selftests/bpf: Add CPU mask parsing tests

Add a bunch of test validating CPU mask parsing logic and error handling.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191212013559.1690898-1-andriin@fb.com

tools/testing/selftests/bpf/prog_tests/cpu_mask.c

+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "libbpf_internal.h"
+
+static int duration = 0;
+
+static void validate_mask(int case_nr, const char *exp, bool *mask, int n)
+{
+	int i;
+
+	for (i = 0; exp[i]; i++) {
+		if (exp[i] == '1') {
+			if (CHECK(i + 1 > n, "mask_short",
+				  "case #%d: mask too short, got n=%d, need at least %d\n",
+				  case_nr, n, i + 1))
+				return;
+			CHECK(!mask[i], "cpu_not_set",
+			      "case #%d: mask differs, expected cpu#%d SET\n",
+			      case_nr, i);
+		} else {
+			CHECK(i < n && mask[i], "cpu_set",
+			      "case #%d: mask differs, expected cpu#%d UNSET\n",
+			      case_nr, i);
+		}
+	}
+	CHECK(i < n, "mask_long",
+	      "case #%d: mask too long, got n=%d, expected at most %d\n",
+	      case_nr, n, i);
+}
+
+static struct {
+	const char *cpu_mask;
+	const char *expect;
+	bool fails;
+} test_cases[] = {
+	{ "0\n", "1", false },
+	{ "0,2\n", "101", false },
+	{ "0-2\n", "111", false },
+	{ "0-2,3-4\n", "11111", false },
+	{ "0", "1", false },
+	{ "0-2", "111", false },
+	{ "0,2", "101", false },
+	{ "0,1-3", "1111", false },
+	{ "0,1,2,3", "1111", false },
+	{ "0,2-3,5", "101101", false },
+	{ "3-3", "0001", false },
+	{ "2-4,6,9-10", "00111010011", false },
+	/* failure cases */
+	{ "", "", true },
+	{ "0-", "", true },
+	{ "0 ", "", true },
+	{ "0_1", "", true },
+	{ "1-0", "", true },
+	{ "-1", "", true },
+};
+
+void test_cpu_mask()
+{
+	int i, err, n;
+	bool *mask;
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		mask = NULL;
+		err = parse_cpu_mask_str(test_cases[i].cpu_mask, &mask, &n);
+		if (test_cases[i].fails) {
+			CHECK(!err, "should_fail",
+			      "case #%d: parsing should fail!\n", i + 1);
+		} else {
+			if (CHECK(err, "parse_err",
+				  "case #%d: cpu mask parsing failed: %d\n",
+				  i + 1, err))
+				continue;
+			validate_mask(i + 1, test_cases[i].expect, mask, n);
+		}
+		free(mask);
+	}
+}