[1/2] tools/nolibc: add support for [v]sscanf()

diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h
index c968dbbc4ef8..d63c45c06d8e 100644
--- a/tools/include/nolibc/stdio.h
+++ b/tools/include/nolibc/stdio.h
@@ -348,6 +348,99 @@  int printf(const char *fmt, ...)
 	return ret;
 }
 
+static __attribute__((unused))
+int vsscanf(const char *str, const char *format, va_list args)
+{
+	uintmax_t uval;
+	intmax_t ival;
+	int base;
+	char *endptr;
+	int matches;
+	int lpref;
+
+	matches = 0;
+
+	while (1) {
+		if (*format == '%') {
+			lpref = 0;
+			format++;
+
+			if (*format == 'l') {
+				lpref = 1;
+				format++;
+				if (*format == 'l') {
+					lpref = 2;
+					format++;
+				}
+			}
+
+			if (*format == '%') {
+				if ('%' != *str)
+					goto done;
+				str++;
+				format++;
+				continue;
+			} else if (*format == 'd') {
+				ival = strtoll(str, &endptr, 10);
+				if (lpref == 0)
+					*va_arg(args, int *) = ival;
+				else if (lpref == 1)
+					*va_arg(args, long *) = ival;
+				else if (lpref == 2)
+					*va_arg(args, long long *) = ival;
+			} else if (*format == 'u' || *format == 'x' || *format == 'X') {
+				base = *format == 'u' ? 10 : 16;
+				uval = strtoull(str, &endptr, base);
+				if (lpref == 0)
+					*va_arg(args, unsigned int *) = uval;
+				else if (lpref == 1)
+					*va_arg(args, unsigned long *) = uval;
+				else if (lpref == 2)
+					*va_arg(args, unsigned long long *) = uval;
+			} else if (*format == 'p') {
+				*va_arg(args, void **) = (void *)strtoul(str, &endptr, 16);
+			} else {
+				SET_ERRNO(EILSEQ);
+				goto done;
+			}
+
+			format++;
+			str = endptr;
+			matches++;
+
+		} else if (*format == '\0') {
+			goto done;
+		} else if (isspace(*format)) {
+			while (isspace(*format))
+				format++;
+			while (isspace(*str))
+				str++;
+		} else if (*format == *str) {
+			format++;
+			str++;
+		} else {
+			if (!matches)
+				matches = EOF;
+			goto done;
+		}
+	}
+
+done:
+	return matches;
+}
+
+static __attribute__((unused, format(scanf, 2, 3)))
+int sscanf(const char *str, const char *format, ...)
+{
+	va_list args;
+	int ret;
+
+	va_start(args, format);
+	ret = vsscanf(str, format, args);
+	va_end(args);
+	return ret;
+}
+
 static __attribute__((unused))
 void perror(const char *msg)
 {
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 093d0512f4c5..addbceb0b276 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1277,6 +1277,64 @@  static int expect_vfprintf(int llen, int c, const char *expected, const char *fm
 	return ret;
 }
 
+static int test_scanf(void)
+{
+	unsigned long long ull;
+	unsigned long ul;
+	unsigned int u;
+	long long ll;
+	long l;
+	void *p;
+	int i;
+
+	if (sscanf("", "foo") != EOF)
+		return 1;
+
+	if (sscanf("foo", "foo") != 0)
+		return 2;
+
+	if (sscanf("123", "%d", &i) != 1)
+		return 3;
+
+	if (i != 123)
+		return 4;
+
+	if (sscanf("a123b456c0x90", "a%db%uc%p", &i, &u, &p) != 3)
+		return 5;
+
+	if (i != 123)
+		return 6;
+
+	if (u != 456)
+		return 7;
+
+	if (p != (void *)0x90)
+		return 8;
+
+	if (sscanf("a    b1", "a b%d", &i) != 1)
+		return 9;
+
+	if (i != 1)
+		return 10;
+
+	if (sscanf("a%1", "a%%%d", &i) != 1)
+		return 11;
+
+	if (i != 1)
+		return 12;
+
+	if (sscanf("1|2|3|4|5|6",
+		   "%d|%ld|%lld|%u|%lu|%llu",
+		   &i, &l, &ll, &u, &ul, &ull) != 6)
+		return 13;
+
+	if (i != 1 || l != 2 || ll != 3 ||
+	    u != 4 || ul != 5 || ull != 6)
+		return 14;
+
+	return 0;
+}
+
 static int run_vfprintf(int min, int max)
 {
 	int test;
@@ -1298,6 +1356,7 @@  static int run_vfprintf(int min, int max)
 		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, "0x1", "%p", (void *) 0x1); break;
+		CASE_TEST(scanf);        EXPECT_ZR(1, test_scanf()); break;
 		case __LINE__:
 			return ret; /* must be last */
 		/* note: do not set any defaults so as to permit holes above */