2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California.
4 * Copyright (c) 2005 Robert N. M. Watson
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 4. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * @(#)kern_ktrace.c 8.2 (Berkeley) 9/23/93
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
37 #include "opt_ktrace.h"
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/fcntl.h>
43 #include <sys/kernel.h>
44 #include <sys/kthread.h>
46 #include <sys/mutex.h>
47 #include <sys/malloc.h>
48 #include <sys/mount.h>
49 #include <sys/namei.h>
52 #include <sys/unistd.h>
53 #include <sys/vnode.h>
54 #include <sys/socket.h>
56 #include <sys/ktrace.h>
58 #include <sys/sysctl.h>
59 #include <sys/syslog.h>
60 #include <sys/sysproto.h>
62 #include <security/mac/mac_framework.h>
65 * The ktrace facility allows the tracing of certain key events in user space
66 * processes, such as system calls, signal delivery, context switches, and
67 * user generated events using utrace(2). It works by streaming event
68 * records and data to a vnode associated with the process using the
69 * ktrace(2) system call. In general, records can be written directly from
70 * the context that generates the event. One important exception to this is
71 * during a context switch, where sleeping is not permitted. To handle this
72 * case, trace events are generated using in-kernel ktr_request records, and
73 * then delivered to disk at a convenient moment -- either immediately, the
74 * next traceable event, at system call return, or at process exit.
76 * When dealing with multiple threads or processes writing to the same event
77 * log, ordering guarantees are weak: specifically, if an event has multiple
78 * records (i.e., system call enter and return), they may be interlaced with
79 * records from another event. Process and thread ID information is provided
80 * in the record, and user applications can de-interlace events if required.
83 static MALLOC_DEFINE(M_KTRACE, "KTRACE", "KTRACE");
87 #ifndef KTRACE_REQUEST_POOL
88 #define KTRACE_REQUEST_POOL 100
92 struct ktr_header ktr_header;
95 struct ktr_syscall ktr_syscall;
96 struct ktr_sysret ktr_sysret;
97 struct ktr_genio ktr_genio;
98 struct ktr_psig ktr_psig;
99 struct ktr_csw ktr_csw;
101 STAILQ_ENTRY(ktr_request) ktr_list;
104 static int data_lengths[] = {
106 offsetof(struct ktr_syscall, ktr_args), /* KTR_SYSCALL */
107 sizeof(struct ktr_sysret), /* KTR_SYSRET */
109 sizeof(struct ktr_genio), /* KTR_GENIO */
110 sizeof(struct ktr_psig), /* KTR_PSIG */
111 sizeof(struct ktr_csw), /* KTR_CSW */
116 static STAILQ_HEAD(, ktr_request) ktr_free;
118 static SYSCTL_NODE(_kern, OID_AUTO, ktrace, CTLFLAG_RD, 0, "KTRACE options");
120 static u_int ktr_requestpool = KTRACE_REQUEST_POOL;
121 TUNABLE_INT("kern.ktrace.request_pool", &ktr_requestpool);
123 static u_int ktr_geniosize = PAGE_SIZE;
124 TUNABLE_INT("kern.ktrace.genio_size", &ktr_geniosize);
125 SYSCTL_UINT(_kern_ktrace, OID_AUTO, genio_size, CTLFLAG_RW, &ktr_geniosize,
126 0, "Maximum size of genio event payload");
128 static int print_message = 1;
129 struct mtx ktrace_mtx;
130 static struct sx ktrace_sx;
132 static void ktrace_init(void *dummy);
133 static int sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS);
134 static u_int ktrace_resize_pool(u_int newsize);
