"Naveen N. Rao" <naveen.n....@linux.ibm.com> writes:
> Hi Qian,
>
> Qian Cai wrote:
>> OK, reverted the commit,
>>
>> c55d7b5e6426 (“powerpc: Remove STRICT_KERNEL_RWX incompatibility with
>> RELOCATABLE”)
>>
>> or set STRICT_KERNEL_RWX=n fixed the crash below and also mentioned in this
>> thread,
>>
>> https://lore.kernel.org/lkml/15ac5b0e-a221-4b8c-9039-fa96b8ef7...@lca.pw/
>
> Do you see any errors logged in dmesg when you see the crash?
> STRICT_KERNEL_RWX changes how patch_instruction() works, so it would be
> interesting to see if there are any ftrace-related errors thrown before
> the crash.
I've been able to reproduce with STRICT_KERNEL_RWX=y and concurrently
running:
# while true; do echo function > /sys/kernel/debug/tracing/current_tracer ;
echo nop > /sys/kernel/debug/tracing/current_tracer ; done
and:
# while true; do find /lib/modules/$(uname -r) -name '*.ko' -printf "%f\n" |
sed -e "s/\.ko//" | xargs -i modprobe -va {}; lsmod | awk '{print $1}' | xargs
-i modprobe -vr {}; done
ie. stressing module loading/unloading and ftrace at the same time.
It's not 100% but it usually reproduces within 10-20 minutes.
It looks like sometimes our __patch_instruction() fails, and then that
somehow leads to things getting further messed up. Presumably we have
some bad error handling somewhere.
cheers
