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

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Date:   Wed, 27 Jun 2018 10:35:03 +0100
From:   Allan Xavier <allan.x.xavier@...cle.com>
To:     Josh Poimboeuf <jpoimboe@...hat.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

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)