From b21edf205a9249482732ed8e0a0b872044ff17d7 Mon Sep 17 00:00:00 2001
From: "Nicholas J. Kain" <nicholas@kain.us>
Date: Tue, 8 Mar 2022 13:45:52 -0500
Subject: [PATCH] nk/hwrng: Use libc wrapper for getrandom by default.

---
 nk/hwrng.c | 33 +++++++++++++++++++++------------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/nk/hwrng.c b/nk/hwrng.c
index ee7c2b0..335649c 100644
--- a/nk/hwrng.c
+++ b/nk/hwrng.c
@@ -1,4 +1,4 @@
-// Copyright 2013-2018 Nicholas J. Kain <njkain at gmail dot com>
+// Copyright 2013-2022 Nicholas J. Kain <njkain at gmail dot com>
 // SPDX-License-Identifier: MIT
 #include <stdint.h>
 #include <string.h>
@@ -13,22 +13,36 @@
 #include "nk/log.h"
 #include "nk/io.h"
 
-#ifdef NK_USE_GETRANDOM_SYSCALL
+#ifdef NK_NO_GETRANDOM_SYSCALL
+static bool nk_getrandom(char *seed, size_t len)
+{
+    (void)seed;
+    (void)len;
+    return false;
+}
+#else
+#ifdef NK_NO_GETRANDOM_LIBC
 #include <sys/syscall.h>
 #include <linux/random.h>
+#define NK_GETRANDOM_CALL(A,B,C) syscall(SYS_getrandom, (A), (B), (C))
+#else
+#include <sys/random.h>
+#define NK_GETRANDOM_CALL(A,B,C) getrandom((A), (B), (C))
+#endif
+
 static bool nk_getrandom(char *seed, size_t len)
 {
     size_t fetched = 0;
     while (fetched < len) {
-        int r = syscall(SYS_getrandom, seed + fetched, len - fetched, 0);
+        int r = NK_GETRANDOM_CALL(seed + fetched, len - fetched, 0);
         if (r <= 0) {
             if (r == 0) {
                 // Failsafe to guard against infinite loops.
                 log_line("%s: getrandom() returned no entropy", __func__);
                 return false;
             }
-            if (errno == EINTR)
-                continue;
+            if (errno == EINTR) continue;
+            if (errno == ENOSYS) return false; // Kernel doesn't support syscall
             log_line("%s: getrandom() failed: %s", __func__, strerror(errno));
             return false;
         }
@@ -36,14 +50,9 @@ static bool nk_getrandom(char *seed, size_t len)
     }
     return true;
 }
-#else
-static bool nk_getrandom(char *seed, size_t len)
-{
-    (void)seed;
-    (void)len;
-    return false;
-}
 #endif
+#undef NK_GETRANDOM_CALL
+
 static bool nk_get_rnd_clk(char *seed, size_t len)
 {
     struct timespec ts;