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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL 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 253DDC5519A for ; Mon, 27 Apr 2020 16:00:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 043E1206D4 for ; Mon, 27 Apr 2020 16:00:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LKPo6Bc/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728552AbgD0QAh (ORCPT ); Mon, 27 Apr 2020 12:00:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1728517AbgD0QAe (ORCPT ); Mon, 27 Apr 2020 12:00:34 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 841AEC0610D5 for ; Mon, 27 Apr 2020 09:00:34 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id j14so20899138ybt.10 for ; Mon, 27 Apr 2020 09:00:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=kikYfFSTfca/HkjJiT4VwZFMKgohIqKorfyIql1wDNc=; b=LKPo6Bc/Q5MtQzUK3oQa6NKadNaC15z3lO/zjdaounxLr3Yr/P6IlUdUGblL+xU5k4 spAtU8NF5ubk32gUq0m5VXjp6kv3GAFhZ4b47WHO1jV9Re1P0wgxqNnIy78PYlqK6iHg Lz7JdX7MXdIx+DHcDceIZRSq68+3ppbTa32fDBBMVQUsXCdSeZ2Rk0+iayOXLcIpH0mh 1y8jfaqoFffOSgqi3glfbRygtn76YwRgqeTcaTsWT5Ma8vEPSbQu5Sf1lQXSpiWIQ5jH osRX2DeCrw1RtV2JiczAkw6ANMNeNCpzDPw4w/B5fxj55cgpesof+s+eghyxXIYIpJqz Cp7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=kikYfFSTfca/HkjJiT4VwZFMKgohIqKorfyIql1wDNc=; b=gbzteNDEEiJ2C2oosz4Y0fKUOO27RWPGhp7CBNZJ8/u93GFsNpSG7Ft09TO3I+5w7q n9oltMGyg+mot4ex1gQoaFULSuBSW0VNMNyWnBuJBknZoMRLzux9qQhyl61Clrp8THqV DPRQRgmYXRDK5oeUSg9xGoiOnmVjfZS19xA8Dam2XTNFITxjSt7fLxjGwFDK96+XmbqV mecQipRnW8GRqngw60Bx21AHBzo2WIjwEagEYDss3MTmHd4OzL7DxcbogFFcep6kt2AY 044Cc31vwrGsL4u/B6ZUewcy6vnEKgTOVhW5LA0OFQz7lHkC/RS3zBv9lsWd44Nie+Wq e8SA== X-Gm-Message-State: AGi0PubYv4piYN69PZDtIXqXe6zOcP8ADnBEH1+2Rh6zcDyGaTbSc2HL 5IWT/Coqh2ZoRCykGxhOtoSS3wDFOe8fBszT9ug= X-Google-Smtp-Source: APiQypIgO4clcO6Z7kvhUaBuvYACtL+F9hDoKmeBmaTp5Edf0BzJT+qKnh+MwC69KhaGLcQ8wc5C0JEBbMo44i2AOQM= X-Received: by 2002:a25:ddc3:: with SMTP id u186mr36888616ybg.383.1588003232559; Mon, 27 Apr 2020 09:00:32 -0700 (PDT) Date: Mon, 27 Apr 2020 09:00:09 -0700 In-Reply-To: <20200427160018.243569-1-samitolvanen@google.com> Message-Id: <20200427160018.243569-4-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20200427160018.243569-1-samitolvanen@google.com> X-Mailer: git-send-email 2.26.2.303.gf8c07b1a785-goog Subject: [PATCH v13 03/12] scs: add support for stack usage debugging From: Sami Tolvanen To: Will Deacon , Catalin Marinas , James Morse , Steven Rostedt , Ard Biesheuvel , Mark Rutland , Masahiro Yamada , Michal Marek , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot Cc: Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Masami Hiramatsu , Nick Desaulniers , Jann Horn , Miguel Ojeda , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Acked-by: Will Deacon --- kernel/scs.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/kernel/scs.c b/kernel/scs.c index 8769016c714c..2a96573f2b1b 100644 --- a/kernel/scs.c +++ b/kernel/scs.c @@ -68,6 +68,43 @@ int scs_prepare(struct task_struct *tsk, int node) return 0; } +#ifdef CONFIG_DEBUG_STACK_USAGE +static unsigned long __scs_used(struct task_struct *tsk) +{ + unsigned long *p = task_scs(tsk); + unsigned long *end = __scs_magic(p); + unsigned long s = (unsigned long)p; + + while (p < end && READ_ONCE_NOCHECK(*p)) + p++; + + return (unsigned long)p - s; +} + +static void scs_check_usage(struct task_struct *tsk) +{ + static unsigned long highest; + unsigned long used = __scs_used(tsk); + unsigned long prev; + unsigned long curr = highest; + + while (used > curr) { + prev = cmpxchg_relaxed(&highest, curr, used); + + if (prev == curr) { + pr_info("%s (%d): highest shadow stack usage: " + "%lu bytes\n", + tsk->comm, task_pid_nr(tsk), used); + break; + } + + curr = prev; + } +} +#else +static inline void scs_check_usage(struct task_struct *tsk) {} +#endif + void scs_release(struct task_struct *tsk) { void *s; @@ -77,6 +114,7 @@ void scs_release(struct task_struct *tsk) return; WARN_ON(scs_corrupted(tsk)); + scs_check_usage(tsk); scs_account(tsk, -1); scs_free(s); -- 2.26.2.303.gf8c07b1a785-goog