135 static struct ktr_request *ktr_getrequest(int type);
136 static void ktr_submitrequest(struct thread *td, struct ktr_request *req);
137 static void ktr_freerequest(struct ktr_request *req);
138 static void ktr_writerequest(struct thread *td, struct ktr_request *req);
139 static int ktrcanset(struct thread *,struct proc *);
140 static int ktrsetchildren(struct thread *,struct proc *,int,int,struct vnode *);
141 static int ktrops(struct thread *,struct proc *,int,int,struct vnode *);
144 * ktrace itself generates events, such as context switches, which we do not
145 * wish to trace. Maintain a flag, TDP_INKTRACE, on each thread to determine
146 * whether or not it is in a region where tracing of events should be
150 ktrace_enter(struct thread *td)
153 KASSERT(!(td->td_pflags & TDP_INKTRACE), ("ktrace_enter: flag set"));
154 td->td_pflags |= TDP_INKTRACE;
158 ktrace_exit(struct thread *td)
161 KASSERT(td->td_pflags & TDP_INKTRACE, ("ktrace_exit: flag not set"));
162 td->td_pflags &= ~TDP_INKTRACE;
166 ktrace_assert(struct thread *td)
169 KASSERT(td->td_pflags & TDP_INKTRACE, ("ktrace_assert: flag not set"));
173 ktrace_init(void *dummy)
175 struct ktr_request *req;
178 mtx_init(&ktrace_mtx, "ktrace", NULL, MTX_DEF | MTX_QUIET);
179 sx_init(&ktrace_sx, "ktrace_sx");
180 STAILQ_INIT(&ktr_free);
181 for (i = 0; i < ktr_requestpool; i++) {
182 req = malloc(sizeof(struct ktr_request), M_KTRACE, M_WAITOK);
183 STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
186 SYSINIT(ktrace_init, SI_SUB_KTRACE, SI_ORDER_ANY, ktrace_init, NULL);
189 sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS)
192 u_int newsize, oldsize, wantsize;
195 /* Handle easy read-only case first to avoid warnings from GCC. */
197 mtx_lock(&ktrace_mtx);
198 oldsize = ktr_requestpool;
199 mtx_unlock(&ktrace_mtx);
200 return (SYSCTL_OUT(req, &oldsize, sizeof(u_int)));
203 error = SYSCTL_IN(req, &wantsize, sizeof(u_int));
208 mtx_lock(&ktrace_mtx);
209 oldsize = ktr_requestpool;
210 newsize = ktrace_resize_pool(wantsize);
211 mtx_unlock(&ktrace_mtx);
213 error = SYSCTL_OUT(req, &oldsize, sizeof(u_int));
216 if (wantsize > oldsize && newsize < wantsize)
220 SYSCTL_PROC(_kern_ktrace, OID_AUTO, request_pool, CTLTYPE_UINT|CTLFLAG_RW,
221 &ktr_requestpool, 0, sysctl_kern_ktrace_request_pool, "IU", "");
224 ktrace_resize_pool(u_int newsize)
226 struct ktr_request *req;
229 mtx_assert(&ktrace_mtx, MA_OWNED);
231 bound = newsize - ktr_requestpool;
233 return (ktr_requestpool);
235 /* Shrink pool down to newsize if possible. */
236 while (bound++ < 0) {
237 req = STAILQ_FIRST(&ktr_free);
239 return (ktr_requestpool);
240 STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
242 mtx_unlock(&ktrace_mtx);
244 mtx_lock(&ktrace_mtx);
247 /* Grow pool up to newsize. */
248 while (bound-- > 0) {
249 mtx_unlock(&ktrace_mtx);
250 req = malloc(sizeof(struct ktr_request), M_KTRACE,
252 mtx_lock(&ktrace_mtx);
253 STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
256 return (ktr_requestpool);
259 static struct ktr_request *
260 ktr_getrequest(int type)
262 struct ktr_request *req;
263 struct thread *td = curthread;
264 struct proc *p = td->td_proc;
267 ktrace_enter(td); /* XXX: In caller instead? */
268 mtx_lock(&ktrace_mtx);
269 if (!KTRCHECK(td, type)) {
270 mtx_unlock(&ktrace_mtx);
274 req = STAILQ_FIRST(&ktr_free);
