From nobody Fri Dec 19 14:03:08 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4066525DAF0 for ; Fri, 10 Oct 2025 15:46:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760111174; cv=none; b=a9LyCmbZ8W+YRs6UvopHbO4RYcU0cxh9m34571MN3oT5SJ1NmUcoxCE1lHChlMG72a8sUljiJ997TRaHeo8m9iI1gAKL1jlRRo3YnjuYkxW4rG2VAQMDgPL76lBT1yULpbuHBToNOquSnAgFw0S485A2nOaOg2L56M98XXkwsVs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760111174; c=relaxed/simple; bh=92WgOr/L7Y/V6EOqk5yqhdIN8frbNq+p2gxO+Cx1iK8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LIOrZt3gwPmGGbMMHLRgDTd1aJq4+TZVIrbCu/K1YeLZN9DfKqbOcVx+W3oHrz9g5H4Q5MS/UBivL+p3xXcuRWtWT2MqtBs2TNZ66iVpFiNClcrFVEoaprVJSQv/LpdUFZvkFwl9/adOZ6JgazT4wFnjWd5I3YSuO2ctHwIEv9w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=R7JWT+0W; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="R7JWT+0W" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760111172; 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=R7JWT+0W8Fn7pbn96HuA2qsNdDtohJOOI04BVnkPa8k5HMnG/07Xigbn5GBDtwLUEb0Fk2 aFDjMejqHT+Ztio1QtpoBzVXIU520wMC6I7b1GUa+14Km7oDevs4w6gJtplVFqKInmyQ19 E+GKCmzDJCXf7JQPeK0RMogQURTbUWw= 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" 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 runti= me (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 =20 -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); =20 #ifdef CONFIG_SYSCTL static int stack_erasing_sysctl(const struct ctl_table *table, int write, --=20 2.51.0