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=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,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 3BAB9C38A30 for ; Mon, 20 Apr 2020 17:17:58 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0BC4A21744 for ; Mon, 20 Apr 2020 17:17:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="kdpAS1vL"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ph/dGiaW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BC4A21744 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9Yga4t8JftcNcbcV4Q6T3fsIjniHQldPIqvxqL1yHk8=; b=kdpAS1vLruSb/3 ojlGYHNTMs6Usb3Lh34xXkvKPiKAKwWS+d+pZNa20WvvfIiTvXr73rEHSeORFNtd+YoljrfY0VymS mCnhnwCsaCiRupZj1emkgF93o1rSBgyqavvXEpXeTTRNQ/YidH8zYRaJA5y5uGcLk9XjUQF1p7B0D taFU9OJ15E1jly280URf7dehIp3QGupnPT+dFmi2COcBPlVielTUxqgp+oqg/NjiEvhaJh8Z6RGFC idg8fN/WNI/Kvi3wJ7ujGB+6dB28KiO4whnVcZUObXJI3f/5tLUVYVEkd54jOR4IglhPAWax0i3tK xSRYfBuzsFU66ODaYgtw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQa3P-000216-E3; Mon, 20 Apr 2020 17:17:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jQa3J-0001ve-Qu for linux-arm-kernel@lists.infradead.org; Mon, 20 Apr 2020 17:17:51 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 54EF720B1F; Mon, 20 Apr 2020 17:17:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587403069; bh=wXEAfThnDs14N1G/spAtmfJQE33jZSGAx1cIEKIIuc0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ph/dGiaW6TygCcuAfJaNmpuzQDZkB3Fcj9NIV3BJO6mMxd7giMQgjXFhuJSUDQYFR gZ3RV//pTvooHvX3I1ePN4Q//oI89A9oXCSzfPmLTT3Eh9DIizNl4CnAJKoR6P7BEw Y5eQXMPJpUVmD5phFHnzKLJXCdESnzk7IjbYWxfk= Date: Mon, 20 Apr 2020 18:17:42 +0100 From: Will Deacon To: Sami Tolvanen Subject: Re: [PATCH v11 03/12] scs: add support for stack usage debugging Message-ID: <20200420171741.GC24386@willie-the-truck> References: <20191018161033.261971-1-samitolvanen@google.com> <20200416161245.148813-1-samitolvanen@google.com> <20200416161245.148813-4-samitolvanen@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200416161245.148813-4-samitolvanen@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200420_101750_018519_8BD5A830 X-CRM114-Status: GOOD ( 16.90 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Juri Lelli , kernel-hardening@lists.openwall.com, Peter Zijlstra , Catalin Marinas , Marc Zyngier , Masahiro Yamada , clang-built-linux@googlegroups.com, Ingo Molnar , Laura Abbott , Dave Martin , Kees Cook , Jann Horn , Steven Rostedt , linux-arm-kernel@lists.infradead.org, Michal Marek , Ard Biesheuvel , Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , James Morse , Masami Hiramatsu Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Apr 16, 2020 at 09:12:36AM -0700, Sami Tolvanen wrote: > Implements CONFIG_DEBUG_STACK_USAGE for shadow stacks. When enabled, > also prints out the highest shadow stack usage per process. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Kees Cook > --- > kernel/scs.c | 39 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 39 insertions(+) > > diff --git a/kernel/scs.c b/kernel/scs.c > index 5245e992c692..ad74d13f2c0f 100644 > --- a/kernel/scs.c > +++ b/kernel/scs.c > @@ -184,6 +184,44 @@ int scs_prepare(struct task_struct *tsk, int node) > return 0; > } > > +#ifdef CONFIG_DEBUG_STACK_USAGE > +static inline unsigned long scs_used(struct task_struct *tsk) > +{ > + unsigned long *p = __scs_base(tsk); > + unsigned long *end = scs_magic(p); > + unsigned long s = (unsigned long)p; > + > + while (p < end && READ_ONCE_NOCHECK(*p)) > + p++; I think the expectation is that the caller has already checked that the stack is not corrupted, so I'd probably throw a couple of underscores in front of the function name, along with a comment. Also, is tsk ever != current? > + > + return (unsigned long)p - s; > +} > + > +static void scs_check_usage(struct task_struct *tsk) > +{ > + static DEFINE_SPINLOCK(lock); > + static unsigned long highest; > + unsigned long used = scs_used(tsk); > + > + if (used <= highest) > + return; > + > + spin_lock(&lock); > + > + if (used > highest) { > + pr_info("%s (%d): highest shadow stack usage: %lu bytes\n", > + tsk->comm, task_pid_nr(tsk), used); > + highest = used; > + } > + > + spin_unlock(&lock); Do you really need this lock? I'd have thought you could cmpxchg() highest instead. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel