Since glibc 2.26, posix_spawn (2) function accepts the
POSIX_SPAWN_SETSID flag. This flag has been accepted by POSIX and
should be added to the next major revision. The current support
can be enabled with _GNU_SOURCE.
Upstream commit in glibc.git:
daeb1fa2e1 [BZ 21340] add support for POSIX_SPAWN_SETSID
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Olivier Gayot <olivier.gayot@sigexec.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The implementation of the fork() step in posix_spawn(2) relies on
either fork(2), vfork(2) or clone(2) depending on the version of
the glibc and the arguments passed to posix_spawn(2).
It is sometimes ambiguous whether, when we are mentioning
"fork(2)", we are referring to the fork() step or the actual
fork(2) syscall.
This patch hopefully avoids the ambiguity by replacing confusing
occurrences by "the xxx() step" where appropriate.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Olivier Gayot <olivier.gayot@sigexec.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Added a few lines about POSIX_SPAWN_USEVFORK so that it appears
clearly that since glibc 2.24, the flag has no effect.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Olivier Gayot <olivier.gayot@sigexec.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Since glibc 2.24, the use of posix_spawn (2) makes an
unconditional call to clone(CLONE_VM | CLONE_VFORK ...) rather
than relying on fork (2) or vfork (2).
As a consequence, the statements regarding the use of the flag
POSIX_SPAWN_USEVFORK and how the function decides whether it
should use fork (2) or vfork (2) are obsolete since glibc 2.24.
This patch makes a distinction in the manual page between glibc
2.24 and older versions.
Upstream commit in glibc.git:
9ff72da471 posix: New Linux posix_spawn{p} implementation
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Olivier Gayot <olivier.gayot@sigexec.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Taken from Linux v5.3-rc2. Add a reference to the header file to
save the future reader some time figuring out whether more entries
exist.
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
In Linux 4.4, the allowed BPF helper functions that could
be called was governed by a check in sk_filter_func_proto().
Nowadays (Linux 5.6), it is I think governed by the check in
sk_filter_func_proto().
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This notes that the kernel now allows calls to bpf() without CAP_SYS_ADMIN
under some circumstances.
Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The cgroup.sane_behavior file returns the hard-coded value "0" and
is kept for legacy purposes. Mention this in the man-page.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"), the
semantic of move_pages() has changed to return the number of
non-migrated pages if they were result of a non-fatal reasons
(usually a busy page). This was an unintentional change that
hasn't been noticed except for LTP tests which checked for the
documented behavior.
There are two ways to go around this change. We can even get back
to the original behavior and return -EAGAIN whenever migrate_pages
is not able to migrate pages due to non-fatal reasons. Another
option would be to simply continue with the changed semantic and
extend move_pages documentation to clarify that -errno is returned
on an invalid input or when migration simply cannot succeed (e.g.
-ENOMEM, -EBUSY) or the number of pages that couldn't have been
migrated due to ephemeral reasons (e.g. page is pinned or locked
for other reasons).
We decided to keep the second option in kernel because this
behavior is in place for some time without anybody complaining and
possibly new users depending on it. Also it allows to have a
slightly easier error handling as the caller knows that it is
worth to retry when err > 0.
Update man pages to reflect the new semantic.
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Document that the signum argument is ignored in newer kernels, but
that user space should pass a valid real-time signal number for
backwards compatibility.
Cowritten-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Verified from inspection of kernel source code.
Reported-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The paragraph on Linux VM is rather generic, and does not belong
in DESCRIPTION. In fact, I'm not sure it even belongs in this
page. At the least, let's move it to NOTES.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
And while we are at it, remove a sentence that makes an obvious
point (that mremap() uses the Linux page table scheme).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Details of glibc 2.4, which is by now fairly old, would be
better at the end of NOTES than at the start.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
From a mailing list conversation:
On 5/24/18 9:03 PM, Heinrich Schuchardt wrote:
> Hello Michael,
>
> in the mmap(2) man page MAP_ANON is described as deprecated.
>
> When I look at the NetBSD manpage
> http://netbsd.gw.com/cgi-bin/man-cgi?mmap+2+NetBSD-current
> I found that MAP_ANONYMOUS is not defined.
>
> https://www.dragonflybsd.org/cgi/web-man?command=mmap§ion=2
> indicates MAP_ANONYMOUS is an alias for MAP_ANON and is provided for
> compatibility.
>
> https://man.openbsd.org/mmap.2 also knows MAP_ANONYMOUS as a synonym.
>
> https://www.unix.com/man-page/osx/2/mmap/ does not know MAP_ANONYMOUS.
>
> So shouldn't the man page indicate that MAP_ANON is to be favored to
> write portable code? And correspondingly mark MAP_ANONYMOUS as synonym
> only kept for compatibility.
>
> The Open Group Base Specifications Issue 7, 2018 Edition does not
> reference either of both. So both values are not POSIX but it is not
> correct to describe them as Linux only.
The text saying that MAP_ANON is deprecated is ancient (at least
20 years old). I don't know why that text was added.
Things are not simple though: it looks like there's at least
one historical implementation (HP-US) that defines MAP_ANONYMOUS
but not MAP_ANON.
I've applied the patch below.
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
As noted by Heinrich Schuchardt:
he list contains hex values of different constants. I just wonder for
which architecture (alpha, i386, mips, or sparc at that time). No
information is supplied.
Current values depend on the architecture, e.g.
On amd64
0x82307201 VFAT_IOCTL_READDIR_BOTH
0x82307202 VFAT_IOCTL_READDIR_SHORT
0x80047210 FAT_IOCTL_GET_ATTRIBUTES
0x40047211 FAT_IOCTL_SET_ATTRIBUTES
0x80047213 FAT_IOCTL_GET_VOLUME_ID
On mips
0x42187201 VFAT_IOCTL_READDIR_BOTH
0x42187202 VFAT_IOCTL_READDIR_SHORT
0x40047210 FAT_IOCTL_GET_ATTRIBUTES
0x80047211 FAT_IOCTL_SET_ATTRIBUTES
0x40047213 FAT_IOCTL_GET_VOLUME_ID
Hence hex values should be removed.
Reported-by:
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk