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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 51362C43603 for ; Fri, 20 Dec 2019 20:33:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25282206D8 for ; Fri, 20 Dec 2019 20:33:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="tPOJqZVL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727563AbfLTUdb (ORCPT ); Fri, 20 Dec 2019 15:33:31 -0500 Received: from mail.efficios.com ([167.114.142.138]:55672 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727402AbfLTUd3 (ORCPT ); Fri, 20 Dec 2019 15:33:29 -0500 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id DC3DA68F2C3; Fri, 20 Dec 2019 15:33:27 -0500 (EST) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id CPvs-XqN2J55; Fri, 20 Dec 2019 15:33:27 -0500 (EST) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 8158E68F2C0; Fri, 20 Dec 2019 15:33:27 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 8158E68F2C0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1576874007; bh=MLuS/W5sZSrwoLRlQgBwaQH1/R/vS60vCofiQLnlPSk=; h=From:To:Date:Message-Id; b=tPOJqZVLrBaH5LTY6w1DuHdR4nvKrKri63giVIVjGB6uqPAO12be2G1QfC6RtPp7w EmE+moleow1aajwnYoqLkuoXV2fdB4QzpHSPrEveoaZJZSffBmPkXh/v9Gk4d33HaJ 2XNIcZs2OCSH9ylEXn6V9r2EbIJ/YK7wLKENE/DMWW9MVTWZ4mr7PmgKkXpZDTuQro BOxufjrG5M0dbTikKfG6twfIug88XLYrBtXqqEjbesEZ+65RvdB3QIh5PrgSQfRMPH omhOemKiDL6wZp+rGxyOXqgshvBIbKMtIIUTPiliKMzXCB7YwXgi7Y32Ef+DNBjI32 rZPf/WwDsUSZA== 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 rsMdaeLaeLZr; Fri, 20 Dec 2019 15:33:27 -0500 (EST) Received: from localhost.localdomain (192-222-181-218.qc.cable.ebox.net [192.222.181.218]) by mail.efficios.com (Postfix) with ESMTPSA id 4019968F2BA; Fri, 20 Dec 2019 15:33:27 -0500 (EST) From: Mathieu Desnoyers To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, stable@vger.kernel.org, Mathieu Desnoyers , Shuah Khan , Florian Weimer , Dmitry Vyukov Subject: [PATCH for 5.5 2/2 v2] rseq/selftests: Clarify rseq_prepare_unload() helper requirements Date: Fri, 20 Dec 2019 15:33:18 -0500 Message-Id: <20191220203318.18739-2-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191220203318.18739-1-mathieu.desnoyers@efficios.com> References: <20191220203318.18739-1-mathieu.desnoyers@efficios.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The rseq.h UAPI now documents that the rseq_cs field must be cleared before reclaiming memory that contains the targeted struct rseq_cs, but also that the rseq_cs field must be cleared before reclaiming memory of the code pointed to by the rseq_cs start_ip and post_commit_offset fields. While we can expect that use of dlclose(3) will typically unmap both struct rseq_cs and its associated code at once, nothing would theoretically prevent a JIT from reclaiming the code without reclaiming the struct rseq_cs, which would erroneously allow the kernel to consider new code which is not a rseq critical section as a rseq critical section following a code reclaim. Suggested-by: Florian Weimer Signed-off-by: Mathieu Desnoyers Cc: Shuah Khan Cc: Florian Weimer Cc: Thomas Gleixner Cc: Peter Zijlstra (Intel) Cc: "Paul E. McKenney" Cc: Boqun Feng Cc: "H . Peter Anvin" Cc: Paul Turner Cc: Dmitry Vyukov --- tools/testing/selftests/rseq/rseq.h | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h index d40d60e7499e..3f63eb362b92 100644 --- a/tools/testing/selftests/rseq/rseq.h +++ b/tools/testing/selftests/rseq/rseq.h @@ -149,11 +149,13 @@ static inline void rseq_clear_rseq_cs(void) /* * rseq_prepare_unload() should be invoked by each thread executing a rseq * critical section at least once between their last critical section and - * library unload of the library defining the rseq critical section - * (struct rseq_cs). This also applies to use of rseq in code generated by - * JIT: rseq_prepare_unload() should be invoked at least once by each - * thread executing a rseq critical section before reclaim of the memory - * holding the struct rseq_cs. + * library unload of the library defining the rseq critical section (struct + * rseq_cs) or the code referred to by the struct rseq_cs start_ip and + * post_commit_offset fields. This also applies to use of rseq in code + * generated by JIT: rseq_prepare_unload() should be invoked at least once by + * each thread executing a rseq critical section before reclaim of the memory + * holding the struct rseq_cs or reclaim of the code pointed to by struct + * rseq_cs start_ip and post_commit_offset fields. */ static inline void rseq_prepare_unload(void) { -- 2.17.1