On Mon, Jul 10, 2023 at 04:58:15PM +0100, Pedro Falcato wrote:
> On Mon, Jul 10, 2023 at 2:28 PM <o...@turing.llc> wrote:
> >
> > I have an existing install of Ubuntu 22.04 on a QEMU virtual machine which
> > I've decided to update the UEFI firmware. After doing so, GRUB no longer
> > boots ("Synchronous Exception" message seen). After a git bisect session, I
> > found the problematic 2997ae38739756ecba9b0de19e86032ebc689ef9. The comment
> > says GRUB should have been fixed in 2017, but for one reason or another, my
> > VM which was built in 2022 still had the issue. Regardless, I don't think
> > it's a good idea to break GRUB, even if it's fixed in 2017. In the very
> > least, a better error message would be preferable to crashing with an
> > "Synchronous Exception." Googling this error message shows that other
> > people may be hitting this issue as well but the vague error symptom means
> > its impossible to know if it's the same issue or not.
>
> +CC Some of the folks involved in the original discussion
>
> In the original thread, people discussed some alternative behavior to
> just crashing on a NX fault. Is this still an alternative?
The idea is: Improve page fault handler to (a) print a big'n'fat
warning, and (b) loosening up memory permissions for the faulting
page address.
No patch for that emerged (yet?).
> I'm kind of thinking this should be addressed by distros anyway....
> How is $CURRENT_YEAR Ubuntu still shipping bad GRUBs? I know the
> situation around GRUB and distro patching is complicated but...
> Do we have any idea of how many distros/GRUBs are affected by this?
Too many :(
> Personally, I would like to avoid loosening up memory permissions.
Well, you can't have both. You have to pick between strict nx handling
and grub bug compatibility ...
take care,
Gerd
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