Add memfd_create to os module

[tiran]

BPO	26836
Nosy	@pitrou, @vstinner, @tiran, @jdemeyer, @applio, @pslacerda, @ZackerySpytz, @miss-islington, @pierreglaser
PRs	bpo-26836: Add os.memfd_create() #13567 bpo-26836: Add ifdefs for all MFD_HUGE* constants #13666 bpo-26836: Document os.memfd_create() name parameter #13838 [3.8] bpo-26836: Document os.memfd_create() name parameter (GH-13838) #13839

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-06-05.08:46:01.091>
created_at = <Date 2016-04-24.13:56:03.106>
labels = ['extension-modules', 'type-feature', '3.8']
title = 'Add memfd_create to os module'
updated_at = <Date 2019-06-05.11:16:04.046>
user = 'https://github.com/tiran'

bugs.python.org fields:

activity = <Date 2019-06-05.11:16:04.046>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-06-05.08:46:01.091>
closer = 'christian.heimes'
components = ['Extension Modules']
creation = <Date 2016-04-24.13:56:03.106>
creator = 'christian.heimes'
dependencies = []
files = []
hgrepos = []
issue_num = 26836
keywords = ['patch']
message_count = 12.0
messages = ['264109', '268643', '343916', '343917', '343921', '343954', '344033', '344302', '344684', '344685', '344699', '344705']
nosy_count = 9.0
nosy_names = ['pitrou', 'vstinner', 'christian.heimes', 'jdemeyer', 'davin', 'Pedro Lacerda', 'ZackerySpytz', 'miss-islington', 'pierreglaser']
pr_nums = ['13567', '13666', '13838', '13839']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue26836'
versions = ['Python 3.8']

[tiran]

Add memfd_create() and constants MFD_ALLOW_SEALING, MFD_CLOEXEC to the os module. A glibc wrapper for memfd_create() is not available yet but the interface has been standardized.

http://man7.org/linux/man-pages/man2/memfd_create.2.html
https://dvdhrm.wordpress.com/tag/memfd/

[pslacerda]

Maybe useful at mmapmodule.c replacing

    /* SVR4 method to map anonymous memory is to open /dev/zero */
    fd = devzero = _Py_open("/dev/zero", O_RDWR);

tagname is unused at UNIX version of new_mmap_object() so if provided something like could be added for Linux only
fd = memfd_create(tagname, O_RDWR);

[tiran]

New changeset 43fdbd2 by Christian Heimes (Zackery Spytz) in branch 'master':
bpo-26836: Add os.memfd_create() (bpo-13567)
43fdbd2

[tiran]

https://buildbot.python.org/all/#builders/99/builds/2738 is failing because some HUGE TLB constants are not defined on Gentoo.

[miss-islington]

New changeset e70bfa9 by Miss Islington (bot) (Zackery Spytz) in branch 'master':
bpo-26836: Add ifdefs for all MFD_HUGE* constants (GH-13666)
e70bfa9

[jdemeyer]

Testsuite breakage: https://bugs.python.org/issue37098

[pitrou]

Davin, Pierre, it looks like this could simplify lifetime management of shared memory pools, what do you think?

[pierreglaser]

From a quick skim at the man page of memfd_create, this looks promising.

[vstinner]

It seems like this issue can now be closed, no?

[tiran]

Yes, the feature is implemented and buildbots are green.