From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by sourceware.org (Postfix) with ESMTPS id E62DD39730B5 for ; Tue, 29 Sep 2020 21:01:26 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org E62DD39730B5 IronPort-SDR: Woqg1kL1HbZd5UZ/tMh5984GKAOgvGxcViFGc1eAhY1MKjk4camN/ZRx2wMSWy8F9othQL/c+N Ex0EkC4EHuEA== X-IronPort-AV: E=McAfee;i="6000,8403,9759"; a="223888246" X-IronPort-AV: E=Sophos;i="5.77,319,1596524400"; d="scan'208";a="223888246" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Sep 2020 14:01:22 -0700 IronPort-SDR: bFn8JtJ42VossFrlSUkzKDjyua51j/jF2FeiiAoBoXvDILU7PlBemmWR34TyuRuKfxE1NraZ6/ TvBROEA/0eLg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,319,1596524400"; d="scan'208";a="514024807" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga006.fm.intel.com with ESMTP; 29 Sep 2020 14:01:22 -0700 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: [RFC PATCH 0/4] x86: Improve Minimum Alternate Stack Size Date: Tue, 29 Sep 2020 13:57:42 -0700 Message-Id: <20200929205746.6763-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 X-Spam-Status: No, score=-2.9 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-List-Received-Date: Tue, 29 Sep 2020 21:01:28 -0000 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 [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 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 | 66 +++++++++++- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 126 ++++++++++++++++++++++ 10 files changed, 258 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/x86/sigaltstack.c -- 2.17.1