The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_ktrace.c

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    1 /*-
    2  * Copyright (c) 1989, 1993
    3  *      The Regents of the University of California.
    4  * Copyright (c) 2005 Robert N. M. Watson
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   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.
   18  *
   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
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)kern_ktrace.c       8.2 (Berkeley) 9/23/93
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: stable/10/sys/kern/kern_ktrace.c 315562 2017-03-19 15:56:06Z kib $");
   36 
   37 #include "opt_ktrace.h"
   38 
   39 #include <sys/param.h>
   40 #include <sys/capsicum.h>
   41 #include <sys/systm.h>
   42 #include <sys/fcntl.h>
   43 #include <sys/kernel.h>
   44 #include <sys/kthread.h>
   45 #include <sys/lock.h>
   46 #include <sys/mutex.h>
   47 #include <sys/malloc.h>
   48 #include <sys/mount.h>
   49 #include <sys/namei.h>
   50 #include <sys/priv.h>
   51 #include <sys/proc.h>
   52 #include <sys/unistd.h>
   53 #include <sys/vnode.h>
   54 #include <sys/socket.h>
   55 #include <sys/stat.h>
   56 #include <sys/ktrace.h>
   57 #include <sys/sx.h>
   58 #include <sys/sysctl.h>
   59 #include <sys/sysent.h>
   60 #include <sys/syslog.h>
   61 #include <sys/sysproto.h>
   62 
   63 #include <security/mac/mac_framework.h>
   64 
   65 /*
   66  * The ktrace facility allows the tracing of certain key events in user space
   67  * processes, such as system calls, signal delivery, context switches, and
   68  * user generated events using utrace(2).  It works by streaming event
   69  * records and data to a vnode associated with the process using the
   70  * ktrace(2) system call.  In general, records can be written directly from
   71  * the context that generates the event.  One important exception to this is
   72  * during a context switch, where sleeping is not permitted.  To handle this
   73  * case, trace events are generated using in-kernel ktr_request records, and
   74  * then delivered to disk at a convenient moment -- either immediately, the
   75  * next traceable event, at system call return, or at process exit.
   76  *
   77  * When dealing with multiple threads or processes writing to the same event
   78  * log, ordering guarantees are weak: specifically, if an event has multiple
   79  * records (i.e., system call enter and return), they may be interlaced with
   80  * records from another event.  Process and thread ID information is provided
   81  * in the record, and user applications can de-interlace events if required.
   82  */
   83 
   84 static MALLOC_DEFINE(M_KTRACE, "KTRACE", "KTRACE");
   85 
   86 #ifdef KTRACE
   87 
   88 FEATURE(ktrace, "Kernel support for system-call tracing");
   89 
   90 #ifndef KTRACE_REQUEST_POOL
   91 #define KTRACE_REQUEST_POOL     100
   92 #endif
   93 
   94 struct ktr_request {
   95         struct  ktr_header ktr_header;
   96         void    *ktr_buffer;
   97         union {
   98                 struct  ktr_proc_ctor ktr_proc_ctor;
   99                 struct  ktr_cap_fail ktr_cap_fail;
  100                 struct  ktr_syscall ktr_syscall;
  101                 struct  ktr_sysret ktr_sysret;
  102                 struct  ktr_genio ktr_genio;
  103                 struct  ktr_psig ktr_psig;
  104                 struct  ktr_csw ktr_csw;
  105                 struct  ktr_fault ktr_fault;
  106                 struct  ktr_faultend ktr_faultend;
  107         } ktr_data;
  108         STAILQ_ENTRY(ktr_request) ktr_list;
  109 };
  110 
  111 static int data_lengths[] = {
  112         [KTR_SYSCALL] = offsetof(struct ktr_syscall, ktr_args),
  113         [KTR_SYSRET] = sizeof(struct ktr_sysret),
  114         [KTR_NAMEI] = 0,
  115         [KTR_GENIO] = sizeof(struct ktr_genio),
  116         [KTR_PSIG] = sizeof(struct ktr_psig),
  117         [KTR_CSW] = sizeof(struct ktr_csw),
  118         [KTR_USER] = 0,
  119         [KTR_STRUCT] = 0,
  120         [KTR_SYSCTL] = 0,
  121         [KTR_PROCCTOR] = sizeof(struct ktr_proc_ctor),
  122         [KTR_PROCDTOR] = 0,
  123         [KTR_CAPFAIL] = sizeof(struct ktr_cap_fail),
  124         [KTR_FAULT] = sizeof(struct ktr_fault),
  125         [KTR_FAULTEND] = sizeof(struct ktr_faultend),
  126 };
  127 
  128 static STAILQ_HEAD(, ktr_request) ktr_free;
  129 
  130 static SYSCTL_NODE(_kern, OID_AUTO, ktrace, CTLFLAG_RD, 0, "KTRACE options");
  131 
  132 static u_int ktr_requestpool = KTRACE_REQUEST_POOL;
  133 TUNABLE_INT("kern.ktrace.request_pool", &ktr_requestpool);
  134 
  135 u_int ktr_geniosize = PAGE_SIZE;
  136 TUNABLE_INT("kern.ktrace.genio_size", &ktr_geniosize);
  137 SYSCTL_UINT(_kern_ktrace, OID_AUTO, genio_size, CTLFLAG_RW, &ktr_geniosize,
  138     0, "Maximum size of genio event payload");
  139 
  140 static int print_message = 1;
  141 static struct mtx ktrace_mtx;
  142 static struct sx ktrace_sx;
  143 
  144 static void ktrace_init(void *dummy);
  145 static int sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS);
  146 static u_int ktrace_resize_pool(u_int oldsize, u_int newsize);
  147 static struct ktr_request *ktr_getrequest_entered(struct thread *td, int type);
  148 static struct ktr_request *ktr_getrequest(int type);
  149 static void ktr_submitrequest(struct thread *td, struct ktr_request *req);
  150 static void ktr_freeproc(struct proc *p, struct ucred **uc,
  151     struct vnode **vp);
  152 static void ktr_freerequest(struct ktr_request *req);
  153 static void ktr_freerequest_locked(struct ktr_request *req);
  154 static void ktr_writerequest(struct thread *td, struct ktr_request *req);
  155 static int ktrcanset(struct thread *,struct proc *);
  156 static int ktrsetchildren(struct thread *,struct proc *,int,int,struct vnode *);
  157 static int ktrops(struct thread *,struct proc *,int,int,struct vnode *);
  158 static void ktrprocctor_entered(struct thread *, struct proc *);
  159 
  160 /*
  161  * ktrace itself generates events, such as context switches, which we do not
  162  * wish to trace.  Maintain a flag, TDP_INKTRACE, on each thread to determine
  163  * whether or not it is in a region where tracing of events should be
  164  * suppressed.
