Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

On Tue, Aug 9, 2016 at 10:02 PM, Jiri Kosina [off-list ref] wrote:

On Tue, 9 Aug 2016, Rafael J. Wysocki wrote:

quoted

I have a murky suspicion, but it is really weird.  Namely, what if
restore_jump_address in set_up_temporary_text_mapping() happens to be
covered by the restore kernel's identity mapping?  Then, the image
kernel's entry point may get overwritten by something else in
core_restore_code().

So this made me to actually test a scenario where I'd suspend a kernel
that's known-broken (i.e. contains 021182e52fe), and then have it resumed
by a kernel that has 021182e52fe reverted. It resumed successfully.

Just a datapoint.

That indicates the problem is somewhere in the restore kernel and no
surprises there.

I am able to reproduce the original problem (a triple fault on resume
with CONFIG_RANDOMIZE_MEMORY set) without the $subject patch, but the
patch fixes it for me.

Question is why it is not sufficient for you and Boris and the above
theory is about the only one I can come up with ATM.

I'm going to compare the configs etc, but I guess I just end up
writing a patch to test that theory unless someone has any other idea
in the meantime.

Thanks,
Rafael