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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 D746EC433E2 for ; Mon, 14 Sep 2020 16:45:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82152206A5 for ; Mon, 14 Sep 2020 16:45:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726019AbgINQpE (ORCPT ); Mon, 14 Sep 2020 12:45:04 -0400 Received: from foss.arm.com ([217.140.110.172]:39600 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726064AbgINPKn (ORCPT ); Mon, 14 Sep 2020 11:10:43 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3D2B41396; Mon, 14 Sep 2020 08:10:37 -0700 (PDT) Received: from seattle-bionic.arm.com.Home (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3CDBC3F718; Mon, 14 Sep 2020 08:10:36 -0700 (PDT) From: Oliver Swede To: catalin.marinas@arm.com, will@kernel.org Cc: robin.murphy@arm.com, linux-arm-kernel@lists.indradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 02/14] arm64: kprobes: Drop open-coded exception fixup Date: Mon, 14 Sep 2020 15:09:46 +0000 Message-Id: <20200914150958.2200-3-oli.swede@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200914150958.2200-1-oli.swede@arm.com> References: <20200914150958.2200-1-oli.swede@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Robin Murphy The short-circuit call to fixup_exception() from kprobe_fault_handler() poses a problem now that the former wants to consume the fault address too, since the common kprobes API offers us no way to pass it through. Fortunately, however, it works out to be unnecessary: - uaccess instructions themselves are not probeable, so at most we should only ever expect to take a fixable fault from the pre or post handlers. - the pre and post handler run with preemption disabled, thus for any fault they may cause, an unhandled return from kprobe_page_fault() will proceed directly to __do_kernel_fault() thanks to the faulthandler_disabled() check. - __do_kernel_fault() will immediately call fixup_exception() unless we're in an EL1 instruction abort, and if we've somehow taken one of those on what we think is the middle of a uaccess routine, then the world is already very on fire. Thus we can reasonably drop the call from kprobe_fault_handler() and leave uaccess fixups to the regular flow. Signed-off-by: Robin Murphy Signed-off-by: Oliver Swede --- arch/arm64/kernel/probes/kprobes.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index 5290f17a4d80..c54c8252b32f 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -328,13 +328,6 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) */ if (cur->fault_handler && cur->fault_handler(cur, regs, fsr)) return 1; - - /* - * In case the user-specified fault handler returned - * zero, try to fix up. - */ - if (fixup_exception(regs)) - return 1; } return 0; } -- 2.17.1