Re: [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 [off-list ref] wrote:

quoted

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.