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SubjectRe: [PATCH v2 20/20] ppc: propagate the calling conventions change down to csum_partial_copy_generic()
On Wed, Oct 14, 2020 at 03:51:00PM -0700, Linus Torvalds wrote:
> On Wed, Oct 14, 2020 at 3:27 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> >
> > This patch is causing crashes in WireGuard's CI over at
> > https://www.wireguard.com/build-status/ . Apparently sending a simple
> > network packet winds up triggering refcount_t's warn-on-saturate code. I
>
> Ouch.
>
> The C parts look fairly straightforward, and I don't see how they
> could cause that odd refcount issue.
>
> So I assume it's the low-level asm code conversion that is buggy. And
> it's apparently the 32-bit conversion, since your ppc64 status looks
> fine.
>
> I think it's this instruction:
>
> addi r1,r1,16
>
> that should be removed from the function exit, because Al removed the
>
> - stwu r1,-16(r1)
>
> on function entry.
>
> So I think you end up with a corrupt stack pointer and basically
> random behavior.

Gyahh... ACK, and I really wonder how the hell has it managed to avoid
crashing on testing.

Mea culpa, folks.

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