276 STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
277 req->ktr_header.ktr_type = type;
278 if (p->p_traceflag & KTRFAC_DROP) {
279 req->ktr_header.ktr_type |= KTR_DROP;
280 p->p_traceflag &= ~KTRFAC_DROP;
282 mtx_unlock(&ktrace_mtx);
283 microtime(&req->ktr_header.ktr_time);
284 req->ktr_header.ktr_pid = p->p_pid;
285 req->ktr_header.ktr_tid = td->td_tid;
286 bcopy(p->p_comm, req->ktr_header.ktr_comm, MAXCOMLEN + 1);
287 req->ktr_buffer = NULL;
288 req->ktr_header.ktr_len = 0;
290 p->p_traceflag |= KTRFAC_DROP;
293 mtx_unlock(&ktrace_mtx);
295 printf("Out of ktrace request objects.\n");
302 * Some trace generation environments don't permit direct access to VFS,
303 * such as during a context switch where sleeping is not allowed. Under these
304 * circumstances, queue a request to the thread to be written asynchronously
308 ktr_enqueuerequest(struct thread *td, struct ktr_request *req)
311 mtx_lock(&ktrace_mtx);
312 STAILQ_INSERT_TAIL(&td->td_proc->p_ktr, req, ktr_list);
313 mtx_unlock(&ktrace_mtx);
318 * Drain any pending ktrace records from the per-thread queue to disk. This
319 * is used both internally before committing other records, and also on
320 * system call return. We drain all the ones we can find at the time when
321 * drain is requested, but don't keep draining after that as those events
322 * may me approximately "after" the current event.
325 ktr_drain(struct thread *td)
327 struct ktr_request *queued_req;
328 STAILQ_HEAD(, ktr_request) local_queue;
331 sx_assert(&ktrace_sx, SX_XLOCKED);
333 STAILQ_INIT(&local_queue); /* XXXRW: needed? */
335 if (!STAILQ_EMPTY(&td->td_proc->p_ktr)) {
336 mtx_lock(&ktrace_mtx);
337 STAILQ_CONCAT(&local_queue, &td->td_proc->p_ktr);
338 mtx_unlock(&ktrace_mtx);
340 while ((queued_req = STAILQ_FIRST(&local_queue))) {
341 STAILQ_REMOVE_HEAD(&local_queue, ktr_list);
342 ktr_writerequest(td, queued_req);
343 ktr_freerequest(queued_req);
349 * Submit a trace record for immediate commit to disk -- to be used only
350 * where entering VFS is OK. First drain any pending records that may have
351 * been cached in the thread.
354 ktr_submitrequest(struct thread *td, struct ktr_request *req)
359 sx_xlock(&ktrace_sx);
361 ktr_writerequest(td, req);
362 ktr_freerequest(req);
363 sx_xunlock(&ktrace_sx);
369 ktr_freerequest(struct ktr_request *req)
372 if (req->ktr_buffer != NULL)
373 free(req->ktr_buffer, M_KTRACE);
374 mtx_lock(&ktrace_mtx);
375 STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
376 mtx_unlock(&ktrace_mtx);
380 ktrsyscall(code, narg, args)
384 struct ktr_request *req;
385 struct ktr_syscall *ktp;
389 buflen = sizeof(register_t) * narg;
391 buf = malloc(buflen, M_KTRACE, M_WAITOK);
392 bcopy(args, buf, buflen);
394 req = ktr_getrequest(KTR_SYSCALL);
400 ktp = &req->ktr_data.ktr_syscall;
401 ktp->ktr_code = code;
402 ktp->ktr_narg = narg;
404 req->ktr_header.ktr_len = buflen;
405 req->ktr_buffer = buf;
407 ktr_submitrequest(curthread, req);
411 ktrsysret(code, error, retval)
415 struct ktr_request *req;
416 struct ktr_sysret *ktp;
418 req = ktr_getrequest(KTR_SYSRET);
421 ktp = &req->ktr_data.ktr_sysret;
422 ktp->ktr_code = code;
423 ktp->ktr_error = error;
424 ktp->ktr_retval = retval; /* what about val2 ? */
425 ktr_submitrequest(curthread, req);
429 * When a process exits, drain per-process asynchronous trace records.
