Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933456AbdIXUxg (ORCPT ); Sun, 24 Sep 2017 16:53:36 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60814 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932993AbdIXUmj (ORCPT ); Sun, 24 Sep 2017 16:42:39 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Zhouyi Zhou , Kieran Bingham , Jan Kiszka , Jonathan Corbet , Natale Patriciello Subject: [PATCH 4.13 029/109] docs: disable KASLR when debugging kernel Date: Sun, 24 Sep 2017 22:32:50 +0200 Message-Id: <20170924203354.248820364@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170924203353.104695385@linuxfoundation.org> References: <20170924203353.104695385@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1673 Lines: 43 4.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhouyi Zhou commit e604f1cb85367d2e5fd4cf253296d190996da81a upstream. commit 6807c84652b0 ("x86: Enable KASLR by default") enables KASLR by default on x86. While KASLR will confuse gdb which resolve kernel symbol address from symbol table of vmlinux. We should turn off KASLR for kernel debugging. Signed-off-by: Zhouyi Zhou Reviewed-by: Kieran Bingham Acked-by: Jan Kiszka Signed-off-by: Jonathan Corbet Cc: Natale Patriciello Signed-off-by: Greg Kroah-Hartman --- Documentation/dev-tools/gdb-kernel-debugging.rst | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/Documentation/dev-tools/gdb-kernel-debugging.rst +++ b/Documentation/dev-tools/gdb-kernel-debugging.rst @@ -31,11 +31,13 @@ Setup CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports CONFIG_FRAME_POINTER, keep it enabled. -- Install that kernel on the guest. +- Install that kernel on the guest, turn off KASLR if necessary by adding + "nokaslr" to the kernel command line. Alternatively, QEMU allows to boot the kernel directly using -kernel, -append, -initrd command line switches. This is generally only useful if you do not depend on modules. See QEMU documentation for more details on - this mode. + this mode. In this case, you should build the kernel with + CONFIG_RANDOMIZE_BASE disabled if the architecture supports KASLR. - Enable the gdb stub of QEMU/KVM, either