Re: FVP: kernel BUG at arch/arm64/kernel/traps.c:497 - Internal error: Oops - BUG: 0

[Naresh Kamboju]

Hi Mark,

On Thu, 14 Jul 2022 at 19:09, Mark Rutland <mark.rutland@xxxxxxx> wrote:
>
> On Thu, Jul 14, 2022 at 02:06:28PM +0100, Mark Rutland wrote:
>
> > ... and I've just reproduced the issue by running the script from a different
> > directory, since apprarently the semihosting interface just grabs the file from
> > the current directory.
> >
> > I'm pretty sure this means that *something* is clobbering the Image early on
> > during boot, and the semihisting loading happens to refresh it.
>
> I had a go with my own kernel built from my arm64/traps/rework branch:
>
>   https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/traps/rework
>
> ... and Naresh's config:
>
>   https://builds.tuxbuild.com/2BnQMpJj3kDTJXoCwd2pY5gW9CN/config
>
> When *only* using the initial loading into memory, that blows up in stackdepot
> and with a subsequent bogus pointer dereference (full log below), and when
> loaded via semihosting that just works. Note that my kernel is based on the
> arm64 for-next/core branch, which itself is based on v5.19-rc3.
>
> My failing kernel Image is ~47M, as is Naresh's original Image. When using
> smaller Images (as large as 43M so far), I don't see any issues.
>
> I also note that if I enable KASAN_OUTLINE, the kernel is so big that it
> clobbers the DTB, and cannot be booted. So this looks liek a problem with tha
> arbitrary placement / limits chosen for U-Boot being too small, and this is not
> a kernel bug.

Now I have understood the reason.

> Naresh, please can you fix your boot flow before reporting any further issues?

Yes.

> This sort of corruption will manifest in a number of ways, and we need to rule
> that out for any other bug reports.

Any further reports I will do needful initial investigation.

- Naresh