HPET 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/hpet.c | 18 ++++++++++++++++++
1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 6781765..cf23090 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -10,6 +10,7 @@
#include <linux/cpu.h>
#include <linux/pm.h>
#include <linux/io.h>
+#include <linux/random.h>
#include <asm/fixmap.h>
#include <asm/i8253.h>
@@ -63,6 +64,22 @@ static inline void hpet_writel(unsigned int d, unsigned int a)
writel(d, hpet_virt_address + a);
}
+static void hpet_add_entropy(void)
+{
+ static unsigned long last;
+ unsigned long counter;
+ int delta;
+
+ counter = hpet_readl(HPET_COUNTER);
+ delta = (int)(counter - last);
+ last = counter;
+
+ if (delta == counter)
+ return;
+
+ add_clocksource_randomness(delta);
+}
+
#ifdef CONFIG_X86_64
#include <asm/pgtable.h>
#endif
@@ -752,6 +769,7 @@ static struct clocksource clocksource_hpet = {
.mask = HPET_MASK,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
.resume = hpet_resume_counter,
+ .entropy = hpet_add_entropy,
#ifdef CONFIG_X86_64
.vread = vread_hpet,
#endif
--
1.7.1
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