kern_ktrace.c

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/*-
 * Copyright (c) 1989, 1993
 *      The Regents of the University of California.
 * Copyright (c) 2005 Robert N. M. Watson
 * 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.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *      @(#)kern_ktrace.c       8.2 (Berkeley) 9/23/93
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include "opt_ktrace.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/ktrace.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/syslog.h>
#include <sys/sysproto.h>

#include <security/mac/mac_framework.h>

/*
 * The ktrace facility allows the tracing of certain key events in user space
 * processes, such as system calls, signal delivery, context switches, and
 * user generated events using utrace(2).  It works by streaming event
 * records and data to a vnode associated with the process using the
 * ktrace(2) system call.  In general, records can be written directly from
 * the context that generates the event.  One important exception to this is
 * during a context switch, where sleeping is not permitted.  To handle this
 * case, trace events are generated using in-kernel ktr_request records, and
 * then delivered to disk at a convenient moment -- either immediately, the
 * next traceable event, at system call return, or at process exit.
 *
 * When dealing with multiple threads or processes writing to the same event
 * log, ordering guarantees are weak: specifically, if an event has multiple
 * records (i.e., system call enter and return), they may be interlaced with
 * records from another event.  Process and thread ID information is provided
 * in the record, and user applications can de-interlace events if required.
 */

static MALLOC_DEFINE(M_KTRACE, "KTRACE", "KTRACE");

#ifdef KTRACE

FEATURE(ktrace, "Kernel support for system-call tracing");

#ifndef KTRACE_REQUEST_POOL
#define KTRACE_REQUEST_POOL     100
#endif

struct ktr_request {
        struct  ktr_header ktr_header;
        void    *ktr_buffer;
        union {
                struct  ktr_proc_ctor ktr_proc_ctor;
                struct  ktr_syscall ktr_syscall;
                struct  ktr_sysret ktr_sysret;
                struct  ktr_genio ktr_genio;
                struct  ktr_psig ktr_psig;
                struct  ktr_csw ktr_csw;
                struct  ktr_fault ktr_fault;
                struct  ktr_faultend ktr_faultend;
        } ktr_data;
        STAILQ_ENTRY(ktr_request) ktr_list;
};

static int data_lengths[] = {
        0,                                      /* none */
        offsetof(struct ktr_syscall, ktr_args), /* KTR_SYSCALL */
        sizeof(struct ktr_sysret),              /* KTR_SYSRET */
        0,                                      /* KTR_NAMEI */
        sizeof(struct ktr_genio),               /* KTR_GENIO */
        sizeof(struct ktr_psig),                /* KTR_PSIG */
        sizeof(struct ktr_csw),                 /* KTR_CSW */
        0,                                      /* KTR_USER */
        0,                                      /* KTR_STRUCT */
        0,                                      /* KTR_SYSCTL */
        sizeof(struct ktr_proc_ctor),           /* KTR_PROCCTOR */
        0,                                      /* KTR_PROCDTOR */
        0,                                      /* unused */
        sizeof(struct ktr_fault),               /* KTR_FAULT */
        sizeof(struct ktr_faultend),            /* KTR_FAULTEND */
};

static STAILQ_HEAD(, ktr_request) ktr_free;

static SYSCTL_NODE(_kern, OID_AUTO, ktrace, CTLFLAG_RD, 0, "KTRACE options");

static u_int ktr_requestpool = KTRACE_REQUEST_POOL;
TUNABLE_INT("kern.ktrace.request_pool", &ktr_requestpool);

static u_int ktr_geniosize = PAGE_SIZE;
TUNABLE_INT("kern.ktrace.genio_size", &ktr_geniosize);
SYSCTL_UINT(_kern_ktrace, OID_AUTO, genio_size, CTLFLAG_RW, &ktr_geniosize,
    0, "Maximum size of genio event payload");

static int print_message = 1;
static struct mtx ktrace_mtx;
static struct sx ktrace_sx;

static void ktrace_init(void *dummy);
static int sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS);
static u_int ktrace_resize_pool(u_int oldsize, u_int newsize);
static struct ktr_request *ktr_getrequest_entered(struct thread *td, int type);
static struct ktr_request *ktr_getrequest(int type);
static void ktr_submitrequest(struct thread *td, struct ktr_request *req);
static void ktr_freeproc(struct proc *p, struct ucred **uc,
    struct vnode **vp);
static void ktr_freerequest(struct ktr_request *req);
static void ktr_freerequest_locked(struct ktr_request *req);
static void ktr_writerequest(struct thread *td, struct ktr_request *req);
static int ktrcanset(struct thread *,struct proc *);
static int ktrsetchildren(struct thread *,struct proc *,int,int,struct vnode *);
static int ktrops(struct thread *,struct proc *,int,int,struct vnode *);
static void ktrprocctor_entered(struct thread *, struct proc *);

