Extend the support for exempting processes from being killed when swap is

exhausted.
- Add a new protect(1) command that can be used to set or revoke protection
  from arbitrary processes.  Similar to ktrace it can apply a change to all
  existing descendants of a process as well as future descendants.
- Add a new procctl(2) system call that provides a generic interface for
  control operations on processes (as opposed to the debugger-specific
  operations provided by ptrace(2)).  procctl(2) uses a combination of
  idtype_t and an id to identify the set of processes on which to operate
  similar to wait6().
- Add a PROC_SPROTECT control operation to manage the protection status
  of a set of processes.  MADV_PROTECT still works for backwards
  compatability.
- Add a p_flag2 to struct proc (and a corresponding ki_flag2 to kinfo_proc)
  the first bit of which is used to track if P_PROTECT should be inherited
  by new child processes.

Reviewed by:	kib, jilles (earlier version)
Approved by:	re (delphij)
MFC after:	1 month

3 files changed, 146 insertions, 0 deletions

diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc
index 4cc87ae..ac5907b 100644
--- a/lib/libc/sys/Makefile.inc
+++ b/lib/libc/sys/Makefile.inc
@@ -197,6 +197,7 @@ MAN+=	abort2.2 \
 	posix_fadvise.2 \
 	posix_fallocate.2 \
 	posix_openpt.2 \
+	procctl.2 \
 	profil.2 \
 	pselect.2 \
 	ptrace.2 \
diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
index 222f5f0..fe887c3 100644
--- a/lib/libc/sys/Symbol.map
+++ b/lib/libc/sys/Symbol.map
@@ -395,6 +395,7 @@ FBSD_1.3 {
 	ffclock_setestimate;
 	pipe2;
 	posix_fadvise;
+	procctl;
 	wait6;
 };
 
@@ -822,6 +823,8 @@ FBSDprivate_1.0 {
 	__sys_poll;
 	_preadv;
 	__sys_preadv;
+	_procctl;
+	__sys_procctl;
 	_profil;
 	__sys_profil;
 	_pselect;
diff --git a/lib/libc/sys/procctl.2 b/lib/libc/sys/procctl.2
new file mode 100644
index 0000000..ee49bc8
--- /dev/null
+++ b/lib/libc/sys/procctl.2
@@ -0,0 +1,142 @@
+.\" Copyright (c) 2013 Advanced Computing Technologies LLC
+.\" Written by: John H. Baldwin <jhb@FreeBSD.org>
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd September 19, 2013
+.Dt PROCCTL 2
+.Os
+.Sh NAME
+.Nm procctl
+.Nd control processes
+.Sh LIBRARY
+.Lb libc
+.Sh SYNOPSIS
+.In sys/procctl.h
+.Ft int
+.Fn procctl "idtype_t idtype" "id_t id" "int cmd" "void *arg"
+.Sh DESCRIPTION
+The
+.Fn procctl
+system call provides for control over processes.
+The
+.Fa idtype
+and
+.Fa id
+arguments specify the set of processes to control.
+If multiple processes match the identifier,
+.Nm
+will make a
+.Dq best effort
+to control as many of the selected possibles as possible.
+An error is only returned if no selected processes successfully complete
+the request.
+The following identifier types are supported:
+.Bl -tag -width Dv P_PGID
+.It Dv P_PID
+Control the process with the process ID
+.Fa id .
+.It Dv P_PGID
+Control processes belonging to the process group with the ID
+.Fa id .
+.El
+.Pp
+The control request to perform is specified by the
+.Fa cmd
+argument.
+The following commands are supported:
+.Bl -tag -width Dv PROC_SPROTECT
+.It Dv PROC_SPROTECT
+Set process protection state.
+This is used to mark a process as protected from being killed if the system
+exhausts available memory and swap.
+The
+.Fa arg
+parameter must point to an integer containing an operation and zero or more
+optional flags.
+The following operations are supported:
+.Bl -tag -width Dv PPROT_CLEAR
+.It Dv PPROT_SET
+Mark the selected processes as protected.
+.It Dv PPROT_CLEAR
+Clear the protected state of selected processes.
+.El
+.Pp
+The following optional flags are supported:
+.Bl -tag -width Dv PPROT_DESCEND
+.It Dv PPROT_DESCEND
+Apply the requested operation to all child processes of each selected process
+in addition to each selected process.
+.It Dv PPROT_INHERIT
+When used with
+.Dv PPROT_SET ,
+mark all future child processes of each selected process as protected.
+Future child processes will also mark all of their future child processes.
+.El
+.El
+.Sh RETURN VALUES
+If an error occurs, a value of -1 is returned and
+.Va errno
+is set to indicate the error.
+.Sh ERRORS
+The
+.Fn procctl
+system call
+will fail if:
+.Bl -tag -width Er
+.It Bq Er EFAULT
+The
+.Fa arg
+points outside the process's allocated address space.
+.It Bq Er EINVAL
+The
+.Fa cmd
+argument specifies an unsupported command.
+.Pp
+The
+.Fa idtype
+argument specifies an unsupported identifier type.
+.It Bq Er EPERM
+The calling process does not have permission to perform the requested
+operation on any of the selected processes.
+.It Bq Er ESRCH
+No processes matched the requested
+.Fa idtype
+and
+.Fa id .
+.It Bq Er EINVAL
+An invalid operation or flag was passed in
+.Fa arg
+for a
+.Dv PROC_SPROTECT
+command.
+.El
+.Sh SEE ALSO
+.Xr ptrace 2
+.Sh HISTORY
+The
+.Fn procctl
+function appeared in
+.Fx 10 .