From patchwork Thu Nov 19 19:02:33 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: 41132 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 228EA39ACC0B; Thu, 19 Nov 2020 19:07:05 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 228EA39ACC0B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1605812825; bh=8iSBULCPtcS6f/As46qn1olfZyufeJiiJ1ZxRIky70M=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=i5YV266GhOZ4Y3g8V18BwCQcGvIDYqCCQb5XbwCGmqwAs/S1pdifDgmJ9/itSiMy6 RCS/K9nrD10BCslAE8MW8qRQWx39zWZcvHgVpYBB2vkmlppGT+bBm01n1MDQsyo2QC YVcGU2R5oMBNlPHN9QBHSEq++9Lt5Uigb6k2EGxU= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by sourceware.org (Postfix) with ESMTPS id C702F3857804 for ; Thu, 19 Nov 2020 19:07:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org C702F3857804 IronPort-SDR: HNsw5DjE+J4dUoRTVqSD56P+RvFKkmQWnA6yDP0b5oxfJ6d33MCkiDgXEQx5QCoMAo2gLM8fma d8usHIEpbFQQ== X-IronPort-AV: E=McAfee;i="6000,8403,9810"; a="170563946" X-IronPort-AV: E=Sophos;i="5.78,354,1599548400"; d="scan'208";a="170563946" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Nov 2020 11:06:40 -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 To: tglx@linutronix.de, mingo@kernel.org, bp@suse.de, luto@kernel.org, x86@kernel.org 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 X-Spam-Status: No, score=-3.7 required=5.0 tests=AC_FROM_MANY_DOTS, BAYES_00, KAM_DMARC_STATUS, KAM_SHORT, 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, 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" [ 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