/*
 * ktrace itself generates events, such as context switches, which we do not
 * wish to trace.  Maintain a flag, TDP_INKTRACE, on each thread to determine
 * whether or not it is in a region where tracing of events should be
 * suppressed.
 */
static void
ktrace_enter(struct thread *td)
{

        KASSERT(!(td->td_pflags & TDP_INKTRACE), ("ktrace_enter: flag set"));
        td->td_pflags |= TDP_INKTRACE;
}

static void
ktrace_exit(struct thread *td)
{

        KASSERT(td->td_pflags & TDP_INKTRACE, ("ktrace_exit: flag not set"));
        td->td_pflags &= ~TDP_INKTRACE;
}

static void
ktrace_assert(struct thread *td)
{

        KASSERT(td->td_pflags & TDP_INKTRACE, ("ktrace_assert: flag not set"));
}

static void
ktrace_init(void *dummy)
{
        struct ktr_request *req;
        int i;

        mtx_init(&ktrace_mtx, "ktrace", NULL, MTX_DEF | MTX_QUIET);
        sx_init(&ktrace_sx, "ktrace_sx");
        STAILQ_INIT(&ktr_free);
        for (i = 0; i < ktr_requestpool; i++) {
                req = malloc(sizeof(struct ktr_request), M_KTRACE, M_WAITOK);
                STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
        }
}
SYSINIT(ktrace_init, SI_SUB_KTRACE, SI_ORDER_ANY, ktrace_init, NULL);

static int
sysctl_kern_ktrace_request_pool(SYSCTL_HANDLER_ARGS)
{
        struct thread *td;
        u_int newsize, oldsize, wantsize;
        int error;

        /* Handle easy read-only case first to avoid warnings from GCC. */
        if (!req->newptr) {
                oldsize = ktr_requestpool;
                return (SYSCTL_OUT(req, &oldsize, sizeof(u_int)));
        }

        error = SYSCTL_IN(req, &wantsize, sizeof(u_int));
        if (error)
                return (error);
        td = curthread;
        ktrace_enter(td);
        oldsize = ktr_requestpool;
        newsize = ktrace_resize_pool(oldsize, wantsize);
        ktrace_exit(td);
        error = SYSCTL_OUT(req, &oldsize, sizeof(u_int));
        if (error)
                return (error);
        if (wantsize > oldsize && newsize < wantsize)
                return (ENOSPC);
        return (0);
}
SYSCTL_PROC(_kern_ktrace, OID_AUTO, request_pool, CTLTYPE_UINT|CTLFLAG_RW,
    &ktr_requestpool, 0, sysctl_kern_ktrace_request_pool, "IU",
    "Pool buffer size for ktrace(1)");

static u_int
ktrace_resize_pool(u_int oldsize, u_int newsize)
{
        STAILQ_HEAD(, ktr_request) ktr_new;
        struct ktr_request *req;
        int bound;

        print_message = 1;
        bound = newsize - oldsize;
        if (bound == 0)
                return (ktr_requestpool);
        if (bound < 0) {
                mtx_lock(&ktrace_mtx);
                /* Shrink pool down to newsize if possible. */
                while (bound++ < 0) {
                        req = STAILQ_FIRST(&ktr_free);
                        if (req == NULL)
                                break;
                        STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
                        ktr_requestpool--;
                        free(req, M_KTRACE);
                }
        } else {
                /* Grow pool up to newsize. */
                STAILQ_INIT(&ktr_new);
                while (bound-- > 0) {
                        req = malloc(sizeof(struct ktr_request), M_KTRACE,
                            M_WAITOK);
                        STAILQ_INSERT_HEAD(&ktr_new, req, ktr_list);
                }
                mtx_lock(&ktrace_mtx);
                STAILQ_CONCAT(&ktr_free, &ktr_new);
                ktr_requestpool += (newsize - oldsize);
        }
        mtx_unlock(&ktrace_mtx);
        return (ktr_requestpool);
}

/* ktr_getrequest() assumes that ktr_comm[] is the same size as td_name[]. */
CTASSERT(sizeof(((struct ktr_header *)NULL)->ktr_comm) ==
    (sizeof((struct thread *)NULL)->td_name));

static struct ktr_request *
ktr_getrequest_entered(struct thread *td, int type)
{
        struct ktr_request *req;
        struct proc *p = td->td_proc;
        int pm;

