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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 71BE8C4727D for ; Tue, 6 Oct 2020 13:46:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 167EC20782 for ; Tue, 6 Oct 2020 13:46:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726127AbgJFNqd (ORCPT ); Tue, 6 Oct 2020 09:46:33 -0400 Received: from foss.arm.com ([217.140.110.172]:47872 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725902AbgJFNqc (ORCPT ); Tue, 6 Oct 2020 09:46:32 -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 B85C6143D; Tue, 6 Oct 2020 06:46:31 -0700 (PDT) Received: from [192.168.122.166] (unknown [10.119.48.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 38BF03F71F; Tue, 6 Oct 2020 06:46:31 -0700 (PDT) Subject: Re: [BUG][PATCH] crypto: arm64: Avoid indirect branch to bti_c To: Catalin Marinas , Dave Martin Cc: herbert@gondor.apana.org.au, linux-kernel@vger.kernel.org, davem@davemloft.net, broonie@kernel.org, linux-crypto@vger.kernel.org, Will Deacon , ardb@kernel.org, linux-arm-kernel@lists.infradead.org References: <20201006034854.2277538-1-jeremy.linton@arm.com> <20201006082748.GB25305@willie-the-truck> <20201006100121.GW6642@arm.com> <20201006102507.GA19213@gaia> <20201006104313.GX6642@arm.com> <20201006123350.GB19213@gaia> From: Jeremy Linton Message-ID: <877e948c-2903-5537-05a6-654f4753407c@arm.com> Date: Tue, 6 Oct 2020 08:45:47 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20201006123350.GB19213@gaia> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 10/6/20 7:33 AM, Catalin Marinas wrote: > On Tue, Oct 06, 2020 at 11:43:14AM +0100, Dave P Martin wrote: >> On Tue, Oct 06, 2020 at 11:25:11AM +0100, Catalin Marinas wrote: >>> On Tue, Oct 06, 2020 at 11:01:21AM +0100, Dave P Martin wrote: >>>> On Tue, Oct 06, 2020 at 09:27:48AM +0100, Will Deacon wrote: >>>>> On Mon, Oct 05, 2020 at 10:48:54PM -0500, Jeremy Linton wrote: >>>>>> The AES code uses a 'br x7' as part of a function called by >>>>>> a macro. That branch needs a bti_j as a target. This results >>>>>> in a panic as seen below. Instead of trying to replace the branch >>>>>> target with a bti_jc, lets replace the indirect branch with a >>>>>> bl/ret, bl sequence that can target the existing bti_c. >>>>>> >>>>>> Bad mode in Synchronous Abort handler detected on CPU1, code 0x34000003 -- BTI >>>>>> CPU: 1 PID: 265 Comm: cryptomgr_test Not tainted 5.8.11-300.fc33.aarch64 #1 >>>>>> pstate: 20400c05 (nzCv daif +PAN -UAO BTYPE=j-) >>>>>> pc : aesbs_encrypt8+0x0/0x5f0 [aes_neon_bs] >>>>>> lr : aesbs_xts_encrypt+0x48/0xe0 [aes_neon_bs] >>>>>> sp : ffff80001052b730 >>>>>> >>>>>> aesbs_encrypt8+0x0/0x5f0 [aes_neon_bs] >>>>>> __xts_crypt+0xb0/0x2dc [aes_neon_bs] >>>>>> xts_encrypt+0x28/0x3c [aes_neon_bs] >>>>>> crypto_skcipher_encrypt+0x50/0x84 >>>>>> simd_skcipher_encrypt+0xc8/0xe0 >>>>>> crypto_skcipher_encrypt+0x50/0x84 >>>>>> test_skcipher_vec_cfg+0x224/0x5f0 >>>>>> test_skcipher+0xbc/0x120 >>>>>> alg_test_skcipher+0xa0/0x1b0 >>>>>> alg_test+0x3dc/0x47c >>>>>> cryptomgr_test+0x38/0x60 >>>>>> >>>>>> Fixes: commit 0e89640b640d ("crypto: arm64 - Use modern annotations for assembly functions") >>>>> >>>>> nit: the "commit" string shouldn't be here, and I think the linux-next >>>>> scripts will yell at us if we don't remove it. >>>>> >>>>>> Signed-off-by: Jeremy Linton >>>>>> --- >>>>>> arch/arm64/crypto/aes-neonbs-core.S | 6 +++--- >>>>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>>>> >>>>>> diff --git a/arch/arm64/crypto/aes-neonbs-core.S b/arch/arm64/crypto/aes-neonbs-core.S >>>>>> index b357164379f6..32f53ebe5e2c 100644 >>>>>> --- a/arch/arm64/crypto/aes-neonbs-core.S >>>>>> +++ b/arch/arm64/crypto/aes-neonbs-core.S >>>>>> @@ -788,7 +788,7 @@ SYM_FUNC_START_LOCAL(__xts_crypt8) >>>>>> >>>>>> 0: mov bskey, x21 >>>>>> mov rounds, x22 >>>>>> - br x7 >>>>>> + ret >>>> >>>> Dang, replied on an old version. >>> >>> Which I ignored (by default, when the kbuild test robot complains ;)). >>> >>>> Since this is logically a tail call, could we simply be using br x16 or >>>> br x17 for this? >>>> >>>> The architecture makes special provision for that so that the compiler >>>> can generate tail-calls. >>> >>> So a "br x16" is compatible with a bti_c landing pad. I think it makes >>> more sense to keep it as a tail call. >> >> Just to be clear, I'm happy either way, but I thought it would make >> sense to point this out. > > I'd prefer the replacement with a br x16/17, it keeps the code pretty > much unchanged. > > Jeremy, could you please respin this patch and give it a try? Sounds like a plan. I'm probably going to change the subject again, guess I will put a v3 on it too. :)