mailing list of musl libc

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 #include <sys/random.h>
#include <errno.h>
#include "syscall.h"

int getentropy(void *buffer, size_t length)
{
	int ret;
	char *pos = buffer;
	size_t rem = length;

	if (length > 256) {
		return __syscall_ret(-EIO);
	}

	while (rem) {
		ret = __syscall_cp(SYS_getrandom, pos, rem, 0);
		if (ret == -EINTR) {
			continue;
		} else if (ret == -EFAULT || ret == -ENOSYS) {
			return __syscall_ret(ret);
		} else if (ret <= 0) {
			return __syscall_ret(-EIO);
		}

		pos += ret;
		rem -= ret;
	}
	return 0;
}