  165  */
  166 static void
  167 ktrace_enter(struct thread *td)
  168 {
  169 
  170         KASSERT(!(td->td_pflags & TDP_INKTRACE), ("ktrace_enter: flag set"));
  171         td->td_pflags |= TDP_INKTRACE;
  172 }
  173 
  174 static void
  175 ktrace_exit(struct thread *td)
  176 {
  177 
  178         KASSERT(td->td_pflags & TDP_INKTRACE, ("ktrace_exit: flag not set"));
  179         td->td_pflags &= ~TDP_INKTRACE;
  180 }
  181 
  182 static void
  183 ktrace_assert(struct thread *td)
  184 {
  185 
  186         KASSERT(td->td_pflags & TDP_INKTRACE, ("ktrace_assert: flag not set"));
  187 }
  188 
  189 static void
  190 ktrace_init(void *dummy)
  191 {
  192         struct ktr_request *req;
  193         int i;
  194 
  195         mtx_init(&ktrace_mtx, "ktrace", NULL, MTX_DEF | MTX_QUIET);
  196         sx_init(&ktrace_sx, "ktrace_sx");
  197         STAILQ_INIT(&ktr_free);
  198         for (i = 0; i < ktr_requestpool; i++) {
  199                 req = malloc(sizeof(struct ktr_request), M_KTRACE, M_WAITOK);
  200                 STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
  201         }
  202 }
  203 SYSINIT(ktrace_init, SI_SUB_KTRACE, SI_ORDER_ANY, ktrace_init, NULL);
  204 
  205 static int
  206 sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS)
  207 {
  208         struct thread *td;
  209         u_int newsize, oldsize, wantsize;
  210         int error;
  211 
  212         /* Handle easy read-only case first to avoid warnings from GCC. */
  213         if (!req->newptr) {
  214                 oldsize = ktr_requestpool;
  215                 return (SYSCTL_OUT(req, &oldsize, sizeof(u_int)));
  216         }
  217 
  218         error = SYSCTL_IN(req, &wantsize, sizeof(u_int));
  219         if (error)
  220                 return (error);
  221         td = curthread;
  222         ktrace_enter(td);
  223         oldsize = ktr_requestpool;
  224         newsize = ktrace_resize_pool(oldsize, wantsize);
  225         ktrace_exit(td);
  226         error = SYSCTL_OUT(req, &oldsize, sizeof(u_int));
  227         if (error)
  228                 return (error);
  229         if (wantsize > oldsize && newsize < wantsize)
  230                 return (ENOSPC);
  231         return (0);
  232 }
  233 SYSCTL_PROC(_kern_ktrace, OID_AUTO, request_pool, CTLTYPE_UINT|CTLFLAG_RW,
  234     &ktr_requestpool, 0, sysctl_kern_ktrace_request_pool, "IU",
  235     "Pool buffer size for ktrace(1)");
  236 
  237 static u_int
  238 ktrace_resize_pool(u_int oldsize, u_int newsize)
  239 {
  240         STAILQ_HEAD(, ktr_request) ktr_new;
  241         struct ktr_request *req;
  242         int bound;
  243 
  244         print_message = 1;
  245         bound = newsize - oldsize;
  246         if (bound == 0)
  247                 return (ktr_requestpool);
  248         if (bound < 0) {
  249                 mtx_lock(&ktrace_mtx);
  250                 /* Shrink pool down to newsize if possible. */
  251                 while (bound++ < 0) {
  252                         req = STAILQ_FIRST(&ktr_free);
  253                         if (req == NULL)
  254                                 break;
  255                         STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
  256                         ktr_requestpool--;
  257                         free(req, M_KTRACE);
  258                 }
  259         } else {
  260                 /* Grow pool up to newsize. */
  261                 STAILQ_INIT(&ktr_new);
  262                 while (bound-- > 0) {
  263                         req = malloc(sizeof(struct ktr_request), M_KTRACE,
  264                             M_WAITOK);
  265                         STAILQ_INSERT_HEAD(&ktr_new, req, ktr_list);
  266                 }
  267                 mtx_lock(&ktrace_mtx);
  268                 STAILQ_CONCAT(&ktr_free, &ktr_new);
  269                 ktr_requestpool += (newsize - oldsize);
  270         }
  271         mtx_unlock(&ktrace_mtx);
  272         return (ktr_requestpool);
  273 }
  274 
  275 /* ktr_getrequest() assumes that ktr_comm[] is the same size as td_name[]. */
  276 CTASSERT(sizeof(((struct ktr_header *)NULL)->ktr_comm) ==
  277     (sizeof((struct thread *)NULL)->td_name));
  278 
  279 static struct ktr_request *
  280 ktr_getrequest_entered(struct thread *td, int type)
  281 {
  282         struct ktr_request *req;
  283         struct proc *p = td->td_proc;
  284         int pm;
  285 
  286         mtx_lock(&ktrace_mtx);
  287         if (!KTRCHECK(td, type)) {
  288                 mtx_unlock(&ktrace_mtx);
  289                 return (NULL);
  290         }
  291         req = STAILQ_FIRST(&ktr_free);
  292         if (req != NULL) {
  293                 STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
  294                 req->ktr_header.ktr_type = type;
  295                 if (p->p_traceflag & KTRFAC_DROP) {
  296                         req->ktr_header.ktr_type |= KTR_DROP;
  297                         p->p_traceflag &= ~KTRFAC_DROP;
  298                 }
  299                 mtx_unlock(&ktrace_mtx);
  300                 microtime(&req->ktr_header.ktr_time);
  301                 req->ktr_header.ktr_pid = p->p_pid;
  302                 req->ktr_header.ktr_tid = td->td_tid;
  303                 bcopy(td->td_name, req->ktr_header.ktr_comm,
  304                     sizeof(req->ktr_header.ktr_comm));
  305                 req->ktr_buffer = NULL;
  306                 req->ktr_header.ktr_len = 0;
  307         } else {
  308                 p->p_traceflag |= KTRFAC_DROP;
  309                 pm = print_message;
  310                 print_message = 0;
  311                 mtx_unlock(&ktrace_mtx);
  312                 if (pm)
  313                         printf("Out of ktrace request objects.\n");
  314         }
  315         return (req);
  316 }
  317 
  318 static struct ktr_request *
  319 ktr_getrequest(int type)
  320 {
  321         struct thread *td = curthread;
  322         struct ktr_request *req;
  323 
  324         ktrace_enter(td);
  325         req = ktr_getrequest_entered(td, type);
  326         if (req == NULL)
  327                 ktrace_exit(td);
  328 
  329         return (req);
  330 }
  331 
  332 /*
  333  * Some trace generation environments don't permit direct access to VFS,
  334  * such as during a context switch where sleeping is not allowed.  Under these
  335  * circumstances, queue a request to the thread to be written asynchronously
  336  * later.
