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2 .\" Written by: John H. Baldwin <jhb@FreeBSD.org>
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6 .\" Portions of this documentation were written by Konstantin Belousov
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43 .Fn procctl "idtype_t idtype" "id_t id" "int cmd" "void *arg"
47 system call provides for control over processes.
52 arguments specify the set of processes to control.
53 If multiple processes match the identifier,
57 to control as many of the selected processes as possible.
58 An error is only returned if no selected processes successfully complete
60 The following identifier types are supported:
61 .Bl -tag -width "Dv P_PGID"
63 Control the process with the process ID
66 Control processes belonging to the process group with the ID
70 The control request to perform is specified by the
73 The following commands are supported:
74 .Bl -tag -width "PROC_REAP_GETPIDS"
76 Set process protection state.
77 This is used to mark a process as protected from being killed if the system
78 exhausts the available memory and swap.
81 parameter must point to an integer containing an operation and zero or more
83 The following operations are supported:
84 .Bl -tag -width "Dv PPROT_CLEAR"
86 Mark the selected processes as protected.
88 Clear the protected state of selected processes.
91 The following optional flags are supported:
92 .Bl -tag -width "Dv PPROT_DESCEND"
94 Apply the requested operation to all child processes of each selected process
95 in addition to each selected process.
99 mark all future child processes of each selected process as protected.
100 Future child processes will also mark all of their future child processes.
102 .It Dv PROC_REAP_ACQUIRE
103 Acquires the reaper status for the current process.
104 Reaper status means that children orphaned by the reaper's descendants
105 that were forked after the acquisition of reaper status are reparented to the
107 After system initialization,
109 is the default reaper.
110 .It Dv PROC_REAP_RELEASE
111 Release the reaper state for the current process.
112 The reaper of the current process becomes the new reaper of the
113 current process's descendants.
114 .It Dv PROC_REAP_STATUS
115 Provides information about the reaper of the specified process,
116 or the process itself when it is a reaper.
119 argument must point to a
120 .Vt procctl_reaper_status
121 structure which is filled in by the syscall on successful return.
123 struct procctl_reaper_status {
126 u_int rs_descendants;
133 may have the following flags returned:
134 .Bl -tag -width "Dv REAPER_STATUS_REALINIT"
135 .It Dv REAPER_STATUS_OWNED
136 The specified process has acquired reaper status and has not
138 When the flag is returned, the specified process
140 pid, identifies the reaper, otherwise the
142 field of the structure is set to the pid of the reaper
143 for the specified process id.
144 .It Dv REAPER_STATUS_REALINIT
145 The specified process is the root of the reaper tree, i.e.,
151 field returns the number of children of the reaper among the descendants.
152 It is possible to have a child whose reaper is not the specified process,
153 since the reaper for any existing children is not reset on the
154 .Dv PROC_REAP_ACQUIRE
158 field returns the total number of descendants of the reaper(s),
159 not counting descendants of the reaper in the subtree.
162 field returns the reaper pid.
165 returns the pid of one reaper child if there are any descendants.
166 .It Dv PROC_REAP_GETPIDS
167 Queries the list of descendants of the reaper of the specified process.
168 The request takes a pointer to a
169 .Vt procctl_reaper_pids
174 struct procctl_reaper_pids {
176 struct procctl_reaper_pidinfo *rp_pids;
181 field must point to an array of
182 .Vt procctl_reaper_pidinfo
183 structures, to be filled in on return,
186 field must specify the size of the array,
187 into which no more than
189 elements will be filled in by the kernel.
192 .Vt "struct procctl_reaper_pidinfo"
193 structure provides some information about one of the reaper's descendants.
194 Note that for a descendant that is not a child, it may be incorrectly
195 identified because of a race in which the original child process exited
196 and the exited process's pid was reused for an unrelated process.
198 struct procctl_reaper_pidinfo {
206 field is the process id of the descendant.
209 field provides the pid of the child of the reaper, which is the (grand-)parent
213 field returns the following flags, further describing the descendant:
214 .Bl -tag -width "Dv REAPER_PIDINFO_VALID"
215 .It Dv REAPER_PIDINFO_VALID
216 Set to indicate that the
217 .Vt procctl_reaper_pidinfo
218 structure was filled in by the kernel.
