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 EFBB5C44506 for ; Thu, 9 Jul 2026 13:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:To:Subject :MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=01sbm6fVaYiiHHkJ7k1n3+ePoevqsPaJoT53HbHV54E=; b=CCtILX1Z9h3o/b o0r3Aw049hEpDDLm4GEzSxAeYgoQaj57BZKRo8OnNzaEoaOYcapVVdcnLmHomgOMSXxp3KEQfN8NI yKZIlKBkC0AVFkbVIDtBRh9Fb2mgGK0CNvh6OjGdCLjsDJeo8pt1Z/D8yoHt5vfxCpqHir+0owzIk VsbRKbVfmj3oLFBVpI78YP5tgCDW11rVPe0t+l3y0xTcKMj9GyY/WWrQywNoQimZQI/qgxw3UJYpd wrU1D/wsND5/vbaF8gt0koGfEapnHuk/ECLQ5j6oO5n6k4CBI4VAJDksL1tw37EP4ONhTQxEPq3ci 2dTQ0F7koTR/w9lbhxVA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1whoey-00000002WvG-3zYV; Thu, 09 Jul 2026 13:19:24 +0000 Received: from canpmsgout04.his.huawei.com ([113.46.200.219]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1whoeu-00000002Wu2-25Ok for linux-arm-kernel@lists.infradead.org; Thu, 09 Jul 2026 13:19:23 +0000 dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=01sbm6fVaYiiHHkJ7k1n3+ePoevqsPaJoT53HbHV54E=; b=5O5fmDEaomiQ+EJyla6QRBz082huhFYV38AWcOlauQHnWVZ38T+ZKsG6w2AGgt351KjsgboqZ rmGqSNFzo/mdm+rEeQ2TFQsNyyKQj+o5ClBb8Ndrk0lKbWo3MP0yFZjdnHRRLfKq9cJaIbpwt12 Ixu2nf+1848XJ4bO1htVDD4= Received: from mail.maildlp.com (unknown [172.19.162.223]) by canpmsgout04.his.huawei.com (SkyGuard) with ESMTPS id 4gwwKm6L2kz1prLD; Thu, 9 Jul 2026 21:09:48 +0800 (CST) Received: from dggpemf500011.china.huawei.com (unknown [7.185.36.131]) by mail.maildlp.com (Postfix) with ESMTPS id 9AF3240561; Thu, 9 Jul 2026 21:19:05 +0800 (CST) Received: from [10.67.109.254] (10.67.109.254) by dggpemf500011.china.huawei.com (7.185.36.131) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 9 Jul 2026 21:19:04 +0800 Message-ID: Date: Thu, 9 Jul 2026 21:19:03 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 03/36] arm64: hibernate: mask DAIF before restoring hibernated kernel To: Vladimir Murzin , References: <20260709121333.23507-1-vladimir.murzin@arm.com> <20260709121333.23507-4-vladimir.murzin@arm.com> From: Jinjie Ruan In-Reply-To: <20260709121333.23507-4-vladimir.murzin@arm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.109.254] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To dggpemf500011.china.huawei.com (7.185.36.131) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260709_061921_199142_CDA26E1B X-CRM114-Status: GOOD ( 23.18 ) 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: , Cc: mark.rutland@arm.com, maz@kernel.org, stable@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/9/2026 8:13 PM, Vladimir Murzin wrote: > From: Ada Couprie Diaz > > The arm64 hibernate code manages the exception masking in an unsound > way, leading to potential crashes and/or warnings during resume. > > When a hibernation image is saved in `swsusp_arch_suspend()`, all DAIF > exceptions are masked (by virtue of `local_daif_save()`), and the > suspended image is saved assuming that all DAIF exceptions will remain > masked when the image is restored. > > When a hibernation image is resumed by `swsusp_arch_resume()`, only > interrupts are masked (by virtue of `local_irq_save()` in local_irq_disable()? > `resume_target_kernel()`). When pseudo-NMI is enabled the DAIF.IF bits > will be clear, and regardless of pseudo-NMI the DAIF.DA bits will be > clear. > > This means that there are two problems: > > (1) It is possible to take Debug, SError, or pseudo-NMI exceptions > during the resume process. This is unsafe, as during the resume > process both the old ane new kernels will tranisently be in an > inconsistent state, and swsusp_arch_suspend_exit() won't retain > an executable mapping of any exception vectors. > > Any exception taken here will be fatal and silent. > > (2) When re-entering the resumed kernel, some DAIF bits will be clear > unexpectedly. This permits Debug, SError, or pseudo-NMI exceptions > to be taken for a short period while the resumed kernel is not yet > in a consistent state. > > This is detected by CONFIG_ARM64_DEBUG_PRIORITY_MASKING. > > Avoid these issues by masking all DAIF exceptions during resume. > > Cc: stable@vger.kernel.org > Signed-off-by: Ada Couprie Diaz > Signed-off-by: Vladimir Murzin > --- > arch/arm64/kernel/hibernate.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c > index 9717568518ba..d0d9bd91e639 100644 > --- a/arch/arm64/kernel/hibernate.c > +++ b/arch/arm64/kernel/hibernate.c > @@ -405,6 +405,7 @@ int swsusp_arch_suspend(void) > int __nocfi swsusp_arch_resume(void) > { > int rc; > + unsigned long flags; > void *zero_page; > size_t exit_size; > pgd_t *tmp_pg_dir; > @@ -465,9 +466,21 @@ int __nocfi swsusp_arch_resume(void) > if (el2_reset_needed()) > __hyp_set_vectors(el2_vectors); > > + /* > + * It is necessary to mask all DAIF exceptions here as: > + * > + * - The copy of swsusp_arch_suspend_exit() in the hibernation > + * text cannot handle taking any exceptions. > + * > + * - The suspended kernel masked all DAIF exceptions in > + * swsusp_arch_resume(), and expects to be re-entered in the > + * same state : with all DAIF exceptions masked. > + */ > + flags = local_daif_save(); > hibernate_exit(virt_to_phys(tmp_pg_dir), resume_hdr.ttbr1_el1, > resume_hdr.reenter_kernel, restore_pblist, > resume_hdr.__hyp_stub_vectors, virt_to_phys(zero_page)); > + local_daif_restore(flags); > > return 0; > }