linux-kernel - Re: [PATCH] powerpc: fix function annotations to avoid section mismatch warnings with gcc-10

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Message-ID: <20200729224427.GI17447@gate.crashing.org>
Date:   Wed, 29 Jul 2020 17:44:27 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Vladis Dronov <vdronov@...hat.com>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH] powerpc: fix function annotations to avoid section mismatch warnings with gcc-10

On Wed, Jul 29, 2020 at 03:44:56PM -0400, Vladis Dronov wrote:
> > > Certain warnings are emitted for powerpc code when building with a gcc-10
> > > toolset:
> > > 
> > >     WARNING: modpost: vmlinux.o(.text.unlikely+0x377c): Section mismatch in
> > >     reference from the function remove_pmd_table() to the function
> > >     .meminit.text:split_kernel_mapping()
> > >     The function remove_pmd_table() references
> > >     the function __meminit split_kernel_mapping().
> > >     This is often because remove_pmd_table lacks a __meminit
> > >     annotation or the annotation of split_kernel_mapping is wrong.
> > > 
> > > Add the appropriate __init and __meminit annotations to make modpost not
> > > complain. In all the cases there are just a single callsite from another
> > > __init or __meminit function:
> > > 
> > > __meminit remove_pagetable() -> remove_pud_table() -> remove_pmd_table()
> > > __init prom_init() -> setup_secure_guest()
> > > __init xive_spapr_init() -> xive_spapr_disabled()
> > 
> > So what changed?  These functions were inlined with older compilers, but
> > not anymore?
> 
> Yes, exactly. Gcc-10 does not inline them anymore. If this is because of my
> build system, this can happen to others also.
> 
> The same thing was fixed by Linus in e99332e7b4cd ("gcc-10: mark more functions
> __init to avoid section mismatch warnings").

It sounds like this is part of "-finline-functions was retuned" on
<https://gcc.gnu.org/gcc-10/changes.html>?  So everyone should see it
(no matter what config or build system), and it is a good thing too :-)

Thanks for the confirmation,


Segher