Introduce qemu_guest_getrandom.

Use qemu_guest_getrandom in aspeed, nrf51, bcm2835, exynos4210 rng devices.
 Use qemu_guest_getrandom in target/ppc darn instruction.
 Support ARMv8.5-RNG extension.
 Support x86 RDRAND extension.
 
 Acked-by: Daniel P. Berrangé <berrange@redhat.com>
 Acked-by: Laurent Vivier <laurent@vivier.eu>
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Merge remote-tracking branch 'remotes/rth/tags/pull-rng-20190522' into staging

Introduce qemu_guest_getrandom.
Use qemu_guest_getrandom in aspeed, nrf51, bcm2835, exynos4210 rng devices.
Use qemu_guest_getrandom in target/ppc darn instruction.
Support ARMv8.5-RNG extension.
Support x86 RDRAND extension.

Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Laurent Vivier <laurent@vivier.eu>

# gpg: Signature made Wed 22 May 2019 19:36:43 BST
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [full]
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-rng-20190522: (25 commits)
  target/i386: Implement CPUID_EXT_RDRAND
  target/ppc: Use qemu_guest_getrandom for DARN
  target/ppc: Use gen_io_start/end around DARN
  target/arm: Implement ARMv8.5-RNG
  target/arm: Put all PAC keys into a structure
  hw/misc/exynos4210_rng: Use qemu_guest_getrandom
  hw/misc/bcm2835_rng: Use qemu_guest_getrandom_nofail
  hw/misc/nrf51_rng: Use qemu_guest_getrandom_nofail
  aspeed/scu: Use qemu_guest_getrandom_nofail
  linux-user: Remove srand call
  linux-user/aarch64: Use qemu_guest_getrandom for PAUTH keys
  linux-user: Use qemu_guest_getrandom_nofail for AT_RANDOM
  linux-user: Call qcrypto_init if not using -seed
  linux-user: Initialize pseudo-random seeds for all guest cpus
  cpus: Initialize pseudo-random seeds for all guest cpus
  util: Add qemu_guest_getrandom and associated routines
  ui/vnc: Use gcrypto_random_bytes for start_auth_vnc
  ui/vnc: Split out authentication_failed
  crypto: Change the qcrypto_random_bytes buffer type to void*
  crypto: Use getrandom for qcrypto_random_bytes
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

util/Makefile.objs

@@ -54,5 +54,6 @@ util-obj-y += iova-tree.o
 util-obj-$(CONFIG_INOTIFY1) += filemonitor-inotify.o
 util-obj-$(CONFIG_LINUX) += vfio-helpers.o
 util-obj-$(CONFIG_OPENGL) += drm.o
+util-obj-y += guest-random.o
 
 stub-obj-y += filemonitor-stub.o

util/guest-random.c

@@ -0,0 +1,93 @@
+/*
+ * QEMU guest-visible random functions
+ *
+ * Copyright 2019 Linaro, Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "qemu/cutils.h"
+#include "qapi/error.h"
+#include "qemu/guest-random.h"
+#include "crypto/random.h"
+
+
+static __thread GRand *thread_rand;
+static bool deterministic;
+
+
+static int glib_random_bytes(void *buf, size_t len)
+{
+    GRand *rand = thread_rand;
+    size_t i;
+    uint32_t x;
+
+    if (unlikely(rand == NULL)) {
+        /* Thread not initialized for a cpu, or main w/o -seed.  */
+        thread_rand = rand = g_rand_new();
+    }
+
+    for (i = 0; i + 4 <= len; i += 4) {
+        x = g_rand_int(rand);
+        __builtin_memcpy(buf + i, &x, 4);
+    }
+    if (i < len) {
+        x = g_rand_int(rand);
+        __builtin_memcpy(buf + i, &x, i - len);
+    }
+    return 0;
+}
+
+int qemu_guest_getrandom(void *buf, size_t len, Error **errp)
+{
+    if (unlikely(deterministic)) {
+        /* Deterministic implementation using Glib's Mersenne Twister.  */
+        return glib_random_bytes(buf, len);
+    } else {
+        /* Non-deterministic implementation using crypto routines.  */
+        return qcrypto_random_bytes(buf, len, errp);
+    }
+}
+
+void qemu_guest_getrandom_nofail(void *buf, size_t len)
+{
+    qemu_guest_getrandom(buf, len, &error_fatal);
+}
+
+uint64_t qemu_guest_random_seed_thread_part1(void)
+{
+    if (deterministic) {
+        uint64_t ret;
+        glib_random_bytes(&ret, sizeof(ret));
+        return ret;
+    }
+    return 0;
+}
+
+void qemu_guest_random_seed_thread_part2(uint64_t seed)
+{
+    g_assert(thread_rand == NULL);
+    if (deterministic) {
+        thread_rand =
+            g_rand_new_with_seed_array((const guint32 *)&seed,
+                                       sizeof(seed) / sizeof(guint32));
+    }
+}
+
+int qemu_guest_random_seed_main(const char *optarg, Error **errp)
+{
+    unsigned long long seed;
+    if (parse_uint_full(optarg, &seed, 0)) {
+        error_setg(errp, "Invalid seed number: %s", optarg);
+        return -1;
+    } else {
+        deterministic = true;
+        qemu_guest_random_seed_thread_part2(seed);
+        return 0;
+    }
+}