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

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Date:   Wed, 29 Jul 2020 15:44:56 -0400 (EDT)
From:   Vladis Dronov <vdronov@...hat.com>
To:     Segher Boessenkool <segher@...nel.crashing.org>
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

Hello,

----- Original Message -----
> 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>
> Sent: Wednesday, July 29, 2020 4:49:49 PM
> Subject: Re: [PATCH] powerpc: fix function annotations to avoid section mismatch warnings with gcc-10
> 
> On Wed, Jul 29, 2020 at 03:37:41PM +0200, 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").

> 
> Segher

Best regards,
Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer