TSC is high enough resolution that we can use its low-order byte to
stir new data into the random number generator entropy pool.
CC: Matt Mackall <mpm@xxxxxxxxxxx>
CC: "Venkatesh Pallipadi (Venki)" <venki@xxxxxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxx>
CC: John Stultz <johnstul@xxxxxxxxxx>
CC: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
---
arch/x86/kernel/tsc.c | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 6cc6922..d206ec3 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -10,6 +10,7 @@
#include <linux/clocksource.h>
#include <linux/percpu.h>
#include <linux/timex.h>
+#include <linux/random.h>
#include <asm/hpet.h>
#include <asm/timer.h>
@@ -768,11 +769,28 @@ static void resume_tsc(struct clocksource *cs)
clocksource_tsc.cycle_last = 0;
}
+static void tsc_add_entropy(void)
+{
+ static u64 last;
+ u64 counter;
+ int delta;
+
+ rdtscll(counter);
+ delta = (int)(counter - last);
+ last = counter;
+
+ if (delta == counter)
+ return;
+
+ add_clocksource_randomness(delta);
+}
+
static struct clocksource clocksource_tsc = {
.name = "tsc",
.rating = 300,
.read = read_tsc,
.resume = resume_tsc,
+ .entropy = tsc_add_entropy,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS |
CLOCK_SOURCE_MUST_VERIFY,
--
1.7.1
--
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