The parisc gateway page currently only exports 3 functions:
The lws_entry for CAS operations (at 0xb0), the set_thread_pointer
function for usage in glibc (at 0xe0) and the Linux syscall entry
(at 0x100).
All other symbols in the manpage are internal labels and
shouldn't be used directly by userspace or glibc, so drop them
from the man page documentation.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Note ENOTDIR error that occurs when requesting a watch on a
nondirectory with IN_ONLYDIR.
Reported-by: Paul Millar <paul.millar@desy.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Add background details on ambient and bounding set when
discussing capability transformations during execve(2).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
capset(2) and capget(2) apply operate only on the permitted,
effective, and inheritable process capability sets.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
When comparing two namespaces symlinks to see if they refer to
the same namespace, both the inode number and the device ID
should be compared. This point was already made clear in
ioctl_ns(2), but was missing from this page.
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
There was some confused missing of concepts between the
two subsections, and some other details that needed fixing up.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Confirmed with Serge Hallyn that: "nsroot" means the UID 0
in the namespace as it would be mapped into the initial userns.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Use more consistent layout for lists of functions, and
remove punctuation from the lists to make them less cluttered.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
We define in detail the X/Open System Interfaces i.e. _XOPEN_UNIX
and all of the X/Open System Interfaces (XSI) Options Groups.
The XSI options groups include encryption, realtime, advanced
realtime, realtime threads, advanced realtime threads, tracing,
streams, and legacy interfaces.
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
As noted by Rusty Russell:
I was really surprised that sendmsg() returned EBADF on a valid fd;
turns out I was using sendmsg with SCM_RIGHTS to send a closed fd,
which gives EBADF (see test program below).
But this is only obliquely referenced in unix(7):
SCM_RIGHTS
Send or receive a set of open file descriptors
from another process. The data portion contains
an integer array of the file descriptors. The
passed file descriptors behave as though they have
been created with dup(2).
EBADF is not mentioned in the unix(7) ERRORS (it's mentioned in
dup(2)).
int fdpass_send(int sockout, int fd)
{
/* From the cmsg(3) manpage: */
struct msghdr msg = { 0 };
struct cmsghdr *cmsg;
struct iovec iov;
char c = 0;
union { /* Ancillary data buffer, wrapped in a union
in order to ensure it is suitably aligned */
char buf[CMSG_SPACE(sizeof(fd))];
struct cmsghdr align;
} u;
msg.msg_control = u.buf;
msg.msg_controllen = sizeof(u.buf);
memset(&u, 0, sizeof(u));
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_flags = 0;
/* Keith Packard reports that 0-length sends don't work, so we
* always send 1 byte. */
iov.iov_base = &c;
iov.iov_len = 1;
return sendmsg(sockout, &msg, 0);
}
int fdpass_recv(int sockin)
{
/* From the cmsg(3) manpage: */
struct msghdr msg = { 0 };
struct cmsghdr *cmsg;
struct iovec iov;
int fd;
char c;
union { /* Ancillary data buffer, wrapped in a union
in order to ensure it is suitably aligned */
char buf[CMSG_SPACE(sizeof(fd))];
struct cmsghdr align;
} u;
msg.msg_control = u.buf;
msg.msg_controllen = sizeof(u.buf);
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_flags = 0;
iov.iov_base = &c;
iov.iov_len = 1;
if (recvmsg(sockin, &msg, 0) < 0)
return -1;
cmsg = CMSG_FIRSTHDR(&msg);
if (!cmsg
|| cmsg->cmsg_len != CMSG_LEN(sizeof(fd))
|| cmsg->cmsg_level != SOL_SOCKET
|| cmsg->cmsg_type != SCM_RIGHTS) {
errno = -EINVAL;
return -1;
}
memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd));
return fd;
}
static void child(int sockfd)
{
int newfd = fdpass_recv(sockfd);
assert(newfd < 0);
exit(0);
}
int main(void)
{
int sv[2];
int pid, ret;
assert(socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == 0);
pid = fork();
if (pid == 0) {
close(sv[1]);
child(sv[0]);
}
close(sv[0]);
ret = fdpass_send(sv[1], sv[0]);
printf("fdpass of bad fd return %i (%s)\n", ret, strerror(errno));
return 0;
}
Reported-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The last argument is passed by value, not reference.
Reported-by: Tomi Salminen <tsalminen@forcepoint.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
gettimeofday() is declared obsolete by POSIX. Mention instead
the modern APIs for working with the realtime clock.
See https://bugzilla.kernel.org/show_bug.cgi?id=199049
Reported-by: Enrique Garcia <cquike@arcor.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
/proc/[pid]/ns/pid_for_children has a value only after first
child is created in PID namespace. Verified by experiment.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Some notes from a conversation with Tejun Heo:
Subject: Re: cgroups(7): documenting cgroups v2 delegation
Date: Wed, 10 Jan 2018 14:27:26 -0800
From: Tejun Heo <tj@kernel.org>
> > 1. When delegating, cgroup.threads should be delegated. Doing that
> > selectively doesn't achieve anything meaningful.
