linux-kernel - Re: linux-next: build warning after merge of the akpm-current tree

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Date:   Thu, 5 Mar 2020 06:54:07 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Walter Wu <walter-zh.wu@...iatek.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: linux-next: build warning after merge of the akpm-current tree

On Thu, Mar 5, 2020 at 6:37 AM Stephen Rothwell <sfr@...b.auug.org.au> wrote:
>
> Hi all,
>
> After merging the akpm-current tree, today's linux-next build (x86_64
> allmodconfig) produced this warning:
>
> mm/kasan/common.o: warning: objtool: kasan_report()+0x17: call to report_enabled() with UACCESS enabled
> In file included from include/linux/bitmap.h:9,
>                  from include/linux/cpumask.h:12,
>                  from arch/x86/include/asm/paravirt.h:17,
>                  from arch/x86/include/asm/irqflags.h:72,
>                  from include/linux/irqflags.h:16,
>                  from include/linux/rcupdate.h:26,
>                  from include/linux/rculist.h:11,
>                  from include/linux/pid.h:5,
>                  from include/linux/sched.h:14,
>                  from include/linux/uaccess.h:6,
>                  from arch/x86/include/asm/fpu/xstate.h:5,
>                  from arch/x86/include/asm/pgtable.h:26,
>                  from include/linux/kasan.h:15,
>                  from lib/test_kasan.c:12:
> In function 'memmove',
>     inlined from 'kmalloc_memmove_invalid_size' at lib/test_kasan.c:301:2:
> include/linux/string.h:441:9: warning: '__builtin_memmove' specified bound 18446744073709551614 exceeds maximum object size 9223372036854775807 [-Wstringop-overflow=]

+kasan-dev

We probably need to make this 18446744073709551614 constant "dynamic"
so that compiler does not see it.

Walter, will you take a look? Thanks

>   441 |  return __builtin_memmove(p, q, size);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Introduced by commit
>
>   519e500fac64 ("kasan: add test for invalid size in memmove")
>
> That's a bit annoying during a normal x86_64 allmodconfig build ...
>
> --
> Cheers,
> Stephen Rothwell