Index: sys/kern/kern_cpuset.c
===================================================================
--- sys/kern/kern_cpuset.c
+++ sys/kern/kern_cpuset.c
@@ -34,6 +34,7 @@
 __FBSDID("$FreeBSD$");
 
 #include "opt_ddb.h"
+#include "opt_ktrace.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -61,6 +62,7 @@
 #include <sys/bus.h>
 #include <sys/interrupt.h>
 #include <sys/vmmeter.h>
+#include <sys/ktrace.h>
 
 #include <vm/uma.h>
 #include <vm/vm.h>
@@ -1974,6 +1976,11 @@
 		PROC_UNLOCK(p);
 	if (error == 0)
 		error = copyout(mask, maskp, size);
+#ifdef KTRACE
+	if (KTRPOINT(td, KTR_STRUCT))
+		ktrcpuset_t(mask, size);
+#endif
+
 out:
 	free(mask, M_TEMP);
 	return (error);
@@ -2016,6 +2023,10 @@
 	error = copyin(maskp, mask, size);
 	if (error)
 		goto out;
+#ifdef KTRACE
+	if (KTRPOINT(td, KTR_STRUCT))
+		ktrcpuset_t(mask, size);
+#endif
 	if (CPU_EMPTY(mask)) {
 		error = EDEADLK;
 		goto out;
Index: sys/sys/ktrace.h
===================================================================
--- sys/sys/ktrace.h
+++ sys/sys/ktrace.h
@@ -307,6 +307,8 @@
 	ktrstruct("stat", (s), sizeof(struct stat))
 #define ktrstat_error(s, error) \
 	ktrstruct_error("stat", (s), sizeof(struct stat), error)
+#define ktrcpuset_t(s, l) \
+	ktrstruct("cpuset_t", (s), l)
 extern u_int ktr_geniosize;
 #ifdef	KTRACE
 extern int ktr_filesize_limit_signal;
Index: usr.bin/kdump/kdump.c
===================================================================
--- usr.bin/kdump/kdump.c
+++ usr.bin/kdump/kdump.c
@@ -48,8 +48,11 @@
 #define	_WANT_KEVENT32
 #endif
 #define	_WANT_FREEBSD11_KEVENT
+#define	_WANT_FREEBSD_BITSET
 #include <sys/param.h>
 #include <sys/capsicum.h>
+#include <sys/_bitset.h>
+#include <sys/bitset.h>
 #include <sys/errno.h>
 #include <sys/time.h>
 #include <sys/uio.h>
@@ -119,6 +122,7 @@
 void ktrfaultend(struct ktr_faultend *);
 void ktrkevent(struct kevent *);
 void ktrstructarray(struct ktr_struct_array *, size_t);
+void ktrbitset(char *, struct bitset *, size_t);
 void usage(void);
 
 #define	TIMESTAMP_NONE		0x0
@@ -1967,6 +1971,23 @@
 	printf(" }\n");
 }
 
+void
+ktrbitset(char *name, struct bitset *set, size_t setlen)
+{
+	unsigned long i;
+	int bit;
+
+	printf("%s [ ", name);
+	for (i = 0; i < setlen * CHAR_BIT; i++) {
+		bit = BIT_ISSET(setlen, i, set);
+		if (i == 0)
+			printf("%c", '0' + bit);
+		else
+			printf(", %c", '0' + bit);
+	}
+	printf(" ]\n");
+}
+
 void
 ktrstruct(char *buf, size_t buflen)
 {
@@ -1977,6 +1998,7 @@
 	struct itimerval it;
 	struct stat sb;
 	struct sockaddr_storage ss;
+	struct bitset *set;
 
 	for (name = buf, namelen = 0;
 	     namelen < buflen && name[namelen] != '\0';
@@ -1992,7 +2014,7 @@
 		goto invalid;
 	/* sanity check */
 	for (i = 0; i < (int)namelen; ++i)
-		if (!isalpha(name[i]))
+		if (!isalpha(name[i]) && name[i] != '_')
 			goto invalid;
 	if (strcmp(name, "caprights") == 0) {
 		if (datalen != sizeof(cap_rights_t))
@@ -2016,6 +2038,15 @@
 		if (datalen != ss.ss_len)
 			goto invalid;
 		ktrsockaddr((struct sockaddr *)&ss);
+	} else if (strcmp(name, "cpuset_t") == 0) {
+		if (datalen < 1)
+			goto invalid;
+		set = malloc(datalen);
+		if (set == NULL)
+			errx(1, "%s", strerror(ENOMEM));
+		memcpy(set, data, datalen);
+		ktrbitset(name, set, datalen);
+		free(set);
 	} else {
 		printf("unknown structure\n");
 	}