linux-kernel - Re: [PATCH v3 2/4] objtool: Move orc outside of check

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Date:   Fri, 31 Jul 2020 09:56:42 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Julien Thierry <jthierry@...hat.com>
cc:     Josh Poimboeuf <jpoimboe@...hat.com>, peterz@...radead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] objtool: Move orc outside of check

On Thu, 30 Jul 2020, Julien Thierry wrote:

> 
> 
> On 7/30/20 3:15 PM, Josh Poimboeuf wrote:
> > On Thu, Jul 30, 2020 at 02:29:20PM +0100, Julien Thierry wrote:
> >>
> >>
> >> On 7/30/20 2:22 PM, peterz@...radead.org wrote:
> >>> On Thu, Jul 30, 2020 at 01:40:42PM +0100, Julien Thierry wrote:
> >>>>
> >>>>
> >>>> On 7/30/20 10:57 AM, peterz@...radead.org wrote:
> >>>>> On Thu, Jul 30, 2020 at 10:41:41AM +0100, Julien Thierry wrote:
> >>>>>> +		if (file->elf->changed)
> >>>>>> +			return elf_write(file->elf);
> >>>>>> +		else
> >>>>>> +			return 0;
> >>>>>>      }
> >>>>>
> >>>>> I think we can do without that else :-)
> >>>>>
> >>>>
> >>>> I did wonder and was not 100% confident about it, but the orc gen will
> >>>> always change the file, correct?
> >>>
> >>> Not if it already has orc, iirc.
> >>>
> >>> But what I was trying to say is that:
> >>>
> >>>  if (file->elf->changed)
> >>>   return elf_write(file->elf)
> >>>
> >>>  return 0;
> >>>
> >>> is identical code and, IMO, easier to read.
> >>>
> >>
> >> Much easier yes, I'll change it.
> > 
> > But I think file->elf->changed can be assumed at this point anyway, so
> > it could just be an unconditional
> > 
> >  return elf_write(file->elf);
> > 
> 
> I'll triple check whether that's the case and remove the if if possible.

I think it is the case. And even if not, it would only cause a pointless 
call to elf_update() in the end and that should not do any harm anyway if 
I am not mistaken.

However, I think there is a problem with the rebase on top of the current 
code. The patch moves elf_write() call to orc_gen.c which was ok before 
Peterz introduced elf_write_insn() et al. We need to keep elf_write() in 
check.c for this case too.

Miroslav