Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1686303

Re: [PATCH v2 2/2] docs: disable KASLR when debugging kernel

Show all headers | View raw

On 2017-07-07 10:51, Zhouyi Zhou wrote:
> 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 <zhouzhouyi@gmail.com>
> Reviewed-by: Kieran Bingham <kbingham@kernel.org>
> ---
>  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
>  
> 

FWIW: Acked-by: Jan Kiszka <jan.kiszka@siemens.com>

Who's taking this? Jon?

Jan

-- 
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v2 2/2] docs: disable KASLR when debugging kernel Zhouyi Zhou <zhouzhouyi@gmail.com> - 2017-07-07 11:00 +0200
  Re: [PATCH v2 2/2] docs: disable KASLR when debugging kernel Jan Kiszka <jan.kiszka@siemens.com> - 2017-07-13 09:00 +0200
    Re: [PATCH v2 2/2] docs: disable KASLR when debugging kernel Jonathan Corbet <corbet@lwn.net> - 2017-07-13 21:00 +0200

csiph-web