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=-11.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 A6C64C6379D for ; Thu, 19 Nov 2020 19:07:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 570B2246A5 for ; Thu, 19 Nov 2020 19:07:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727392AbgKSTGl (ORCPT ); Thu, 19 Nov 2020 14:06:41 -0500 Received: from mga12.intel.com ([192.55.52.136]:21738 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727160AbgKSTGl (ORCPT ); Thu, 19 Nov 2020 14:06:41 -0500 IronPort-SDR: BEutbUlwzYkRLSFFuYoTIIw9J/Ud7cYFOkeZeot0N6uNOXxD+VcSchYAM+BeOpAlsyIQlmnpxB 9FlkcI+XdzTw== X-IronPort-AV: E=McAfee;i="6000,8403,9810"; a="150614461" X-IronPort-AV: E=Sophos;i="5.78,354,1599548400"; d="scan'208";a="150614461" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Nov 2020 11:06:39 -0800 IronPort-SDR: /LycEAwuD7D8NTvjhQxukEXdB9131AkvjDRbv7YVI1eXzkJ/47ZWL81OOQKr1Z9f7wuTYGB47H oc9i+TynSF4Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,354,1599548400"; d="scan'208";a="431333987" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga001.fm.intel.com with ESMTP; 19 Nov 2020 11:06:39 -0800 From: "Chang S. Bae" To: tglx@linutronix.de, mingo@kernel.org, bp@suse.de, luto@kernel.org, x86@kernel.org Cc: len.brown@intel.com, dave.hansen@intel.com, hjl.tools@gmail.com, Dave.Martin@arm.com, mpe@ellerman.id.au, tony.luck@intel.com, ravi.v.shankar@intel.com, libc-alpha@sourceware.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, chang.seok.bae@intel.com Subject: [PATCH v2 0/4] x86: Improve Minimum Alternate Stack Size Date: Thu, 19 Nov 2020 11:02:33 -0800 Message-Id: <20201119190237.626-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org [ We know there are a lot of Intel patches out there this week. We're posting this as early as we can in case anyone has bandwidth to take a look. We don't think these are quite ready to be merged, but any review is appreciated. ] During signal entry, the kernel pushes data onto the normal userspace stack. On x86, the data pushed onto the user stack includes XSAVE state, which has grown over time as new features and larger registers have been added to the architecture. MINSIGSTKSZ is a constant provided in the kernel signal.h headers and typically distributed in lib-dev(el) packages, e.g. [1]. Its value is compiled into programs and is part of the user/kernel ABI. The MINSIGSTKSZ constant indicates to userspace how much data the kernel expects to push on the user stack, [2][3]. However, this constant is much too small and does not reflect recent additions to the architecture. For instance, when AVX-512 states are in use, the signal frame size can be 3.5KB while MINSIGSTKSZ remains 2KB. The bug report [4] explains this as an ABI issue. The small MINSIGSTKSZ can cause user stack overflow when delivering a signal. In this series, we suggest a couple of things: 1. Provide a variable minimum stack size to userspace, as a similar approach to [5] 2. Avoid using a too-small alternate stack Changes from v1 [6]: * Took stack alignment into account for sigframe size (Dave Martin) [1]: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/bits/sigstack.h;h=b9dca794da093dc4d41d39db9851d444e1b54d9b;hb=HEAD [2]: https://www.gnu.org/software/libc/manual/html_node/Signal-Stack.html [3]: https://man7.org/linux/man-pages/man2/sigaltstack.2.html [4]: https://bugzilla.kernel.org/show_bug.cgi?id=153531 [5]: https://blog.linuxplumbersconf.org/2017/ocw/system/presentations/4671/original/plumbers-dm-2017.pdf [6]: https://lore.kernel.org/lkml/20200929205746.6763-1-chang.seok.bae@intel.com/ Chang S. Bae (4): x86/signal: Introduce helpers to get the maximum signal frame size x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ x86/signal: Prevent an alternate stack overflow before a signal delivery selftest/x86/signal: Include test cases for validating sigaltstack arch/x86/ia32/ia32_signal.c | 11 +- arch/x86/include/asm/elf.h | 4 + arch/x86/include/asm/fpu/signal.h | 2 + arch/x86/include/asm/sigframe.h | 25 +++++ arch/x86/include/uapi/asm/auxvec.h | 6 +- arch/x86/kernel/cpu/common.c | 3 + arch/x86/kernel/fpu/signal.c | 20 ++++ arch/x86/kernel/signal.c | 82 +++++++++++++- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 126 ++++++++++++++++++++++ 10 files changed, 272 insertions(+), 9 deletions(-) create mode 100644 tools/testing/selftests/x86/sigaltstack.c -- 2.17.1