221 array and testing the
222 .Dv REAPER_PIDINFO_VALID
223 flag allows the caller to detect the end
224 of the returned array.
225 .It Dv REAPER_PIDINFO_CHILD
228 field identifies the direct child of the reaper.
230 .It Dv PROC_REAP_KILL
231 Request to deliver a signal to some subset of the descendants of the reaper.
234 parameter must point to a
235 .Vt procctl_reaper_kill
236 structure, which is used both for parameters and status return.
238 struct procctl_reaper_kill {
248 field specifies the signal to be delivered.
249 Zero is not a valid signal number, unlike for
253 field further directs the operation.
254 It is or-ed from the following flags:
255 .Bl -tag -width "Dv REAPER_KILL_CHILDREN"
256 .It Dv REAPER_KILL_CHILDREN
257 Deliver the specified signal only to direct children of the reaper.
258 .It Dv REAPER_KILL_SUBTREE
259 Deliver the specified signal only to descendants that were forked by
260 the direct child with pid specified in the
265 .Dv REAPER_KILL_CHILDREN
267 .Dv REAPER_KILL_SUBTREE
268 flags are specified, all current descendants of the reaper are signalled.
270 If a signal was delivered to any process, the return value from the request
274 field identifies the number of processes signalled.
277 field is set to the pid of the first process for which signal
278 delivery failed, e.g., due to permission problems.
279 If no such process exists, the
282 .It Dv PROC_TRACE_CTL
283 Enable or disable tracing of the specified process(es), according to the
284 value of the integer argument.
285 Tracing includes attachment to the process using the
293 Possible values for the
296 .Bl -tag -width "Dv PROC_TRACE_CTL_DISABLE_EXEC"
297 .It Dv PROC_TRACE_CTL_ENABLE
298 Enable tracing, after it was disabled by
299 .Dv PROC_TRACE_CTL_DISABLE .
300 Only allowed for self.
301 .It Dv PROC_TRACE_CTL_DISABLE
302 Disable tracing for the specified process.
303 Tracing is re-enabled when the process changes the executing
307 A child inherits the trace settings from the parent on
309 .It Dv PROC_TRACE_CTL_DISABLE_EXEC
311 .Dv PROC_TRACE_CTL_DISABLE ,
312 but the setting persists for the process even after
315 .It Dv PROC_TRACE_STATUS
316 Returns the current tracing status for the specified process in
317 the integer variable pointed to by
319 If tracing is disabled,
322 If tracing is enabled, but no debugger is attached by the
327 If a debugger is attached,
329 is set to the pid of the debugger process.
332 Disabling tracing on a process should not be considered a security
333 feature, as it is bypassable both by the kernel and privileged processes,
334 and via other system mechanisms.
335 As such, it should not be utilized to reliably protect cryptographic
336 keying material or other confidential data.
338 If an error occurs, a value of -1 is returned and
340 is set to indicate the error.
350 parameter points outside the process's allocated address space.
354 argument specifies an unsupported command.
358 argument specifies an unsupported identifier type.
360 The calling process does not have permission to perform the requested
361 operation on any of the selected processes.
363 No processes matched the requested
368 An invalid operation or flag was passed in
376 argument is not equal to
380 is not equal to the pid of the calling process, for
381 .Dv PROC_REAP_ACQUIRE
383 .Dv PROC_REAP_RELEASE
386 Invalid or undefined flags were passed to a
390 An invalid or zero signal number was requested for a
395 .Dv PROC_REAP_RELEASE
396 request was issued by the
401 .Dv PROC_REAP_ACQUIRE
402 request was issued by a process that had already acquired reaper status
403 and has not yet released it.
407 request was issued for a process already being traced.
411 request to re-enable tracing of the process
412 .Po Dv PROC_TRACE_CTL_ENABLE Pc ,
413 or to disable persistence of
414 .Dv PROC_TRACE_CTL_DISABLE
417 was issued for a non-current process.
419 The value of the integer
438 The reaper facility is based on a similar feature of Linux and
439 DragonflyBSD, and first appeared in