selftests/bpf: Exercise veristat filtering logic in a selftest

Test cases for veristat file/prog name filtering logic.
Check various formulations for any (*foo*), file (*foo*/),
prog (/bar) and file/prog (*foo*/bar) filters, alongside
erroneous filters and mixed allow/deny filter expressions.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260811-veristat-filter-fix-v2-2-6c234c4cd6ef@gmail.com

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

@@ -37,6 +37,14 @@ static struct fixture *init_fixture(void)
 	return fix;
 }
 
+static void read_output(struct fixture *fix)
+{
+	ssize_t len = pread(fix->fd, fix->output, fix->sz - 1, 0);
+
+	fix->output[len < 0 ? 0 : len] = 0;
+	ASSERT_GE(len, 0, "pread");
+}
+
 static void teardown_fixture(struct fixture *fix)
 {
 	free(fix->output);
@@ -230,6 +238,97 @@ static void test_no_array_index_for_array(void)
 	teardown_fixture(fix);
 }
 
+/*
+ * Name filter tests below run veristat on veristat_foo.bpf.o and
+ * veristat_bar.bpf.o, both defining programs 'foo', 'bar' and 'buz'.
+ * Every entry describes a single (filters, file, prog) combination and
+ * tells whether that program is expected in the veristat output:
+ * 'true' if it is, 'false' if it is not and -1 if veristat is expected
+ * to reject the filter.
+ */
+#define FILTER_OBJS "veristat_foo.bpf.o veristat_bar.bpf.o"
+
+static const struct name_filter_case {
+	const char *filters;
+	const char *file;
+	const char *prog;
+	int included;
+} name_filter_cases[] = {
+	/* no filters, every program is processed */
+	{ "",			"foo", "foo", true  },
+	{ "",			"foo", "bar", true  },
+	{ "",			"foo", "buz", true  },
+	{ "",			"bar", "foo", true  },
+	{ "",			"bar", "bar", true  },
+	{ "",			"bar", "buz", true  },
+	/* deny filters */
+	{ "-f '!*foo*'",	"foo", "bar", false },
+	{ "-f '!*foo*'",	"bar", "foo", false },
+	{ "-f '!*foo*'",	"bar", "bar", true  },
+	{ "-f '!*foo*/bar'",	"foo", "bar", false },
+	{ "-f '!*foo*/bar'",	"foo", "buz", true  },
+	{ "-f '!*foo*/bar'",	"bar", "bar", true  },
+	{ "-f '!*foo*/'",	"foo", "bar", false },
+	{ "-f '!*foo*/'",	"bar", "bar", true  },
+	{ "-f '!/bar'",		"foo", "bar", false },
+	{ "-f '!/bar'",		"foo", "foo", true  },
+	{ "-f '!/'",		"foo", "bar", -1    },
+	{ "-f '!'",		"foo", "bar", -1    },
+	/* allow filters */
+	{ "-f '*foo*'",		"foo", "bar", true  },
+	{ "-f '*foo*'",		"bar", "foo", true  },
+	{ "-f '*foo*'",		"bar", "bar", false },
+	{ "-f '*foo*/bar'",	"foo", "bar", true  },
+	{ "-f '*foo*/bar'",	"foo", "buz", false },
+	{ "-f '*foo*/bar'",	"bar", "bar", false },
+	{ "-f '*foo*/'",	"foo", "bar", true  },
+	{ "-f '*foo*/'",	"bar", "bar", false },
+	{ "-f '/bar'",		"foo", "bar", true  },
+	{ "-f '/bar'",		"foo", "foo", false },
+	{ "-f '/'",		"foo", "bar", -1    },
+	{ "-f ''",		"foo", "bar", -1    },
+	/* allow and deny filters combined */
+	{ "-f '*foo*/' -f '!/bar'", "foo", "foo", true  },
+	{ "-f '*foo*/' -f '!/bar'", "foo", "bar", false },
+	{ "-f '*foo*/' -f '!/bar'", "bar", "foo", false },
+};
+
+static void test_name_filters(void)
+{
+	struct fixture *fix = init_fixture();
+	const struct name_filter_case *t;
+	char cmd[512], row[64], name[128];
+	int i, err;
+
+	for (i = 0; i < ARRAY_SIZE(name_filter_cases); i++) {
+		t = &name_filter_cases[i];
+		/* stderr is merged with stdout in order to catch error messages */
+		snprintf(cmd, sizeof(cmd), "%s " FILTER_OBJS " -q -o csv -e file,prog %s > %s 2>&1",
+			 fix->veristat, t->filters, fix->tmpfile);
+		err = system(cmd);
+		read_output(fix);
+
+		snprintf(row, sizeof(row), "veristat_%s.bpf.o,%s", t->file, t->prog);
+		snprintf(name, sizeof(name), "veristat %s: %s", t->filters, row);
+		switch (t->included) {
+		case true:
+			ASSERT_OK(err, name);
+			ASSERT_HAS_SUBSTR(fix->output, row, name);
+			break;
+		case false:
+			ASSERT_OK(err, name);
+			ASSERT_FALSE(!!strstr(fix->output, row), name);
+			break;
+		case -1:
+			ASSERT_NEQ(err, 0, name);
+			ASSERT_HAS_SUBSTR(fix->output, "Invalid filter", name);
+			break;
+		}
+	}
+
+	teardown_fixture(fix);
+}
+
 void test_veristat(void)
 {
 	if (test__start_subtest("set_global_vars_succeeds"))
@@ -256,6 +355,8 @@ void test_veristat(void)
 	if (test__start_subtest("test_no_array_index_for_array"))
 		test_no_array_index_for_array();
 
+	if (test__start_subtest("name_filters"))
+		test_name_filters();
 }
 
 #undef __CHECK_STR

tools/testing/selftests/bpf/progs/veristat_bar.c

@@ -0,0 +1,3 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+#include "veristat_foo.c"

tools/testing/selftests/bpf/progs/veristat_foo.c

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+/*
+ * Programs below exist only to exercise veristat's -f name filters,
+ * their bodies are irrelevant, only the names matter.
+ * This file is also included by veristat_bar.c, so that the same set of
+ * program names is available in two differently named object files.
+ */
+
+SEC("socket")
+int foo(void *ctx)
+{
+	return 0;
+}
+
+SEC("socket")
+int bar(void *ctx)
+{
+	return 0;
+}
+
+SEC("socket")
+int buz(void *ctx)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";