This also fixes a minor issue that was missed in the initial review; the
layout of the MFD_HUGE_* flags is actually not 1:1 bit:flag -- it instead
borrowed the Linux convention of how this is laid out since it was
originally implemented on Linux, the top 6 bits represent the shift required
for the requested page size.
This allows us to remove the flag <-> pgsize mapping table and simplify the
logic just prior to validation of the requested page size.
While we're here, fix two small nits:
- HUGETLB memfd shouldn't exhibit the SHM_GROW_ON_WRITE behavior. We can
only grow largepage shm by appropriately aligned (i.e. requested pagesize)
sizes, so it can't work in the typical/sane fashion. Furthermore, Linux
does the same, so let's be compatible.
- We don't allow MFD_HUGETLB without specifying a pagesize, so no need to
check for that later.
Reviewed by: kib (slightly earlier version)
Literally returning EINVAL from a function designed to return an fd makes
for interesting scenarios.
I cannot assign enough pointy hats to cover this one.
r365524 did accidentally invert this check that sets SHM_LARGEPAGE, leading
non-hugetlb memfd as unconfigured largepage shm and thus test failures when
we try to ftruncate or write to them.
PR: 249236
Discussed with: kib
largepage shm objects.
And since we can, add memfd_create(MFD_HUGETLB) support, hopefully
close enough to the Linux feature.
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D24652
memfd_create fds will no longer require an ftruncate(2) to set the size;
they'll grow (to the extent that it's possible) upon write(2)-like syscalls.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D25502
This had been introduced to ease any pain for using slightly older kernels
with a newer libc, e.g., for bisecting a kernel across the introduction of
shm_open2(2). 6 months has passed, retire the fallback and let shm_open()
unconditionally call shm_open2().
Stale includes are removed as well.
memfd_create is effectively a SHM_ANON shm_open(2) mapping with optional
CLOEXEC and file sealing support. This is used by some mesa parts, some
linux libs, and qemu can also take advantage of it and uses the sealing to
prevent resizing the region.
This reimplements shm_open in terms of shm_open2(2) at the same time.
shm_open(2) will be moved to COMPAT12 shortly.
Reviewed by: markj, kib
Differential Revision: https://reviews.freebsd.org/D21393
