linux-kernel - Re: [PATCH] linkage: Fix issue with missing symbol size

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Message-ID: <CAFP8O3K=UuTesf3o9QhhRLgzYsP5RnNVBJDqL1v9FrsSFQPM9A@mail.gmail.com>
Date:   Fri, 29 Apr 2022 14:06:46 -0700
From:   Fāng-ruì Sòng <maskray@...gle.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-toolchains@...r.kernel.org
Subject: Re: [PATCH] linkage: Fix issue with missing symbol size

On Fri, Apr 29, 2022 at 1:13 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> On Fri, Apr 29, 2022 at 11:18:59AM +0200, Peter Zijlstra wrote:
> >
> > Occasionally, typically when a function doesn't end with 'ret', an
> > alias on that function will have 0 size.
> >
> > The difference between what GCC generates and our linkage magic, is
> > that GCC doesn't appear to provide .size for the alias'ed symbol at
> > all. And indeed, removing this directive cures the issue.
> >
> > Additionally, GCC also doesn't emit .type for alias symbols either, so
> > also omit that.
> >
> > Fixes: e0891269a8c2 ("linkage: add SYM_FUNC_ALIAS{,_LOCAL,_WEAK}()")
> > Suggested-by: Mark Rutland <mark.rutland@....com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>
> Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
>
> --
> Josh
>

Yeah, an alias inherits the original symbol's st_size.
In case you are interested in the internals, see
https://sourceware.org/bugzilla/show_bug.cgi?id=29012 ("gas: .set
should copy st_size only if src's st_size is unset")