linux-kernel - Re: [PATCH 1/4] selftests/mm: remove flaky header check

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <e971e44e-5539-4fc4-8128-0ce9c3d10a38@arm.com>
Date: Thu, 18 Dec 2025 14:24:10 +0100
From: Kevin Brodsky <kevin.brodsky@....com>
To: Mark Brown <broonie@...nel.org>
Cc: linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...nel.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Ryan Roberts <ryan.roberts@....com>, Shuah Khan <shuah@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Yunsheng Lin <linyunsheng@...wei.com>
Subject: Re: [PATCH 1/4] selftests/mm: remove flaky header check

On 17/12/2025 11:04, Mark Brown wrote:
> On Tue, Dec 16, 2025 at 02:26:30PM +0000, Kevin Brodsky wrote:
>> Commit 96ed62ea0298 ("mm: page_frag: fix a compile error when kernel
>> is not compiled") introduced a check to avoid attempting to build
>> the page_frag module if <linux/page_frag_cache.h> is missing.
>>
>> Unfortunately this check only works if KDIR points to
>> /lib/modules/... or an in-tree kernel build. It always fails if KDIR
>> points to an out-of-tree build (i.e. when the kernel was built with
>> O=$KDIR make) because only generated headers are present under
>> $KDIR/include/ in that case.
>>
>> <linux/page_frag_cache.h> was added more than a year ago (v6.13) so
>> we can probably live without that check.
> More generally building selftests with random older kernel versions
> isn't really something that's expected to be robust:

I suppose that Documentation/dev-tools/kselftest.rst talks about
*running* against older kernels, not *building* against them. That said,
we are dealing with an out-of-tree kernel module here, so the two are
essentially the same... Yunsheng suggested an updated check that I think
is reasonable, maybe it is a reasonable compromise?

- Kevin