Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752403AbdGGIwC (ORCPT ); Fri, 7 Jul 2017 04:52:02 -0400 Received: from mail-pg0-f68.google.com ([74.125.83.68]:35123 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751785AbdGGIwA (ORCPT ); Fri, 7 Jul 2017 04:52:00 -0400 From: Zhouyi Zhou To: corbet@lwn.net, jan.kiszka@siemens.com, kieran@ksquared.org.uk, akpm@linux-foundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kbingham@kernel.org Cc: Zhouyi Zhou Subject: [PATCH v2 2/2] docs: disable KASLR when debugging kernel Date: Fri, 7 Jul 2017 16:51:45 +0800 Message-Id: <1499417505-31574-1-git-send-email-zhouzhouyi@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1413 Lines: 33 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 --- Documentation/dev-tools/gdb-kernel-debugging.rst | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/Documentation/dev-tools/gdb-kernel-debugging.rst b/Documentation/dev-tools/gdb-kernel-debugging.rst index 5e93c9b..60fec6d 100644 --- a/Documentation/dev-tools/gdb-kernel-debugging.rst +++ b/Documentation/dev-tools/gdb-kernel-debugging.rst @@ -31,12 +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 -- 1.9.1