        mtx_lock(&ktrace_mtx);
        if (!KTRCHECK(td, type)) {
                mtx_unlock(&ktrace_mtx);
                return (NULL);
        }
        req = STAILQ_FIRST(&ktr_free);
        if (req != NULL) {
                STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
                req->ktr_header.ktr_type = type;
                if (p->p_traceflag & KTRFAC_DROP) {
                        req->ktr_header.ktr_type |= KTR_DROP;
                        p->p_traceflag &= ~KTRFAC_DROP;
                }
                mtx_unlock(&ktrace_mtx);
                microtime(&req->ktr_header.ktr_time);
                req->ktr_header.ktr_pid = p->p_pid;
                req->ktr_header.ktr_tid = td->td_tid;
                bcopy(td->td_name, req->ktr_header.ktr_comm,
                    sizeof(req->ktr_header.ktr_comm));
                req->ktr_buffer = NULL;
                req->ktr_header.ktr_len = 0;
        } else {
                p->p_traceflag |= KTRFAC_DROP;
                pm = print_message;
                print_message = 0;
                mtx_unlock(&ktrace_mtx);
                if (pm)
                        printf("Out of ktrace request objects.\n");
        }
        return (req);
}

static struct ktr_request *
ktr_getrequest(int type)
{
        struct thread *td = curthread;
        struct ktr_request *req;

        ktrace_enter(td);
        req = ktr_getrequest_entered(td, type);
        if (req == NULL)
                ktrace_exit(td);

        return (req);
}

/*
 * Some trace generation environments don't permit direct access to VFS,
 * such as during a context switch where sleeping is not allowed.  Under these
 * circumstances, queue a request to the thread to be written asynchronously
 * later.
 */
static void
ktr_enqueuerequest(struct thread *td, struct ktr_request *req)
{

        mtx_lock(&ktrace_mtx);
        STAILQ_INSERT_TAIL(&td->td_proc->p_ktr, req, ktr_list);
        mtx_unlock(&ktrace_mtx);
}

/*
 * Drain any pending ktrace records from the per-thread queue to disk.  This
 * is used both internally before committing other records, and also on
 * system call return.  We drain all the ones we can find at the time when
 * drain is requested, but don't keep draining after that as those events
 * may be approximately "after" the current event.
 */
static void
ktr_drain(struct thread *td)
{
        struct ktr_request *queued_req;
        STAILQ_HEAD(, ktr_request) local_queue;

        ktrace_assert(td);
        sx_assert(&ktrace_sx, SX_XLOCKED);

        STAILQ_INIT(&local_queue);

        if (!STAILQ_EMPTY(&td->td_proc->p_ktr)) {
                mtx_lock(&ktrace_mtx);
                STAILQ_CONCAT(&local_queue, &td->td_proc->p_ktr);
                mtx_unlock(&ktrace_mtx);

                while ((queued_req = STAILQ_FIRST(&local_queue))) {
                        STAILQ_REMOVE_HEAD(&local_queue, ktr_list);
                        ktr_writerequest(td, queued_req);
                        ktr_freerequest(queued_req);
                }
        }
}

/*
 * Submit a trace record for immediate commit to disk -- to be used only
 * where entering VFS is OK.  First drain any pending records that may have
 * been cached in the thread.
 */
static void
ktr_submitrequest(struct thread *td, struct ktr_request *req)
{

        ktrace_assert(td);

        sx_xlock(&ktrace_sx);
        ktr_drain(td);
        ktr_writerequest(td, req);
        ktr_freerequest(req);
        sx_xunlock(&ktrace_sx);
        ktrace_exit(td);
}

static void
ktr_freerequest(struct ktr_request *req)
{

        mtx_lock(&ktrace_mtx);
        ktr_freerequest_locked(req);
        mtx_unlock(&ktrace_mtx);
}

static void
ktr_freerequest_locked(struct ktr_request *req)
{

        mtx_assert(&ktrace_mtx, MA_OWNED);
        if (req->ktr_buffer != NULL)
                free(req->ktr_buffer, M_KTRACE);
        STAILQ_INSERT_HEAD(&ktr_free, req, ktr_list);
}

/*
 * Disable tracing for a process and release all associated resources.
 * The caller is responsible for releasing a reference on the returned
 * vnode and credentials.
 */
static void
ktr_freeproc(struct proc *p, struct ucred **uc, struct vnode **vp)
{
        struct ktr_request *req;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        mtx_assert(&ktrace_mtx, MA_OWNED);
        *uc = p->p_tracecred;
        p->p_tracecred = NULL;
        if (vp != NULL)
                *vp = p->p_tracevp;
        p->p_tracevp = NULL;
        p->p_traceflag = 0;
        while ((req = STAILQ_FIRST(&p->p_ktr)) != NULL) {
                STAILQ_REMOVE_HEAD(&p->p_ktr, ktr_list);
                ktr_freerequest_locked(req);
        }
}

void
ktrsyscall(code, narg, args)
        int code, narg;
        register_t args[];
{
        struct ktr_request *req;
        struct ktr_syscall *ktp;
        size_t buflen;
        char *buf = NULL;

