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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 61139C2BB1D for ; Tue, 7 Apr 2020 10:42:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 23E3B20644 for ; Tue, 7 Apr 2020 10:42:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728409AbgDGKm2 (ORCPT ); Tue, 7 Apr 2020 06:42:28 -0400 Received: from foss.arm.com ([217.140.110.172]:54894 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726399AbgDGKm2 (ORCPT ); Tue, 7 Apr 2020 06:42:28 -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 4D2B431B; Tue, 7 Apr 2020 03:42:27 -0700 (PDT) Received: from [10.37.12.154] (unknown [10.37.12.154]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 268C13F73D; Tue, 7 Apr 2020 03:42:25 -0700 (PDT) Subject: Re: [PATCH] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend To: catalin.marinas@arm.com, fredrik@strupe.net Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, will.deacon@arm.com References: <911db2f1-e078-a460-32ee-154a0b4de5d4@strupe.net> <20200407092744.GA2665@gaia> From: Suzuki K Poulose Message-ID: Date: Tue, 7 Apr 2020 11:47:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20200407092744.GA2665@gaia> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/07/2020 10:27 AM, Catalin Marinas wrote: > On Mon, Apr 06, 2020 at 04:16:05PM +0200, Fredrik Strupe wrote: >> Use a full 32-bit mask to prevent accidental matchings of thumb32 >> instructions where the second half-word is equal to the thumb16 setend >> encoding. >> >> This fixes the same problem as the following patch: >> >> https://lkml.org/lkml/2020/3/16/341 > > This link is not guaranteed to be stable and the commit should have the > full description rather than referring to another email. > >> but for setend emulation instead. >> >> Signed-off-by: Fredrik Strupe > > It also needs Fixes: and Cc: stable tags. > >> --- >> arch/arm64/kernel/armv8_deprecated.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c >> index 9d3442d62..8c06dfee0 100644 >> --- a/arch/arm64/kernel/armv8_deprecated.c >> +++ b/arch/arm64/kernel/armv8_deprecated.c >> @@ -609,7 +609,7 @@ static struct undef_hook setend_hooks[] = { >> }, >> { >> /* Thumb mode */ >> - .instr_mask = 0x0000fff7, >> + .instr_mask = 0xfffffff7, >> .instr_val = 0x0000b650, > > I can see how this could happen but it would be useful to provide a > concrete example in the commit log. > > The instruction opcode built by call_undef_hook() first reads a u16 as a > T16 instruction and the above should be fine. However, if this looks > like a T32 opcode, it reads a subsequent u16 which becomes the lowest > half-word and the above mask/val may inadvertently match it. > We also do a check on the pstate_val, along with the instr_val to confirm the mode. So this should be fine as it is ? Suzuki