Add a new function pointer to struct clocksource that can optionally be
filled in by clocksources deemed to be high enough resolution to feed
the random number generator entropy pool.
CC: Matt Mackall <m...@selenic.com>
CC: "Venkatesh Pallipadi (Venki)" <ve...@google.com>
CC: Thomas Gleixner <t...@linutronix.de>
CC: Ingo Molnar <mi...@elte.hu>
CC: John Stultz <johns...@us.ibm.com>
CC: Herbert Xu <herb...@gondor.apana.org.au>
CC: "David S. Miller" <da...@davemloft.net>
Signed-off-by: Jarod Wilson <ja...@redhat.com>
---
include/linux/clocksource.h | 6 ++++++
kernel/time/clocksource.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 39 insertions(+), 0 deletions(-)
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index d4646b4..c74bcf2 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -156,6 +156,8 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
* @vread: vsyscall based read
* @suspend: suspend function for the clocksource, if necessary
* @resume: resume function for the clocksource, if necessary
+ * @entropy: random entropy pool addition function (optional, and
+ * requires a fairly high-resolution clocksource)
*/
struct clocksource {
/*
@@ -184,6 +186,7 @@ struct clocksource {
unsigned long flags;
void (*suspend)(struct clocksource *cs);
void (*resume)(struct clocksource *cs);
+ void (*entropy)(struct clocksource *cs);
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
/* Watchdog related data, used by the framework */
@@ -279,6 +282,9 @@ extern void clocksource_resume(void);
extern struct clocksource * __init __weak clocksource_default_clock(void);
extern void clocksource_mark_unstable(struct clocksource *cs);
+extern bool clocksource_entropy_available(void);
+extern void clocksource_add_entropy(void);
+
extern void
clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 1c95fd6..71006ef 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -745,6 +745,39 @@ void clocksource_unregister(struct clocksource *cs)
}
EXPORT_SYMBOL(clocksource_unregister);
+/**
+ * Do we have at least one clocksource that can generate entropy?
+ */
+bool clocksource_entropy_available(void)
+{
+ struct clocksource *src;
+ bool entropy_possible = false;
+
+ mutex_lock(&clocksource_mutex);
+ list_for_each_entry(src, &clocksource_list, list) {
+ if (src->entropy) {
+ entropy_possible = true;
+ break;
+ }
+ }
+ mutex_unlock(&clocksource_mutex);
+
+ return entropy_possible;
+}
+EXPORT_SYMBOL(clocksource_entropy_available);
+
+/**
+ * Call the clocksource's entropy-generation function, if set
+ */
+void clocksource_add_entropy(void)
+{
+ if (!curr_clocksource->entropy)
+ return;
+
+ curr_clocksource->entropy(curr_clocksource);
+}
+EXPORT_SYMBOL(clocksource_add_entropy);
+
#ifdef CONFIG_SYSFS
/**
* sysfs_show_current_clocksources - sysfs interface for current clocksource
--
1.7.1
--
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