linux-kernel - Re: [ammarfaizi2-block:google/android/kernel/common/android12-trusty-5.10 4036/5872] WARNING: modpost: vmlinux.o(.text+0x4111c4): Section mismatch in reference from the function memblock_bottom_up() to the variable .meminit.data:memblock

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Date:   Thu, 31 Mar 2022 09:11:43 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Roman Gushchin <roman.gushchin@...ux.dev>,
        kernel test robot <lkp@...el.com>,
        Roman Gushchin <guro@...com>, llvm@...ts.linux.dev,
        kbuild-all@...ts.01.org,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
        linux-kernel@...r.kernel.org,
        Suren Baghdasaryan <surenb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Minchan Kim <minchan@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re:
 [ammarfaizi2-block:google/android/kernel/common/android12-trusty-5.10
 4036/5872] WARNING: modpost: vmlinux.o(.text+0x4111c4): Section mismatch in
 reference from the function memblock_bottom_up() to the variable
 .meminit.data:memblock

On Thu, Mar 31, 2022 at 12:42:04PM +0300, Mike Rapoport wrote:
> (added llvm folks)
> 
> Hi,
> 
> On Wed, Mar 30, 2022 at 02:47:43PM -0700, Roman Gushchin wrote:
> > On Wed, Mar 30, 2022 at 02:53:14PM +0800, kbuild test robot wrote:
> > > Hi Roman,
> > > 
> > > FYI, the error/warning still remains.
> > > 
> > > tree:   https://github.com/ammarfaizi2/linux-block google/android/kernel/common/android12-trusty-5.10
> > > head:   07055bfd3d810d41a38354693dfaa55a6f8c0025
> > > commit: 0e0bfc41fdf4d79d39ebe929844cdee44f97366d [4036/5872] UPSTREAM: mm: cma: allocate cma areas bottom-up
> > > config: x86_64-randconfig-a005 (https://download.01.org/0day-ci/archive/20220330/202203301412.MZ7wQvQz-lkp@intel.com/config)
> > > compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 0f6d9501cf49ce02937099350d08f20c4af86f3d)
> > > reproduce (this is a W=1 build):
> > >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # https://github.com/ammarfaizi2/linux-block/commit/0e0bfc41fdf4d79d39ebe929844cdee44f97366d
> > >         git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
> > >         git fetch --no-tags ammarfaizi2-block google/android/kernel/common/android12-trusty-5.10
> > >         git checkout 0e0bfc41fdf4d79d39ebe929844cdee44f97366d
> > >         # save the config file to linux build tree
> > >         mkdir build_dir
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> > > 
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <lkp@...el.com>
> > > 
> > > All warnings (new ones prefixed by >>, old ones prefixed by <<):
> > > 
> > > >> WARNING: modpost: vmlinux.o(.text+0x4111c4): Section mismatch in reference from the function memblock_bottom_up() to the variable .meminit.data:memblock
> > > The function memblock_bottom_up() references
> > > the variable __meminitdata memblock.
> > > This is often because memblock_bottom_up lacks a __meminitdata
> > > annotation or the annotation of memblock is wrong.
> > 
> > I guess this patch should fix it, however I fail to reproduce the original issue.
> > Maybe it's up to the specific compiler version.
> > 
> > --
> > 
> > From b55a8dd19f4156d7e24ec39b18ede06965ce1c4f Mon Sep 17 00:00:00 2001
> > From: Roman Gushchin <roman.gushchin@...ux.dev>
> > Date: Wed, 30 Mar 2022 14:42:12 -0700
> > Subject: [PATCH] memblock: fix memblock_bottom_up() and
> >  memblock_set_bottom_up() annotations
> > 
> > memblock_bottom_up() and memblock_set_bottom_up() lack __meminitdata
> > annotations causing compiler warnings like:
> >   WARNING: modpost: vmlinux.o(.text+0x4111c4): Section mismatch in reference from the function memblock_bottom_up() to the
> >   variable .meminit.data:memblock
> > 
> > Fix it by adding the missing annotation and removing the wrong
> > __meminit annotation.
> > 
> > Reported-by: kernel test robot <lkp@...el.com>
> > Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
> > ---
> >  include/linux/memblock.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> > index 50ad19662a32..536bc2fc31e6 100644
> > --- a/include/linux/memblock.h
> > +++ b/include/linux/memblock.h
> > @@ -460,7 +460,7 @@ static inline void *memblock_alloc_node(phys_addr_t size,
> >  /*
> >   * Set the allocation direction to bottom-up or top-down.
> >   */
> > -static inline __init_memblock void memblock_set_bottom_up(bool enable)
> > +static inline __initdata_memblock void memblock_set_bottom_up(bool enable)
> 
> I think putting __initdata_memlock won't help here, because there should be
> nothing wrong with __meminit function accessing __meminitdata data.
> 
> My guesstimate would be that the compiler decided not to inline this and
> still dropped section attribute because of 'inline'.
> 
> If this is the case we I think we should 
> 
> 	s/inline __init_memblock/__always_inline/
> 
> >  {
> >  	memblock.bottom_up = enable;
> >  }
> > @@ -470,7 +470,7 @@ static inline __init_memblock void memblock_set_bottom_up(bool enable)
> >   * if this is true, that said, memblock will allocate memory
> >   * in bottom-up direction.
> >   */
> > -static inline __init_memblock bool memblock_bottom_up(void)
> > +static inline __initdata_memblock bool memblock_bottom_up(void)
> >  {
> >  	return memblock.bottom_up;
> >  }
> > -- 
> > 2.30.2
> > 
> 

For the record, I cannot reproduce this on mainline, which has commits
34dc2efb39a2 ("memblock: fix section mismatch warning") and a024b7c2850d
("mm: memblock: fix section mismatch warning again"). That first commit
has the same exact warning as this report, which is against an Android
tree (android12-trusty-5.10).

While I do not see the commit that 34dc2efb39a2 claims to fix in
android12-trusty-5.10, I do see the three commits in android12-5.10:

a46e3fa13968 ("UPSTREAM: mm: memblock: drop __init from memblock functions to make it inline")
5f7ec0f4c383 ("UPSTREAM: memblock: fix section mismatch warning")
8cf5bb6946a2 ("UPSTREAM: mm: memblock: fix section mismatch warning again")

I think we can just discard this report for now, unless someone from
Google's trusty team wants to address it in that branch.

Cheers,
Nathan