Re: [PATCH] [RFC] x86: avoid -mtune=atom for objtool warnings

From: Arnd Bergmann
Date: Tue Oct 11 2016 - 04:18:29 EST


On Monday, October 10, 2016 3:23:22 PM CEST Josh Poimboeuf wrote:
>
> Thanks for reporting it. It looks like 'mtune=atom' sometimes makes a
> slight change to one of the stack frame setup instructions. Instead of:
>
> move rsp, rbp
>
> It sometimes does:
>
> lea (%rsp),%rbp
>
> They're two different instructions, but they have the same result. It's
> an easy fix for objtool. I'll post a patch soon.
>
>

Ah, good to hear. I've replaced my patch with yours in my randconfig
tests now and will let you know if there are any other warnings on
atom. I've done a few thousand x86 randconfig builds now and done private
patches for all warnings I got (I previously had fixes only for the arm
warnings). I found objtool warnings for a few files in some configurations
that do not involve -mtune=atom, maybe you can also look at what
is going on there as I have no idea for how to address them:

drivers/scsi/fnic/fnic_main.o: warning: objtool: fnic_log_q_error() falls through to next function fnic_handle_link_event()
drivers/scsi/snic/snic_res.o: warning: objtool: .text: unexpected end of section
drivers/infiniband/sw/rxe/rxe_comp.o: warning: objtool: rxe_completer()+0x2f3: sibling call from callable instruction with changed frame pointer
drivers/infiniband/sw/rxe/rxe_resp.o: warning: objtool: rxe_responder()+0x10f: sibling call from callable instruction with changed frame pointer
kernel/locking/rwsem.o: warning: objtool: down_write_killable()+0x16: call without frame pointer save/setup

I can provide additional information for reproducing them if it's
not immediately obvious what the problems are.

Thanks,

Arnd