        buflen = sizeof(register_t) * narg;
        if (buflen > 0) {
                buf = malloc(buflen, M_KTRACE, M_WAITOK);
                bcopy(args, buf, buflen);
        }
        req = ktr_getrequest(KTR_SYSCALL);
        if (req == NULL) {
                if (buf != NULL)
                        free(buf, M_KTRACE);
                return;
        }
        ktp = &req->ktr_data.ktr_syscall;
        ktp->ktr_code = code;
        ktp->ktr_narg = narg;
        if (buflen > 0) {
                req->ktr_header.ktr_len = buflen;
                req->ktr_buffer = buf;
        }
        ktr_submitrequest(curthread, req);
}

void
ktrsysret(code, error, retval)
        int code, error;
        register_t retval;
{
        struct ktr_request *req;
        struct ktr_sysret *ktp;

        req = ktr_getrequest(KTR_SYSRET);
        if (req == NULL)
                return;
        ktp = &req->ktr_data.ktr_sysret;
        ktp->ktr_code = code;
        ktp->ktr_error = error;
        ktp->ktr_retval = ((error == 0) ? retval: 0);           /* what about val2 ? */
        ktr_submitrequest(curthread, req);
}

/*
 * When a setuid process execs, disable tracing.
 *
 * XXX: We toss any pending asynchronous records.
 */
void
ktrprocexec(struct proc *p, struct ucred **uc, struct vnode **vp)
{

        PROC_LOCK_ASSERT(p, MA_OWNED);
        mtx_lock(&ktrace_mtx);
        ktr_freeproc(p, uc, vp);
        mtx_unlock(&ktrace_mtx);
}

/*
 * When a process exits, drain per-process asynchronous trace records
 * and disable tracing.
 */
void
ktrprocexit(struct thread *td)
{
        struct ktr_request *req;
        struct proc *p;
        struct ucred *cred;
        struct vnode *vp;
        int vfslocked;

        p = td->td_proc;
        if (p->p_traceflag == 0)
                return;

        ktrace_enter(td);
        req = ktr_getrequest_entered(td, KTR_PROCDTOR);
        if (req != NULL)
                ktr_enqueuerequest(td, req);
        sx_xlock(&ktrace_sx);
        ktr_drain(td);
        sx_xunlock(&ktrace_sx);
        PROC_LOCK(p);
        mtx_lock(&ktrace_mtx);
        ktr_freeproc(p, &cred, &vp);
        mtx_unlock(&ktrace_mtx);
        PROC_UNLOCK(p);
        if (vp != NULL) {
                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                vrele(vp);
                VFS_UNLOCK_GIANT(vfslocked);
        }
        if (cred != NULL)
                crfree(cred);
        ktrace_exit(td);
}

static void
ktrprocctor_entered(struct thread *td, struct proc *p)
{
        struct ktr_proc_ctor *ktp;
        struct ktr_request *req;
        struct thread *td2;

        ktrace_assert(td);
        td2 = FIRST_THREAD_IN_PROC(p);
        req = ktr_getrequest_entered(td2, KTR_PROCCTOR);
        if (req == NULL)
                return;
        ktp = &req->ktr_data.ktr_proc_ctor;
        ktp->sv_flags = p->p_sysent->sv_flags;
        ktr_enqueuerequest(td2, req);
}

void
ktrprocctor(struct proc *p)
{
        struct thread *td = curthread;

        if ((p->p_traceflag & KTRFAC_MASK) == 0)
                return;

        ktrace_enter(td);
        ktrprocctor_entered(td, p);
        ktrace_exit(td);
}

/*
 * When a process forks, enable tracing in the new process if needed.
 */
void
ktrprocfork(struct proc *p1, struct proc *p2)
{

        PROC_LOCK(p1);
        mtx_lock(&ktrace_mtx);
        KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode"));
        if (p1->p_traceflag & KTRFAC_INHERIT) {
                p2->p_traceflag = p1->p_traceflag;
                if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
                        VREF(p2->p_tracevp);
                        KASSERT(p1->p_tracecred != NULL,
                            ("ktrace vnode with no cred"));
                        p2->p_tracecred = crhold(p1->p_tracecred);
                }
        }
        mtx_unlock(&ktrace_mtx);
        PROC_UNLOCK(p1);

        ktrprocctor(p2);
}

/*
 * When a thread returns, drain any asynchronous records generated by the
 * system call.
 */
void
ktruserret(struct thread *td)
{

        ktrace_enter(td);
        sx_xlock(&ktrace_sx);
        ktr_drain(td);
        sx_xunlock(&ktrace_sx);
        ktrace_exit(td);
}

void
ktrnamei(path)
        char *path;
{
        struct ktr_request *req;
        int namelen;
        char *buf = NULL;

        namelen = strlen(path);
        if (namelen > 0) {
                buf = malloc(namelen, M_KTRACE, M_WAITOK);
                bcopy(path, buf, namelen);
        }
        req = ktr_getrequest(KTR_NAMEI);
        if (req == NULL) {
                if (buf != NULL)
                        free(buf, M_KTRACE);
                return;
        }
        if (namelen > 0) {
                req->ktr_header.ktr_len = namelen;
                req->ktr_buffer = buf;
        }
        ktr_submitrequest(curthread, req);
}

void
ktrsysctl(name, namelen)
        int *name;
        u_int namelen;
{
        struct ktr_request *req;
        u_int mib[CTL_MAXNAME + 2];
        char *mibname;
        size_t mibnamelen;
        int error;

