diff --git a/include/unistd.h b/include/unistd.h
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -519,6 +519,7 @@
 int	 iruserok_sa(const void *, int, int, const char *, const char *);
 int	 issetugid(void);
 void	__FreeBSD_libc_enter_restricted_mode(void);
+int	 kcmp(pid_t pid1, pid_t pid2, int type, uintptr_t idx1, uintptr_t idx2);
 long	 lpathconf(const char *, int);
 #ifndef _MKDTEMP_DECLARED
 char	*mkdtemp(char *);
diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
--- a/lib/libc/sys/Symbol.map
+++ b/lib/libc/sys/Symbol.map
@@ -424,6 +424,10 @@
 	timerfd_settime;
 };
 
+FBSD_1.8 {
+	 kcmp;
+};
+
 FBSDprivate_1.0 {
 	/* System call stubs */
 	___acl_aclcheck_fd;
diff --git a/sys/compat/linuxkpi/common/src/linux_compat.c b/sys/compat/linuxkpi/common/src/linux_compat.c
--- a/sys/compat/linuxkpi/common/src/linux_compat.c
+++ b/sys/compat/linuxkpi/common/src/linux_compat.c
@@ -1721,6 +1721,19 @@
 	return (minor(ldev->dev));
 }
 
+static int
+linux_file_kcmp(struct file *fp1, struct file *fp2, struct thread *td)
+{
+	struct linux_file *filp1, *filp2;
+
+	if (fp2->f_type != DTYPE_DEV)
+		return (3);
+
+	filp1 = fp1->f_data;
+	filp2 = fp2->f_data;
+	return (kcmp_cmp((uintptr_t)filp1->f_cdev, (uintptr_t)filp2->f_cdev));
+}
+
 struct fileops linuxfileops = {
 	.fo_read = linux_file_read,
 	.fo_write = linux_file_write,
@@ -1735,6 +1748,7 @@
 	.fo_chmod = invfo_chmod,
 	.fo_chown = invfo_chown,
 	.fo_sendfile = invfo_sendfile,
+	.fo_cmp = linux_file_kcmp,
 	.fo_flags = DFLAG_PASSABLE,
 };
 
diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c
--- a/sys/fs/devfs/devfs_vnops.c
+++ b/sys/fs/devfs/devfs_vnops.c
@@ -2010,6 +2010,14 @@
 	return (cdev2priv(x)->cdp_inode);
 }
 
+static int
+devfs_cmp_f(struct file *fp1, struct file *fp2, struct thread *td)
+{
+	if (fp2->f_type != DTYPE_VNODE || fp2->f_ops != &devfs_ops_f)
+		return (3);
+	return (kcmp_cmp((uintptr_t)fp1->f_data, (uintptr_t)fp2->f_data));
+}
+
 static struct fileops devfs_ops_f = {
 	.fo_read =	devfs_read_f,
 	.fo_write =	devfs_write_f,
@@ -2025,6 +2033,7 @@
 	.fo_seek =	vn_seek,
 	.fo_fill_kinfo = vn_fill_kinfo,
 	.fo_mmap =	devfs_mmap_f,
+	.fo_cmp =	devfs_cmp_f,
 	.fo_flags =	DFLAG_PASSABLE | DFLAG_SEEKABLE
 };
 
diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -2960,6 +2960,38 @@
 }
 #endif
 
+int
+fget_remote(struct thread *td, struct proc *p, int fd, struct file **fpp)
+{
+	struct filedesc *fdp;
+	struct file *fp;
+	int error;
+
+	if (p == td->td_proc)	/* curproc */
+		return (fget_unlocked(td, fd, &cap_no_rights, fpp));
+
+	PROC_LOCK(p);
+	fdp = fdhold(p);
+	PROC_UNLOCK(p);
+	if (fdp == NULL)
+		return (ENOENT);
+	FILEDESC_SLOCK(fdp);
+	if (refcount_load(&fdp->fd_refcnt) != 0) {
+		fp = fget_noref(fdp, fd);
+		if (fp != NULL && fhold(fp)) {
+			*fpp = fp;
+			error = 0;
+		} else {
+			error = EBADF;
+		}
+	} else {
+		error = ENOENT;
+	}
+	FILEDESC_SUNLOCK(fdp);
+	fddrop(fdp);
+	return (error);
+}
+
 #ifdef CAPABILITIES
 int
 fgetvp_lookup_smr(struct nameidata *ndp, struct vnode **vpp, bool *fsearch)
@@ -5253,6 +5285,7 @@
 	.fo_chown = badfo_chown,
 	.fo_sendfile = badfo_sendfile,
 	.fo_fill_kinfo = vn_fill_kinfo,
+	.fo_cmp = vn_cmp,
 	.fo_flags = DFLAG_PASSABLE,
 };
 
diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -139,6 +139,7 @@
 	.fo_chmod = invfo_chmod,
 	.fo_chown = invfo_chown,
 	.fo_sendfile = invfo_sendfile,
+	.fo_cmp = file_kcmp_generic,
 	.fo_fill_kinfo = kqueue_fill_kinfo,
 };
 
diff --git a/sys/kern/sys_eventfd.c b/sys/kern/sys_eventfd.c
--- a/sys/kern/sys_eventfd.c
+++ b/sys/kern/sys_eventfd.c
@@ -76,6 +76,7 @@
 	.fo_chown = invfo_chown,
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = eventfd_fill_kinfo,
+	.fo_cmp = file_kcmp_generic,
 	.fo_flags = DFLAG_PASSABLE
 };
 
diff --git a/sys/kern/sys_generic.c b/sys/kern/sys_generic.c
--- a/sys/kern/sys_generic.c
+++ b/sys/kern/sys_generic.c
@@ -65,6 +65,7 @@
 #include <sys/sysctl.h>
 #include <sys/sysent.h>
 #include <sys/vnode.h>
+#include <sys/unistd.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
 #include <sys/condvar.h>
@@ -2071,3 +2072,97 @@
 	td->td_retval[0] = error;
 	return (0);
 }
+
+int
+kcmp_cmp(uintptr_t a, uintptr_t b)
+{
+	if (a == b)
+		return (0);
+	else if (a < b)
+		return (1);
+	return (2);
+}
+
+static int
+kcmp_pget(struct thread *td, pid_t pid, struct proc **pp)
+{
+	if (pid == td->td_proc->p_pid) {
+		*pp = td->td_proc;
+		return (0);
+	}
+	return (pget(pid, PGET_CANDEBUG | PGET_NOTWEXIT | PGET_HOLD, pp));
+}
+
+int
+kern_kcmp(struct thread *td, pid_t pid1, pid_t pid2, int type,
+    uintptr_t idx1, uintptr_t idx2)
+{
+	struct proc *p1, *p2;
+	struct file *fp1, *fp2;
+	int error, res;
+
+	res = -1;
+	p1 = p2 = NULL;
+	error = kcmp_pget(td, pid1, &p1);
+	if (error == 0)
+		error = kcmp_pget(td, pid2, &p2);
+	if (error != 0)
+		goto out;
+
+	switch (type) {
+	case KCMP_FILE:
+	case KCMP_FILEOBJ:
+		error = fget_remote(td, p1, idx1, &fp1);
+		if (error == 0) {
+			error = fget_remote(td, p2, idx2, &fp2);
+			if (error == 0) {
+				if (type == KCMP_FILEOBJ)
+					res = fo_cmp(fp1, fp2, td);
+				else
+					res = kcmp_cmp((uintptr_t)fp1,
+					    (uintptr_t)fp2);
+				fdrop(fp2, td);
+			}
+			fdrop(fp1, td);
+		}
+		break;
+	case KCMP_FILES:
+		res = kcmp_cmp((uintptr_t)p1->p_fd, (uintptr_t)p2->p_fd);
+		break;
+	case KCMP_SIGHAND:
+		res = kcmp_cmp((uintptr_t)p1->p_sigacts,
+		    (uintptr_t)p2->p_sigacts);
+		break;
+	case KCMP_VM:
+		res = kcmp_cmp((uintptr_t)p1->p_vmspace,
+		    (uintptr_t)p2->p_vmspace);
+		break;
+	default:
+		error = EINVAL;
+		break;
+	}
+
+out:
+	if (p1 != NULL && p1 != td->td_proc)
+		PRELE(p1);
+	if (p2 != NULL && p2 != td->td_proc)
+		PRELE(p2);
+
+	td->td_retval[0] = res;
+	return (error);
+}
+
+int
+sys_kcmp(struct thread *td, struct kcmp_args *uap)
+{
+	return (kern_kcmp(td, uap->pid1, uap->pid2, uap->type,
+	    uap->idx1, uap->idx2));
+}
+
+int
+file_kcmp_generic(struct file *fp1, struct file *fp2, struct thread *td)
+{
+	if (fp1->f_type != fp2->f_type)
+		return (3);
+	return (kcmp_cmp((uintptr_t)fp1->f_data, (uintptr_t)fp2->f_data));
+}
diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -165,6 +165,7 @@
 	.fo_chown = pipe_chown,
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = pipe_fill_kinfo,
+	.fo_cmp = file_kcmp_generic,
 	.fo_flags = DFLAG_PASSABLE
 };
 
diff --git a/sys/kern/sys_procdesc.c b/sys/kern/sys_procdesc.c
--- a/sys/kern/sys_procdesc.c
+++ b/sys/kern/sys_procdesc.c
@@ -94,6 +94,7 @@
 static fo_stat_t	procdesc_stat;
 static fo_close_t	procdesc_close;
 static fo_fill_kinfo_t	procdesc_fill_kinfo;
+static fo_cmp_t		procdesc_cmp;
 
 static struct fileops procdesc_ops = {
 	.fo_read = invfo_rdwr,
@@ -108,6 +109,7 @@
 	.fo_chown = invfo_chown,
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = procdesc_fill_kinfo,
+	.fo_cmp = procdesc_cmp,
 	.fo_flags = DFLAG_PASSABLE,
 };
 
@@ -552,3 +554,15 @@
 	kif->kf_un.kf_proc.kf_pid = pdp->pd_pid;
 	return (0);
 }
+
+static int
+procdesc_cmp(struct file *fp1, struct file *fp2, struct thread *td)
+{
+	struct procdesc *pdp1, *pdp2;
+
+	if (fp2->f_type != DTYPE_PROCDESC)
+		return (3);
+	pdp1 = fp1->f_data;
+	pdp2 = fp2->f_data;
+	return (kcmp_cmp((uintptr_t)pdp1->pd_pid, (uintptr_t)pdp2->pd_pid));
+}
diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
--- a/sys/kern/sys_socket.c
+++ b/sys/kern/sys_socket.c
@@ -109,6 +109,7 @@
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = soo_fill_kinfo,
 	.fo_aio_queue = soo_aio_queue,
+	.fo_cmp = file_kcmp_generic,
 	.fo_flags = DFLAG_PASSABLE
 };
 
diff --git a/sys/kern/sys_timerfd.c b/sys/kern/sys_timerfd.c
--- a/sys/kern/sys_timerfd.c
+++ b/sys/kern/sys_timerfd.c
@@ -371,6 +371,7 @@
 	.fo_chown = invfo_chown,
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = timerfd_fill_kinfo,
+	.fo_cmp = file_kcmp_generic,
 	.fo_flags = DFLAG_PASSABLE,
 };
 
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -3329,6 +3329,14 @@
 		    _Out_opt_ _Contains_long_timet_ struct itimerspec *old_value
 		);
 	}
-
+588	AUE_NULL	STD {
+		int kcmp(
+		    pid_t pid1,
+		    pid_t pid2,
+		    int type,
+		    uintptr_t idx1,
+		    uintptr_t idx2
+		);
+	}
 
 ; vim: syntax=off
diff --git a/sys/kern/tty_pts.c b/sys/kern/tty_pts.c
--- a/sys/kern/tty_pts.c
+++ b/sys/kern/tty_pts.c
@@ -610,6 +610,7 @@
 	.fo_chown	= invfo_chown,
 	.fo_sendfile	= invfo_sendfile,
 	.fo_fill_kinfo	= ptsdev_fill_kinfo,
+	.fo_cmp		= file_kcmp_generic,
 	.fo_flags	= DFLAG_PASSABLE,
 };
 
diff --git a/sys/kern/uipc_mqueue.c b/sys/kern/uipc_mqueue.c
--- a/sys/kern/uipc_mqueue.c
+++ b/sys/kern/uipc_mqueue.c
@@ -2661,6 +2661,7 @@
 	.fo_chown		= mqf_chown,
 	.fo_sendfile		= invfo_sendfile,
 	.fo_fill_kinfo		= mqf_fill_kinfo,
+	.fo_cmp			= file_kcmp_generic,
 	.fo_flags		= DFLAG_PASSABLE,
 };
 
diff --git a/sys/kern/uipc_sem.c b/sys/kern/uipc_sem.c
--- a/sys/kern/uipc_sem.c
+++ b/sys/kern/uipc_sem.c
@@ -153,6 +153,7 @@
 	.fo_chown = ksem_chown,
 	.fo_sendfile = invfo_sendfile,
 	.fo_fill_kinfo = ksem_fill_kinfo,
+	.fo_cmp = file_kcmp_generic,
 	.fo_flags = DFLAG_PASSABLE
 };
 
diff --git a/sys/kern/uipc_shm.c b/sys/kern/uipc_shm.c
--- a/sys/kern/uipc_shm.c
+++ b/sys/kern/uipc_shm.c
@@ -169,6 +169,7 @@
 	.fo_add_seals = shm_add_seals,
 	.fo_fallocate = shm_fallocate,
 	.fo_fspacectl = shm_fspacectl,
+	.fo_cmp = file_kcmp_generic,
 	.fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE,
 };
 
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -123,6 +123,7 @@
 	.fo_mmap = vn_mmap,
 	.fo_fallocate = vn_fallocate,
 	.fo_fspacectl = vn_fspacectl,
+	.fo_cmp = vn_cmp,
 	.fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
 };
 
@@ -4228,3 +4229,11 @@
 		return (LK_SHARED);
 	return (LK_EXCLUSIVE);
 }
+
+int
+vn_cmp(struct file *fp1, struct file *fp2, struct thread *td)
+{
+	if (fp2->f_type != DTYPE_VNODE)
+		return (3);
+	return (kcmp_cmp((uintptr_t)fp1->f_vnode, (uintptr_t)fp2->f_vnode));
+}
diff --git a/sys/sys/file.h b/sys/sys/file.h
--- a/sys/sys/file.h
+++ b/sys/sys/file.h
@@ -129,6 +129,7 @@
 typedef int fo_fspacectl_t(struct file *fp, int cmd,
 		    off_t *offset, off_t *length, int flags,
 		    struct ucred *active_cred, struct thread *td);
+typedef int fo_cmp_t(struct file *fp, struct file *fp1, struct thread *td);
 typedef int fo_spare_t(struct file *fp);
 typedef	int fo_flags_t;
 
@@ -152,6 +153,7 @@
 	fo_get_seals_t	*fo_get_seals;
 	fo_fallocate_t	*fo_fallocate;
 	fo_fspacectl_t	*fo_fspacectl;
+	fo_cmp_t	*fo_cmp;
 	fo_spare_t	*fo_spares[8];	/* Spare slots */
 	fo_flags_t	fo_flags;	/* DFLAG_* below */
 };
@@ -261,6 +263,7 @@
 int fget_fcntl(struct thread *td, int fd, cap_rights_t *rightsp,
     int needfcntl, struct file **fpp);
 int _fdrop(struct file *fp, struct thread *td);
+int fget_remote(struct thread *td, struct proc *p, int fd, struct file **fpp);
 
