lxip: use xoroshiro128+ as random backend

repos/dde_linux/lib/mk/lxip.mk

@@ -27,7 +27,7 @@ CC_C_OPT  += -include $(LIB_INC_DIR)/lx_emul.h
 CC_CXX_OPT = -fpermissive
 
 SRC_CC = dummies.cc lxcc_emul.cc nic_handler.cc socket_handler.cc \
-         timer_handler.cc
+         timer_handler.cc random.cc
 
 SRC_CC += malloc.cc printf.cc
 

repos/dde_linux/src/lib/lxip/include/lx_emul.h

@@ -3186,22 +3186,14 @@ static inline bool ipv4_is_loopback(__be32 addr)
  ** linux/random.h **
  ********************/
 
-static inline void get_random_bytes(void *buf, int nbytes)
-{
-	char *b = (char *)buf;
-
-	/* FIXME not random */
-	int i;
-	for (i = 0; i < nbytes; ++i)
-		b[i] = i + 1;
-}
+void get_random_bytes(void *buf, int nbytes);
 
 static inline void get_random_once(void *buf, int nbytes)
 {
 	return get_random_bytes(buf, nbytes);
 }
 
-static inline u32 prandom_u32(void) { return 4; /* fair dice roll */ }
+u32 prandom_u32(void);
 
 static inline void prandom_bytes(void *buf, size_t nbytes)
 {

repos/dde_linux/src/lib/lxip/random.cc

@@ -0,0 +1,104 @@
+/**
+ * \brief  Linux random emulation code
+ * \author Josef Soentgen
+ * \date   2016-10-19
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <base/fixed_stdint.h>
+#include <util/string.h>
+
+
+using Genode::uint64_t;
+
+/*
+ * Xoroshiro128+ written in 2014-2016 by Sebastiano Vigna (vigna@acm.org)
+ *
+ * (see http://xoroshiro.di.unimi.it/xorshift128plus.c and
+ *      http://xoroshiro.di.unimi.it/splitmix64.c)
+ */
+
+struct Xoroshiro
+{
+	uint64_t seed;
+
+	uint64_t splitmix64()
+	{
+		uint64_t z = (seed += __UINT64_C(0x9E3779B97F4A7C15));
+		z = (z ^ (z >> 30)) * __UINT64_C(0xBF58476D1CE4E5B9);
+		z = (z ^ (z >> 27)) * __UINT64_C(0x94D049BB133111EB);
+		return z ^ (z >> 31);
+	}
+
+	Xoroshiro(uint64_t seed) : seed(seed)
+	{
+		s[0] = splitmix64();
+		s[1] = splitmix64();
+	}
+
+	uint64_t s[2];
+
+	static uint64_t rotl(uint64_t const x, int k) {
+		return (x << k) | (x >> (64 - k));
+	}
+
+	uint64_t get()
+	{
+		uint64_t const s0 = s[0];
+		uint64_t       s1 = s[1];
+		uint64_t const result = s0 + s1;
+
+		s1 ^= s0;
+
+		s[0] = rotl(s0, 55) ^ s1 ^ (s1 << 14);
+		s[1] = rotl(s1, 36);
+
+		return result;
+	}
+};
+
+
+static Xoroshiro xoroshiro(42);
+
+
+/********************
+ ** linux/random.h **
+ ********************/
+
+extern "C" void get_random_bytes(void *buf, int nbytes)
+{
+	if (nbytes <= 0) {
+		return;
+	}
+
+	char *p = reinterpret_cast<char*>(buf);
+
+	int const rounds = nbytes / 8;
+	for (int i = 0; i < rounds; i++) {
+		uint64_t const v = xoroshiro.get();
+
+		Genode::memcpy(p, &v, 8);
+		p += 8;
+	}
+
+	int const remain = nbytes - rounds * 8;
+	if (!remain) {
+		return;
+	}
+
+	uint64_t const v = xoroshiro.get();
+	Genode::memcpy(p, &v, remain);
+}
+
+
+extern "C" unsigned int prandom_u32(void)
+{
+	return xoroshiro.get();
+}