From patchwork Mon Aug 7 18:35:51 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 109581 Delivered-To: patch@linaro.org Received: by 10.140.95.78 with SMTP id h72csp1951606qge; Mon, 7 Aug 2017 11:37:22 -0700 (PDT) X-Received: by 10.84.176.131 with SMTP id v3mr1705480plb.142.1502131042206; Mon, 07 Aug 2017 11:37:22 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1502131042; cv=none; d=google.com; s=arc-20160816; b=DB81nPyFRXBBClnQ1nHR0haVoTSas0Y7He3JI/+z964+VV2fKXyI04cCCRHNch3mla l+QNCvDKzsCScWpq1d3TDtIoEMvXDcbfzylX/STXsEOTLVEVhREAyVLaflEHVJiuJTxI BHWzcNOekEZj+REDJHWDbVoC4bbmi8jLXTXMbR8urY745NG3l2wPajOSH7qFJDNbgJ36 KSXB7YO8R4lROFwWe0wm/qp/ZzEfGc5RutXzYK0vdXbKTZLBylegJO4ytJ7iznExxfKk RTnQz61U+uIiHnuubyqUOcFzwG0NXLLsxss7a8e85qArM84dtjDhAoOaWCw2eRWxnFsP EEwQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:message-id:date:subject:cc:to:from :arc-authentication-results; bh=jOFm+kpa55zeTQKtareKMsdXS9pFqnH5S3xnFGebtcE=; b=OZuHg4lZ+UeMcxL/KDKptEop6o25MUY1Xz1PqdEAK5Lkbc6kjZo8PphWibhtkz7a4F BQwpZ1ILysA+YO/TM9fcfWiDecNtw/vx/tnUaiq8V5AW4GEWHMNmNcrzBvXQZcqbs07a 6LfQYAITzA5Kb/GmgJMh54QezePtU9Z6rUswjIpdrT2YqoKRLL0/g9qH5osZHXoln8Ay CXJWZEsfjcb9668kdIg2qACx/dSXSy8xiMKyqEWRNmoDsIDA/e7hsLpZK01FMhKL5LTd drujqSEhCnFfbpvMLz0PNG8WRdgCAibHxVJAqRuY2rSZ2r+wEAgDTixVtPYYnX10+Fqj O/Sw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id 186si5049288pfu.378.2017.08.07.11.37.21; Mon, 07 Aug 2017 11:37:22 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751901AbdHGShT (ORCPT + 25 others); Mon, 7 Aug 2017 14:37:19 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:52448 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751564AbdHGShS (ORCPT ); Mon, 7 Aug 2017 14:37:18 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6EAB715A2; Mon, 7 Aug 2017 11:37:17 -0700 (PDT) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 7E9313F577; Mon, 7 Aug 2017 11:37:15 -0700 (PDT) From: Mark Rutland To: linux-arm-kernel@lists.infradead.org Cc: ard.biesheuvel@linaro.org, catalin.marinas@arm.com, james.morse@arm.com, labbott@redhat.com, linux-kernel@vger.kernel.org, luto@amacapital.net, mark.rutland@arm.com, matt@codeblueprint.co.uk, will.deacon@arm.com, kernel-hardening@lists.openwall.com, keescook@chromium.org Subject: [PATCH 00/14] arm64: VMAP_STACK support Date: Mon, 7 Aug 2017 19:35:51 +0100 Message-Id: <1502130965-18710-1-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Ard and I have worked together to implement vmap stack support for arm64. This supersedes our earlier vmap stack RFCs [0,1]. The git author stats are a little misleading, as I've teased parts out into smaller patches for review. The series is based on our stack dump rework [2,3], which can be found in the arm64/exception-stack branch [4] of my kernel.org repo. This series can be found in the arm64/vmap-stack branch [5] of the same repo. On arm64, there is no double-fault exception, as software saves exception context to the stack. An erroneous memory access taken during exception handling results in a data abort, as with any other erroneous memory access. To avoid taking these recursively, we must detect overflow by checking the SP before we attempt to store any context to the stack. Doing this efficiently requires a couple of tricks. For a naturally aligned stack, bits THREAD_SHIFT-1:0 of a valid SP may contain any arbitrary value: 0bXX .. 11111111111111 0bXX .. 11011001011100 0bXX .. 00000000000000 By aligning stacks to double their natural alignment, we know that the THREAD_SHIFT bit of any valid SP must be zero: 0bXX .. 0 11111111111111 0bXX .. 0 11011001011100 0bXX .. 