  337  */
  338 static void
  339 ktr_enqueuerequest(struct thread *td, struct ktr_request *req)
  340 {
  341 
  342         mtx_lock(&ktrace_mtx);
  343         STAILQ_INSERT_TAIL(&td->td_proc->p_ktr, req, ktr_list);
  344         mtx_unlock(&ktrace_mtx);
  345 }
  346 
  347 /*
  348  * Drain any pending ktrace records from the per-thread queue to disk.  This
  349  * is used both internally before committing other records, and also on
  350  * system call return.  We drain all the ones we can find at the time when
  351  * drain is requested, but don't keep draining after that as those events
  352  * may be approximately "after" the current event.
  353  */
  354 static void
  355 ktr_drain(struct thread *td)
  356 {
  357         struct ktr_request *queued_req;
  358         STAILQ_HEAD(, ktr_request) local_queue;
  359 
  360         ktrace_assert(td);
  361         sx_assert(&ktrace_sx, SX_XLOCKED);
  362 
  363         STAILQ_INIT(&local_queue);
  364 
  365         if (!STAILQ_EMPTY(&td->td_proc->p_ktr)) {
  366                 mtx_lock(&ktrace_mtx);
  367                 STAILQ_CONCAT(&local_queue, &td->td_proc->p_ktr);
  368                 mtx_unlock(&ktrace_mtx);
  369 
  370                 while ((queued_req = STAILQ_FIRST(&local_queue))) {
  371                         STAILQ_REMOVE_HEAD(&local_queue, ktr_list);
  372                         ktr_writerequest(td, queued_req);
  373                         ktr_freerequest(queued_req);
  374                 }
  375         }
  376 }
  377 
  378 /*
  379  * Submit a trace record for immediate commit to disk -- to be used only
  380  * where entering VFS is OK.  First drain any pending records that may have
  381  * been cached in the thread.
  382  */
  383 static void
  384 ktr_submitrequest(struct thread *td, struct ktr_request *req)
  385 {
  386 
  387         ktrace_assert(td);
  388 
  389         sx_xlock(&ktrace_sx);
  390         ktr_drain(td);
  391         ktr_writerequest(td, req);
  392         ktr_freerequest(req);
  393         sx_xunlock(&ktrace_sx);
  394         ktrace_exit(td);
  395 }
  396 
  397 static void
  398 ktr_freerequest(struct ktr_request *req)
  399 {
  400 
  401         mtx_lock(&ktrace_mtx);
  402         ktr_freerequest_locked(req);
  403         mtx_unlock(&ktrace_mtx);
  404 }
  405 
  406 static void
  407 ktr_freerequest_locked(struct ktr_request *req)
  408 {
  409 
  410         mtx_assert(&ktrace_mtx, MA_OWNED);
  411         if (req->ktr_buffer != NULL)
  412                 free(req->ktr_buffer, M_KTRACE);
  413         STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
  414 }
  415 
  416 /*
  417  * Disable tracing for a process and release all associated resources.
  418  * The caller is responsible for releasing a reference on the returned
  419  * vnode and credentials.
