From patchwork Thu Jul 30 18:03:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nick Desaulniers X-Patchwork-Id: 247281 Delivered-To: patch@linaro.org Received: by 2002:a92:d244:0:0:0:0:0 with SMTP id v4csp2630070ilg; Thu, 30 Jul 2020 11:03:44 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxmlNyxhOY+dDNCX1NVCXNqhOHTD3AofWQFVvoMGsvrMf2q49el0cQQ7466KYixQSVBrVNn X-Received: by 2002:aa7:c84b:: with SMTP id g11mr182774edt.292.1596132224815; Thu, 30 Jul 2020 11:03:44 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1596132224; cv=none; d=google.com; s=arc-20160816; b=glLzUf/6CJWfzuM0JSO+ZWRrLzOxi2nyQLpiXQHeV4T/X7FT4hi5dC5PcRnU5crFn+ 0lbeMjI6TbHzpxsXRiP+jQLDlQhFhShdEyJ1BZPMAk6ZTPnCYqyAW8Uz9toSNj//l3za XvaOrUWUuP84N/L1+qti+0eVryToWtnc+1nSbwwUa6361BocyLSqfPm65RCYiNGFXeHg g30YTCbMmGYcn6FPSRpV1yPcMVUEwhbsWvV0HHr0iAECLbongvyAJWoXzghn02e5ketZ sMYFTO1PWqKnY+UIr7KUDVdspsnXzsl1Rk5cbVkgvH5G448oxrpiXgo+xi/HeBUE/za4 8W0w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:cc:to:from:subject:mime-version :message-id:date:dkim-signature; bh=RKbdLkq470ddFEAhoN8dslKMFuIe6gCNhu2f+gFLXbo=; b=VJIiejIdiAw3sRLe8RVaw1UGcHCNj5Nh3sSRjrkLbwNMTk7eeJ5k+NEB2tgx+akHaG ba/eeUKmKoPO8MA7FIicj2EJzIz09AgzNBNe44xJBKcwxCwrJZn8ZumkcgLi+UgkNCd5 F3n5PwIHOboQC1rUzRmUETu+SzmpAbKUNlBI2W8T0slum0MO7oRVjQIDCLTMf1TUl53O /0v1oWkMyBOgRrGBzUGahdTXSTKXgWxUBhlVPN9UKOGCxPMKLX5hPjOZcoCiYje+83a8 TU14kOEzdvIcBMoH5ISe0ziSwiFzUSVC6h5vM2dsM1E1dPaTyg41JlpooOvxBSngiXa6 7BRA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=AYXD98CY; spf=pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id v21si3512152ejx.513.2020.07.30.11.03.44; Thu, 30 Jul 2020 11:03:44 -0700 (PDT) Received-SPF: pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=AYXD98CY; spf=pass (google.com: domain of stable-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730363AbgG3SDn (ORCPT + 15 others); Thu, 30 Jul 2020 14:03:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730204AbgG3SDn (ORCPT ); Thu, 30 Jul 2020 14:03:43 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEBCDC061574 for ; Thu, 30 Jul 2020 11:03:42 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id x10so16198026ybj.19 for ; Thu, 30 Jul 2020 11:03:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=RKbdLkq470ddFEAhoN8dslKMFuIe6gCNhu2f+gFLXbo=; b=AYXD98CYJaxvZj351bCuwkKEgAp6qB/0qN45oav4U0Nku0PPI6vQQepfwhNZwK5CzC 52/y5L32aXsIbe29yg94Cqy9MvAEm96xKtPkB2dSYH2KycwLmjduog0vbxc4ojTa/V+E 9CPEXlIfrIkVGaC5PRqvkOHDAPKdVv8YpTYlYaaISqauubNyhXD+gI8+5K7xiQpSFoz+ JjlCnAGoRSbZD06iL62nOu+N8EjiYphpi1xa8+zL9hYs/HsVMYTRTP40c++87vPuOGLS bPFcimYL5LPAweRbKHbAzuI8iG0BUkR1QgPxWFwwqpHV0Czt54NauY+hefqA3c3ViC2U XWMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=RKbdLkq470ddFEAhoN8dslKMFuIe6gCNhu2f+gFLXbo=; b=UpiswCngoVoL4qVDYaJaeYdlBelXOmijYwhgznMJms/BsfAFG5iKpPzOYd+VsEULPM