linux-kernel - Re: Warnings whilst building 5.2.0+

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Date:   Tue, 9 Jul 2019 12:39:34 +0100
From:   Chris Clayton <chris2553@...glemail.com>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Warnings whilst building 5.2.0+



On 09/07/2019 11:37, Enrico Weigelt, metux IT consult wrote:
> On 09.07.19 08:06, Chris Clayton wrote:
> 
> Hi,
> 
>> I've pulled Linus' tree this morning and, after running 'make oldconfig', tried a build. During that build I got the
>> following warnings, which look to me like they should be fixed. 'git describe' shows v5.2-915-g5ad18b2e60b7 and my
>> compiler is the 20190706 snapshot of gcc 9.
> 
> Thanks for the report. I'm rebuilding right know anyways, so I'll look
> out for it.

Thanks for the reply.

>> In file included from arch/x86/kernel/head64.c:35:
>> In function 'sanitize_boot_params',
>>     inlined from 'copy_bootdata' at arch/x86/kernel/head64.c:391:2:
>> ./arch/x86/include/asm/bootparam_utils.h:40:3: warning: 'memset' offset [197, 448] from the object at 'boot_params' is
>> out of the bounds of referenced subobject 'ext_ramdisk_image' with type 'unsigned int' at offset 192 [-Warray-bounds]
>>    40 |   memset(&boot_params->ext_ramdisk_image, 0,
>>       |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>    41 |          (char *)&boot_params->efi_info -
>>       |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>    42 |    (char *)&boot_params->ext_ramdisk_image);
>>       |    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ./arch/x86/include/asm/bootparam_utils.h:43:3: warning: 'memset' offset [493, 497] from the object at 'boot_params' is
>> out of the bounds of referenced subobject 'kbd_status' with type 'unsigned char' at offset 491 [-Warray-bounds]
>>    43 |   memset(&boot_params->kbd_status, 0,
>>       |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>    44 |          (char *)&boot_params->hdr -
>>       |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>    45 |          (char *)&boot_params->kbd_status);
>>       |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Can you check older versions, too ? Maybe also trying older gcc ?
> 

I see the same warnings building linux-5.2.0 with gcc9. However, I don't see the warnings building linux-5.2.0 with the
the 20190705 of gcc8. So the warnings could result from an improvement (i.e. the problem was in the kernel, but
undiscovered by gcc8) or from a regression in gcc9.

> 
> --mtx
>