432 ktrprocexit(struct thread *td)
436 sx_xlock(&ktrace_sx);
438 sx_xunlock(&ktrace_sx);
443 * When a thread returns, drain any asynchronous records generated by the
447 ktruserret(struct thread *td)
451 sx_xlock(&ktrace_sx);
453 sx_xunlock(&ktrace_sx);
461 struct ktr_request *req;
465 namelen = strlen(path);
467 buf = malloc(namelen, M_KTRACE, M_WAITOK);
468 bcopy(path, buf, namelen);
470 req = ktr_getrequest(KTR_NAMEI);
477 req->ktr_header.ktr_len = namelen;
478 req->ktr_buffer = buf;
480 ktr_submitrequest(curthread, req);
484 ktrgenio(fd, rw, uio, error)
490 struct ktr_request *req;
491 struct ktr_genio *ktg;
500 uio->uio_rw = UIO_WRITE;
501 datalen = imin(uio->uio_resid, ktr_geniosize);
502 buf = malloc(datalen, M_KTRACE, M_WAITOK);
503 error = uiomove(buf, datalen, uio);
509 req = ktr_getrequest(KTR_GENIO);
514 ktg = &req->ktr_data.ktr_genio;
517 req->ktr_header.ktr_len = datalen;
518 req->ktr_buffer = buf;
519 ktr_submitrequest(curthread, req);
523 ktrpsig(sig, action, mask, code)
529 struct ktr_request *req;
532 req = ktr_getrequest(KTR_PSIG);
535 kp = &req->ktr_data.ktr_psig;
536 kp->signo = (char)sig;
540 ktr_enqueuerequest(curthread, req);
547 struct ktr_request *req;
550 req = ktr_getrequest(KTR_CSW);
553 kc = &req->ktr_data.ktr_csw;
556 ktr_enqueuerequest(curthread, req);
560 ktrstruct(name, namelen, data, datalen)
566 struct ktr_request *req;
572 buflen = namelen + 1 + datalen;
573 buf = malloc(buflen, M_KTRACE, M_WAITOK);
574 bcopy(name, buf, namelen);
576 bcopy(data, buf + namelen + 1, datalen);
577 if ((req = ktr_getrequest(KTR_STRUCT)) == NULL) {
581 req->ktr_buffer = buf;
582 req->ktr_header.ktr_len = buflen;
583 ktr_submitrequest(curthread, req);
587 /* Interface and common routines */
589 #ifndef _SYS_SYSPROTO_H_
601 register struct ktrace_args *uap;
604 register struct vnode *vp = NULL;
605 register struct proc *p;
607 int facs = uap->facs & ~KTRFAC_ROOT;
608 int ops = KTROP(uap->ops);
609 int descend = uap->ops & KTRFLAG_DESCEND;
611 int flags, error = 0, vfslocked;
616 * Need something to (un)trace.
618 if (ops != KTROP_CLEARFILE && facs == 0)
622 if (ops != KTROP_CLEAR) {
624 * an operation which requires a file argument.
626 NDINIT(&nd, LOOKUP, NOFOLLOW | MPSAFE, UIO_USERSPACE,
628 flags = FREAD | FWRITE | O_NOFOLLOW;
629 error = vn_open(&nd, &flags, 0, NULL);
634 vfslocked = NDHASGIANT(&nd);
635 NDFREE(&nd, NDF_ONLY_PNBUF);
637 VOP_UNLOCK(vp, 0, td);
638 if (vp->v_type != VREG) {
639 (void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
640 VFS_UNLOCK_GIANT(vfslocked);
644 VFS_UNLOCK_GIANT(vfslocked);
647 * Clear all uses of the tracefile.
649 if (ops == KTROP_CLEARFILE) {
653 sx_slock(&allproc_lock);
654 FOREACH_PROC_IN_SYSTEM(p) {
656 if (p->p_tracevp == vp) {
657 if (ktrcanset(td, p)) {
658 mtx_lock(&ktrace_mtx);
659 cred = p->p_tracecred;
660 p->p_tracecred = NULL;
663 mtx_unlock(&ktrace_mtx);
671 sx_sunlock(&allproc_lock);
672 if (vrele_count > 0) {
673 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
674 while (vrele_count-- > 0)
676 VFS_UNLOCK_GIANT(vfslocked);
683 sx_slock(&proctree_lock);
688 pg = pgfind(-uap->pid);
690 sx_sunlock(&proctree_lock);
695 * ktrops() may call vrele(). Lock pg_members
696 * by the proctree_lock rather than pg_mtx.