tboUwjMPyR81QMuj4XZMKIVL6E1HK/XHXHapFc8cydXA28VjFN23aUzN0ZVRPdI53iBg bUjxttoBspdr39bh8tlTN6DF/PcXvmlE4l/yDYoqk65k2NQAx+G6NfelApgxQPUeQW1/ 59EpxO45MnbAWMb5gMLL/K/9GdvJpKRlvMEO6vH0BcoO/av7pvP3KfhH2BIcV+7+YIeY YovxYjZwd2NFH9FXKC+hQh4bq2xrdR5x9d1I/TV8EZrJda2drZIfRyfTz7DBi6Tefy9S cItA== X-Gm-Message-State: AOAM531pw5gfbA+0kxcn8N/dmgqZqaC8FHCxLEIKex0KCOhfr7c5Tixr rwWrGDID1GHa3F26Jt5JXTv2q1u1Dt7Xllqt2w1AxeIW1QyDbHi95gRI9sCaRQDB41+sbXZQ93g 8A5WlFdsjZgqvaOhACpAO40CTk8G4WCuNsvr+YlnBwPj3R/ZUGTt1pjq10R+Kd6YnEUAoqW+6zq UVpA== X-Received: by 2002:a25:f40a:: with SMTP id q10mr172146ybd.192.1596132221796; Thu, 30 Jul 2020 11:03:41 -0700 (PDT) Date: Thu, 30 Jul 2020 11:03:40 -0700 Message-Id: <20200730180340.1724137-1-ndesaulniers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.rc0.142.g3c755180ce-goog Subject: [PATCH 4.14.y] ARM: 8702/1: head-common.S: Clear lr before jumping to start_kernel() From: Nick Desaulniers To: stable@vger.kernel.org Cc: Miles Chen , Geert Uytterhoeven , Ard Biesheuvel , Nicolas Pitre , Nick Desaulniers Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Geert Uytterhoeven commit 59b6359dd92d18f5dc04b14a4c926fa08ab66f7c upstream. If CONFIG_DEBUG_LOCK_ALLOC=y, the kernel log is spammed with a few hundred identical messages: unwind: Unknown symbol address c0800300 unwind: Index not found c0800300 c0800300 is the return address from the last subroutine call (to __memzero()) in __mmap_switched(). Apparently having this address in the link register confuses the unwinder. To fix this, reset the link register to zero before jumping to start_kernel(). Fixes: 9520b1a1b5f7a348 ("ARM: head-common.S: speed up startup code") Suggested-by: Ard Biesheuvel Signed-off-by: Geert Uytterhoeven Acked-by: Nicolas Pitre Signed-off-by: Russell King Signed-off-by: Nick Desaulniers --- Looks like this first landed in v4.15-rc1. Without this, we can't tell during an unwind initiated from start_kernel() when to stop unwinding, which for the clang specific implementation of the arm frame pointer unwinder leads to dereferencing a garbage value, triggering an exception which has no fixup, triggering a panic, triggering an unwind, triggering an infinite loop that prevents booting. I have more patches to send upstream to make the unwinder more resilient, but it's ambiguous as to when to stop unwinding without this patch. arch/arm/kernel/head-common.S | 1 + 1 file changed, 1 insertion(+) -- 2.28.0.rc0.142.g3c755180ce-goog diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S index 7e662bdd5cb3..932b2244e709 100644 --- a/arch/arm/kernel/head-common.S +++ b/arch/arm/kernel/head-common.S @@ -101,6 +101,7 @@ __mmap_switched: str r2, [r6] @ Save atags pointer cmp r7, #0 strne r0, [r7] @ Save control register values + mov lr, #0 b start_kernel ENDPROC(__mmap_switched)