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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EAD22C433ED for ; Fri, 7 May 2021 01:05:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C221061041 for ; Fri, 7 May 2021 01:05:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234110AbhEGBGK (ORCPT ); Thu, 6 May 2021 21:06:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:47050 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231489AbhEGBGJ (ORCPT ); Thu, 6 May 2021 21:06:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id AF197613C2; Fri, 7 May 2021 01:05:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620349510; bh=Jb8Agu7UTIkAs9BZPaHvrNgl1/X+HXJSY9J7Fh148Zk=; h=Date:From:To:Subject:In-Reply-To:From; b=uGnrSnj5zc7MsIzyfv5J3KNHhtASxXzL2ceD3xHtp67lpT3xI4IaJZZtVW7WMs7Tn Y/clBGFQIp13oP6hWxoibPpWiq4LujnOqlYdSKC4d7rT3WmT0C6yVnW1HDH6tnA1Bw BmtZwO8sO/vHqOnJi6+swkOhnrebFHoPL4Agl1jU= Date: Thu, 06 May 2021 18:05:09 -0700 From: Andrew Morton To: akpm@linux-foundation.org, corbet@lwn.net, jan.kiszka@siemens.com, kbingham@kernel.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, song.bao.hua@hisilicon.com, torvalds@linux-foundation.org Subject: [patch 60/91] scripts/gdb: add lx_current support for arm64 Message-ID: <20210507010509.ZVraMwd2d%akpm@linux-foundation.org> In-Reply-To: <20210506180126.03e1baee7ca52bedb6cc6003@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Barry Song Subject: scripts/gdb: add lx_current support for arm64 arm64 uses SP_EL0 to save the current task_struct address. While running in EL0, SP_EL0 is clobbered by userspace. So if the upper bit is not 1 (not TTBR1), the current address is invalid. This patch checks the upper bit of SP_EL0, if the upper bit is 1, lx_current() of arm64 will return the derefrence of current task. Otherwise, lx_current() will tell users they are running in userspace(EL0). While arm64 is running in EL0, it is actually pointless to print current task as the memory of kernel space is not accessible in EL0. Link: https://lkml.kernel.org/r/20210314203444.15188-3-song.bao.hua@hisilicon.com Signed-off-by: Barry Song Cc: Jan Kiszka Cc: Jonathan Corbet Cc: Kieran Bingham Signed-off-by: Andrew Morton --- Documentation/dev-tools/gdb-kernel-debugging.rst | 2 +- scripts/gdb/linux/cpus.py | 13 +++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-) --- a/Documentation/dev-tools/gdb-kernel-debugging.rst~scripts-gdb-add-lx_current-support-for-arm64 +++ a/Documentation/dev-tools/gdb-kernel-debugging.rst @@ -114,7 +114,7 @@ Examples of using the Linux-provided gdb [ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved .... -- Examine fields of the current task struct(supported by x86 only):: +- Examine fields of the current task struct(supported by x86 and arm64 only):: (gdb) p $lx_current().pid $1 = 4998 --- a/scripts/gdb/linux/cpus.py~scripts-gdb-add-lx_current-support-for-arm64 +++ a/scripts/gdb/linux/cpus.py @@ -16,6 +16,9 @@ import gdb from linux import tasks, utils +task_type = utils.CachedType("struct task_struct") + + MAX_CPUS = 4096 @@ -157,9 +160,19 @@ Note that VAR has to be quoted as string PerCpu() def get_current_task(cpu): + task_ptr_type = task_type.get_type().pointer() + if utils.is_target_arch("x86"): var_ptr = gdb.parse_and_eval("¤t_task") return per_cpu(var_ptr, cpu).dereference() + elif utils.is_target_arch("aarch64"): + current_task_addr = gdb.parse_and_eval("$SP_EL0") + if((current_task_addr >> 63) != 0): + current_task = current_task_addr.cast(task_ptr_type) + return current_task.dereference() + else: + raise gdb.GdbError("Sorry, obtaining the current task is not allowed " + "while running in userspace(EL0)") else: raise gdb.GdbError("Sorry, obtaining the current task is not yet " "supported with this arch") _