700 LIST_FOREACH(p, &pg->pg_members, p_pglist) {
702 if (p_cansee(td, p) != 0) {
709 ret |= ktrsetchildren(td, p, ops, facs, vp);
711 ret |= ktrops(td, p, ops, facs, vp);
714 sx_sunlock(&proctree_lock);
724 sx_sunlock(&proctree_lock);
728 error = p_cansee(td, p);
730 * The slock of the proctree lock will keep this process
731 * from going away, so unlocking the proc here is ok.
735 sx_sunlock(&proctree_lock);
739 ret |= ktrsetchildren(td, p, ops, facs, vp);
741 ret |= ktrops(td, p, ops, facs, vp);
743 sx_sunlock(&proctree_lock);
748 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
749 (void) vn_close(vp, FWRITE, td->td_ucred, td);
750 VFS_UNLOCK_GIANT(vfslocked);
763 register struct utrace_args *uap;
767 struct ktr_request *req;
771 if (!KTRPOINT(td, KTR_USER))
773 if (uap->len > KTR_USER_MAXLEN)
775 cp = malloc(uap->len, M_KTRACE, M_WAITOK);
776 error = copyin(uap->addr, cp, uap->len);
781 req = ktr_getrequest(KTR_USER);
786 req->ktr_buffer = cp;
787 req->ktr_header.ktr_len = uap->len;
788 ktr_submitrequest(td, req);
797 ktrops(td, p, ops, facs, vp)
803 struct vnode *tracevp = NULL;
804 struct ucred *tracecred = NULL;
807 if (!ktrcanset(td, p)) {
811 mtx_lock(&ktrace_mtx);
812 if (ops == KTROP_SET) {
813 if (p->p_tracevp != vp) {
815 * if trace file already in use, relinquish below
817 tracevp = p->p_tracevp;
821 if (p->p_tracecred != td->td_ucred) {
822 tracecred = p->p_tracecred;
823 p->p_tracecred = crhold(td->td_ucred);
825 p->p_traceflag |= facs;
826 if (priv_check(td, PRIV_KTRACE) == 0)
827 p->p_traceflag |= KTRFAC_ROOT;
830 if (((p->p_traceflag &= ~facs) & KTRFAC_MASK) == 0) {
831 /* no more tracing */
833 tracevp = p->p_tracevp;
835 tracecred = p->p_tracecred;
836 p->p_tracecred = NULL;
839 mtx_unlock(&ktrace_mtx);
841 if (tracevp != NULL) {
844 vfslocked = VFS_LOCK_GIANT(tracevp->v_mount);
846 VFS_UNLOCK_GIANT(vfslocked);
848 if (tracecred != NULL)
855 ktrsetchildren(td, top, ops, facs, vp)
861 register struct proc *p;
862 register int ret = 0;
865 sx_assert(&proctree_lock, SX_LOCKED);
867 ret |= ktrops(td, p, ops, facs, vp);
869 * If this process has children, descend to them next,
870 * otherwise do any siblings, and if done with this level,
871 * follow back up the tree (but not past top).
873 if (!LIST_EMPTY(&p->p_children))
874 p = LIST_FIRST(&p->p_children);
878 if (LIST_NEXT(p, p_sibling)) {
879 p = LIST_NEXT(p, p_sibling);
889 ktr_writerequest(struct thread *td, struct ktr_request *req)
891 struct ktr_header *kth;
896 struct iovec aiov[3];
898 int datalen, buflen, vrele_count;
899 int error, vfslocked;
902 * We hold the vnode and credential for use in I/O in case ktrace is
903 * disabled on the process as we write out the request.
905 * XXXRW: This is not ideal: we could end up performing a write after
906 * the vnode has been closed.
