[PATCH] crypto: use timespec64 for jent_get_nstime

Arnd Bergmann
2016-06-17T15:58:24Z

The jent_get_nstime() function uses __getnstimeofday() to get
something similar to a 64-bit nanosecond counter. As we want
to get rid of struct timespec to fix the y2038 overflow,
this patch changes the code to use __getnstimeofday64()
instead, which returns a timespec64 structure.

Nothing changes about the algorithm, but it looks like it
might be better to use

*out = ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;

or even

*out = ktime_get_raw_fast_ns();

to get an actual nanosecond value and avoid the predictable
jitter that happens at the end of a second. Checking whether
or not this would be good needs investigation by someone who
understands the code better than me.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
crypto/jitterentropy-kcapi.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c
index 597cedd3531c..82ac44eff20d 100644
--- a/crypto/jitterentropy-kcapi.c
+++ b/crypto/jitterentropy-kcapi.c
@@ -89,7 +89,7 @@ void jent_memcpy(void *dest, const void *src, unsigned int n)

void jent_get_nstime(__u64 *out)
{
- struct timespec ts;
+ struct timespec64 ts;
__u64 tmp = 0;

tmp = random_get_entropy();
@@ -98,9 +98,11 @@ void jent_get_nstime(__u64 *out)
* If random_get_entropy does not return a value (which is possible on,
* for example, MIPS), invoke __getnstimeofday
* hoping that there are timers we can work with.
+ *
+ * should we have a __ktime_get_ns() instead?
*/
if ((0 == tmp) &&
- (0 == __getnstimeofday(&ts))) {
+ (0 == __getnstimeofday64(&ts))) {
tmp = ts.tv_sec;
tmp = tmp << 32;
tmp = tmp | ts.tv_nsec;
--
2.9.0