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.