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From:   Florian Weimer <fweimer@redhat.com>
To:     Alexey Dobriyan <adobriyan@gmail.com>
Cc:     Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
        linux-api@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v2] ELF: supply userspace with available page shifts
 (AT_PAGE_SHIFT_MASK)
References: <6b399b86-a478-48b0-92a1-25240a8ede54@p183>
        <87v89dvuxg.fsf@oldenburg.str.redhat.com>
        <1d679805-8a82-44a4-ba14-49d4f28ff597@p183>
        <202312061236.DE847C52AA@keescook>
        <4f5f29d4-9c50-453c-8ad3-03a92fed192e@p183>
Date:   Thu, 07 Dec 2023 16:32:51 +0100
In-Reply-To: <4f5f29d4-9c50-453c-8ad3-03a92fed192e@p183> (Alexey Dobriyan's
        message of "Thu, 7 Dec 2023 17:57:05 +0300")
Message-ID: <8734wehvto.fsf@oldenburg.str.redhat.com>
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* Alexey Dobriyan:

> On Wed, Dec 06, 2023 at 12:47:27PM -0800, Kees Cook wrote:
>> On Tue, Dec 05, 2023 at 07:01:34PM +0300, Alexey Dobriyan wrote:
>> > Report available page shifts in arch independent manner, so that
>> > userspace developers won't have to parse /proc/cpuinfo hunting
>> > for arch specific strings:
>> > 
>> > Note!
>> > 
>> > This is strictly for userspace, if some page size is shutdown due
>> > to kernel command line option or CPU bug workaround, than is must not
>> > be reported in aux vector!
>> 
>> Given Florian in CC, I assume this is something glibc would like to be
>> using? Please mention this in the commit log.
>
> glibc can use it. Main user is libhugetlbfs, I guess:
>
> 	https://github.com/libhugetlbfs/libhugetlbfs/blob/master/hugeutils.c#L915
>
> Loop inside getauxval() can run faster than opendir().

Is libhugetlbfs still maintained?  Last commit was three years ago?

Thanks,
Florian