From: Florian Weimer <fweimer@redhat.com>
To: Pavel Machek <pavel@ucw.cz>, Michael Ellerman <mpe@ellerman.id.au>
Cc: Matthew Wilcox <willy@infradead.org>,
Kees Cook <keescook@chromium.org>, Cyril Hrubis <chrubis@suse.cz>,
Michal Hocko <mhocko@kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Khalid Aziz <khalid.aziz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Andrea Arcangeli <aarcange@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
John Hubbard <jhubbard@nvidia.com>,
Abdul Haleem <abdhalee@linux.vnet.ibm.com>,
Joel Stanley <joel@jms.id.au>
Subject: Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE
Date: Fri, 8 Dec 2017 21:47:21 +0100 [thread overview]
Message-ID: <289f0cc8-9e24-fc38-cb83-4223f9923940@redhat.com> (raw)
In-Reply-To: <20171208142714.GB7793@amd>
On 12/08/2017 03:27 PM, Pavel Machek wrote:
> On Fri 2017-12-08 22:08:07, Michael Ellerman wrote:
>> If we had a time machine, the right set of flags would be:
>>
>> - MAP_FIXED: don't treat addr as a hint, fail if addr is not free
>> - MAP_REPLACE: replace an existing mapping (or force or clobber)
> Actually, if we had a time machine... would we even provide
> MAP_REPLACE functionality?
Probably yes. ELF loading needs to construct a complex set of mappings
from a single file. munmap (to create a hole) followed by mmap would be
racy because another thread could have reused the gap in the meantime.
The only alternative to overriding existing mappings would be mremap
with MREMAP_FIXED, and that doesn't look like an improvement API-wise.
(The glibc dynamic linker uses an mmap call with an increased length to
reserve address space and then loads additional segments with MAP_FIXED
at the offsets specified in the program header.)
Thanks,
Florian
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next prev parent reply other threads:[~2017-12-08 20:47 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 14:42 [PATCH 0/2] mm: introduce MAP_FIXED_SAFE Michal Hocko
2017-11-29 14:42 ` [PATCH 1/2] " Michal Hocko
2017-12-06 5:15 ` Michael Ellerman
2017-12-06 9:27 ` Michal Hocko
2017-12-06 10:02 ` Michal Hocko
2017-12-07 12:07 ` Pavel Machek
2017-11-29 14:42 ` [PATCH 2/2] fs, elf: drop MAP_FIXED usage from elf_map Michal Hocko
2017-11-29 17:45 ` Khalid Aziz
2018-05-29 22:21 ` Mike Kravetz
2018-05-30 8:02 ` Michal Hocko
2018-05-30 15:00 ` Mike Kravetz
2018-05-30 16:25 ` Michal Hocko
2018-05-31 0:51 ` Mike Kravetz
2018-05-31 9:24 ` Michal Hocko
2018-05-31 21:46 ` Mike Kravetz
2017-11-29 14:45 ` [PATCH] mmap.2: document new MAP_FIXED_SAFE flag Michal Hocko
2017-11-30 3:16 ` John Hubbard
2017-11-30 8:23 ` Michal Hocko
2017-11-30 8:24 ` [PATCH v2] " Michal Hocko
2017-11-30 18:31 ` John Hubbard
2017-11-30 18:39 ` Michal Hocko
2017-11-29 15:13 ` [PATCH 0/2] mm: introduce MAP_FIXED_SAFE Rasmus Villemoes
2017-11-29 15:50 ` Michal Hocko
2017-11-29 22:15 ` Kees Cook
2017-11-29 22:12 ` Kees Cook
2017-11-29 22:25 ` Kees Cook
2017-11-30 6:58 ` Michal Hocko
2017-12-01 15:26 ` Cyril Hrubis
2017-12-06 4:51 ` Michael Ellerman
2017-12-06 4:54 ` Matthew Wilcox
2017-12-06 7:03 ` Matthew Wilcox
2017-12-06 7:33 ` John Hubbard
2017-12-06 7:35 ` Florian Weimer
2017-12-06 8:06 ` John Hubbard
2017-12-06 8:54 ` Florian Weimer
2017-12-07 5:46 ` Michael Ellerman
2017-12-07 19:14 ` Kees Cook
2017-12-07 19:57 ` Matthew Wilcox
2017-12-08 8:33 ` Michal Hocko
2017-12-08 20:13 ` Kees Cook
2017-12-08 20:57 ` Matthew Wilcox
2017-12-08 11:08 ` Michael Ellerman
2017-12-08 14:27 ` Pavel Machek
2017-12-08 20:31 ` Cyril Hrubis
2017-12-08 20:47 ` Florian Weimer [this message]
2017-12-08 14:33 ` David Laight
2017-12-06 4:50 ` Michael Ellerman
2017-12-06 7:33 ` Rasmus Villemoes
2017-12-06 9:08 ` Michal Hocko
2017-12-07 0:19 ` Kees Cook
2017-12-07 1:08 ` John Hubbard
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