  420  */
  421 static void
  422 ktr_freeproc(struct proc *p, struct ucred **uc, struct vnode **vp)
  423 {
  424         struct ktr_request *req;
  425 
  426         PROC_LOCK_ASSERT(p, MA_OWNED);
  427         mtx_assert(&ktrace_mtx, MA_OWNED);
  428         *uc = p->p_tracecred;
  429         p->p_tracecred = NULL;
  430         if (vp != NULL)
  431                 *vp = p->p_tracevp;
  432         p->p_tracevp = NULL;
  433         p->p_traceflag = 0;
  434         while ((req = STAILQ_FIRST(&p->p_ktr)) != NULL) {
  435                 STAILQ_REMOVE_HEAD(&p->p_ktr, ktr_list);
  436                 ktr_freerequest_locked(req);
  437         }
  438 }
  439 
  440 void
  441 ktrsyscall(code, narg, args)
  442         int code, narg;
  443         register_t args[];
  444 {
  445         struct ktr_request *req;
  446         struct ktr_syscall *ktp;
  447         size_t buflen;
  448         char *buf = NULL;
  449 
  450         buflen = sizeof(register_t) * narg;
  451         if (buflen > 0) {
  452                 buf = malloc(buflen, M_KTRACE, M_WAITOK);
  453                 bcopy(args, buf, buflen);
  454         }
  455         req = ktr_getrequest(KTR_SYSCALL);
  456         if (req == NULL) {
  457                 if (buf != NULL)
  458                         free(buf, M_KTRACE);
  459                 return;
  460         }
  461         ktp = &req->ktr_data.ktr_syscall;
  462         ktp->ktr_code = code;
  463         ktp->ktr_narg = narg;
  464         if (buflen > 0) {
  465                 req->ktr_header.ktr_len = buflen;
  466                 req->ktr_buffer = buf;
  467         }
  468         ktr_submitrequest(curthread, req);
  469 }
  470 
  471 void
  472 ktrsysret(code, error, retval)
  473         int code, error;
  474         register_t retval;
  475 {
  476         struct ktr_request *req;
  477         struct ktr_sysret *ktp;
  478 
  479         req = ktr_getrequest(KTR_SYSRET);
  480         if (req == NULL)
  481                 return;
  482         ktp = &req->ktr_data.ktr_sysret;
  483         ktp->ktr_code = code;
  484         ktp->ktr_error = error;
  485         ktp->ktr_retval = ((error == 0) ? retval: 0);           /* what about val2 ? */
  486         ktr_submitrequest(curthread, req);
  487 }
  488 
  489 /*
  490  * When a setuid process execs, disable tracing.
  491  *
  492  * XXX: We toss any pending asynchronous records.
  493  */
  494 void
  495 ktrprocexec(struct proc *p, struct ucred **uc, struct vnode **vp)
  496 {
  497 
  498         PROC_LOCK_ASSERT(p, MA_OWNED);
  499         mtx_lock(&ktrace_mtx);
  500         ktr_freeproc(p, uc, vp);
  501         mtx_unlock(&ktrace_mtx);
  502 }
  503 
  504 /*
  505  * When a process exits, drain per-process asynchronous trace records
  506  * and disable tracing.
  507  */
  508 void
  509 ktrprocexit(struct thread *td)
  510 {
  511         struct ktr_request *req;
  512         struct proc *p;
  513         struct ucred *cred;
  514         struct vnode *vp;
  515 
  516         p = td->td_proc;
  517         if (p->p_traceflag == 0)
  518                 return;
  519 
  520         ktrace_enter(td);
  521         req = ktr_getrequest_entered(td, KTR_PROCDTOR);
  522         if (req != NULL)
  523                 ktr_enqueuerequest(td, req);
  524         sx_xlock(&ktrace_sx);
  525         ktr_drain(td);
  526         sx_xunlock(&ktrace_sx);
  527         PROC_LOCK(p);
  528         mtx_lock(&ktrace_mtx);
  529         ktr_freeproc(p, &cred, &vp);
  530         mtx_unlock(&ktrace_mtx);
  531         PROC_UNLOCK(p);
  532         if (vp != NULL)
  533                 vrele(vp);
  534         if (cred != NULL)
  535                 crfree(cred);
  536         ktrace_exit(td);
  537 }
  538 
  539 static void
  540 ktrprocctor_entered(struct thread *td, struct proc *p)
  541 {
  542         struct ktr_proc_ctor *ktp;
  543         struct ktr_request *req;
  544         struct thread *td2;
  545 
  546         ktrace_assert(td);
  547         td2 = FIRST_THREAD_IN_PROC(p);
  548         req = ktr_getrequest_entered(td2, KTR_PROCCTOR);
  549         if (req == NULL)
  550                 return;
  551         ktp = &req->ktr_data.ktr_proc_ctor;
  552         ktp->sv_flags = p->p_sysent->sv_flags;
  553         ktr_enqueuerequest(td2, req);
  554 }
  555 
  556 void
  557 ktrprocctor(struct proc *p)
  558 {
  559         struct thread *td = curthread;
  560 
  561         if ((p->p_traceflag & KTRFAC_MASK) == 0)
  562                 return;
  563 
  564         ktrace_enter(td);
  565         ktrprocctor_entered(td, p);
  566         ktrace_exit(td);
  567 }
  568 
  569 /*
  570  * When a process forks, enable tracing in the new process if needed.
  571  */
  572 void
  573 ktrprocfork(struct proc *p1, struct proc *p2)
  574 {
  575 
  576         PROC_LOCK(p1);
  577         mtx_lock(&ktrace_mtx);
  578         KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
  579         if (p1->p_traceflag & KTRFAC_INHERIT) {
  580                 p2->p_traceflag = p1->p_traceflag;
  581                 if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
  582                         VREF(p2->p_tracevp);
  583                         KASSERT(p1->p_tracecred != NULL,
  584                             ("ktrace vnode with no cred"));
  585                         p2->p_tracecred = crhold(p1->p_tracecred);
  586                 }
  587         }
  588         mtx_unlock(&ktrace_mtx);
  589         PROC_UNLOCK(p1);
  590 
  591         ktrprocctor(p2);
  592 }
  593 
  594 /*
  595  * When a thread returns, drain any asynchronous records generated by the
  596  * system call.
