Re: [edk2-devel] ArmVirtPkg: non-executable EFI_LOADER_DATA breaks GRUB on Ubuntu 22.04

["Gerd Hoffmann" <kraxel@redhat.com>]

On Mon, Jul 10, 2023 at 04:58:15PM +0100, Pedro Falcato wrote:
> On Mon, Jul 10, 2023 at 2:28 PM <osy@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