diff -r ee1390c9b585 Python/random.c

--- a/Python/random.c	Wed Jan 04 12:02:30 2017 +0100

+++ b/Python/random.c	Wed Jan 04 18:32:21 2017 +0100

@@ -77,45 +77,8 @@ win32_urandom(unsigned char *buffer, Py_

     return 0;

 }

-/* Issue #25003: Don't use getentropy() on Solaris (available since

- * Solaris 11.3), it is blocking whereas os.urandom() should not block. */

-#elif defined(HAVE_GETENTROPY) && !defined(sun)

-#define PY_GETENTROPY 1

-

-/* Fill buffer with size pseudo-random bytes generated by getentropy().

-   Return 0 on success, or raise an exception and return -1 on error.

-

-   If raise is zero, don't raise an exception on error. */

-static int

-py_getentropy(char *buffer, Py_ssize_t size, int raise)

-{

-    while (size > 0) {

-        Py_ssize_t len = Py_MIN(size, 256);

-        int res;

+#else   /* !MS_WINDOWS */

-        if (raise) {

-            Py_BEGIN_ALLOW_THREADS

-            res = getentropy(buffer, len);

-            Py_END_ALLOW_THREADS

-        }

-        else {

-            res = getentropy(buffer, len);

-        }

-

-        if (res < 0) {

-            if (raise) {

-                PyErr_SetFromErrno(PyExc_OSError);

-            }

-            return -1;

-        }

-

-        buffer += len;

-        size -= len;

-    }

-    return 0;

-}

-

-#else

 #if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)

 #define PY_GETRANDOM 1

@@ -217,6 +180,59 @@ py_getrandom(void *buffer, Py_ssize_t si

     }

     return 1;

 }

+

+/* Issue #25003: Don't use getentropy() on Solaris (available since

+ * Solaris 11.3), it is blocking whereas os.urandom() should not block. */

+#elif defined(HAVE_GETENTROPY) && !defined(sun)

+#define PY_GETENTROPY 1

+

+/* Fill buffer with size pseudo-random bytes generated by getentropy().

+   Return 1 on success, or raise an exception and return -1 on error.

+

+   If raise is zero, don't raise an exception on error. */

+static int

+py_getentropy(char *buffer, Py_ssize_t size, int raise)

+{

+    /* Is getentropy() supported by the running kernel? Set to 0 if

+       getentropy() failed with ENOSYS. */

+    static int getentropy_works = 1;

+

+    if (!getentropy_works) {

+        return 0;

+    }

+

+    while (size > 0) {

+        Py_ssize_t len = Py_MIN(size, 256);

+        int res;

+

+        if (raise) {

+            Py_BEGIN_ALLOW_THREADS

+            res = getentropy(buffer, len);

+            Py_END_ALLOW_THREADS

+        }

+        else {

+            res = getentropy(buffer, len);

+        }

+

+        if (res < 0) {

+            /* ENOSYS: the inner syscall is not supported by the running

+               kernel. */

+            if (errno == ENOSYS) {

+                getentropy_works = 0;

+                return 0;

+            }

+

+            if (raise) {

+                PyErr_SetFromErrno(PyExc_OSError);

+            }

+            return -1;

+        }

+

+        buffer += len;

+        size -= len;

+    }

+    return 1;

+}

 #endif

 static struct {

@@ -236,7 +252,7 @@ dev_urandom(char *buffer, Py_ssize_t siz

 {

     int fd;

     Py_ssize_t n;

-#ifdef PY_GETRANDOM

+#if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)

     int res;

 #endif

@@ -244,17 +260,20 @@ dev_urandom(char *buffer, Py_ssize_t siz

 #ifdef PY_GETRANDOM

     res = py_getrandom(buffer, size, blocking, raise);

+#elif defined(PY_GETENTROPY)

+    res = py_getentropy(buffer, size, raise);

+#endif

+#if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)

     if (res < 0) {

         return -1;

     }

     if (res == 1) {

         return 0;

     }

-    /* getrandom() failed with ENOSYS or EPERM,

-       fall back on reading /dev/urandom */

+    /* function failed with ENOSYS or EPERM, fall back on reading

+       from /dev/urandom */

 #endif

-

     if (raise) {

         struct _Py_stat_struct st;

@@ -349,8 +368,8 @@ dev_urandom_close(void)

         urandom_cache.fd = -1;

     }

 }

+#endif   /* !MS_WINDOWS */

-#endif

 /* Fill buffer with pseudo-random bytes generated by a linear congruent

    generator (LCG):

@@ -395,8 +414,6 @@ pyurandom(void *buffer, Py_ssize_t size,

 #ifdef MS_WINDOWS

     return win32_urandom((unsigned char *)buffer, size, raise);

-#elif defined(PY_GETENTROPY)

-    return py_getentropy(buffer, size, raise);

 #else

     return dev_urandom(buffer, size, blocking, raise);

 #endif

@@ -491,8 +508,6 @@ void

         CryptReleaseContext(hCryptProv, 0);

         hCryptProv = 0;

     }

-#elif defined(PY_GETENTROPY)

-    /* nothing to clean */

 #else

     dev_urandom_close();

 #endif