[3/3] tools/nolibc: add testcases for vfprintf

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 47013b78972e..cc60c0f7363d 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -667,6 +667,82 @@  int run_stdlib(int min, int max)
 	return ret;
 }
 
+#define EXPECT_VFPRINTF(c, expected, fmt, ...)				\
+	ret += expect_vfprintf(llen, c, expected, fmt, ##__VA_ARGS__)
+
+static int expect_vfprintf(int llen, size_t c, const char *expected, const char *fmt, ...)
+{
+	int ret, fd, w, r;
+	char buf[100];
+	va_list args;
+
+	fd = memfd_create("vfprintf", 0);
+	if (fd == -1) {
+		pad_spc(llen, 64, "[FAIL]\n");
+		return 1;
+	}
+
+	va_start(args, fmt);
+	w = vfprintf(&(FILE) { fd }, fmt, args);
+	va_end(args);
+
+	if (w != c) {
+		llen += printf(" written(%d) != %d", w, (int) c);
+		pad_spc(llen, 64, "[FAIL]\n");
+		return 1;
+	}
+
+	lseek(fd, 0, SEEK_SET);
+
+	r = read(fd, buf, sizeof(buf) - 1);
+	buf[r] = '\0';
+
+	close(fd);
+
+	if (r != w) {
+		llen += printf(" written(%d) != read(%d)", w, r);
+		pad_spc(llen, 64, "[FAIL]\n");
+		return 1;
+	}
+
+	llen += printf(" \"%s\" = \"%s\"", expected, buf);
+	ret = strncmp(expected, buf, c);
+
+	pad_spc(llen, 64, ret ? "[FAIL]\n" : " [OK]\n");
+	return ret;
+}
+
+static int run_vfprintf(int min, int max)
+{
+	int test;
+	int tmp;
+	int ret = 0;
+	void *p1, *p2;
+
+	for (test = min; test >= 0 && test <= max; test++) {
+		int llen = 0; // line length
+
+		/* avoid leaving empty lines below, this will insert holes into
+		 * test numbers.
+		 */
+		switch (test + __LINE__ + 1) {
+		CASE_TEST(empty);        EXPECT_VFPRINTF(0, "", ""); break;
+		CASE_TEST(simple);       EXPECT_VFPRINTF(3, "foo", "foo"); break;
+		CASE_TEST(string);       EXPECT_VFPRINTF(3, "foo", "%s", "foo"); break;
+		CASE_TEST(number);       EXPECT_VFPRINTF(4, "1234", "%d", 1234); break;
+		CASE_TEST(negnumber);    EXPECT_VFPRINTF(5, "-1234", "%d", -1234); break;
+		CASE_TEST(unsigned);     EXPECT_VFPRINTF(5, "12345", "%u", 12345); break;
+		CASE_TEST(char);         EXPECT_VFPRINTF(1, "c", "%c", 'c'); break;
+		CASE_TEST(hex);          EXPECT_VFPRINTF(1, "f", "%x", 0xf); break;
+		CASE_TEST(pointer);      EXPECT_VFPRINTF(3, "0x0", "%p", NULL); break;
+		case __LINE__:
+			return ret; /* must be last */
+		/* note: do not set any defaults so as to permit holes above */
+		}
+	}
+	return ret;
+}
+
 static int smash_stack(void)
 {
 	char buf[100];
@@ -774,6 +850,7 @@  static const struct test test_names[] = {
 	/* add new tests here */
 	{ .name = "syscall",    .func = run_syscall    },
 	{ .name = "stdlib",     .func = run_stdlib     },
+	{ .name = "vfprintf",   .func = run_vfprintf   },
 	{ .name = "protection", .func = run_protection },
 	{ 0 }
 };