Replace the implementation of DTrace's RAND subroutine for generating

low-quality random numbers with a modern implementation (xoroshiro128+)
that is capable of generating better quality randomness without compromising performance.

Submitted by:	Graeme Jenkinson
Reviewed by:	markj
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D9051

sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrace.c

@@ -124,6 +124,7 @@
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/ptrace.h>
+#include <sys/random.h>
 #include <sys/rwlock.h>
 #include <sys/sx.h>
 #include <sys/sysctl.h>
@@ -136,6 +137,8 @@
 #include "dtrace_debug.c"
 #endif
 
+#include "dtrace_xoroshiro128_plus.h"
+
 /*
  * DTrace Tunable Variables
  *
@@ -298,7 +301,6 @@ static kmutex_t		dtrace_meta_lock;	/* meta-provider state lock */
 #define vuprintf	vprintf
 #define ttoproc(_a)	((_a)->td_proc)
 #define crgetzoneid(_a)	0
-#define	NCPU		MAXCPU
 #define SNOCD		0
 #define CPU_ON_INTR(_a)	0
 
@@ -4236,7 +4238,8 @@ dtrace_dif_subr(uint_t subr, uint_t rd, uint64_t *regs,
 
 	switch (subr) {
 	case DIF_SUBR_RAND:
-		regs[rd] = (dtrace_gethrtime() * 2416 + 374441) % 1771875;
+		regs[rd] = dtrace_xoroshiro128_plus_next(
+		    state->dts_rstate[curcpu]);
 		break;
 
 #ifdef illumos
@@ -14495,6 +14498,7 @@ dtrace_state_create(struct cdev *dev, struct ucred *cred __unused)
 	dtrace_state_t *state;
 	dtrace_optval_t *opt;
 	int bufsize = NCPU * sizeof (dtrace_buffer_t), i;
+	int cpu_it;
 
 	ASSERT(MUTEX_HELD(&dtrace_lock));
 	ASSERT(MUTEX_HELD(&cpu_lock));
@@ -14550,6 +14554,21 @@ dtrace_state_create(struct cdev *dev, struct ucred *cred __unused)
 	state->dts_buffer = kmem_zalloc(bufsize, KM_SLEEP);
 	state->dts_aggbuffer = kmem_zalloc(bufsize, KM_SLEEP);
 
+	/*
+         * Allocate and initialise the per-process per-CPU random state.
+	 * SI_SUB_RANDOM < SI_SUB_DTRACE_ANON therefore entropy device is
+         * assumed to be seeded at this point (if from Fortuna seed file).
+	 */
+	(void) read_random(&state->dts_rstate[0], 2 * sizeof(uint64_t));
+	for (cpu_it = 1; cpu_it < NCPU; cpu_it++) {
+		/*
+		 * Each CPU is assigned a 2^64 period, non-overlapping
+		 * subsequence.
+		 */
+		dtrace_xoroshiro128_plus_jump(state->dts_rstate[cpu_it-1],
+		    state->dts_rstate[cpu_it]); 
+	}
+
 #ifdef illumos
 	state->dts_cleaner = CYCLIC_NONE;
 	state->dts_deadman = CYCLIC_NONE;

sys/cddl/contrib/opensolaris/uts/common/sys/dtrace_impl.h

@@ -50,6 +50,7 @@ extern "C" {
  */
 
 #include <sys/dtrace.h>
+
 #ifndef illumos
 #ifdef __sparcv9
 typedef uint32_t		pc_t;
@@ -65,6 +66,10 @@ typedef	u_long			greg_t;
 #define	DTRACE_MAXPROPLEN		128
 #define	DTRACE_DYNVAR_CHUNKSIZE		256
 
+#ifdef __FreeBSD__
+#define	NCPU		MAXCPU
+#endif /* __FreeBSD__ */
+
 struct dtrace_probe;
 struct dtrace_ecb;
 struct dtrace_predicate;
@@ -1169,6 +1174,7 @@ struct dtrace_state {
 	dtrace_cred_t dts_cred;			/* credentials */
 	size_t dts_nretained;			/* number of retained enabs */
 	int dts_getf;				/* number of getf() calls */
+	uint64_t dts_rstate[NCPU][2];		/* per-CPU random state */
 };
 
 struct dtrace_provider {

sys/modules/dtrace/dtrace/Makefile

@@ -12,6 +12,7 @@ ARCHDIR=	${MACHINE_CPUARCH}
 
 KMOD=		dtrace
 SRCS=		dtrace.c \
+		dtrace_xoroshiro128_plus.c \
 		dtrace_asm.S \
 		dtrace_subr.c
 
@@ -42,6 +43,7 @@ CFLAGS+=	-I${SYSDIR}/cddl/compat/opensolaris \
 		-I${SYSDIR}/cddl/dev/dtrace \
 		-I${SYSDIR}/cddl/dev/dtrace/${ARCHDIR} \
 		-I${SYSDIR}/cddl/contrib/opensolaris/uts/common \
+		-I${SYSDIR}/cddl/contrib/opensolaris/uts/common/dtrace \
 		-I${SYSDIR}/cddl/contrib/opensolaris/common/util \
 		-I${SYSDIR} -DDIS_MEM
 

sys/modules/dtrace/fasttrap/Makefile

@@ -10,6 +10,7 @@ SRCS+=		vnode_if.h
 
 CFLAGS+=	-I${SYSDIR}/cddl/compat/opensolaris \
 		-I${SYSDIR}/cddl/contrib/opensolaris/uts/common \
+		-I${SYSDIR}/cddl/contrib/opensolaris/uts/common/dtrace \
 		-I${SYSDIR}
 
 .if ${MACHINE_CPUARCH} == "amd64" ||  ${MACHINE_CPUARCH} == "i386"

sys/modules/dtrace/systrace/Makefile

@@ -10,6 +10,7 @@ SRCS+=		vnode_if.h
 
 CFLAGS+=	-I${SYSDIR}/cddl/compat/opensolaris \
 		-I${SYSDIR}/cddl/contrib/opensolaris/uts/common \
+		-I${SYSDIR}/cddl/contrib/opensolaris/uts/common/dtrace \
 		-I${SYSDIR}
 
 .include <bsd.kmod.mk>