>
> Understood. But surely delegating cgroup.threads is effectively
> meaningless when delegating a "domain" cgroup tree? (Obviously it's
> not harmful to delegate the the cgroup.threads file in this case;
> it's just not useful to do so.)
Yeap, unless we can somehow support non-root mixed domains.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
As discussed with Tejun Heo and Roman Gushchin, the
omission of this file from the list is a bug, and
is about to be fixed by a kernel patch from Roman.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
We are about to add description of a different kind
of delegation (nsdelegate) with its own subheading.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Existing cgroups under threaded root *must*, by definition,
be either domain or part of threaded subtrees, so this is not
a constraint on the creation of threaded subtrees.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The placement of a thread in the run queue for its new
priority depends on the direction of movement in priority.
(This appears to contradict POSIX, except in the case of
pthread_setschedprio().)
As reported by Andrea, and followed up by me:
> I point out that the semantics of sched_setscheduler(2) for RT threads
> indicated in sched(7) and, in particular, in
>
> "A call to sched_setscheduler(2), sched_setparam(2), or
> sched_setattr(2) will put the SCHED_FIFO (or SCHED_RR) thread
> identified by pid at the start of the list if it was runnable."
>
> does not "reflect" the current implementation of this syscall(s) that, in
> turn; based on the source, I think a more appropriate description of this
> semantics would be:
>
> "... the effect on its position in the thread list depends on the
> direction of the modification, as follows:
>
> a. if the priority is raised, the thread becomes the tail of the
> thread list.
> b. if the priority is unchanged, the thread does not change position
> in the thread list.
> c. if the priority is lowered, the thread becomes the head of the
> thread list."
>
> (copied from
> http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_08_04_01
> ).
So, I did some testing, and can confirm that the above is the behavior
on Linux for changes to scheduling priorities for RT processes.
(My tests consisted of creating a multithreaded process where all
threads are confined to the same CPU with taskset(), and each thread
is in a CPU-bound loop. I then maipulated their priorities with
chrt(1) and watched the CPU time being consumed with ps(1).)
Back in SUSv2 there was this text:
[[
6. If a thread whose policy or priority has been modified is a running
thread or is runnable, it then becomes the tail of the thread list for
its new priority.
]]
And certainly Linux used to behave this way. I remember testing it,
and when one looks at the Linux 2.2 source code for example, one can
see that there is a call to move_first_runqueue() in this case. At some
point, things changed, and I have not investigated exactly where that
change occurred (but I imagine it was quite a long time ago).
Looking at SUSv4, let's expand the range of your quote, since
point 7 is interesting. Here's text from Section 2.8.4
"Process Scheduling" in POSIX.1-2008/SUSv4 TC2:
[[
7. If a thread whose policy or priority has been modified other
than by pthread_setschedprio() is a running thread or is runnable,
it then becomes the tail of the thread list for its new priority.
8. If a thread whose priority has been modified by pthread_setschedprio()
is a running thread or is runnable, the effect on its position in the
thread list depends on the direction of the modification, as follows:
a. If the priority is raised, the thread becomes the tail of the
thread list.
b. If the priority is unchanged, the thread does not change position
in the thread list.
c. If the priority is lowered, the thread becomes the head of the
thread list.
]]
(Note that the preceding points mention variously sched_setscheduler(),
sched_setsparam(), and pthread_setschedprio(), so that the mention of
just pthread_setschedprio() in points 7 and 8 is significant.)
Now, since chrt(1) uses sched_setscheduler(), rather than
pthread_setschedprio(), then arguably the Linux behavior is a
violation of POSIX. (Indeed, buried in the man-pages source, I find
that I many years ago wrote the comment:
In 2.2.x and 2.4.x, the thread is placed at the front of the queue
In 2.0.x, the Right Thing happened: the thread went to the back -- MTK
But the Linux behavior seems reasonable to me and I'm inclined
to just document it (see the patch below).
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Logically, this section should follow the section that
describes cgroup.subtree_control.
No content changes in this patch.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
According to The Open Group Base Specifications Issue 7, RATIONALE
section of
http://pubs.opengroup.org/onlinepubs/9699919799/ basedefs/netinet_in.h.html
some INADDR_* values must be converted using htonl().
INADDR_ANY and INADDR_BROADCAST are byte-order-neutral so they do
not require htonl(), however I only comment this fact in NOTES.
On the text I recommend to use htonl(), "even if for some subset
it's not necessary".
Signed-off-by: Ricardo Biehl Pasquali <pasqualirb@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Sockets support both read(2)/write(2) and send(2)/recv(2) system
calls. Each of these is actually a family of multiple system
calls such as send(2), sendfile(2), sendmsg(2), sendmmsg(2), and
sendto(2).
This patch claries which families of system calls can be used.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The AF_VSOCK address family has been available since Linux 3.9.
This patch adds vsock.7 and describes its use along the same lines as
existing ip.7, unix.7, and netlink.7 man pages.
CC: Jorgen Hansen <jhansen@vmware.com>
CC: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Jorgen Hansen <jhansen@vmware.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Note explicitly that SECBIT_NO_SETUID_FIXUP is relevant for
the permitted, effective, and ambient capability sets.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk