target/i386: Implement CPUID_EXT_RDRAND

We now have an interface for guest visible random numbers.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/target/i386/int_helper.c b/target/i386/int_helper.c
index 4dc5c65991..334469ca8c 100644
--- a/target/i386/int_helper.c
+++ b/target/i386/int_helper.c
@@ -22,6 +22,8 @@
 #include "exec/exec-all.h"
 #include "qemu/host-utils.h"
 #include "exec/helper-proto.h"
+#include "qapi/error.h"
+#include "qemu/guest-random.h"
 
 //#define DEBUG_MULDIV
 
@@ -470,3 +472,22 @@ void helper_cr4_testbit(CPUX86State *env, uint32_t bit)
         raise_exception_ra(env, EXCP06_ILLOP, GETPC());
     }
 }
+
+target_ulong HELPER(rdrand)(CPUX86State *env)
+{
+    Error *err = NULL;
+    target_ulong ret;
+
+    if (qemu_guest_getrandom(&ret, sizeof(ret), &err) < 0) {
+        qemu_log_mask(LOG_UNIMP, "rdrand: Crypto failure: %s",
+                      error_get_pretty(err));
+        error_free(err);
+        /* Failure clears CF and all other flags, and returns 0.  */
+        env->cc_src = 0;
+        return 0;
+    }
+
+    /* Success sets CF and clears all others.  */
+    env->cc_src = CC_C;
+    return ret;
+}