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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8556FC433EF for ; Tue, 12 Jul 2022 18:49:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234572AbiGLSt5 (ORCPT ); Tue, 12 Jul 2022 14:49:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234626AbiGLStX (ORCPT ); Tue, 12 Jul 2022 14:49:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92C553139D; Tue, 12 Jul 2022 11:43:50 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 092C461AC9; Tue, 12 Jul 2022 18:43:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BCE39C3411E; Tue, 12 Jul 2022 18:43:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657651427; bh=v2jQRb/cwYZnNJNo6P3W1xJ1OpzzWBGK68XPPMII0hA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tUrsly+J265bbTu6V59u9lBmuL5VefTyjVzkIfkYQQTB2zxzlG7XS9qaBpoVBgT9A 9SAdYZvQiwGTRGJ0SEFy6vGswerljc+HZ+tFZ5L/VXZDBmFJBXBSQIKqhFwWfJ1W8U n0WR3tG9paQ5bfcARlUI6gMLdxyLINsnOs2EXyBE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Sasha Levin , Ben Hutchings Subject: [PATCH 5.10 071/130] objtool: Fix SLS validation for kcov tail-call replacement Date: Tue, 12 Jul 2022 20:38:37 +0200 Message-Id: <20220712183249.741563131@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220712183246.394947160@linuxfoundation.org> References: <20220712183246.394947160@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra commit 7a53f408902d913cd541b4f8ad7dbcd4961f5b82 upstream. Since not all compilers have a function attribute to disable KCOV instrumentation, objtool can rewrite KCOV instrumentation in noinstr functions as per commit: f56dae88a81f ("objtool: Handle __sanitize_cov*() tail calls") However, this has subtle interaction with the SLS validation from commit: 1cc1e4c8aab4 ("objtool: Add straight-line-speculation validation") In that when a tail-call instrucion is replaced with a RET an additional INT3 instruction is also written, but is not represented in the decoded instruction stream. This then leads to false positive missing INT3 objtool warnings in noinstr code. Instead of adding additional struct instruction objects, mark the RET instruction with retpoline_safe to suppress the warning (since we know there really is an INT3). Fixes: 1cc1e4c8aab4 ("objtool: Add straight-line-speculation validation") Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220323230712.GA8939@worktop.programming.kicks-ass.net Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- tools/objtool/check.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -961,6 +961,17 @@ static void annotate_call_site(struct ob : arch_nop_insn(insn->len)); insn->type = sibling ? INSN_RETURN : INSN_NOP; + + if (sibling) { + /* + * We've replaced the tail-call JMP insn by two new + * insn: RET; INT3, except we only have a single struct + * insn here. Mark it retpoline_safe to avoid the SLS + * warning, instead of adding another insn. + */ + insn->retpoline_safe = true; + } + return; } }