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 9F4C2C0218F for ; Fri, 31 Jan 2025 12:42:48 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XsDlwBaMuIS17pJVY5RsL5wyk14DUnumCFdCtmFC7lA=; b=ot5gH+MXYD8rYbrf7BCzhCF4na yLhFRkhOL43wYZnONRqxBnK5Lmr6BKUv+pX3oQUOqlt2q7mqcAnuXMMF+0cFICcPLRzetD48KTKBc oagP8bJs/s9ZLGeH1t/REIA5tXUSCxGED1Nll3eanYl/OIAeRHFROhvc0/NQ5vpU2c4pP45cuJ10I +cISoTGv+Er6ZF1S9vi+voVKMPXmAY+U9bzi70gHHdcc67VBmX5bexsi2OLvzM3XH7pX//XeE38Tl Hh330piXJACeLt1ICpc0tWikMfdVFEdDPlUxzodwHyQiuW10GTcNfEya1Y0hoxkZIGFzhQyZ6hv20 e2ft8gQg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tdqLw-0000000AcY2-18rC; Fri, 31 Jan 2025 12:42:32 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tdqKd-0000000AcWp-1dcr for linux-arm-kernel@lists.infradead.org; Fri, 31 Jan 2025 12:41:12 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 339F3A41E03; Fri, 31 Jan 2025 12:39:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1FE8C4CEE1; Fri, 31 Jan 2025 12:41:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738327268; bh=361MpZRIBEfqHuYP7WFilCBvDowjHwoFCsg4xWfX68A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pm7aI4oVMqAH0wPbXGij15rq1Vzb9kmgs/BjEj2Z3fePSdIBzy566uncTjYV0x2NG kLpORUXCma5k6OR6kznpOE3ZIPzuL38Pi/Wp/v6QibUYq2+7mh6/NM7frXHtZC3Ldz lGqtUxB9GjTrjlJm8XZdgW5LU5BTy6IyRDtTnkDKEvNrMohRMePGmPYbsLwU+IZ4Kd Q4Ekpkyqhm7OTdK1SWGyHgk+KjojTOKAZFV9OVN14oQoRecWRyk/8UmpzX2LA3Lgic lbHNhLAInIw3AagoLNhrojAHxguNhRbZyqnQaoLJLuD1a+gUTPvuCuY/nj6g4P2Ag8 Jp089AP9Cu+JA== Date: Fri, 31 Jan 2025 12:41:04 +0000 From: Will Deacon To: Emanuele Rocca Cc: Mark Rutland , linux-arm-kernel@lists.infradead.org Subject: Re: [BUG] ARM64 regression: NULL pointer dereference in arm_smccc_version_init+0x90/0x1ac Message-ID: <20250131124103.GA29766@willie-the-truck> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250131_044111_571161_A96A5E29 X-CRM114-Status: GOOD ( 21.77 ) 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 On Thu, Jan 30, 2025 at 03:56:10PM +0100, Emanuele Rocca wrote: > On 2025-01-30 12:19, Mark Rutland wrote: > > For the benefit others, when we looked into this a few days ago it > > appeared that a GPR was being clobbered across an SMCCC call, resulting > > in a later crash (as that GPR should hold the ADRP'd base address of > > 'smccc_version'). I didn't have the time to dig more into that (e.g. to > > figure out whether kernel/compiler/firmware was to blame). > > > > Emanuele, could you please dump the result of: > > > > objdump --disassemble=arm_smccc_version_init vmlinux > > > > ... for this kernel? That'd make it possible for others to > > perform/verify the analysis I mentioned above. > > Sure, here it is: > https://people.debian.org/~ema/Z5OpGluX6oX5NLxh@NH27D9T0LF.objdump.txt > > > If you can share any more details from the crash, that'd be helpful. The > > GPR dump would be *enormously* helpful in this case, and even a photo of > > the crash log might be useful. > > pc : arm_smccc_version_init+0x90/0x1ac > lr : psci_probe+0x1fc/0x2c0 > sp : ffffa3d8eea33ca0 > x29: ffffa3d8eea33ce0 x28: 0000000081000200 x27: ffffa3d8edd72a80 > x26: ffffa3d8edd728b0 x25: ffffa3d8eec66248 x24: ffffa3d8edc528d8 > x23: ffffa3d8eed7f4f8 x22: 0000000000000001 x21: ffffa3d8eea58410 > x20: ffffa3d8eed7f000 x19: 0000000000010001 x18: 0000000000000006 > x17: 0000000009f69730 x16: 00000008760968d0 x15: 0000000000000000 > x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 > x11: 00000000ffffefff x10: ffffa3d8eeac09c8 x9 : ffffa3d8eea687d8 > x8 : ffffa3d8eea33cb8 x7 : 0000000000000000 x6 : 0000000000000000 > x5 : ffffa3d8eed7f000 x4 : ffffa3d8edeb0000 x3 : 0000000000000000 > x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000000000 > > Call trace: > arm_smccc_version_init+0x90/0x1ac > psci_0_2_init+0x20/0x2c > psci_1_0_init+0x1c/0x58 > psci_dt_init+0x6c/0x98 > setup_arch+0x400/0x5ec > start_kernel+0x90/0x788 > __primary_switched+0xbc/0xc4 > Code: d29fffe1 eb01001f 1a9f97e0 f0ffd384 (b94264c2) > > The above was transcribed by hand. I double-checked, but there may be > mistakes. > > Photo here: https://people.debian.org/~ema/Z5OpGluX6oX5NLxh@NH27D9T0LF.jpg Crikey, you transcribed all that junk by _hand_?! Thanks for the effort, but next time please don't waste your time! The screenshot is fine. Anyway, it looks like x6 gets trashed across the SMC. I think that's fine per the SMCCC spec: | Unused result and scratch registers can leak information after an | SMC or HVC call. An implementation can mitigate this risk by either | preserving the register state over the call, or returning a constant | value,such as zero, in each register. so the question is whether or not the compiler should be relying on the register being preserved. It looks to me like the arm_smccc_1_1_smc() macro is actually broken in this regard: it constructs the input list based on the number of arguments passed and doesn't take the above into account at all. So I think we should change that so unused arguments are clobbered instead. Mark -- what do you think? Will