Olivier Gayot [Tue, 16 Oct 2018 19:37:51 +0000 (21:37 +0200)]
posix_spawn.3: Document the POSIX_SPAWN_SETSID attribute
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
Olivier Gayot [Tue, 16 Oct 2018 19:37:50 +0000 (21:37 +0200)]
posix_spawn.3: Clarify by using name of steps rather than syscalls
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.
Olivier Gayot [Tue, 16 Oct 2018 19:37:48 +0000 (21:37 +0200)]
posix_spawn.3: Document implementation using clone() since glibc 2.24
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
Michael Kerrisk [Fri, 17 Apr 2020 09:55:13 +0000 (11:55 +0200)]
bpf.2: srcfix: Add a note on check for unprivileged BPF_PROG_TYPE_SOCKET_FILTER programs
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>
Yang Shi [Mon, 3 Feb 2020 19:18:27 +0000 (03:18 +0800)]
move_pages.2: Returning positive value is a new error case
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>
YunQiang Su [Sun, 22 Mar 2020 09:55:27 +0000 (17:55 +0800)]
getauxval.3: MIPS, AT_BASE_PLATFORM passes ISA level
Since Linux 5.7, on MIPS, we use AT_BASE_PLATFORM to pass ISA level.
The values may be:
mips2, mips3, mips4, mips5,
mips32, mips32r2, mips32r6,
mips64, mips64r2, mips64r6.
s390_runtime_instr.2: Document signum argument behavior change
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.
Michael Kerrisk [Thu, 16 Apr 2020 06:16:01 +0000 (08:16 +0200)]
mremap.2: Move a paragraph from DESCRIPTION to NOTES
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>
Michael Kerrisk [Tue, 14 Apr 2020 11:21:26 +0000 (13:21 +0200)]
mmap.2: Don't mark MAP_ANON as deprecated
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>
Michael Kerrisk [Tue, 14 Apr 2020 11:06:24 +0000 (13:06 +0200)]
ioctl_list.2: Remove hex values from constants
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.
Linux kernel commit 337684a1746f "fs: return EPERM on immutable
inode" changed (nd unified the return value of the utimensat(2)
from -EACCES to -EPERM in case of an immutable flag. Modify the
man page to reflect the same.
The entire discussion of returning the correct return value is at:
http://lists.linux.it/pipermail/ltp/2017-January/003424.html
[mtk: The change was in Linux 4.8]
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
strftime.3: ISO week number can be 52, add example
A year cannot only begin with week number 53 of the previous year but
also with week number 52. Year 2011 is an example for this case, as
can be easily seen with GNU date:
$ date -d "jan 1 2011" "+%c %V %G"
Sat Jan 1 00:00:00 2011 52 2010
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk [Mon, 13 Apr 2020 10:03:27 +0000 (12:03 +0200)]
io_setup.2: Tweak description of /proc/sys/fs/aio-max-nr
As far as I can see, /proc/sys/fs/aio-max-nr is a
system-wide limit, not a per-user limit. This seems to be
confirmed by comments in fs/aio.c (Linux 5.6) sources).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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