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 185C8C433F5 for ; Wed, 4 May 2022 09:57:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347607AbiEDKBL (ORCPT ); Wed, 4 May 2022 06:01:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232653AbiEDKBK (ORCPT ); Wed, 4 May 2022 06:01:10 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9261426AFB; Wed, 4 May 2022 02:57:35 -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 3625E61A95; Wed, 4 May 2022 09:57:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F749C385A5; Wed, 4 May 2022 09:57:33 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="LgiOdaZg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1651658252; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7QxTQmRrU2TPE1t9O7hHsX1uS6rLbGna3bwCr6dOHKs=; b=LgiOdaZgjat5AfzZ+JngxczZs4gg59ImR+qNyDKmwNLroONljXjLYnSgEmdveQcEw2eBOM T3mCyB6rnxs4w/diOMepTIbhU25q5no41388p6Hx6UWUNz6a8ifQ3kKTHUONn7+2u3VRIx mrfhEjCpmlNf0MfkShTqF8vlmqkMFlA= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id ebcdca06 (TLSv1.3:AEAD-AES256-GCM-SHA384:256:NO); Wed, 4 May 2022 09:57:31 +0000 (UTC) Date: Wed, 4 May 2022 11:57:29 +0200 From: "Jason A. Donenfeld" To: Stafford Horne Cc: Mikulas Patocka , Linus Torvalds , Andy Shevchenko , device-mapper development , Linux Kernel Mailing List , Linux Crypto Mailing List , Herbert Xu , "David S. Miller" , Mike Snitzer , Mimi Zohar , Milan Broz Subject: Re: [PATCH v2] hex2bin: make the function hex_to_bin constant-time Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Wed, May 04, 2022 at 11:42:27AM +0200, Jason A. Donenfeld wrote: > So more likely is that this patch just helps unmask a real issue > elsewhere -- linker, compiler, or register restoration after preemption. > I don't think there's anything to do with regards to the patch of this > thread, as it's clearly fine. The problem even goes away if I just add a nop... diff --git a/lib/hexdump.c b/lib/hexdump.c index 06833d404398..ace74f9b3d5a 100644 --- a/lib/hexdump.c +++ b/lib/hexdump.c @@ -46,6 +46,7 @@ EXPORT_SYMBOL(hex_asc_upper); int hex_to_bin(unsigned char ch) { unsigned char cu = ch & 0xdf; + __asm__("l.nop 0"); return -1 + ((ch - '0' + 1) & (unsigned)((ch - '9' - 1) & ('0' - 1 - ch)) >> 8) + ((cu - 'A' + 11) & (unsigned)((cu - 'F' - 1) & ('A' - 1 - cu)) >> 8);