diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c
index 9c9b2a6e63c6..469924a255e7 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_open.c
@@ -311,6 +311,10 @@ static const dt_ident_t _dtrace_globals[] = {
 	&dt_idops_func, "void(@)" },
 { "memref", DT_IDENT_FUNC, 0, DIF_SUBR_MEMREF, DT_ATTR_STABCMN, DT_VERS_1_1,
 	&dt_idops_func, "uintptr_t *(void *, size_t)" },
+#if !defined(sun)
+{ "memstr", DT_IDENT_FUNC, 0, DIF_SUBR_MEMSTR, DT_ATTR_STABCMN, DT_VERS_1_0,
+	&dt_idops_func, "string(void *, char, size_t)" },
+#endif
 { "min", DT_IDENT_AGGFUNC, 0, DTRACEAGG_MIN, DT_ATTR_STABCMN, DT_VERS_1_0,
 	&dt_idops_func, "void(@)" },
 { "mod", DT_IDENT_ACTFUNC, 0, DT_ACT_MOD, DT_ATTR_STABCMN,
diff --git a/cddl/lib/libdtrace/psinfo.d b/cddl/lib/libdtrace/psinfo.d
index 068e72e4756c..c2219f70a35d 100644
--- a/cddl/lib/libdtrace/psinfo.d
+++ b/cddl/lib/libdtrace/psinfo.d
@@ -57,7 +57,8 @@ translator psinfo_t < struct proc *T > {
 	pr_gid = T->p_ucred->cr_rgid;
 	pr_egid = T->p_ucred->cr_groups[0];
 	pr_addr = 0;
-	pr_psargs = stringof(T->p_args->ar_args);
+	pr_psargs = (T->p_args->ar_args == 0) ? "" :
+	    memstr(T->p_args->ar_args, ' ', T->p_args->ar_length);
 	pr_arglen = T->p_args->ar_length;
 	pr_jailid = T->p_ucred->cr_prison->pr_id;
 };
diff --git a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
index dae6dba4d500..f35cf73f1aa0 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c
@@ -185,6 +185,9 @@ hrtime_t	dtrace_deadman_interval = NANOSEC;
 hrtime_t	dtrace_deadman_timeout = (hrtime_t)10 * NANOSEC;
 hrtime_t	dtrace_deadman_user = (hrtime_t)30 * NANOSEC;
 hrtime_t	dtrace_unregister_defunct_reap = (hrtime_t)60 * NANOSEC;
+#if !defined(sun)
+int		dtrace_memstr_max = 4096;
+#endif
 
 /*
  * DTrace External Variables
@@ -4920,6 +4923,45 @@ inetout:	regs[rd] = (uintptr_t)end + 1;
 		break;
 	}
 
+#if !defined(sun)
+	case DIF_SUBR_MEMSTR: {
+		char *str = (char *)mstate->dtms_scratch_ptr;
+		uintptr_t mem = tupregs[0].dttk_value;
+		char c = tupregs[1].dttk_value;
+		size_t size = tupregs[2].dttk_value;
+		uint8_t n;
+		int i;
+
+		regs[rd] = 0;
+
+		if (size == 0)
+			break;
+
+		if (!dtrace_canload(mem, size - 1, mstate, vstate))
+			break;
+
+		if (!DTRACE_INSCRATCH(mstate, size)) {
+			DTRACE_CPUFLAG_SET(CPU_DTRACE_NOSCRATCH);
+			break;
+		}
+
+		if (dtrace_memstr_max != 0 && size > dtrace_memstr_max) {
+			*flags |= CPU_DTRACE_ILLOP;
+			break;
+		}
+
+		for (i = 0; i < size - 1; i++) {
+			n = dtrace_load8(mem++);
+			str[i] = (n == 0) ? c : n;
+		}
+		str[size - 1] = 0;
+
+		regs[rd] = (uintptr_t)str;
+		mstate->dtms_scratch_ptr += size;
+		break;
+	}
+#endif
+
 	case DIF_SUBR_TYPEREF: {
 		uintptr_t size = 4 * sizeof(uintptr_t);
 		uintptr_t *typeref = (uintptr_t *) P2ROUNDUP(mstate->dtms_scratch_ptr, sizeof(uintptr_t));
@@ -9102,6 +9144,9 @@ dtrace_difo_validate_helper(dtrace_difo_t *dp)
 			    subr == DIF_SUBR_NTOHL ||
 			    subr == DIF_SUBR_NTOHLL ||
 			    subr == DIF_SUBR_MEMREF ||
+#if !defined(sun)
+			    subr == DIF_SUBR_MEMSTR ||
+#endif
 			    subr == DIF_SUBR_TYPEREF)
 				break;
 
diff --git a/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h b/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
index 8728e300df94..295457c634a4 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
+++ b/sys/cddl/contrib/opensolaris/uts/common/sys/dtrace.h
@@ -311,8 +311,9 @@ typedef enum dtrace_probespec {
 #define	DIF_SUBR_SX_SHARED_HELD		48
 #define	DIF_SUBR_SX_EXCLUSIVE_HELD	49
 #define	DIF_SUBR_SX_ISEXCLUSIVE		50
+#define	DIF_SUBR_MEMSTR			51
 
-#define	DIF_SUBR_MAX			50	/* max subroutine value */
+#define	DIF_SUBR_MAX			51	/* max subroutine value */
 
 typedef uint32_t dif_instr_t;
 
diff --git a/sys/cddl/dev/dtrace/dtrace_sysctl.c b/sys/cddl/dev/dtrace/dtrace_sysctl.c
index 00ed70916010..1b5b3abf1358 100644
--- a/sys/cddl/dev/dtrace/dtrace_sysctl.c
+++ b/sys/cddl/dev/dtrace/dtrace_sysctl.c
@@ -80,3 +80,5 @@ sysctl_dtrace_providers(SYSCTL_HANDLER_ARGS)
 SYSCTL_PROC(_debug_dtrace, OID_AUTO, providers, CTLTYPE_STRING | CTLFLAG_RD,
     0, 0, sysctl_dtrace_providers, "A", "");
 
+SYSCTL_INT(_debug_dtrace, OID_AUTO, memstr_max, CTLFLAG_RW, &dtrace_memstr_max,
+    0, "largest allowed argument to memstr(), 0 indicates no limit");