[PATCH] random: yell if random_get_entropy() returns a constant

[Sebastian Andrzej Siewior]

A few architectures still return 0 (i.e. a constant) if
random_get_entropy() is invoked. Make them aware of this so they may fix
this.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 drivers/char/random.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 429b75b..48775f8 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -241,6 +241,7 @@
 #include <linux/major.h>
 #include <linux/string.h>
 #include <linux/fcntl.h>
+#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/random.h>
 #include <linux/poll.h>
@@ -1675,3 +1676,23 @@ randomize_range(unsigned long start, unsigned long end, unsigned long len)
 		return 0;
 	return PAGE_ALIGN(get_random_int() % range + start);
 }
+
+static int check_random_get_entropy(void)
+{
+	cycles_t cyc1;
+	cycles_t cyc2;
+
+	cyc1 = random_get_entropy();
+	cyc2 = random_get_entropy();
+	if (cyc1 != cyc2)
+		return 0;
+	udelay(1);
+	cyc2 = random_get_entropy();
+
+	if (cyc1 != cyc2)
+		return 0;
+	pr_err("Error: random_get_entropy() does not return anything random\n");
+	WARN_ON(1);
+	return -EINVAL;
+}
+late_initcall(check_random_get_entropy);
-- 
1.9.1


> Cheers,
> 						- Ted

Sebastian
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