On 3/17/23 17:12, Luis Machado wrote:
On 3/17/23 17:07, Peter Maydell wrote:
On Fri, 17 Mar 2023 at 16:55, Luis Machado <luis.mach...@arm.com> wrote:
On 3/17/23 16:37, Peter Maydell wrote:
Having run into this problem in another couple of situations, one of
which involved gdb 10, I think I'm increasingly favouring option
2 here. The affected gdbs seem to be quite widely deployed, and
the bug results in crashes even for users who didn't really
care about pauth. So I'd rather we didn't release a QEMU 8.0
which crashes these affected deployed gdbs.
Are the affected gdb's packaged by distros? If so, a backport the distros can
pick up
will solve this in a quick package update.
Yes, it's exactly because these gdbs are distro-packaged
that I don't want QEMU to make them crash. I think it's
going to take a long time for the fix to go into gdb branches
and gdb to make a point release and distros to pick up that
point release, and in the meantime that's a lot of crashing
gdb bug reports that we're going to have to field.
Just to clarify, there won't be any point releases for gdb's 9/10/11/12. We
might have a bug fix
release for gdb 13 though (which isn't affected).
Just to complement, my plan is to make the backports available (via stable
branch commits) so distro package
maintainers can pick those up easily. No new releases will be made for older
gdb's, so the package maintainers
can pick the backport up as soon as they are pushed. There won't be waiting for
a new release of gdb.
If we decide qemu should now emit a different xml for pauth, it will fix the
crashes, but it also
means older gdb's (9/10/11/12) will not be able to backtrace properly through
pauth-signed frames.
Maybe that's a reasonable drawback for qemu users?
"No backtrace through pauth frames" is the situation we've
been in ever since we implemented pauth in 2019, so I think
that's fine. It's not regressing something that used to work.
Fair enough.
If someone decides to implement a debugging stub that reports pauth (fast
models, for example), it will
also crash gdb, so I still plan to do the backport anyway.
If you're backporting the fix, you could also backport the
(hopefully tiny) change that says "treat pauth_v2 the same
way we do pauth", and then users with an updated older
gdb will also get working backtraces.
I can negotiate that as well, though it borders being a new feature.
thanks
-- PMM
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