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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 9F57CCCD185 for ; Fri, 10 Oct 2025 15:46:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iD33w+Kf1PLBTVwd7Gs6fvxUpUzwmU6xc5WkYASPV+Q=; b=A/N5TtRraI4fzotH5NAnKlUybq eSJ8L+Z6bvtVj86B1XQJ+uCUqd9s6RON1kbqHFfL8lZB/sS3t/BqyDWVFR82A4F4p9K/3pySe3fYy NOazJiGC+sm6AqFbrHKM2AKMRAml173X/7xjRohRlz2sO0nMBv7hxJo5pINw2mtjOyy92gNoIE4ly rLEZb7jBBHzBM2d3u3fEm34MIeXC8Q79Pm8wy5TL47+Rh4UV0oWxl1e6V76cS082uiLQkKMR3nJF1 ujWLuWF9c9wgot/neYGubwYDsASrh4oNeAtq9LxfhBgwV6tbjEzKP32yn0PmFa4zmkgvYOFE6MUlp lUQ0ul6w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7FJu-00000008tIR-2e5x; Fri, 10 Oct 2025 15:46:14 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v7FJs-00000008tGf-1bPw for linux-arm-kernel@lists.infradead.org; Fri, 10 Oct 2025 15:46:13 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760111171; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iD33w+Kf1PLBTVwd7Gs6fvxUpUzwmU6xc5WkYASPV+Q=; b=AGLSBDKd/h4SanfVEmfWksfMHUUIPmXdSG54F0p4evSrIL2lp2ASBMD2GLlS677y+4KH25 rdIL47P0+8kB5Vxr/+3ogJEU1rff7sbaH+5tmcG5Bc44xoQZoiiMhCjAnqNGt/bx8BhZkt Dp6HO/hYj6hQAF/AyXVZVM5R+CvAz50= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-626-YyfYK7fpOPCOQwG47iM_TQ-1; Fri, 10 Oct 2025 11:46:09 -0400 X-MC-Unique: YyfYK7fpOPCOQwG47iM_TQ-1 X-Mimecast-MFC-AGG-ID: YyfYK7fpOPCOQwG47iM_TQ_1760111157 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DCF321800290; Fri, 10 Oct 2025 15:45:56 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.45.224.29]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CBC601800576; Fri, 10 Oct 2025 15:45:41 +0000 (UTC) From: Valentin Schneider To: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Josh Poimboeuf , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik Subject: [PATCH v6 20/29] stackleack: Mark stack_erasing_bypass key as allowed in .noinstr Date: Fri, 10 Oct 2025 17:38:30 +0200 Message-ID: <20251010153839.151763-21-vschneid@redhat.com> In-Reply-To: <20251010153839.151763-1-vschneid@redhat.com> References: <20251010153839.151763-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251010_084612_495254_5B0D6090 X-CRM114-Status: GOOD ( 14.55 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Later commits will cause objtool to warn about static keys being used in .noinstr sections in order to safely defer instruction patching IPIs targeted at NOHZ_FULL CPUs. stack_erasing_bypass is used in .noinstr code, and can be modified at runtime (proc/sys/kernel/stack_erasing write). However it is not expected that it will be flipped during latency-sensitive operations, and thus shouldn't be a source of interference wrt the text patching IPI. Mark it to let objtool know not to warn about it. Reported-by: Josh Poimboeuf Signed-off-by: Valentin Schneider --- kernel/kstack_erase.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/kstack_erase.c b/kernel/kstack_erase.c index e49bb88b4f0a3..1abc94a38ce14 100644 --- a/kernel/kstack_erase.c +++ b/kernel/kstack_erase.c @@ -19,7 +19,11 @@ #include #include -static DEFINE_STATIC_KEY_FALSE(stack_erasing_bypass); +/* + * This static key can only be modified via its sysctl interface. It is + * expected it will remain stable during latency-senstive operations. + */ +static DEFINE_STATIC_KEY_FALSE_NOINSTR(stack_erasing_bypass); #ifdef CONFIG_SYSCTL static int stack_erasing_sysctl(const struct ctl_table *table, int write, -- 2.51.0