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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 808FBCA9EC9 for ; Fri, 1 Nov 2019 03:55:25 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id CBFAE2083E for ; Fri, 1 Nov 2019 03:55:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="gdpHWq36" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CBFAE2083E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17215-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 26441 invoked by uid 550); 1 Nov 2019 03:55:18 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 26421 invoked from network); 1 Nov 2019 03:55:17 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=zSoUcnGkSf7yfDdI4UPFWole6s3LI6NqVWKcqfKw3S8=; b=gdpHWq36NRa5kgf+gRe/MKxYGjAw3bBoglJCiCxqDG/Z5bLWefay/odv1qRX70dC6u xEQoc/cnbPdiJcOxSIkOgyhVuljqbWzwmQF4cqReWLlUHB1iREij3Bw5hMnU19ZGaFou 2x2RfVCm1NB8MMDbP9OX8d28IFnaJuv0SjjDk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=zSoUcnGkSf7yfDdI4UPFWole6s3LI6NqVWKcqfKw3S8=; b=oqVcaBIL5YLP8AQ2ns9pK3Q25jCKNt1UatUg4+5u0F3EcnYKm6fEw/gNB3TFm4wqg+ Z7a3Om1HAhIRBajFzfNPA0vN9BmEh2mUvtubjxoYegk8v38ybD6BqPfsgUjzDrmkfRHG Nvgi3RlTF667wOFeXigumHFZs+K+77INdrJFCbFFzB0SVb75XiXuRUfmOzs3RzFmGAgp Zu7JH7zrBT2bruxm0nmS0rfZFKzCo8oIdfJtopEYbaCjJpvSHVEAS5iZPI0mQ2blZ2iN KAHTAlBS4W40148m/RTrPpvCbNePeMPnRqd3DJXtoAS3/+5Tc7MAeS3NosqZ/w7zUpaD gcpQ== X-Gm-Message-State: APjAAAWHpi4TKjnYXNNqDXUWvHxyjyy8exmWlfJ8Mo8vhKxfbbXVUoDS RewGyFEKmiJQTs/1D+JiClMlZw== X-Google-Smtp-Source: APXvYqx5k7aF99T5w9h4PpSwUM81mxoH0R6qDLQkK0BR3TP2j37wYiYVIHIkontT/DEGLXmTTHNH0A== X-Received: by 2002:a17:90a:bb0b:: with SMTP id u11mr12349099pjr.94.1572580505585; Thu, 31 Oct 2019 20:55:05 -0700 (PDT) Date: Thu, 31 Oct 2019 20:55:03 -0700 From: Kees Cook To: samitolvanen@google.com Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Dave Martin , Laura Abbott , Mark Rutland , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 07/17] scs: add support for stack usage debugging Message-ID: <201910312054.3064999E@keescook> References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> <20191031164637.48901-8-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191031164637.48901-8-samitolvanen@google.com> On Thu, Oct 31, 2019 at 09:46:27AM -0700, samitolvanen@google.com wrote: > Implements CONFIG_DEBUG_STACK_USAGE for shadow stacks. Did I miss it, or is there no Kconfig section for this? I just realized I can't find it. I was going to say "this commit log should explain why/when this option is used", but then figured it might be explained in the Kconfig ... but I couldn't find it. ;) -Kees > > Signed-off-by: Sami Tolvanen > --- > kernel/scs.c | 39 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 39 insertions(+) > > diff --git a/kernel/scs.c b/kernel/scs.c > index 7780fc4e29ac..67c43af627d1 100644 > --- a/kernel/scs.c > +++ b/kernel/scs.c > @@ -167,6 +167,44 @@ 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(tsk); > + uintptr_t s = (uintptr_t)p; > + > + while (p < end && *p) > + p++; > + > + return (uintptr_t)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: highest shadow stack usage %lu bytes\n", > + __func__, used); > + highest = used; > + } > + > + spin_unlock(&lock); > +} > +#else > +static inline void scs_check_usage(struct task_struct *tsk) > +{ > +} > +#endif > + > bool scs_corrupted(struct task_struct *tsk) > { > return *scs_magic(tsk) != SCS_END_MAGIC; > @@ -181,6 +219,7 @@ void scs_release(struct task_struct *tsk) > return; > > WARN_ON(scs_corrupted(tsk)); > + scs_check_usage(tsk); > > scs_account(tsk, -1); > task_set_scs(tsk, NULL); > -- > 2.24.0.rc0.303.g954a862665-goog > -- Kees Cook