This is a note to let you know that I've just added the patch titled
rtc: wm831x: Feed the write counter into device_add_randomness()
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rtc-wm831x-feed-the-write-counter-into-device_add_randomness.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 9dccf55f4cb011a7552a8a2749a580662f5ed8ed Mon Sep 17 00:00:00 2001
From: Mark Brown <[email protected]>
Date: Thu, 5 Jul 2012 20:19:17 +0000
Subject: rtc: wm831x: Feed the write counter into device_add_randomness()
From: Mark Brown <[email protected]>
commit 9dccf55f4cb011a7552a8a2749a580662f5ed8ed upstream.
The tamper evident features of the RTC include the "write counter" which
is a pseudo-random number regenerated whenever we set the RTC. Since this
value is unpredictable it should provide some useful seeding to the random
number generator.
Only do this on boot since the goal is to seed the pool rather than add
useful entropy.
Signed-off-by: Mark Brown <[email protected]>
Signed-off-by: Theodore Ts'o <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/rtc/rtc-wm831x.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
--- a/drivers/rtc/rtc-wm831x.c
+++ b/drivers/rtc/rtc-wm831x.c
@@ -24,7 +24,7 @@
#include <linux/mfd/wm831x/core.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
-
+#include <linux/random.h>
/*
* R16416 (0x4020) - RTC Write Counter
@@ -96,6 +96,26 @@ struct wm831x_rtc {
unsigned int alarm_enabled:1;
};
+static void wm831x_rtc_add_randomness(struct wm831x *wm831x)
+{
+ int ret;
+ u16 reg;
+
+ /*
+ * The write counter contains a pseudo-random number which is
+ * regenerated every time we set the RTC so it should be a
+ * useful per-system source of entropy.
+ */
+ ret = wm831x_reg_read(wm831x, WM831X_RTC_WRITE_COUNTER);
+ if (ret >= 0) {
+ reg = ret;
+ add_device_randomness(®, sizeof(reg));
+ } else {
+ dev_warn(wm831x->dev, "Failed to read RTC write counter: %d\n",
+ ret);
+ }
+}
+
/*
* Read current time and date in RTC
*/
@@ -431,6 +451,8 @@ static int wm831x_rtc_probe(struct platf
alm_irq, ret);
}
+ wm831x_rtc_add_randomness(wm831x);
+
return 0;
err:
Patches currently in stable-queue which might be from
[email protected] are
queue-3.4/rtc-wm831x-feed-the-write-counter-into-device_add_randomness.patch
queue-3.4/mfd-wm831x-feed-the-device-uuid-into-device_add_randomness.patch
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