        /* Lookup name of mib. */    
        KASSERT(namelen <= CTL_MAXNAME, ("sysctl MIB too long"));
        mib[0] = 0;
        mib[1] = 1;
        bcopy(name, mib + 2, namelen * sizeof(*name));
        mibnamelen = 128;
        mibname = malloc(mibnamelen, M_KTRACE, M_WAITOK);
        error = kernel_sysctl(curthread, mib, namelen + 2, mibname, &mibnamelen,
            NULL, 0, &mibnamelen, 0);
        if (error) {
                free(mibname, M_KTRACE);
                return;
        }
        req = ktr_getrequest(KTR_SYSCTL);
        if (req == NULL) {
                free(mibname, M_KTRACE);
                return;
        }
        req->ktr_header.ktr_len = mibnamelen;
        req->ktr_buffer = mibname;
        ktr_submitrequest(curthread, req);
}

void
ktrgenio(fd, rw, uio, error)
        int fd;
        enum uio_rw rw;
        struct uio *uio;
        int error;
{
        struct ktr_request *req;
        struct ktr_genio *ktg;
        int datalen;
        char *buf;

        if (error) {
                free(uio, M_IOV);
                return;
        }
        uio->uio_offset = 0;
        uio->uio_rw = UIO_WRITE;
        datalen = MIN(uio->uio_resid, ktr_geniosize);
        buf = malloc(datalen, M_KTRACE, M_WAITOK);
        error = uiomove(buf, datalen, uio);
        free(uio, M_IOV);
        if (error) {
                free(buf, M_KTRACE);
                return;
        }
        req = ktr_getrequest(KTR_GENIO);
        if (req == NULL) {
                free(buf, M_KTRACE);
                return;
        }
        ktg = &req->ktr_data.ktr_genio;
        ktg->ktr_fd = fd;
        ktg->ktr_rw = rw;
        req->ktr_header.ktr_len = datalen;
        req->ktr_buffer = buf;
        ktr_submitrequest(curthread, req);
}

void
ktrpsig(sig, action, mask, code)
        int sig;
        sig_t action;
        sigset_t *mask;
        int code;
{
        struct thread *td = curthread;
        struct ktr_request *req;
        struct ktr_psig *kp;

        req = ktr_getrequest(KTR_PSIG);
        if (req == NULL)
                return;
        kp = &req->ktr_data.ktr_psig;
        kp->signo = (char)sig;
        kp->action = action;
        kp->mask = *mask;
        kp->code = code;
        ktr_enqueuerequest(td, req);
        ktrace_exit(td);
}

void
ktrcsw(out, user, wmesg)
        int out, user;
        const char *wmesg;
{
        struct thread *td = curthread;
        struct ktr_request *req;
        struct ktr_csw *kc;

        req = ktr_getrequest(KTR_CSW);
        if (req == NULL)
                return;
        kc = &req->ktr_data.ktr_csw;
        kc->out = out;
        kc->user = user;
        if (wmesg != NULL)
                strlcpy(kc->wmesg, wmesg, sizeof(kc->wmesg));
        else
                bzero(kc->wmesg, sizeof(kc->wmesg));
        ktr_enqueuerequest(td, req);
        ktrace_exit(td);
}

void
ktrstruct(name, data, datalen)
        const char *name;
        void *data;
        size_t datalen;
{
        struct ktr_request *req;
        char *buf = NULL;
        size_t buflen;

        if (!data)
                datalen = 0;
        buflen = strlen(name) + 1 + datalen;
        buf = malloc(buflen, M_KTRACE, M_WAITOK);
        strcpy(buf, name);
        bcopy(data, buf + strlen(name) + 1, datalen);
        if ((req = ktr_getrequest(KTR_STRUCT)) == NULL) {
                free(buf, M_KTRACE);
                return;
        }
        req->ktr_buffer = buf;
        req->ktr_header.ktr_len = buflen;
        ktr_submitrequest(curthread, req);
}

void
ktrfault(vaddr, type)
        vm_offset_t vaddr;
        int type;
{
        struct thread *td = curthread;
        struct ktr_request *req;
        struct ktr_fault *kf;

        req = ktr_getrequest(KTR_FAULT);
        if (req == NULL)
                return;
        kf = &req->ktr_data.ktr_fault;
        kf->vaddr = vaddr;
        kf->type = type;
        ktr_enqueuerequest(td, req);
        ktrace_exit(td);
}

void
ktrfaultend(result)
        int result;
{
        struct thread *td = curthread;
        struct ktr_request *req;
        struct ktr_faultend *kf;

        req = ktr_getrequest(KTR_FAULTEND);
        if (req == NULL)
                return;
        kf = &req->ktr_data.ktr_faultend;
        kf->result = result;
        ktr_enqueuerequest(td, req);
        ktrace_exit(td);
}
#endif /* KTRACE */

