linux-kernel - Re: [PATCH v4 01/11] macintosh/via-pmu: Fix section mismatch warning

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Message-ID: <alpine.LNX.2.21.1807022143570.13@nippy.intranet>
Date:   Mon, 2 Jul 2018 22:07:29 +1000 (AEST)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Mathieu Malaterre <malat@...ian.org>
cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Schmitz <schmitzmic@...il.com>,
        linux-m68k@...ts.linux-m68k.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 01/11] macintosh/via-pmu: Fix section mismatch
 warning

On Mon, 2 Jul 2018, Mathieu Malaterre wrote:

> On Mon, Jul 2, 2018 at 10:25 AM Finn Thain <fthain@...egraphics.com.au> 
> wrote:
> >
> > The pmu_init() function has the __init qualifier, but the ops struct 
> > that holds a pointer to it does not. This causes a build warning. The 
> > driver works fine because the pointer is only dereferenced early.
> >
> > The function is so small that there's negligible benefit from using 
> > the __init qualifier. Remove it to fix the warning, consistent with 
> > the other ADB drivers.
> 
> Would you mind copy/pasting the warning you are seeing.
> 
> Make sure you have:
> 
> 58935176ad17 powerpc/via-pmu: Fix section mismatch warning
> 
> Thanks
> 

It's true, the section mismatch warning from 'make' has disappeared since 
I wrote this patch, but that doesn't mean it is wrong.

Before this patch:

$ powerpc-linux-gnu-objdump -xda vmlinux |egrep -w "via_pmu_driver|pmu_init"
c0711c84 l     F .init.text     0000001c pmu_init
c05eb408 g     O .rodata        00000028 via_pmu_driver
c0711c84 <pmu_init>:
$ 

After:

$ powerpc-linux-gnu-objdump -xda vmlinux |egrep -w "via_pmu_driver|pmu_init"
c038e42c l     F .text  0000001c pmu_init
c05e1e58 g     O .rodata        00000028 via_pmu_driver
c038e42c <pmu_init>:
$

I gather that commit 58935176ad17 ("powerpc/via-pmu: Fix section mismatch 
warning") has moved via_pmu_driver from .data to .rodata, but I'm afraid I 
don't see the point of that change. The commit log entry doesn't explain 
it either.

If .rodata is not discarded then the dangling pointer remains, right?

--