From patchwork Wed Dec 23 01:53:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41523 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id D0BB1383300F; Wed, 23 Dec 2020 01:57:39 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D0BB1383300F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1608688659; bh=6MnNA8CTrb4RwzY+B1SgwALJNsrD7fP2VvS52Z98k5U=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=gAWJixt4/w+G/fmJCORdybu0hM0fwQp5kRpUldKGZnTwc1OokjCxEro9GnZqUOhoW MJBJ/q9ltxJ0ne8aEpDjx/XSFhZsS6mE25k12n+RDJOGk7O83Xo0W8J1/CCUByEubs 8iiW9HVmwpVqKUqPKHPciZxM7KaO/ohh3b30/thI= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by sourceware.org (Postfix) with ESMTPS id 0A3E9385802A for ; Wed, 23 Dec 2020 01:57:35 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 0A3E9385802A IronPort-SDR: EgG2tBEzy3NuR+N1IvtbuSPbcG/xD1pnOdgwFvEmzCG3y5pO+0AVIBa2bECAvbk936cUFlEIIA JjlyBqW0NM6g== X-IronPort-AV: E=McAfee;i="6000,8403,9843"; a="194393117" X-IronPort-AV: E=Sophos;i="5.78,440,1599548400"; d="scan'208";a="194393117" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Dec 2020 17:57:34 -0800 IronPort-SDR: yKGf3adYatD3eoY0tuXwgz1+NJhRrMtTFTzMfHezOqij4PZBXBtISpD1hyJUM8IP5GEQlaQXYY CdJHd91uQlVQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,440,1599548400"; d="scan'208";a="457755715" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga001.fm.intel.com with ESMTP; 22 Dec 2020 17:57:33 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v3 0/4] x86: Improve Minimum Alternate Stack Size Date: Tue, 22 Dec 2020 17:53:08 -0800 Message-Id: <20201223015312.4882-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 X-Spam-Status: No, score=-3.7 required=5.0 tests=AC_FROM_MANY_DOTS, BAYES_00, KAM_DMARC_STATUS, KAM_SHORT, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" 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 v2 [7]: * Simplified the sigaltstack overflow prevention (Jann Horn) * Renamed fpstate size helper with cleanup (Borislav Petkov) * Cleaned up the signframe struct size defines (Borislav Petkov) * Revised the selftest messages (Borislav Petkov) * Revised a changelog (Borislav Petkov) 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/ [7]: https://lore.kernel.org/lkml/20201119190237.626-1-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/include/asm/elf.h | 4 + arch/x86/include/asm/fpu/signal.h | 2 + arch/x86/include/asm/sigframe.h | 2 + arch/x86/include/uapi/asm/auxvec.h | 6 +- arch/x86/kernel/cpu/common.c | 3 + arch/x86/kernel/fpu/signal.c | 19 ++++ arch/x86/kernel/signal.c | 69 +++++++++++- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 128 ++++++++++++++++++++++ 9 files changed, 228 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/x86/sigaltstack.c