re: kern/54486: athn driver panics on arm

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR kern/54486; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: Andreas Gustafsson <gson%gson.org@localhost>
Cc: Rin Okuyama <rokuyama%rk.phys.keio.ac.jp@localhost>,
    Christos Zoulas <christos%astron.com@localhost>, maya%NetBSD.org@localhost,
    gnats-bugs%netbsd.org@localhost
Subject: re: kern/54486: athn driver panics on arm
Date: Sat, 24 Aug 2019 21:11:04 +1000

 > > i forget the status of a real fix.  there's some issue with
 > > unaligned on v6/v7, IIRC.
 > 
 > I found some related discussion in the port-arm archives, starting at:
 > 
 >   http://mail-index.netbsd.org/port-arm/2019/01/06/msg005357.html
 > 
 > My understanding of that discussion is that there are two alternative
 > correct fixes: either apply the patch from the above message to add
 > -mno-unaligned-access to CFLAGS, or stop using PMAP_NOCACHE in
 > bus_dma.c as mentioned in:
 > 
 >   http://mail-index.netbsd.org/port-arm/2019/01/06/msg005358.html
 > 
 > The problem is that *neither* has been done.  Since the patch is less
 > likely to have bad side effects, I think we should apply the patch
 > now, and if or when the pmap change is ever made, the patch can be
 > reverted.
 
 apparently i agreed with you back in january.  Rin, can you
 commit your change for now.  at least until we fix pmap..
 
 i think you're right that this should be aligned.  the buffer
 should be at least 8 byte aligned, and should end up being 4
 byte aligned when copying to the 'struct ar_tx_frame' or
 'struct ar_tx_mgmt'.
 
 > > could you try this patch?
 > 
 > I'm not really interested in work-arounds for individual drivers.
 > Unless we fix the general problem, it's going to continue to bite us
 > again and again.
 
 my patch has a bug, but i still would like an updated version
 to be tested -- the code is dodgy and it would be nice to
 avoid having code that would trigger if poorly copied, if you
 could test that anyway (not ready currently.)
 
 thanks.
 
 
 .mrg.