  597  */
  598 void
  599 ktruserret(struct thread *td)
  600 {
  601 
  602         ktrace_enter(td);
  603         sx_xlock(&ktrace_sx);
  604         ktr_drain(td);
  605         sx_xunlock(&ktrace_sx);
  606         ktrace_exit(td);
  607 }
  608 
  609 void
  610 ktrnamei(path)
  611         char *path;
  612 {
  613         struct ktr_request *req;
  614         int namelen;
  615         char *buf = NULL;
  616 
  617         namelen = strlen(path);
  618         if (namelen > 0) {
  619                 buf = malloc(namelen, M_KTRACE, M_WAITOK);
  620                 bcopy(path, buf, namelen);
  621         }
  622         req = ktr_getrequest(KTR_NAMEI);
  623         if (req == NULL) {
  624                 if (buf != NULL)
  625                         free(buf, M_KTRACE);
  626                 return;
  627         }
  628         if (namelen > 0) {
  629                 req->ktr_header.ktr_len = namelen;
  630                 req->ktr_buffer = buf;
  631         }
  632         ktr_submitrequest(curthread, req);
  633 }
  634 
  635 void
  636 ktrsysctl(name, namelen)
  637         int *name;
  638         u_int namelen;
  639 {
  640         struct ktr_request *req;
  641         u_int mib[CTL_MAXNAME + 2];
  642         char *mibname;
  643         size_t mibnamelen;
  644         int error;
  645 
  646         /* Lookup name of mib. */    
  647         KASSERT(namelen <= CTL_MAXNAME, ("sysctl MIB too long"));
  648         mib[0] = 0;
  649         mib[1] = 1;
  650         bcopy(name, mib + 2, namelen * sizeof(*name));
  651         mibnamelen = 128;
  652         mibname = malloc(mibnamelen, M_KTRACE, M_WAITOK);
  653         error = kernel_sysctl(curthread, mib, namelen + 2, mibname, &mibnamelen,
  654             NULL, 0, &mibnamelen, 0);
  655         if (error) {
  656                 free(mibname, M_KTRACE);
  657                 return;
  658         }
  659         req = ktr_getrequest(KTR_SYSCTL);
  660         if (req == NULL) {
  661                 free(mibname, M_KTRACE);
  662                 return;
  663         }
  664         req->ktr_header.ktr_len = mibnamelen;
  665         req->ktr_buffer = mibname;
  666         ktr_submitrequest(curthread, req);
  667 }
  668 
  669 void
  670 ktrgenio(fd, rw, uio, error)
  671         int fd;
  672         enum uio_rw rw;
  673         struct uio *uio;
  674         int error;
  675 {
  676         struct ktr_request *req;
  677         struct ktr_genio *ktg;
  678         int datalen;
  679         char *buf;
  680 
  681         if (error) {
  682                 free(uio, M_IOV);
  683                 return;
  684         }
  685         uio->uio_offset = 0;
  686         uio->uio_rw = UIO_WRITE;
  687         datalen = MIN(uio->uio_resid, ktr_geniosize);
  688         buf = malloc(datalen, M_KTRACE, M_WAITOK);
  689         error = uiomove(buf, datalen, uio);
  690         free(uio, M_IOV);
  691         if (error) {
  692                 free(buf, M_KTRACE);
  693                 return;
  694         }
  695         req = ktr_getrequest(KTR_GENIO);
  696         if (req == NULL) {
  697                 free(buf, M_KTRACE);
  698                 return;
  699         }
  700         ktg = &req->ktr_data.ktr_genio;
  701         ktg->ktr_fd = fd;
  702         ktg->ktr_rw = rw;
  703         req->ktr_header.ktr_len = datalen;
  704         req->ktr_buffer = buf;
  705         ktr_submitrequest(curthread, req);
  706 }
  707 
  708 void
  709 ktrpsig(sig, action, mask, code)
  710         int sig;
  711         sig_t action;
  712         sigset_t *mask;
  713         int code;
  714 {
  715         struct thread *td = curthread;
  716         struct ktr_request *req;
  717         struct ktr_psig *kp;
  718 
  719         req = ktr_getrequest(KTR_PSIG);
  720         if (req == NULL)
  721                 return;
  722         kp = &req->ktr_data.ktr_psig;
  723         kp->signo = (char)sig;
  724         kp->action = action;
  725         kp->mask = *mask;
  726         kp->code = code;
  727         ktr_enqueuerequest(td, req);
  728         ktrace_exit(td);
  729 }
  730 
  731 void
  732 ktrcsw(out, user, wmesg)
  733         int out, user;
  734         const char *wmesg;
  735 {
  736         struct thread *td = curthread;
  737         struct ktr_request *req;
  738         struct ktr_csw *kc;
  739 
  740         req = ktr_getrequest(KTR_CSW);
  741         if (req == NULL)
  742                 return;
  743         kc = &req->ktr_data.ktr_csw;
  744         kc->out = out;
  745         kc->user = user;
  746         if (wmesg != NULL)
  747                 strlcpy(kc->wmesg, wmesg, sizeof(kc->wmesg));
  748         else
  749                 bzero(kc->wmesg, sizeof(kc->wmesg));
  750         ktr_enqueuerequest(td, req);
  751         ktrace_exit(td);
  752 }
  753 
  754 void
  755 ktrstruct(name, data, datalen)
  756         const char *name;
  757         void *data;
  758         size_t datalen;
  759 {
  760         struct ktr_request *req;
  761         char *buf = NULL;
  762         size_t buflen;
  763 
  764         if (!data)
  765                 datalen = 0;
  766         buflen = strlen(name) + 1 + datalen;
  767         buf = malloc(buflen, M_KTRACE, M_WAITOK);
  768         strcpy(buf, name);
  769         bcopy(data, buf + strlen(name) + 1, datalen);
  770         if ((req = ktr_getrequest(KTR_STRUCT)) == NULL) {
  771                 free(buf, M_KTRACE);
  772                 return;
  773         }
  774         req->ktr_buffer = buf;
  775         req->ktr_header.ktr_len = buflen;
  776         ktr_submitrequest(curthread, req);
  777 }
  778 
  779 void
  780 ktrcapfail(type, needed, held)
  781         enum ktr_cap_fail_type type;