/* Interface and common routines */

#ifndef _SYS_SYSPROTO_H_
struct ktrace_args {
        char    *fname;
        int     ops;
        int     facs;
        int     pid;
};
#endif
/* ARGSUSED */
int
sys_ktrace(td, uap)
        struct thread *td;
        register struct ktrace_args *uap;
{
#ifdef KTRACE
        register struct vnode *vp = NULL;
        register struct proc *p;
        struct pgrp *pg;
        int facs = uap->facs & ~KTRFAC_ROOT;
        int ops = KTROP(uap->ops);
        int descend = uap->ops & KTRFLAG_DESCEND;
        int nfound, ret = 0;
        int flags, error = 0, vfslocked;
        struct nameidata nd;
        struct ucred *cred;

        /*
         * Need something to (un)trace.
         */
        if (ops != KTROP_CLEARFILE && facs == 0)
                return (EINVAL);

        ktrace_enter(td);
        if (ops != KTROP_CLEAR) {
                /*
                 * an operation which requires a file argument.
                 */
                NDINIT(&nd, LOOKUP, NOFOLLOW | MPSAFE, UIO_USERSPACE,
                    uap->fname, td);
                flags = FREAD | FWRITE | O_NOFOLLOW;
                error = vn_open(&nd, &flags, 0, NULL);
                if (error) {
                        ktrace_exit(td);
                        return (error);
                }
                vfslocked = NDHASGIANT(&nd);
                NDFREE(&nd, NDF_ONLY_PNBUF);
                vp = nd.ni_vp;
                VOP_UNLOCK(vp, 0);
                if (vp->v_type != VREG) {
                        (void) vn_close(vp, FREAD|FWRITE, td->td_ucred, td);
                        VFS_UNLOCK_GIANT(vfslocked);
                        ktrace_exit(td);
                        return (EACCES);
                }
                VFS_UNLOCK_GIANT(vfslocked);
        }
        /*
         * Clear all uses of the tracefile.
         */
        if (ops == KTROP_CLEARFILE) {
                int vrele_count;

                vrele_count = 0;
                sx_slock(&allproc_lock);
                FOREACH_PROC_IN_SYSTEM(p) {
                        PROC_LOCK(p);
                        if (p->p_tracevp == vp) {
                                if (ktrcanset(td, p)) {
                                        mtx_lock(&ktrace_mtx);
                                        ktr_freeproc(p, &cred, NULL);
                                        mtx_unlock(&ktrace_mtx);
                                        vrele_count++;
                                        crfree(cred);
                                } else
                                        error = EPERM;
                        }
                        PROC_UNLOCK(p);
                }
                sx_sunlock(&allproc_lock);
                if (vrele_count > 0) {
                        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                        while (vrele_count-- > 0)
                                vrele(vp);
                        VFS_UNLOCK_GIANT(vfslocked);
                }
                goto done;
        }
        /*
         * do it
         */
        sx_slock(&proctree_lock);
        if (uap->pid < 0) {
                /*
                 * by process group
                 */
                pg = pgfind(-uap->pid);
                if (pg == NULL) {
                        sx_sunlock(&proctree_lock);
                        error = ESRCH;
                        goto done;
                }
                /*
                 * ktrops() may call vrele(). Lock pg_members
                 * by the proctree_lock rather than pg_mtx.
                 */
                PGRP_UNLOCK(pg);
                nfound = 0;
                LIST_FOREACH(p, &pg->pg_members, p_pglist) {
                        PROC_LOCK(p);
                        if (p->p_state == PRS_NEW ||
                            p_cansee(td, p) != 0) {
                                PROC_UNLOCK(p); 
                                continue;
                        }
                        nfound++;
                        if (descend)
                                ret |= ktrsetchildren(td, p, ops, facs, vp);
                        else
                                ret |= ktrops(td, p, ops, facs, vp);
                }
                if (nfound == 0) {
                        sx_sunlock(&proctree_lock);
                        error = ESRCH;
                        goto done;
                }
        } else {
                /*
                 * by pid
                 */
                p = pfind(uap->pid);
                if (p == NULL)
                        error = ESRCH;
                else
                        error = p_cansee(td, p);
                if (error) {
                        if (p != NULL)
                                PROC_UNLOCK(p);
                        sx_sunlock(&proctree_lock);
                        goto done;
                }
                if (descend)
                        ret |= ktrsetchildren(td, p, ops, facs, vp);
                else
                        ret |= ktrops(td, p, ops, facs, vp);
        }
        sx_sunlock(&proctree_lock);
        if (!ret)
                error = EPERM;
done:
        if (vp != NULL) {
                vfslocked = VFS_LOCK_GIANT(vp->v_mount);
                (void) vn_close(vp, FWRITE, td->td_ucred, td);
                VFS_UNLOCK_GIANT(vfslocked);
        }
        ktrace_exit(td);
        return (error);
#else /* !KTRACE */
        return (ENOSYS);
#endif /* KTRACE */
}

