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 7ADDACA9ECB for ; Thu, 31 Oct 2019 16:47:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 494342087F for ; Thu, 31 Oct 2019 16:47:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="L6nedrmE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728932AbfJaQrG (ORCPT ); Thu, 31 Oct 2019 12:47:06 -0400 Received: from mail-yw1-f73.google.com ([209.85.161.73]:36528 "EHLO mail-yw1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728900AbfJaQrD (ORCPT ); Thu, 31 Oct 2019 12:47:03 -0400 Received: by mail-yw1-f73.google.com with SMTP id r64so4897830ywb.3 for ; Thu, 31 Oct 2019 09:47:03 -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=ISQCDuiClH+Ob0sv0IF5h/3w79WcDO0VBPNi/N63ddM=; b=L6nedrmEU6JvkHcsnA5dyzyzZUdFX15pwpo+PGFFiFEz0adILiGuaSNCBEk5zwayGV E9E9rgsrq5/1A2h2MtticPSYVLesH41cnymaor0lAwHnDlDWxTf5/4qQBQJbY1uWFtLZ C6sr+tdm50IQTwMHAjyoVlcXkjLcFiHznGojckMYMtDoi/bOtSH0IlV0Tnioy87094XS ezKAXvoCEbuRluKXTl7DxPY8VwUTSt5guCPWasnZX2NkFzFDs5i1SJLDNnu+b65KtE/0 /kLy//TY9FnsnLxzNsp6fluwupXbn29fiFnAO1x5t8/AaHOuDntvEDf7xlit3hYA7ljG EZkg== 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=ISQCDuiClH+Ob0sv0IF5h/3w79WcDO0VBPNi/N63ddM=; b=lpdlkkMagkJmSIgDS1NRo0s2nV9IDnv9U1uFHwTLxvCrPtkQ3wwLdmoIT3aSx1sYxx ajd54g1vTlmZLWJVBBwQIR35SDRFrMH7UJiwm0gC/jUAktvXk5xdYkaiJlI94qMSdfKq AyQJqx7VwNqHOUHlJc1P8Yjv+o9pPOINCOq4VaacHPFMZhwipuOHdMZlPa9Zn1ZMnRLU F2d5zCsugGlWp3JNx5OdfdoeLWg6nxTrnBPzlYb21cvGXueqc2tB46AcCP8SxxGKJArF buGFPBPG2Haa9PHRUaFl9LfoeIfX/2c1EAeV2b4TI2i9J9xDcUQpMdnTxHOuNweA7NEg Pmhg== X-Gm-Message-State: APjAAAWNK5r+XKrZ4cp+vWIDJBR6OtKvKK8SeHYz17d1Gv8fdVZfsbEw QAI4boBXBGaJolW98j4dl/itBXX+9/Gl86cOsZg= X-Google-Smtp-Source: APXvYqylBnOlY6J5yphs6OUfcffeYpoUMccmhuKdcTOrwjC05s5MJ0bhS5H4FPPnPRXOHEgt796GjMyXraMpNUfDtLU= X-Received: by 2002:a0d:e987:: with SMTP id s129mr5018878ywe.111.1572540422670; Thu, 31 Oct 2019 09:47:02 -0700 (PDT) Date: Thu, 31 Oct 2019 09:46:27 -0700 In-Reply-To: <20191031164637.48901-1-samitolvanen@google.com> Message-Id: <20191031164637.48901-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> X-Mailer: git-send-email 2.24.0.rc0.303.g954a862665-goog Subject: [PATCH v3 07/17] scs: add support for stack usage debugging From: samitolvanen@google.com To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel Cc: Dave Martin , Kees Cook , 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, 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. 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