  782         const cap_rights_t *needed;
  783         const cap_rights_t *held;
  784 {
  785         struct thread *td = curthread;
  786         struct ktr_request *req;
  787         struct ktr_cap_fail *kcf;
  788 
  789         req = ktr_getrequest(KTR_CAPFAIL);
  790         if (req == NULL)
  791                 return;
  792         kcf = &req->ktr_data.ktr_cap_fail;
  793         kcf->cap_type = type;
  794         if (needed != NULL)
  795                 kcf->cap_needed = *needed;
  796         else
  797                 cap_rights_init(&kcf->cap_needed);
  798         if (held != NULL)
  799                 kcf->cap_held = *held;
  800         else
  801                 cap_rights_init(&kcf->cap_held);
  802         ktr_enqueuerequest(td, req);
  803         ktrace_exit(td);
  804 }
  805 
  806 void
  807 ktrfault(vaddr, type)
  808         vm_offset_t vaddr;
  809         int type;
  810 {
  811         struct thread *td = curthread;
  812         struct ktr_request *req;
  813         struct ktr_fault *kf;
  814 
  815         req = ktr_getrequest(KTR_FAULT);
  816         if (req == NULL)
  817                 return;
  818         kf = &req->ktr_data.ktr_fault;
  819         kf->vaddr = vaddr;
  820         kf->type = type;
  821         ktr_enqueuerequest(td, req);
  822         ktrace_exit(td);
  823 }
  824 
  825 void
  826 ktrfaultend(result)
  827         int result;
  828 {
  829         struct thread *td = curthread;
  830         struct ktr_request *req;
  831         struct ktr_faultend *kf;
  832 
  833         req = ktr_getrequest(KTR_FAULTEND);
  834         if (req == NULL)
  835                 return;
  836         kf = &req->ktr_data.ktr_faultend;
  837         kf->result = result;
  838         ktr_enqueuerequest(td, req);
  839         ktrace_exit(td);
  840 }
  841 #endif /* KTRACE */
  842 
  843 /* Interface and common routines */
  844 
  845 #ifndef _SYS_SYSPROTO_H_
  846 struct ktrace_args {
  847         char    *fname;
  848         int     ops;
  849         int     facs;
  850         int     pid;
  851 };
  852 #endif
  853 /* ARGSUSED */
  854 int
  855 sys_ktrace(td, uap)
  856         struct thread *td;
  857         register struct ktrace_args *uap;
  858 {
  859 #ifdef KTRACE
  860         register struct vnode *vp = NULL;
  861         register struct proc *p;
  862         struct pgrp *pg;
  863         int facs = uap->facs & ~KTRFAC_ROOT;
  864         int ops = KTROP(uap->ops);
  865         int descend = uap->ops & KTRFLAG_DESCEND;
  866         int nfound, ret = 0;
  867         int flags, error = 0;
  868         struct nameidata nd;
  869         struct ucred *cred;
  870 
  871         /*
  872          * Need something to (un)trace.
  873          */
  874         if (ops != KTROP_CLEARFILE && facs == 0)
  875                 return (EINVAL);
  876 
  877         ktrace_enter(td);
  878         if (ops != KTROP_CLEAR) {
  879                 /*
  880                  * an operation which requires a file argument.
  881                  */
  882                 NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->fname, td);
  883                 flags = FREAD | FWRITE | O_NOFOLLOW;
  884                 error = vn_open(&nd, &flags, 0, NULL);
  885                 if (error) {
  886                         ktrace_exit(td);
  887                         return (error);
  888                 }
  889                 NDFREE(&nd, NDF_ONLY_PNBUF);
  890                 vp = nd.ni_vp;
  891                 VOP_UNLOCK(vp, 0);
  892                 if (vp->v_type != VREG) {
  893                         (void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
  894                         ktrace_exit(td);
  895                         return (EACCES);
  896                 }
  897         }
  898         /*
  899          * Clear all uses of the tracefile.
  900          */
  901         if (ops == KTROP_CLEARFILE) {
  902                 int vrele_count;
  903 
  904                 vrele_count = 0;
  905                 sx_slock(&allproc_lock);
  906                 FOREACH_PROC_IN_SYSTEM(p) {
  907                         PROC_LOCK(p);
  908                         if (p->p_tracevp == vp) {
  909                                 if (ktrcanset(td, p)) {
  910                                         mtx_lock(&ktrace_mtx);
  911                                         ktr_freeproc(p, &cred, NULL);
  912                                         mtx_unlock(&ktrace_mtx);
  913                                         vrele_count++;
  914                                         crfree(cred);
  915                                 } else
  916                                         error = EPERM;
  917                         }
  918                         PROC_UNLOCK(p);
  919                 }
  920                 sx_sunlock(&allproc_lock);
  921                 if (vrele_count > 0) {
  922                         while (vrele_count-- > 0)
  923                                 vrele(vp);
  924                 }
  925                 goto done;
  926         }
  927         /*
  928          * do it
  929          */
  930         sx_slock(&proctree_lock);
  931         if (uap->pid < 0) {
  932                 /*
  933                  * by process group
  934                  */
  935                 pg = pgfind(-uap->pid);
  936                 if (pg == NULL) {
  937                         sx_sunlock(&proctree_lock);
  938                         error = ESRCH;
  939                         goto done;
  940                 }
  941                 /*
  942                  * ktrops() may call vrele(). Lock pg_members
  943                  * by the proctree_lock rather than pg_mtx.
