linux-user: Initialize pseudo-random seeds for all guest cpus

When the -seed option is given, call qemu_guest_random_seed_main,
putting the subsystem into deterministic mode.  Pass derived seeds
to each cpu created during clone; which is a no-op unless the
subsystem is in deterministic mode.
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

linux-user/main.c

@@ -34,6 +34,7 @@
 #include "tcg.h"
 #include "qemu/timer.h"
 #include "qemu/envlist.h"
+#include "qemu/guest-random.h"
 #include "elf.h"
 #include "trace/control.h"
 #include "target_elf.h"
@@ -48,6 +49,7 @@ static int gdbstub_port;
 static envlist_t *envlist;
 static const char *cpu_model;
 static const char *cpu_type;
+static const char *seed_optarg;
 unsigned long mmap_min_addr;
 unsigned long guest_base;
 int have_guest_base;
@@ -290,15 +292,9 @@ static void handle_arg_pagesize(const char *arg)
     }
 }
 
-static void handle_arg_randseed(const char *arg)
+static void handle_arg_seed(const char *arg)
 {
-    unsigned long long seed;
-
-    if (parse_uint_full(arg, &seed, 0) != 0 || seed > UINT_MAX) {
-        fprintf(stderr, "Invalid seed number: %s\n", arg);
-        exit(EXIT_FAILURE);
-    }
-    srand(seed);
+    seed_optarg = arg;
 }
 
 static void handle_arg_gdb(const char *arg)
@@ -433,7 +429,7 @@ static const struct qemu_argument arg_table[] = {
      "",           "run in singlestep mode"},
     {"strace",     "QEMU_STRACE",      false, handle_arg_strace,
      "",           "log system calls"},
-    {"seed",       "QEMU_RAND_SEED",   true,  handle_arg_randseed,
+    {"seed",       "QEMU_RAND_SEED",   true,  handle_arg_seed,
      "",           "Seed for pseudo-random number generator"},
     {"trace",      "QEMU_TRACE",       true,  handle_arg_trace,
      "",           "[[enable=]<pattern>][,events=<file>][,file=<file>]"},
@@ -689,8 +685,20 @@ int main(int argc, char **argv, char **envp)
         do_strace = 1;
     }
 
-    if (getenv("QEMU_RAND_SEED")) {
-        handle_arg_randseed(getenv("QEMU_RAND_SEED"));
+    if (seed_optarg == NULL) {
+        seed_optarg = getenv("QEMU_RAND_SEED");
+    }
+    if (seed_optarg != NULL) {
+        unsigned long long seed;
+
+        /* This will go away with the last user of rand(). */
+        if (parse_uint_full(seed_optarg, &seed, 0) != 0) {
+            fprintf(stderr, "Invalid seed number: %s\n", seed_optarg);
+            exit(EXIT_FAILURE);
+        }
+        srand(seed);
+
+        qemu_guest_random_seed_main(seed_optarg, &error_fatal);
     }
 
     target_environ = envlist_to_environ(envlist, NULL);

linux-user/syscall.c

@@ -107,6 +107,7 @@
 #include "uname.h"
 
 #include "qemu.h"
+#include "qemu/guest-random.h"
 #include "fd-trans.h"
 
 #ifndef CLONE_IO
@@ -5482,6 +5483,7 @@ static void *clone_func(void *arg)
         put_user_u32(info->tid, info->child_tidptr);
     if (info->parent_tidptr)
         put_user_u32(info->tid, info->parent_tidptr);
+    qemu_guest_random_seed_thread_part2(cpu->random_seed);
     /* Enable signals.  */
     sigprocmask(SIG_SETMASK, &info->sigmask, NULL);
     /* Signal to the parent that we're ready.  */
@@ -5568,6 +5570,7 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
            initializing, so temporarily block all signals.  */
         sigfillset(&sigmask);
         sigprocmask(SIG_BLOCK, &sigmask, &info.sigmask);
+        cpu->random_seed = qemu_guest_random_seed_thread_part1();
 
         /* If this is our first additional thread, we need to ensure we
          * generate code for parallel execution and flush old translations.