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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 1D00FC742D2 for ; Mon, 15 Jul 2019 00:38:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2559214AE for ; Mon, 15 Jul 2019 00:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729267AbfGOAiH (ORCPT ); Sun, 14 Jul 2019 20:38:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34882 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729211AbfGOAhz (ORCPT ); Sun, 14 Jul 2019 20:37:55 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BA47A3086272; Mon, 15 Jul 2019 00:37:55 +0000 (UTC) Received: from treble.redhat.com (ovpn-120-170.rdu2.redhat.com [10.10.120.170]) by smtp.corp.redhat.com (Postfix) with ESMTP id AF8565D9D2; Mon, 15 Jul 2019 00:37:54 +0000 (UTC) From: Josh Poimboeuf To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Thomas Gleixner , Nick Desaulniers , Arnd Bergmann , Jann Horn , Randy Dunlap Subject: [PATCH 22/22] objtool: Support conditional retpolines Date: Sun, 14 Jul 2019 19:37:17 -0500 Message-Id: <4db0cb4d1065c8714ee64f0bfc9fc8b7d6331124.1563150885.git.jpoimboe@redhat.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Mon, 15 Jul 2019 00:37:55 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A Clang-built kernel is showing the following warning: arch/x86/kernel/platform-quirks.o: warning: objtool: x86_early_init_platform_quirks()+0x84: unreachable instruction That corresponds to this code: 7e: 0f 85 00 00 00 00 jne 84 80: R_X86_64_PC32 __x86_indirect_thunk_r11-0x4 84: c3 retq This is a conditional retpoline sibling call, which is now possible thanks to retpolines. Objtool hasn't seen that before. It's incorrectly interpreting the conditional jump as an unconditional dynamic jump. Reported-by: Nick Desaulniers Signed-off-by: Josh Poimboeuf --- tools/objtool/arch.h | 1 + tools/objtool/check.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h index 50448c0c4bca..ced3765c4f44 100644 --- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -15,6 +15,7 @@ enum insn_type { INSN_JUMP_CONDITIONAL, INSN_JUMP_UNCONDITIONAL, INSN_JUMP_DYNAMIC, + INSN_JUMP_DYNAMIC_CONDITIONAL, INSN_CALL, INSN_CALL_DYNAMIC, INSN_RETURN, diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5a237fc05cdc..a8411355a80d 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -575,7 +575,11 @@ static int add_jump_destinations(struct objtool_file *file) * Retpoline jumps are really dynamic jumps in * disguise, so convert them accordingly. */ - insn->type = INSN_JUMP_DYNAMIC; + if (insn->type == INSN_JUMP_UNCONDITIONAL) + insn->type = INSN_JUMP_DYNAMIC; + else + insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL; + insn->retpoline_safe = true; continue; } else { @@ -2114,13 +2118,17 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, break; case INSN_JUMP_DYNAMIC: + case INSN_JUMP_DYNAMIC_CONDITIONAL: if (func && is_sibling_call(insn)) { ret = validate_sibling_call(insn, &state); if (ret) return ret; } - return 0; + if (insn->type == INSN_JUMP_DYNAMIC) + return 0; + + break; case INSN_CONTEXT_SWITCH: if (func && (!next_insn || !next_insn->hint)) { -- 2.20.1