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

[Roman Gushchin <roman.gushchin@linux.dev>]

> On Mar 31, 2022, at 9:11 AM, Nathan Chancellor <nathan@kernel.org> wrote:
> 
> 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@intel.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@linux.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@intel.com>
>>> Signed-off-by: Roman Gushchin <roman.gushchin@linux.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.

I agree. Or at least help us with the testing of the proposed fixes.

Thanks!