1 files changed, 70 insertions, 0 deletions
diff --git a/c_src/include/linux/random.h b/c_src/include/linux/random.h
new file mode 100644
index 00000000..3203d13c
--- /dev/null
+++ b/c_src/include/linux/random.h
@@ -0,0 +1,70 @@
+/*
+ * include/linux/random.h
+ *
+ * Include file for the random number generator.
+ */
+#ifndef _LINUX_RANDOM_H
+#define _LINUX_RANDOM_H
+
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <linux/bug.h>
+#include <linux/log2.h>
+
+#ifdef SYS_getrandom
+static inline int getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+	 return syscall(SYS_getrandom, buf, buflen, flags);
+}
+#else
+extern int urandom_fd;
+
+static inline int getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+	return read(urandom_fd, buf, buflen);
+}
+#endif
+
+static inline void get_random_bytes(void *buf, int nbytes)
+{
+	BUG_ON(getrandom(buf, nbytes, 0) != nbytes);
+}
+
+#define get_random_type(type)				\
+static inline type get_random_##type(void)		\
+{							\
+	type v;						\
+							\
+	get_random_bytes(&v, sizeof(v));		\
+	return v;					\
+}
+
+get_random_type(int);
+get_random_type(long);
+get_random_type(u8);
+get_random_type(u16);
+get_random_type(u32);
+get_random_type(u64);
+
+static inline u32 get_random_u32_below(u32 ceil)
+{
+	if (ceil <= 1)
+		return 0;
+	for (;;) {
+		if (ceil <= 1U << 8) {
+			u32 mult = ceil * get_random_u8();
+			if (likely(is_power_of_2(ceil) || (u8)mult >= (1U << 8) % ceil))
+				return mult >> 8;
+		} else if (ceil <= 1U << 16) {
+			u32 mult = ceil * get_random_u16();
+			if (likely(is_power_of_2(ceil) || (u16)mult >= (1U << 16) % ceil))
+				return mult >> 16;
+		} else {
+			u64 mult = (u64)ceil * get_random_u32();
+			if (likely(is_power_of_2(ceil) || (u32)mult >= -ceil % ceil))
+				return mult >> 32;
+		}
+	}
+}
+
+#endif /* _LINUX_RANDOM_H */