Re: [PATCH] Documentation/tracing: Mention that RESET_ATTACK_MITIGATION can clear memory

[Hans de Goede]

Hi,

On 26-Sep-24 7:01 PM, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@xxxxxxxxxxx>
> 
> At the 2024 Linux Plumbers Conference, I was talking with Hans de Goede
> about the persistent buffer to display traces from previous boots. He
> mentioned that UEFI can clear memory. In my own tests I have not seen
> this. He later informed me that it requires the config option:
> 
>  CONFIG_RESET_ATTACK_MITIGATION
> 
> It appears that setting this will allow the memory to be cleared on boot
> up, which will definitely clear out the trace of the previous boot.
> 
> Add this information under the trace_instance in kernel-parameters.txt
> to let people know that this can cause issues.
> 
> Link: https://lore.kernel.org/all/20170825155019.6740-2-ard.biesheuvel@xxxxxxxxxx/
> 
> Reported-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>

Regards,

Hans



> ---
>  Documentation/admin-guide/kernel-parameters.txt | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index bb48ae24ae69..f9b79294f84a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6850,6 +6850,9 @@
>  
>  				reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
>  
> +			Note, CONFIG_RESET_ATTACK_MITIGATION can force a memory reset on boot which
> +			will clear any trace that was stored.
> +
>  			See also Documentation/trace/debugging.rst
>  
>