[kvm-unit-tests PATCH 1/5] lib: Add pseudo random functions

Nina Schoetterl-Glausch
2023-12-13T12:49:54Z

Add functions for generating pseudo random 32 and 64 bit values.
The implementation is very simple and the randomness likely not
of high quality.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
---
Makefile | 1 +
lib/libcflat.h | 7 +++++++
lib/rand.c | 19 +++++++++++++++++++
3 files changed, 27 insertions(+)
create mode 100644 lib/rand.c

diff --git a/Makefile b/Makefile
index 602910dd..7997e035 100644
--- a/Makefile
+++ b/Makefile
@@ -28,6 +28,7 @@ cflatobjs := \
lib/printf.o \
lib/string.o \
lib/abort.o \
+ lib/rand.o \
lib/report.o \
lib/stack.o

diff --git a/lib/libcflat.h b/lib/libcflat.h
index 700f4352..ed947f98 100644
--- a/lib/libcflat.h
+++ b/lib/libcflat.h
@@ -83,6 +83,13 @@ extern void abort(void) __attribute__((noreturn));
extern long atol(const char *ptr);
extern char *getenv(const char *name);

+typedef struct {
+ uint32_t val;
+} rand_state;
+#define RAND_STATE_INIT(x) ((rand_state){ .val = (x) })
+uint32_t rand32(rand_state *state);
+uint64_t rand64(rand_state *state);
+
extern int printf(const char *fmt, ...)
__attribute__((format(printf, 1, 2)));
extern int snprintf(char *buf, int size, const char *fmt, ...)
diff --git a/lib/rand.c b/lib/rand.c
new file mode 100644
index 00000000..658c4cbf
--- /dev/null
+++ b/lib/rand.c
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * pseudo random functions
+ *
+ * Copyright IBM Corp. 2023
+ */
+
+#include "libcflat.h"
+
+uint32_t rand32(rand_state *state)
+{
+ state->val = 0x915f77f5 * state->val + 1;
+ return state->val ^ (state->val >> 16);
+}
+
+uint64_t rand64(rand_state *state)
+{
+ return (uint64_t)rand32(state) << 32 | rand32(state);
+}
--
2.41.0