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]> Signed-off-by: Steven Rostedt (Google) <[email protected]> --- 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 -- 2.45.2
