linux-kernel - Re: [PATCH] objtool: Fix GCC 8 cold function processing without -freorder-functions

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Message-ID: <20180627151544.wieelchsffq3gjel@treble>
Date:   Wed, 27 Jun 2018 10:15:44 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Allan Xavier <allan.x.xavier@...cle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] objtool: Fix GCC 8 cold function processing without
 -freorder-functions

On Wed, Jun 27, 2018 at 10:35:03AM +0100, Allan Xavier wrote:
> Looks good overall, just one comment.
> 
> On 26/06/18 19:44, Josh Poimboeuf wrote:
> > +			/*
> > +			 * Unfortunately, -fnoreorder-functions puts the child
> > +			 * inside the parent.  Remove the overlap so we can
> > +			 * have sane assumptions.
> > +			 */
> > +			if (sym->sec == pfunc->sec &&
> > +			    sym->offset >= pfunc->offset &&
> > +			    sym->offset < pfunc->offset + pfunc->len &&
> > +			    sym->offset + sym->len == pfunc->offset + pfunc->len) {
> > +				pfunc->len -= sym->len;
> 
> It's a bit of a nit but I'd say you could drop the third condition of the if
> since sym->offset would have to be less than pfunc->offset + pfunc->len for the
> fourth condition to ever be true. The only situation it would have caught is
> where sym->len == 0, which I think (hope?) is reasonable to assume wont happen
> and wouldn't have had an effect on pfunc->len anyway.
> 
> if (sym->sec == pfunc->sec &&
>     sym->offset >= pfunc->offset &&
>     sym->offset + sym->len == pfunc->offset + pfunc->len)

Thanks, will do.

-- 
Josh