  944                  */
  945                 PGRP_UNLOCK(pg);
  946                 nfound = 0;
  947                 LIST_FOREACH(p, &pg->pg_members, p_pglist) {
  948                         PROC_LOCK(p);
  949                         if (p->p_state == PRS_NEW ||
  950                             p_cansee(td, p) != 0) {
  951                                 PROC_UNLOCK(p); 
  952                                 continue;
  953                         }
  954                         nfound++;
  955                         if (descend)
  956                                 ret |= ktrsetchildren(td, p, ops, facs, vp);
  957                         else
  958                                 ret |= ktrops(td, p, ops, facs, vp);
  959                 }
  960                 if (nfound == 0) {
  961                         sx_sunlock(&proctree_lock);
  962                         error = ESRCH;
  963                         goto done;
  964                 }
  965         } else {
  966                 /*
  967                  * by pid
  968                  */
  969                 p = pfind(uap->pid);
  970                 if (p == NULL)
  971                         error = ESRCH;
  972                 else
  973                         error = p_cansee(td, p);
  974                 if (error) {
  975                         if (p != NULL)
  976                                 PROC_UNLOCK(p);
  977                         sx_sunlock(&proctree_lock);
  978                         goto done;
  979                 }
  980                 if (descend)
  981                         ret |= ktrsetchildren(td, p, ops, facs, vp);
  982                 else
  983                         ret |= ktrops(td, p, ops, facs, vp);
  984         }
  985         sx_sunlock(&proctree_lock);
  986         if (!ret)
  987                 error = EPERM;
  988 done:
  989         if (vp != NULL)
  990                 (void) vn_close(vp, FWRITE, td->td_ucred, td);
  991         ktrace_exit(td);
  992         return (error);
  993 #else /* !KTRACE */
  994         return (ENOSYS);
  995 #endif /* KTRACE */
  996 }
  997 
  998 /* ARGSUSED */
  999 int
 1000 sys_utrace(td, uap)
 1001         struct thread *td;
 1002         register struct utrace_args *uap;
 1003 {
 1004 
 1005 #ifdef KTRACE
 1006         struct ktr_request *req;
 1007         void *cp;
 1008         int error;
 1009 
 1010         if (!KTRPOINT(td, KTR_USER))
 1011                 return (0);
 1012         if (uap->len > KTR_USER_MAXLEN)
 1013                 return (EINVAL);
 1014         cp = malloc(uap->len, M_KTRACE, M_WAITOK);
 1015         error = copyin(uap->addr, cp, uap->len);
 1016         if (error) {
 1017                 free(cp, M_KTRACE);
 1018                 return (error);
 1019         }
 1020         req = ktr_getrequest(KTR_USER);
 1021         if (req == NULL) {
 1022                 free(cp, M_KTRACE);
 1023                 return (ENOMEM);
 1024         }
 1025         req->ktr_buffer = cp;
 1026         req->ktr_header.ktr_len = uap->len;
 1027         ktr_submitrequest(td, req);
 1028         return (0);
 1029 #else /* !KTRACE */
 1030         return (ENOSYS);
 1031 #endif /* KTRACE */
 1032 }
 1033 
 1034 #ifdef KTRACE
 1035 static int
 1036 ktrops(td, p, ops, facs, vp)
 1037         struct thread *td;
 1038         struct proc *p;
 1039         int ops, facs;
 1040         struct vnode *vp;
 1041 {
 1042         struct vnode *tracevp = NULL;
 1043         struct ucred *tracecred = NULL;
 1044 
 1045         PROC_LOCK_ASSERT(p, MA_OWNED);
 1046         if (!ktrcanset(td, p)) {
 1047                 PROC_UNLOCK(p);
 1048                 return (0);
 1049         }
 1050         if (p->p_flag & P_WEXIT) {
 1051                 /* If the process is exiting, just ignore it. */
 1052                 PROC_UNLOCK(p);
 1053                 return (1);
 1054         }
 1055         mtx_lock(&ktrace_mtx);
 1056         if (ops == KTROP_SET) {
 1057                 if (p->p_tracevp != vp) {
 1058                         /*
 1059                          * if trace file already in use, relinquish below
 1060                          */
 1061                         tracevp = p->p_tracevp;
 1062                         VREF(vp);
 1063                         p->p_tracevp = vp;
 1064                 }
 1065                 if (p->p_tracecred != td->td_ucred) {
 1066                         tracecred = p->p_tracecred;
 1067                         p->p_tracecred = crhold(td->td_ucred);
 1068                 }
 1069                 p->p_traceflag |= facs;
 1070                 if (priv_check(td, PRIV_KTRACE) == 0)
 1071                         p->p_traceflag |= KTRFAC_ROOT;
 1072         } else {
 1073                 /* KTROP_CLEAR */
 1074                 if (((p->p_traceflag &= ~facs) & KTRFAC_MASK) == 0)
 1075                         /* no more tracing */
 1076                         ktr_freeproc(p, &tracecred, &tracevp);
 1077         }
 1078         mtx_unlock(&ktrace_mtx);
 1079         if ((p->p_traceflag & KTRFAC_MASK) != 0)
 1080                 ktrprocctor_entered(td, p);
 1081         PROC_UNLOCK(p);
 1082         if (tracevp != NULL)
 1083                 vrele(tracevp);
 1084         if (tracecred != NULL)
 1085                 crfree(tracecred);
 1086 
 1087         return (1);
 1088 }
 1089 
 1090 static int
 1091 ktrsetchildren(td, top, ops, facs, vp)
 1092         struct thread *td;
 1093         struct proc *top;
 1094         int ops, facs;
 1095         struct vnode *vp;
 1096 {
 1097         register struct proc *p;
 1098         register int ret = 0;
 1099 
 1100         p = top;
 1101         PROC_LOCK_ASSERT(p, MA_OWNED);
 1102         sx_assert(&proctree_lock, SX_LOCKED);
 1103         for (;;) {
 1104                 ret |= ktrops(td, p, ops, facs, vp);
 1105                 /*
 1106                  * If this process has children, descend to them next,
 1107                  * otherwise do any siblings, and if done with this level,
 1108                  * follow back up the tree (but not past top).
 1109                  */
 1110                 if (!LIST_EMPTY(&p->p_children))
 1111                         p = LIST_FIRST(&p->p_children);
 1112                 else for (;;) {
 1113                         if (p == top)
 1114                                 return (ret);
 1115                         if (LIST_NEXT(p, p_sibling)) {
 1116                                 p = LIST_NEXT(p, p_sibling);
 1117                                 break;
 1118                         }
 1119                         p = p->p_pptr;
 1120                 }
 1121                 PROC_LOCK(p);
 1122         }
 1123         /*NOTREACHED*/
 1124 }
 1125 
 1126 static void
 1127 ktr_writerequest(struct thread *td, struct ktr_request *req)
 1128 {
 1129         struct ktr_header *kth;
 1130         struct vnode *vp;
 1131         struct proc *p;
 1132         struct ucred *cred;
 1133         struct uio auio;
 1134         struct iovec aiov[3];
 1135         struct mount *mp;
 1136         int datalen, buflen, vrele_count;
 1137         int error;
 1138 
 1139         /*
 1140          * We hold the vnode and credential for use in I/O in case ktrace is
 1141          * disabled on the process as we write out the request.
