[XEN PATCH v1] libxl: use getrandom() syscall for random data extraction

[Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>]

Simplify libxl__random_bytes() routine by using a newer dedicated syscall.
This allows not only to substantially reduce its footprint, but syscall also
considered to be safer and generally better solution:

https://lwn.net/Articles/606141/

getrandom() available on Linux, FreeBSD and NetBSD.

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
---
 tools/libxl/libxl_utils.c | 23 ++++-------------------
 1 file changed, 4 insertions(+), 19 deletions(-)

diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c
index b039143b8a..f3e56a4026 100644
--- a/tools/libxl/libxl_utils.c
+++ b/tools/libxl/libxl_utils.c
@@ -16,6 +16,7 @@
 #include "libxl_osdeps.h" /* must come before any other headers */
 
 #include <ctype.h>
+#include <sys/random.h>
 
 #include "libxl_internal.h"
 #include "_paths.h"
@@ -1226,26 +1227,10 @@ void libxl_string_copy(libxl_ctx *ctx, char **dst, char 
* const*src)
  */
 int libxl__random_bytes(libxl__gc *gc, uint8_t *buf, size_t len)
 {
-    static const char *dev = "/dev/urandom";
-    int fd;
-    int ret;
-
-    fd = open(dev, O_RDONLY);
-    if (fd < 0) {
-        LOGE(ERROR, "failed to open \"%s\"", dev);
+    ssize_t ret = getrandom(buf, len, 0);
+    if (ret != len)
         return ERROR_FAIL;
-    }
-    ret = libxl_fd_set_cloexec(CTX, fd, 1);
-    if (ret) {
-        close(fd);
-        return ERROR_FAIL;
-    }
-
-    ret = libxl_read_exactly(CTX, fd, buf, len, dev, NULL);
-
-    close(fd);
-
-    return ret;
+    return 0;
 }
 
 int libxl__prepare_sockaddr_un(libxl__gc *gc,
-- 
2.25.1