From: Matthew Wilcox <willy@infradead.org>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
David Hildenbrand <david@redhat.com>,
Rik van Riel <riel@surriel.com>, Michal Hocko <mhocko@suse.com>,
Peter Xu <peterx@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: mprotect and hugetlb mappings
Date: Thu, 6 Jul 2023 00:22:37 +0100 [thread overview]
Message-ID: <ZKX7PerFpnoMT5Pc@casper.infradead.org> (raw)
In-Reply-To: <20230705230808.GA41006@monkey>
On Wed, Jul 05, 2023 at 04:08:08PM -0700, Mike Kravetz wrote:
> I was recently asked about the behavior of mprotect on a hugetlb
> mapping where addr or addr+len is not hugetlb page size aligned. As
> one might expect, EINVAL is returned in such cases. However, the man
> page makes no mention of alignment requirements for hugetlb mappings.
>
> I am happy to submit man page updates if people agree this is the correct
> behavior. We might even want to check alignment earlier in the code
> path as we fail when trying to split the vma today.
>
> An alternative behavior would be to operate on whole hugetlb pages within
> the range addr - addr+len.
After a careful re-reading of the mprotect() man page, I suggest the
following behaviour ...
addr must be a multiple of the hpage size. Otherwise -EINVAL.
len should be rounded up to hpage size.
I wonder how likely this change would be to break userspace code.
Maybe some test cases.
next prev parent reply other threads:[~2023-07-05 23:22 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-05 23:08 mprotect and hugetlb mappings Mike Kravetz
2023-07-05 23:22 ` Matthew Wilcox [this message]
2023-07-05 23:53 ` Mike Kravetz
2023-07-17 16:19 ` Vlastimil Babka
2023-07-17 18:52 ` Mike Kravetz
2023-07-17 19:00 ` David Hildenbrand
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