[libc-dev] ppc64le and 32-bit LE userland compatibility

[Will Springer via libc-dev]

On Saturday, May 30, 2020 3:17:24 PM PDT Will Springer wrote:
> On Saturday, May 30, 2020 8:37:43 AM PDT Christophe Leroy wrote:
> > There is a series at
> > https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=173231
> > to switch powerpc to the Generic C VDSO.
> > 
> > Can you try and see whether it fixes your issue ?
> > 
> > Christophe
> 
> Sure thing, I spotted that after making the initial post. Will report
> back with results.
> 
> Will [she/her]

Sorry for the wait, I just sat down to work on this again yesterday.

Tested this series on top of stable/linux-5.7.y (5.7.0 at the time of 
writing), plus the one-line signal handler patch. Had to rewind to the 
state of powerpc/merge at the time of the mail before the patch would 
apply, then cherry-picked to 5.6 until I realized the patchset used some 
functionality that didn't land until 5.7, so I moved it there.

Good news is that `date` now works correctly with the vdso call in 32-bit 
LE. Bad news is it seems to have broken things on the 64-bit side—in my 
testing, Void kicks off runit but hangs after starting eudev, and in a 
Debian Stretch system, systemd doesn't get to the point of printing 
anything whatsoever. (I had to `init=/bin/sh` to confirm the date worked 
in ppcle, although in ppc64le running `date` also hung the system when it 
made the vdso call...) Not sure how to approach debugging that, so I'd 
appreciate any pointers.

Will [she/her]