linux-kernel - Re: Linux 5.15

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Date:   Mon, 1 Nov 2021 18:17:59 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 5.15

On 11/1/21 1:13 AM, Geert Uytterhoeven wrote:
> Hi Günter.
> 
> On Mon, Nov 1, 2021 at 1:28 AM Guenter Roeck <linux@...ck-us.net> wrote:
>> On Sun, Oct 31, 2021 at 02:09:07PM -0700, Linus Torvalds wrote:
>> Building m68k:allmodconfig ... failed
>> --------------
>> Error log:
>> In file included from include/linux/string.h:20,
>>                   from include/linux/bitmap.h:10,
>>                   from include/linux/cpumask.h:12,
>>                   from include/linux/smp.h:13,
>>                   from include/linux/lockdep.h:14,
>>                   from include/linux/spinlock.h:63,
>>                   from include/linux/mmzone.h:8,
>>                   from include/linux/gfp.h:6,
>>                   from include/linux/slab.h:15,
>>                   from drivers/nvme/target/discovery.c:7:
>> In function 'memcpy_and_pad',
>>      inlined from 'nvmet_execute_disc_identify' at drivers/nvme/target/discovery.c:268:2:
>> arch/m68k/include/asm/string.h:72:25: error: '__builtin_memcpy' reading 8 bytes from a region of size 7
>>
>> Another instance of the same problem:
>>
>> In function 'memcpy_and_pad',
>>      inlined from 'nvmet_execute_identify_ctrl' at drivers/nvme/target/admin-cmd.c:372:2:
>> arch/m68k/include/asm/string.h:72:25: error: '__builtin_memcpy' reading 8 bytes from a region of size 7
>>
>> This is seen with gcc 11.1 and 11.2. gcc 10.3 builds fine.
>> The code in question is
>>
>>          memcpy_and_pad(id->fr, sizeof(id->fr),
>>                         UTS_RELEASE, strlen(UTS_RELEASE), ' ');
>>
>> and UTS_RELEASE is "5.15.0". I have no idea what might be wrong with the code.
> 
> Me neither.  That warning (now error) has been seen with all point
> releases (i.e. strlen(UTS_RELEASE) < 8) since v5.0.
> 

Ah yes, I can see that now. I guess I didn't notice earlier because it was
only reported as warning.

>> Does anyone have an idea ?
> 
> We had a discussion in
> https://lore.kernel.org/all/CAMuHMdX365qmWiii=gQLADpW49EMkdDrVJDPWNBpAZuZM0WQFQ@mail.gmail.com
> but without any definitive conclusion.
> 
>> Do I need to revert to gcc 10.3 for m68k ?
> 
> I'm not sure that might help, as the issue has been seen with
> e.g. 8.1.0 and 8.2.0, too, with a slightly different message:
> warning: ‘__builtin_memcpy’ forming offset 8 is out of the bounds [0,
> 7] [-Warray-bounds]
> 
> Any suggestions? Thanks!
> 

Replacing "strlen(UTS_RELEASE)" with "sizeof(UTS_RELEASE) - 1" seems to do
the trick, at least with gcc 11.2 and v5.15. I just wonder if that would be
acceptable. Any idea ?

Thanks,
Guenter