtYPGhyRqT9WGNA1Ax36s7gE NKt4nG56ycTqleMg5UTzMOUWO7JHejqYtFWkL+g2ECciq5mSkTaSzIWbJI/lkp0hlK osaixfJpGIBXdbsce4J4Y3+DFLCd0KpEzy7ZE6TPTOIltzXDDuhszVX9wz1xug4MEL fhuvbyto8Y7OzV767OoaZKcw7cBXKvH24vbJnDwx+CtknqhND97xaLTnM4x3AyzK2u QxDWA4RTp/Y+w== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id d5TknIPKt2B7; Tue, 26 Jun 2018 13:38:08 -0400 (EDT) Received: from mail02.efficios.com (mail02.efficios.com [167.114.142.138]) by mail.efficios.com (Postfix) with ESMTP id 0A0EF22A828; Tue, 26 Jun 2018 13:38:08 -0400 (EDT) Date: Tue, 26 Jun 2018 13:38:07 -0400 (EDT) From: Mathieu Desnoyers To: Andy Lutomirski Cc: Peter Zijlstra , Boqun Feng , linux-kernel , "Paul E. McKenney" , Thomas Gleixner Message-ID: <1514459655.4190.1530034687884.JavaMail.zimbra@efficios.com> Subject: rseq: How to test for compat task at signal delivery MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.138] X-Mailer: Zimbra 8.8.8_GA_2096 (ZimbraWebClient - FF52 (Linux)/8.8.8_GA_1703) Thread-Index: F0bW3mNX5qaSbdCuC2GA2EC17JUeiA== Thread-Topic: rseq: How to test for compat task at signal delivery Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andy, I would like to make the behavior rseq on compat tasks more robust by ensuring that kernel/rseq.c:rseq_get_rseq_cs() clears the high bits of rseq_cs->abort_ip, rseq_cs->start_ip and rseq_cs->post_commit_offset when a 32-bit binary is run on a 64-bit kernel. The intent here is that if user-space has garbage rather than zeroes in its struct rseq_cs fields padding, the behavior will be the same whether the binary is run on 32-bit or 64 kernels. I know that internally, the kernel is making a transition from is_compat_task() to in_compat_syscall(). I'm fine with using in_compat_syscall() when rseq_get_rseq_cs() is invoked from a system call, but is it OK to call it when it is invoked from signal delivery ? AFAIU, signals can be delivered upon return from interrupt as well. If not, what strategy do you recommend for arch-agnostic code ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com