/* ARGSUSED */
int
sys_utrace(td, uap)
        struct thread *td;
        register struct utrace_args *uap;
{

#ifdef KTRACE
        struct ktr_request *req;
        void *cp;
        int error;

        if (!KTRPOINT(td, KTR_USER))
                return (0);
        if (uap->len > KTR_USER_MAXLEN)
                return (EINVAL);
        cp = malloc(uap->len, M_KTRACE, M_WAITOK);
        error = copyin(uap->addr, cp, uap->len);
        if (error) {
                free(cp, M_KTRACE);
                return (error);
        }
        req = ktr_getrequest(KTR_USER);
        if (req == NULL) {
                free(cp, M_KTRACE);
                return (ENOMEM);
        }
        req->ktr_buffer = cp;
        req->ktr_header.ktr_len = uap->len;
        ktr_submitrequest(td, req);
        return (0);
#else /* !KTRACE */
        return (ENOSYS);
#endif /* KTRACE */
}

#ifdef KTRACE
static int
ktrops(td, p, ops, facs, vp)
        struct thread *td;
        struct proc *p;
        int ops, facs;
        struct vnode *vp;
{
        struct vnode *tracevp = NULL;
        struct ucred *tracecred = NULL;

        PROC_LOCK_ASSERT(p, MA_OWNED);
        if (!ktrcanset(td, p)) {
                PROC_UNLOCK(p);
                return (0);
        }
        if (p->p_flag & P_WEXIT) {
                /* If the process is exiting, just ignore it. */
                PROC_UNLOCK(p);
                return (1);
        }
        mtx_lock(&ktrace_mtx);
        if (ops == KTROP_SET) {
                if (p->p_tracevp != vp) {
                        /*
                         * if trace file already in use, relinquish below
                         */
                        tracevp = p->p_tracevp;
                        VREF(vp);
                        p->p_tracevp = vp;
                }
                if (p->p_tracecred != td->td_ucred) {
                        tracecred = p->p_tracecred;
                        p->p_tracecred = crhold(td->td_ucred);
                }
                p->p_traceflag |= facs;
                if (priv_check(td, PRIV_KTRACE) == 0)
                        p->p_traceflag |= KTRFAC_ROOT;
        } else {
                /* KTROP_CLEAR */
                if (((p->p_traceflag &= ~facs) & KTRFAC_MASK) == 0)
                        /* no more tracing */
                        ktr_freeproc(p, &tracecred, &tracevp);
        }
        mtx_unlock(&ktrace_mtx);
        if ((p->p_traceflag & KTRFAC_MASK) != 0)
                ktrprocctor_entered(td, p);
        PROC_UNLOCK(p);
        if (tracevp != NULL) {
                int vfslocked;

                vfslocked = VFS_LOCK_GIANT(tracevp->v_mount);
                vrele(tracevp);
                VFS_UNLOCK_GIANT(vfslocked);
        }
        if (tracecred != NULL)
                crfree(tracecred);

        return (1);
}

static int
ktrsetchildren(td, top, ops, facs, vp)
        struct thread *td;
        struct proc *top;
        int ops, facs;
        struct vnode *vp;
{
        register struct proc *p;
        register int ret = 0;

        p = top;
        PROC_LOCK_ASSERT(p, MA_OWNED);
        sx_assert(&proctree_lock, SX_LOCKED);
        for (;;) {
                ret |= ktrops(td, p, ops, facs, vp);
                /*
                 * If this process has children, descend to them next,
                 * otherwise do any siblings, and if done with this level,
                 * follow back up the tree (but not past top).
                 */
                if (!LIST_EMPTY(&p->p_children))
                        p = LIST_FIRST(&p->p_children);
                else for (;;) {
                        if (p == top)
                                return (ret);
                        if (LIST_NEXT(p, p_sibling)) {
                                p = LIST_NEXT(p, p_sibling);
                                break;
                        }
                        p = p->p_pptr;
                }
                PROC_LOCK(p);
        }
        /*NOTREACHED*/
}

static void
ktr_writerequest(struct thread *td, struct ktr_request *req)
{
        struct ktr_header *kth;
        struct vnode *vp;
        struct proc *p;
        struct ucred *cred;
        struct uio auio;
        struct iovec aiov[3];
        struct mount *mp;
        int datalen, buflen, vrele_count;
        int error, vfslocked;

        /*
         * We hold the vnode and credential for use in I/O in case ktrace is
         * disabled on the process as we write out the request.
         *
         * XXXRW: This is not ideal: we could end up performing a write after
         * the vnode has been closed.
         */
        mtx_lock(&ktrace_mtx);
        vp = td->td_proc->p_tracevp;
        cred = td->td_proc->p_tracecred;

