Add example programs demonstrating usage of shmget(2), shmat(2),
semget(2), semctl(2), and semop(2).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Document the verity attribute for statx(), which was added in
Linux 5.5.
For more context, see the fs-verity documentation:
https://www.kernel.org/doc/html/latest/filesystems/fsverity.html
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Fix clone3() syscall description for CLONE_PARENT_SETTID: kernel uses
cl_args.parent_tid instead of the specified cl_args.child_tid.
Signed-off-by: Krzysztof Małysa <varqox@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Consecutive calls to clock_gettime(CLOCK_MONOTONIC) are guaranteed
to return MONOTONIC values, which means that they either return
the *SAME* time value like the last call, or a later (higher) time
value.
Due to high resolution counters, like TSC on x86, most people see
that the values returned increase, but on other less common
platforms it's less likely that consecutive calls return newer
values, and instead users may unexpectedly get back the SAME time
value.
I think it makes sense to document that people should not expect
to see "always-growing" time values. For example in Debian I've
seen in quite some source packages where return values of
consecutive calls are compared against each other and then the
package build fails if they are equal (e.g. ruby-hitimes, ...).
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
* man2/syscalls.2 (.SH DESCRIPTION) <\fBgetdtablesize\fP(2)>: Remove "since
Linux 2.0" part for the osf_getdtablesize note, as syscall is generally
available since Linux 2.0; add line break after the word "as".
(.SH DESCRIPTION) <\fBpwrite\fP(2)>: Add line breaks.
(.SH DESCRIPTION) <\fBvm86old\fP(2)>: Add a line break after "in".
Signed-off-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
In many cases, these don't improve readability, and (when stacked)
they sometimes have the side effect of sometimes forcing text
to be justified within a narrow column range.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
And add self to copyright, since, by now, the majority of the
text in the page has now been (re)written by me.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Improve structure and readability, at the same time incorporating
text and details that were formerly in select_tut(2). Also
move a few details in other parts of the page into DESCRIPTION.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The POSIX situation has been the norm for a long time now,
and including ancient details overcomplicates the page.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The discussion about pre-POSIX types for 'timeval' and 'timespec'
is rather old, and these days serves mainly to complicate the
page. Remove it.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The current text layout is a little hard to parse, with details of
pselect() spread in the main description. Move some of that text
to a headed subsection, and add a one-sentence introduction
describing the purpose of pselect().
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Admittedly, the POSIX specification for exit() also uses octal.
However, 0xFF immediately indicates the lowest 8 bits to me
whereas I had to think a bit about the octal mask.
Cowritten-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This was already shown in an earlier version of the page,
but Adam Borowski's patch replaced it with an alternative.
Probably, it is better to show both possibilities.
Reported-by: "Joseph C. Sible" <josephcsible@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
In the example snippet, we already have the fd, thus there's no
need to refer to the file by name. And, /proc/ might be not
mounted or not accessible.
Noticed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
PTRACE_EVENT_STOP does not always report SIGTRAP, can be the
signal which stopped us
While at it, fix an obvious copy/paste error in
PTRACE_GET_SYSCALL_INFO description.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Somewhat surprisingly, perf_event_open() can fail with EINTR when
trying to enable perf reporting for a uprobe that's already been
configured for use with ftrace. Mention this error in the man
page.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The man page contains a trivial bug that's discussed here:
https://stackoverflow.com/q/59628958
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Linux kernel commit e78bbfa82624 ("mm: stop returning -ENOENT from
sys_move_pages() if nothing got migrated") had the effect of
*never* returning -ENOENT, in any situation. So we need to update
the man page to reflect that ENOENT is not a possible return
value.
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Historically (before Linux 2.6.23), base_addr was unsigned long
for 32-bit code and unsigned int for 64-bit code. In other words,
it was always a 32-bit value. When the ldt.h header files were
unified, the type became unsigned int on all systems. Update
modify_ldt.2 and set_thread_area.2 accordingly.
Indeed, on x86, the GDT and LDT specify 32-bit bases for code and
data segments, and this has nothing to do with the kernel.
Reported-by: "Metzger, Markus T" <markus.t.metzger@intel.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The programmer should not need to care about the numeric values,
and their inclusion is verbosity.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Since kernel commit 3dd4d40b4208("xfs: Sanity check flags
of Q_XQUOTARM call"), it has added flags check. If it is
not usr,grp,prj quota type, it will report EINVAL.
Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Added two missing parentheses
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This surely meant to say clone3() and not clone(3).
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The CLONE_PARENT flag cannot but used by init processes. Let's mention
this in the manpages to prevent surprises.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The introductory paragraphs note that "the calling process" is
normally synonymous with the "the parent process", except in the
case of CLONE_PARENT. The same is also true of CLONE_THREAD.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Advertise to userspace that they should use proper pid_t types
for arguments returning a pid.
The kernel-internal struct kernel_clone_args currently uses int
as type and since POSIX mandates that pid_t is a signed integer
type and glibc and friends use int this is not an issue. After
the merge window for v5.5 closes we can switch struct
kernel_clone_args over to using pid_t as well without any danger
in regressing current userspace.
Also note, that the new set tid feature which will be merged for
v5.5 uses pid_t types as well.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
If mmap() fails it will return MAP_FAILED which according to the manpage
is (void *)-1 not NULL.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Fix two spelling mistakes in manpage describing the clone{2,3}()
syscalls/syscall wrappers.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reword a little to allow for the fact that there are now
*two* reasons to consider using this flag.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk