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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E3AEAC433E0 for ; Wed, 3 Feb 2021 12:05:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9828464F77 for ; Wed, 3 Feb 2021 12:05:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234432AbhBCMFb (ORCPT ); Wed, 3 Feb 2021 07:05:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52294 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234205AbhBCMF2 (ORCPT ); Wed, 3 Feb 2021 07:05:28 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 641FEC0613D6 for ; Wed, 3 Feb 2021 04:04:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=vb7kl+r70zVcwHQA3nPHUw9qBZRW9PptA8ud8I52zrA=; b=S9OKT3dmKdMPdP3DHxpChg7LmZ nb+MDWU+dTtcPTmPeiHbRFHCnclRFXJa9dlRL6Nx5UIxiZ46vyyq8LZP7KVq0iL+pdH80a0Q1j00d vTLOg3pLTVH541rjfXieVkNVVHu2tzNml3/nTUsdYhjqWNZw3lyTce5Yc8HABEh8a5LoDBcQbouDm KPwXFJpEDaxasMVs+Cp9LUP+YFvxOXgzyCTQOPtuxmiyMpxbXm1JuHRUB1KG4CDL1vAikf2As/8AC OlUy5wSbzWPlTkZr02t9fp3fAw6pOi64ZNkXgnUO/MMlmDavNoJjt0WBNFZjg9CSkSnnkSQUe5P0M KdYYKCIg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1l7Gtl-0007gw-Jd; Wed, 03 Feb 2021 12:04:41 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6CB0B305C1C; Wed, 3 Feb 2021 13:04:40 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 5ABCB2BD45B6E; Wed, 3 Feb 2021 13:04:40 +0100 (CET) Message-ID: <20210203120401.200627050@infradead.org> User-Agent: quilt/0.66 Date: Wed, 03 Feb 2021 13:02:25 +0100 From: Peter Zijlstra To: Josh Poimboeuf , Thomas Gleixner Cc: Miroslav Benes , Nick Desaulniers , Julien Thierry , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org Subject: [PATCH 3/5] objtool: Prepare for scratch regs References: <20210203120222.451068583@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce __save_reg() which allows using the !arch_callee_saved_reg()s and make sure they're wiped after every stack op so they don't linger, allow for a single op exception so they can be used on the very next stack-op. Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/check.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1775,15 +1775,20 @@ static int update_cfi_state_regs(struct return 0; } -static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) +static void __save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) { - if (arch_callee_saved_reg(reg) && - cfi->regs[reg].base == CFI_UNDEFINED) { + if (cfi->regs[reg].base == CFI_UNDEFINED) { cfi->regs[reg].base = base; cfi->regs[reg].offset = offset; } } +static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset) +{ + if (arch_callee_saved_reg(reg)) + __save_reg(cfi, reg, base, offset); +} + static void restore_reg(struct cfi_state *cfi, unsigned char reg) { cfi->regs[reg].base = initial_func_cfi.regs[reg].base; @@ -1848,6 +1853,7 @@ static int update_cfi_state(struct instr { struct cfi_reg *cfa = &cfi->cfa; struct cfi_reg *regs = cfi->regs; + bool skip_wipe = false; /* stack operations don't make sense with an undefined CFA */ if (cfa->base == CFI_UNDEFINED) { @@ -2192,6 +2198,21 @@ static int update_cfi_state(struct instr return -1; } + /* + * Only callee saved registers are preserved; the rest is scratch space + * preserved at most one instruction. + */ + if (!skip_wipe) { + int i; + + for (i = 0; i < CFI_NUM_REGS; i++) { + if (arch_callee_saved_reg(i)) + continue; + + restore_reg(cfi, i); + } + } + return 0; }