 fo_rdwr_t	invfo_rdwr;
 fo_truncate_t	invfo_truncate;
@@ -276,6 +279,7 @@
 fo_fill_kinfo_t	vn_fill_kinfo;
 fo_kqfilter_t	vn_kqfilter_opath;
 int vn_fill_kinfo_vnode(struct vnode *vp, struct kinfo_file *kif);
+int file_kcmp_generic(struct file *fp1, struct file *fp2, struct thread *td);
 
 void finit(struct file *, u_int, short, void *, struct fileops *);
 void finit_vnode(struct file *, u_int, void *, struct fileops *);
@@ -479,8 +483,9 @@
 	return ((*fp->f_ops->fo_fallocate)(fp, offset, len, td));
 }
 
-static __inline int fo_fspacectl(struct file *fp, int cmd, off_t *offset,
-    off_t *length, int flags, struct ucred *active_cred, struct thread *td)
+static __inline int
+fo_fspacectl(struct file *fp, int cmd, off_t *offset, off_t *length,
+    int flags, struct ucred *active_cred, struct thread *td)
 {
 
 	if (fp->f_ops->fo_fspacectl == NULL)
@@ -489,6 +494,14 @@
 	    active_cred, td));
 }
 
+static __inline int
+fo_cmp(struct file *fp1, struct file *fp2, struct thread *td)
+{
+
+	if (fp1->f_ops->fo_cmp == NULL)
+		return (ENODEV);
+	return ((*fp1->f_ops->fo_cmp)(fp1, fp2, td));
+}
 
 #endif /* _KERNEL */
 
diff --git a/sys/sys/syscallsubr.h b/sys/sys/syscallsubr.h
--- a/sys/sys/syscallsubr.h
+++ b/sys/sys/syscallsubr.h
@@ -198,6 +198,8 @@
 int	kern_jail(struct thread *td, struct jail *j);
 int	kern_jail_get(struct thread *td, struct uio *options, int flags);
 int	kern_jail_set(struct thread *td, struct uio *options, int flags);
+int	kern_kcmp(struct thread *td, pid_t pid1, pid_t pid2, int type,
+	    unsigned long idx1, unsigned long idx2);
 int	kern_kevent(struct thread *td, int fd, int nchanges, int nevents,
 	    struct kevent_copyops *k_ops, const struct timespec *timeout);
 int	kern_kevent_anonymous(struct thread *td, int nevents,
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -485,6 +485,8 @@
 /* XXX: Should be void nanodelay(u_int nsec); */
 void	DELAY(int usec);
 
+int kcmp_cmp(uintptr_t a, uintptr_t b);
+
 /* Root mount holdback API */
 struct root_hold_token {
 	int				flags;
diff --git a/sys/sys/unistd.h b/sys/sys/unistd.h
--- a/sys/sys/unistd.h
+++ b/sys/sys/unistd.h
@@ -195,6 +195,13 @@
     RFPROCDESC | RFSPAWN | RFPPWAIT)
 #define	RFKERNELONLY	(RFSTOPPED | RFHIGHPID | RFPROCDESC)
 
+/* kcmp() options. */
+#define	KCMP_FILE	100
+#define	KCMP_FILEOBJ	101
+#define	KCMP_FILES	102
+#define	KCMP_SIGHAND	103
+#define	KCMP_VM		104
+
 #define	SWAPOFF_FORCE	0x00000001
 
 /*
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -818,6 +818,7 @@
 	    void *alloc_arg, int lkflags, struct vnode **rvp);
 int	vn_utimes_perm(struct vnode *vp, struct vattr *vap,
 	    struct ucred *cred, struct thread *td);
+int	vn_cmp(struct file *, struct file *, struct thread *td);
 
 int	vn_io_fault_uiomove(char *data, int xfersize, struct uio *uio);
 int	vn_io_fault_pgmove(vm_page_t ma[], vm_offset_t offset, int xfersize,