Jon, This version should be good to go.
Thanks, -- Steve On Tue, 1 Oct 2024 09:57:34 -0400 Steven Rostedt <[email protected]> wrote: > From: Steven Rostedt <[email protected]> > > 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/[email protected]/ > > Reported-by: Hans de Goede <[email protected]> > Reviewed-by: Hans de Goede <[email protected]> > Acked-by: Ard Biesheuvel <[email protected]> > Signed-off-by: Steven Rostedt (Google) <[email protected]> > --- > Changes since v1: > https://lore.kernel.org/[email protected] > > - Added more detail explanation that the system may not be able to use > memory to preserve the tracing ring buffer across reboots and use > the CONFIG_RESET_ATTACK_MITIGATION as one example. > > Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt > b/Documentation/admin-guide/kernel-parameters.txt > index 1518343bbe22..9881e3b857d0 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -6867,6 +6867,12 @@ > > reserve_mem=12M:4096:trace > trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq > > + Note, saving the trace buffer across reboots does > require that the system > + is set up to not wipe memory. For instance, > CONFIG_RESET_ATTACK_MITIGATION > + can force a memory reset on boot which will clear any > trace that was stored. > + This is just one of many ways that can clear memory. > Make sure you system > + keeps the content of memory across reboots before > relying on this option. > + > See also Documentation/trace/debugging.rst > >
