The patch below was submitted to be applied to the 3.11-stable tree.
I fail to see how this patch meets the stable kernel rules as found at
Documentation/stable_kernel_rules.txt.
I could be totally wrong, and if so, please respond to
<stable@xxxxxxxxxxxxxxx> and let me know why this patch should be
applied. Otherwise, it is now dropped from my patch queues, never to be
seen again.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 61875f30daf60305712e25b209ef41ced2635bad Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@xxxxxxx>
Date: Sat, 21 Sep 2013 13:58:22 -0400
Subject: [PATCH] random: allow architectures to optionally define
random_get_entropy()
Allow architectures which have a disabled get_cycles() function to
provide a random_get_entropy() function which provides a fine-grained,
rapidly changing counter that can be used by the /dev/random driver.
For example, an architecture might have a rapidly changing register
used to control random TLB cache eviction, or DRAM refresh that
doesn't meet the requirements of get_cycles(), but which is good
enough for the needs of the random driver.
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 92e6c67e..2d5daf9b 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -643,7 +643,7 @@ struct timer_rand_state {
*/
void add_device_randomness(const void *buf, unsigned int size)
{
- unsigned long time = get_cycles() ^ jiffies;
+ unsigned long time = random_get_entropy() ^ jiffies;
mix_pool_bytes(&input_pool, buf, size, NULL);
mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
@@ -680,7 +680,7 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
goto out;
sample.jiffies = jiffies;
- sample.cycles = get_cycles();
+ sample.cycles = random_get_entropy();
sample.num = num;
mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
@@ -747,7 +747,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
struct pt_regs *regs = get_irq_regs();
unsigned long now = jiffies;
- __u32 input[4], cycles = get_cycles();
+ __u32 input[4], cycles = random_get_entropy();
input[0] = cycles ^ jiffies;
input[1] = irq;
@@ -1485,7 +1485,7 @@ unsigned int get_random_int(void)
hash = get_cpu_var(get_random_int_hash);
- hash[0] += current->pid + jiffies + get_cycles();
+ hash[0] += current->pid + jiffies + random_get_entropy();
md5_transform(hash, random_int_secret);
ret = hash[0];
put_cpu_var(get_random_int_hash);
diff --git a/include/linux/timex.h b/include/linux/timex.h
index b3726e61..da4c32db 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -64,6 +64,20 @@
#include <asm/timex.h>
+#ifndef random_get_entropy
+/*
+ * The random_get_entropy() function is used by the /dev/random driver
+ * in order to extract entropy via the relative unpredictability of
+ * when an interrupt takes places versus a high speed, fine-grained
+ * timing source or cycle counter. Since it will be occurred on every
+ * single interrupt, it must have a very low cost/overhead.
+ *
+ * By default we use get_cycles() for this purpose, but individual
+ * architectures may override this in their asm/timex.h header file.
+ */
+#define random_get_entropy() get_cycles()
+#endif
+
/*
* SHIFT_PLL is used as a dampening factor to define how much we
* adjust the frequency correction for a given offset in PLL mode.
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html