908 mtx_lock(&ktrace_mtx);
909 vp = td->td_proc->p_tracevp;
910 cred = td->td_proc->p_tracecred;
913 * If vp is NULL, the vp has been cleared out from under this
914 * request, so just drop it. Make sure the credential and vnode are
915 * in sync: we should have both or neither.
918 KASSERT(cred == NULL, ("ktr_writerequest: cred != NULL"));
919 mtx_unlock(&ktrace_mtx);
923 KASSERT(cred != NULL, ("ktr_writerequest: cred == NULL"));
925 mtx_unlock(&ktrace_mtx);
927 kth = &req->ktr_header;
928 datalen = data_lengths[(u_short)kth->ktr_type & ~KTR_DROP];
929 buflen = kth->ktr_len;
930 auio.uio_iov = &aiov[0];
932 auio.uio_segflg = UIO_SYSSPACE;
933 auio.uio_rw = UIO_WRITE;
934 aiov[0].iov_base = (caddr_t)kth;
935 aiov[0].iov_len = sizeof(struct ktr_header);
936 auio.uio_resid = sizeof(struct ktr_header);
940 aiov[1].iov_base = (caddr_t)&req->ktr_data;
941 aiov[1].iov_len = datalen;
942 auio.uio_resid += datalen;
944 kth->ktr_len += datalen;
947 KASSERT(req->ktr_buffer != NULL, ("ktrace: nothing to write"));
948 aiov[auio.uio_iovcnt].iov_base = req->ktr_buffer;
949 aiov[auio.uio_iovcnt].iov_len = buflen;
950 auio.uio_resid += buflen;
954 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
955 vn_start_write(vp, &mp, V_WAIT);
956 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
957 (void)VOP_LEASE(vp, td, cred, LEASE_WRITE);
959 error = mac_check_vnode_write(cred, NOCRED, vp);
962 error = VOP_WRITE(vp, &auio, IO_UNIT | IO_APPEND, cred);
963 VOP_UNLOCK(vp, 0, td);
964 vn_finished_write(mp);
968 VFS_UNLOCK_GIANT(vfslocked);
971 VFS_UNLOCK_GIANT(vfslocked);
974 * If error encountered, give up tracing on this vnode. We defer
975 * all the vrele()'s on the vnode until after we are finished walking
976 * the various lists to avoid needlessly holding locks.
977 * NB: at this point we still hold the vnode reference that must
978 * not go away as we need the valid vnode to compare with. Thus let
979 * vrele_count start at 1 and the reference will be freed
980 * by the loop at the end after our last use of vp.
982 log(LOG_NOTICE, "ktrace write failed, errno %d, tracing stopped\n",
986 * First, clear this vnode from being used by any processes in the
988 * XXX - If one process gets an EPERM writing to the vnode, should
989 * we really do this? Other processes might have suitable
990 * credentials for the operation.
993 sx_slock(&allproc_lock);
994 FOREACH_PROC_IN_SYSTEM(p) {
996 if (p->p_tracevp == vp) {
997 mtx_lock(&ktrace_mtx);
1000 cred = p->p_tracecred;
1001 p->p_tracecred = NULL;
1002 mtx_unlock(&ktrace_mtx);
1011 sx_sunlock(&allproc_lock);
1014 * We can't clear any pending requests in threads that have cached
1015 * them but not yet committed them, as those are per-thread. The
1016 * thread will have to clear it itself on system call return.
1018 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
1019 while (vrele_count-- > 0)
1021 VFS_UNLOCK_GIANT(vfslocked);
1025 * Return true if caller has permission to set the ktracing state
1026 * of target. Essentially, the target can't possess any
1027 * more permissions than the caller. KTRFAC_ROOT signifies that
1028 * root previously set the tracing status on the target process, and
1029 * so, only root may further change it.
1032 ktrcanset(td, targetp)
1034 struct proc *targetp;
1037 PROC_LOCK_ASSERT(targetp, MA_OWNED);
1038 if (targetp->p_traceflag & KTRFAC_ROOT &&
1039 priv_check(td, PRIV_KTRACE))
1042 if (p_candebug(td, targetp) != 0)