1#define _BSD_SOURCE
 2#include <unistd.h>
 3#include <sys/random.h>
 4#include <pthread.h>
 5#include <errno.h>
 6
 7int getentropy(void *buffer, size_t len)
 8{
 9	int cs, ret = 0;
10	char *pos = buffer;
11
12	if (len > 256) {
13		errno = EIO;
14		return -1;
15	}
16
17	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
18
19	while (len) {
20		ret = getrandom(pos, len, 0);
21		if (ret < 0) {
22			if (errno == EINTR) continue;
23			else break;
24		}
25		pos += ret;
26		len -= ret;
27		ret = 0;
28	}
29
30	pthread_setcancelstate(cs, 0);
31
32	return ret;
33}