tools/nolibc: add getrandom()

This is used in various selftests and will be handy when integrating
those with nolibc.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Acked-by: Willy Tarreau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Thomas Weißschuh <[e-mail]>

tools/include/nolibc/Makefile

···
 		sys.h \
 		sys/auxv.h \
 		sys/mman.h \
+		sys/random.h \
 		sys/stat.h \
 		sys/syscall.h \
 		sys/time.h \

tools/include/nolibc/nolibc.h

···
 #include "sys.h"
 #include "sys/auxv.h"
 #include "sys/mman.h"
+#include "sys/random.h"
 #include "sys/stat.h"
 #include "sys/syscall.h"
 #include "sys/time.h"

tools/include/nolibc/sys/random.h

···
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+/*
+ * random definitions for NOLIBC
+ * Copyright (C) 2025 Thomas Weißschuh <[e-mail]>
+ */
+
+/* make sure to include all global symbols */
+#include "../nolibc.h"
+
+#ifndef _NOLIBC_SYS_RANDOM_H
+#define _NOLIBC_SYS_RANDOM_H
+
+#include "../arch.h"
+#include "../sys.h"
+
+#include <linux/random.h>
+
+/*
+ * ssize_t getrandom(void *buf, size_t buflen, unsigned int flags);
+ */
+
+static __attribute__((unused))
+ssize_t sys_getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+       return my_syscall3(__NR_getrandom, buf, buflen, flags);
+}
+
+static __attribute__((unused))
+ssize_t getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+       return __sysret(sys_getrandom(buf, buflen, flags));
+}
+
+#endif /* _NOLIBC_SYS_RANDOM_H */

tools/testing/selftests/nolibc/nolibc-test.c

···
 #include <sys/mman.h>
 #include <sys/mount.h>
 #include <sys/prctl.h>
+#include <sys/random.h>
 #include <sys/reboot.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
···
 	return 0;
 }
 
+int test_getrandom(void)
+{
+	uint64_t rng = 0;
+	ssize_t ret;
+
+	ret = getrandom(&rng, sizeof(rng), GRND_NONBLOCK);
+	if (ret == -1 && errno == EAGAIN)
+		return 0; /* No entropy available yet */
+
+	if (ret != sizeof(rng))
+		return ret;
+
+	if (!rng) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	return 0;
+}
+
 int test_getpagesize(void)
 {
 	int x = getpagesize();
···
 		CASE_TEST(getdents64_root);   EXPECT_SYSNE(1, test_getdents64("/"), -1); break;
 		CASE_TEST(getdents64_null);   EXPECT_SYSER(1, test_getdents64("/dev/null"), -1, ENOTDIR); break;
 		CASE_TEST(directories);       EXPECT_SYSZR(proc, test_dirent()); break;
+		CASE_TEST(getrandom);         EXPECT_SYSZR(1, test_getrandom()); break;
 		CASE_TEST(gettimeofday_tv);   EXPECT_SYSZR(1, gettimeofday(&tv, NULL)); break;
 		CASE_TEST(gettimeofday_tv_tz);EXPECT_SYSZR(1, gettimeofday(&tv, &tz)); break;
 		CASE_TEST(getpagesize);       EXPECT_SYSZR(1, test_getpagesize()); break;