[S390] Support for s390 Pseudo Random Number Generator

Starting with the z9 the CPU Cryptographic Assist Facility comes with
an integrated Pseudo Random Number Generator. The generator creates
random numbers by an algorithm similar to the ANSI X9.17 standard.
The pseudo-random numbers can be accessed via a character device driver
node called /dev/prandom. Similar to /dev/urandom any amount of bytes
can be read from the device without blocking.

Signed-off-by: Jan Glauber <jan.glauber@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/asm-s390/timex.h b/include/asm-s390/timex.h
index 5cbd55cb40ce..98229db24314 100644
--- a/include/asm-s390/timex.h
+++ b/include/asm-s390/timex.h
@@ -62,6 +62,18 @@ static inline unsigned long long get_clock (void)
 	return clk;
 }
 
+static inline void get_clock_extended(void *dest)
+{
+	typedef struct { unsigned long long clk[2]; } __clock_t;
+
+#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ > 2)
+	asm volatile("stcke %0" : "=Q" (*((__clock_t *)dest)) : : "cc");
+#else /* __GNUC__ */
+	asm volatile("stcke 0(%1)" : "=m" (*((__clock_t *)dest))
+				   : "a" ((__clock_t *)dest) : "cc");
+#endif /* __GNUC__ */
+}
+
 static inline cycles_t get_cycles(void)
 {
 	return (cycles_t) get_clock() >> 2;