 1142          *
 1143          * XXXRW: This is not ideal: we could end up performing a write after
 1144          * the vnode has been closed.
 1145          */
 1146         mtx_lock(&ktrace_mtx);
 1147         vp = td->td_proc->p_tracevp;
 1148         cred = td->td_proc->p_tracecred;
 1149 
 1150         /*
 1151          * If vp is NULL, the vp has been cleared out from under this
 1152          * request, so just drop it.  Make sure the credential and vnode are
 1153          * in sync: we should have both or neither.
 1154          */
 1155         if (vp == NULL) {
 1156                 KASSERT(cred == NULL, ("ktr_writerequest: cred != NULL"));
 1157                 mtx_unlock(&ktrace_mtx);
 1158                 return;
 1159         }
 1160         VREF(vp);
 1161         KASSERT(cred != NULL, ("ktr_writerequest: cred == NULL"));
 1162         crhold(cred);
 1163         mtx_unlock(&ktrace_mtx);
 1164 
 1165         kth = &req->ktr_header;
 1166         KASSERT(((u_short)kth->ktr_type & ~KTR_DROP) <
 1167             sizeof(data_lengths) / sizeof(data_lengths[0]),
 1168             ("data_lengths array overflow"));
 1169         datalen = data_lengths[(u_short)kth->ktr_type & ~KTR_DROP];
 1170         buflen = kth->ktr_len;
 1171         auio.uio_iov = &aiov[0];
 1172         auio.uio_offset = 0;
 1173         auio.uio_segflg = UIO_SYSSPACE;
 1174         auio.uio_rw = UIO_WRITE;
 1175         aiov[0].iov_base = (caddr_t)kth;
 1176         aiov[0].iov_len = sizeof(struct ktr_header);
 1177         auio.uio_resid = sizeof(struct ktr_header);
 1178         auio.uio_iovcnt = 1;
 1179         auio.uio_td = td;
 1180         if (datalen != 0) {
 1181                 aiov[1].iov_base = (caddr_t)&req->ktr_data;
 1182                 aiov[1].iov_len = datalen;
 1183                 auio.uio_resid += datalen;
 1184                 auio.uio_iovcnt++;
 1185                 kth->ktr_len += datalen;
 1186         }
 1187         if (buflen != 0) {
 1188                 KASSERT(req->ktr_buffer != NULL, ("ktrace: nothing to write"));
 1189                 aiov[auio.uio_iovcnt].iov_base = req->ktr_buffer;
 1190                 aiov[auio.uio_iovcnt].iov_len = buflen;
 1191                 auio.uio_resid += buflen;
 1192                 auio.uio_iovcnt++;
 1193         }
 1194 
 1195         vn_start_write(vp, &mp, V_WAIT);
 1196         vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 1197 #ifdef MAC
 1198         error = mac_vnode_check_write(cred, NOCRED, vp);
 1199         if (error == 0)
 1200 #endif
 1201                 error = VOP_WRITE(vp, &auio, IO_UNIT | IO_APPEND, cred);
 1202         VOP_UNLOCK(vp, 0);
 1203         vn_finished_write(mp);
 1204         crfree(cred);
 1205         if (!error) {
 1206                 vrele(vp);
 1207                 return;
 1208         }
 1209 
 1210         /*
 1211          * If error encountered, give up tracing on this vnode.  We defer
 1212          * all the vrele()'s on the vnode until after we are finished walking
 1213          * the various lists to avoid needlessly holding locks.
 1214          * NB: at this point we still hold the vnode reference that must
 1215          * not go away as we need the valid vnode to compare with. Thus let
 1216          * vrele_count start at 1 and the reference will be freed
 1217          * by the loop at the end after our last use of vp.
 1218          */
 1219         log(LOG_NOTICE, "ktrace write failed, errno %d, tracing stopped\n",
 1220             error);
 1221         vrele_count = 1;
 1222         /*
 1223          * First, clear this vnode from being used by any processes in the
 1224          * system.
 1225          * XXX - If one process gets an EPERM writing to the vnode, should
 1226          * we really do this?  Other processes might have suitable
 1227          * credentials for the operation.
 1228          */
 1229         cred = NULL;
 1230         sx_slock(&allproc_lock);
 1231         FOREACH_PROC_IN_SYSTEM(p) {
 1232                 PROC_LOCK(p);
 1233                 if (p->p_tracevp == vp) {
 1234                         mtx_lock(&ktrace_mtx);
 1235                         ktr_freeproc(p, &cred, NULL);
 1236                         mtx_unlock(&ktrace_mtx);
 1237                         vrele_count++;
 1238                 }
 1239                 PROC_UNLOCK(p);
 1240                 if (cred != NULL) {
 1241                         crfree(cred);
 1242                         cred = NULL;
 1243                 }
 1244         }
 1245         sx_sunlock(&allproc_lock);
 1246 
 1247         while (vrele_count-- > 0)
 1248                 vrele(vp);
 1249 }
 1250 
 1251 /*
 1252  * Return true if caller has permission to set the ktracing state
 1253  * of target.  Essentially, the target can't possess any
 1254  * more permissions than the caller.  KTRFAC_ROOT signifies that
 1255  * root previously set the tracing status on the target process, and
 1256  * so, only root may further change it.
 1257  */
 1258 static int
 1259 ktrcanset(td, targetp)
 1260         struct thread *td;
 1261         struct proc *targetp;
 1262 {
 1263 
 1264         PROC_LOCK_ASSERT(targetp, MA_OWNED);
 1265         if (targetp->p_traceflag & KTRFAC_ROOT &&
 1266             priv_check(td, PRIV_KTRACE))
 1267                 return (0);
 1268 
 1269         if (p_candebug(td, targetp) != 0)
 1270                 return (0);
 1271 
 1272         return (1);
 1273 }
 1274 
 1275 #endif /* KTRACE */

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