        /*
         * If vp is NULL, the vp has been cleared out from under this
         * request, so just drop it.  Make sure the credential and vnode are
         * in sync: we should have both or neither.
         */
        if (vp == NULL) {
                KASSERT(cred == NULL, ("ktr_writerequest: cred != NULL"));
                mtx_unlock(&ktrace_mtx);
                return;
        }
        VREF(vp);
        KASSERT(cred != NULL, ("ktr_writerequest: cred == NULL"));
        crhold(cred);
        mtx_unlock(&ktrace_mtx);

        kth = &req->ktr_header;
        KASSERT(((u_short)kth->ktr_type & ~KTR_DROP) <
            sizeof(data_lengths) / sizeof(data_lengths[0]),
            ("data_lengths array overflow"));
        datalen = data_lengths[(u_short)kth->ktr_type & ~KTR_DROP];
        buflen = kth->ktr_len;
        auio.uio_iov = &aiov[0];
        auio.uio_offset = 0;
        auio.uio_segflg = UIO_SYSSPACE;
        auio.uio_rw = UIO_WRITE;
        aiov[0].iov_base = (caddr_t)kth;
        aiov[0].iov_len = sizeof(struct ktr_header);
        auio.uio_resid = sizeof(struct ktr_header);
        auio.uio_iovcnt = 1;
        auio.uio_td = td;
        if (datalen != 0) {
                aiov[1].iov_base = (caddr_t)&req->ktr_data;
                aiov[1].iov_len = datalen;
                auio.uio_resid += datalen;
                auio.uio_iovcnt++;
                kth->ktr_len += datalen;
        }
        if (buflen != 0) {
                KASSERT(req->ktr_buffer != NULL, ("ktrace: nothing to write"));
                aiov[auio.uio_iovcnt].iov_base = req->ktr_buffer;
                aiov[auio.uio_iovcnt].iov_len = buflen;
                auio.uio_resid += buflen;
                auio.uio_iovcnt++;
        }

        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
        vn_start_write(vp, &mp, V_WAIT);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
#ifdef MAC
        error = mac_vnode_check_write(cred, NOCRED, vp);
        if (error == 0)
#endif
                error = VOP_WRITE(vp, &auio, IO_UNIT | IO_APPEND, cred);
        VOP_UNLOCK(vp, 0);
        vn_finished_write(mp);
        crfree(cred);
        if (!error) {
                vrele(vp);
                VFS_UNLOCK_GIANT(vfslocked);
                return;
        }
        VFS_UNLOCK_GIANT(vfslocked);

        /*
         * If error encountered, give up tracing on this vnode.  We defer
         * all the vrele()'s on the vnode until after we are finished walking
         * the various lists to avoid needlessly holding locks.
         * NB: at this point we still hold the vnode reference that must
         * not go away as we need the valid vnode to compare with. Thus let
         * vrele_count start at 1 and the reference will be freed
         * by the loop at the end after our last use of vp.
         */
        log(LOG_NOTICE, "ktrace write failed, errno %d, tracing stopped\n",
            error);
        vrele_count = 1;
        /*
         * First, clear this vnode from being used by any processes in the
         * system.
         * XXX - If one process gets an EPERM writing to the vnode, should
         * we really do this?  Other processes might have suitable
         * credentials for the operation.
         */
        cred = NULL;
        sx_slock(&allproc_lock);
        FOREACH_PROC_IN_SYSTEM(p) {
                PROC_LOCK(p);
                if (p->p_tracevp == vp) {
                        mtx_lock(&ktrace_mtx);
                        ktr_freeproc(p, &cred, NULL);
                        mtx_unlock(&ktrace_mtx);
                        vrele_count++;
                }
                PROC_UNLOCK(p);
                if (cred != NULL) {
                        crfree(cred);
                        cred = NULL;
                }
        }
        sx_sunlock(&allproc_lock);

        vfslocked = VFS_LOCK_GIANT(vp->v_mount);
        while (vrele_count-- > 0)
                vrele(vp);
        VFS_UNLOCK_GIANT(vfslocked);
}

/*
 * Return true if caller has permission to set the ktracing state
 * of target.  Essentially, the target can't possess any
 * more permissions than the caller.  KTRFAC_ROOT signifies that
 * root previously set the tracing status on the target process, and
 * so, only root may further change it.
 */
static int
ktrcanset(td, targetp)
        struct thread *td;
        struct proc *targetp;
{

        PROC_LOCK_ASSERT(targetp, MA_OWNED);
        if (targetp->p_traceflag & KTRFAC_ROOT &&
            priv_check(td, PRIV_KTRACE))
                return (0);

        if (p_candebug(td, targetp) != 0)
                return (0);

        return (1);
}

#endif /* KTRACE */