0 00000000000000 ... while an overflow will result in this bit flipping, along with (some) other high-order bits: 0bXX .. 0 00000000000000 < SP -= 1 > 0bXX .. 1 11111111111111 ... and thus, we can detect overflows of up to THREAD_SIZE by testing the THREAD_SHIFT bit of the SP value. Provided we can get the SP into a general purpose register, we can perform this test with a single TBNZ instruction. We don't have scratch space to store a GPR, but we can (partially) swap the SP with a GPR using arithmetic to perform the test: add sp, sp, x0 // sp' = sp + x0 sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp tbnz x0, #THREAD_SHIFT, overflow_handler sub x0, sp, x0 // sp' - x0' = (sp + x0) - sp = x0 sub sp, sp, x0 // sp' - x0 = (sp + x0) - x0 = sp This series implements this approach, along with the other requisite changes required to make this work. The SP test is performed for all exceptions, after compensating for the size of the exception registers, allowing the original exception context to be preserved in entirety. The tests themselves are folded into the exception vectors, minimizing their impact. To ensure that IRQ stack overflows are detected and handled, IRQ stacks are now dynamically allocated, with guard pages. I've given the series some light testing with LKDTM, Syzkaller, Vince Weaver's perf fuzzer, and a few combinations of debug options. I haven't compared performance of the entire series to a baseline kernel, but from testing so far the cost of the SP test falls in the noise for a kernel build workload on Cortex-A57. Many thanks to Ard for putting up with my meddling, and also to Laura and James for their testing and comments on prior patches. Thanks, Mark. [0] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/518368.html [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/518434.html [2] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/520705.html [3] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-July/521435.html [4] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/exception-stack [5] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/vmap-stack Ard Biesheuvel (2): arm64: kernel: remove {THREAD,IRQ_STACK}_START_SP arm64: assembler: allow adr_this_cpu to use the stack pointer Mark Rutland (12): arm64: remove __die()'s stack dump fork: allow arch-override of VMAP stack alignment arm64: factor out PAGE_* and CONT_* definitions arm64: clean up THREAD_* definitions arm64: clean up irq stack definitions arm64: move SEGMENT_ALIGN to efi/arm64: add EFI_KIMG_ALIGN arm64: factor out entry stack manipulation arm64: use an irq stack pointer arm64: add basic VMAP_STACK support arm64: add on_accessible_stack() arm64: add VMAP_STACK overflow detection arch/arm64/Kconfig | 1 + arch/arm64/include/asm/assembler.h | 3 +- arch/arm64/include/asm/efi.h | 8 +++ arch/arm64/include/asm/irq.h | 25 ------- arch/arm64/include/asm/memory.h | 53 ++++++++++++++ arch/arm64/include/asm/page-def.h | 34 +++++++++ arch/arm64/include/asm/page.h | 12 +--- arch/arm64/include/asm/processor.h | 2 +- arch/arm64/include/asm/stacktrace.h | 62 ++++++++++++++++- arch/arm64/include/asm/thread_info.h | 10 +-- arch/arm64/kernel/entry.S | 110 +++++++++++++++++++++++------- arch/arm64/kernel/irq.c | 40 ++++++++++- arch/arm64/kernel/ptrace.c | 1 + arch/arm64/kernel/smp.c | 2 +- arch/arm64/kernel/stacktrace.c | 7 +- arch/arm64/kernel/traps.c | 44 ++++++++++-- arch/arm64/kernel/vmlinux.lds.S | 18 +---- drivers/firmware/efi/libstub/arm64-stub.c | 6 +- kernel/fork.c | 5 +- 19 files changed, 339 insertions(+), 104 deletions(-) create mode 100644 arch/arm64/include/asm/page-def.h -- 1.9.1