selftests/bpf: add btf_dump BTF-to-C conversion tests

Add new test_btf_dump set of tests, validating BTF-to-C conversion
correctness. Tests rely on clang to generate BTF from provided C test
cases.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 143 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_btf_dump.c b/tools/testing/selftests/bpf/test_btf_dump.c
new file mode 100644
index 000000000000..8f850823d35f
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_btf_dump.c
@@ -0,0 +1,143 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <linux/err.h>
+#include <btf.h>
+
+#define CHECK(condition, format...) ({					\
+	int __ret = !!(condition);					\
+	if (__ret) {							\
+		fprintf(stderr, "%s:%d:FAIL ", __func__, __LINE__);	\
+		fprintf(stderr, format);				\
+	}								\
+	__ret;								\
+})
+
+void btf_dump_printf(void *ctx, const char *fmt, va_list args)
+{
+	vfprintf(ctx, fmt, args);
+}
+
+struct btf_dump_test_case {
+	const char *name;
+	struct btf_dump_opts opts;
+} btf_dump_test_cases[] = {
+	{.name = "btf_dump_test_case_syntax", .opts = {}},
+	{.name = "btf_dump_test_case_ordering", .opts = {}},
+	{.name = "btf_dump_test_case_padding", .opts = {}},
+	{.name = "btf_dump_test_case_packing", .opts = {}},
+	{.name = "btf_dump_test_case_bitfields", .opts = {}},
+	{.name = "btf_dump_test_case_multidim", .opts = {}},
+	{.name = "btf_dump_test_case_namespacing", .opts = {}},
+};
+
+static int btf_dump_all_types(const struct btf *btf,
+			      const struct btf_dump_opts *opts)
+{
+	size_t type_cnt = btf__get_nr_types(btf);
+	struct btf_dump *d;
+	int err = 0, id;
+
+	d = btf_dump__new(btf, NULL, opts, btf_dump_printf);
+	if (IS_ERR(d))
+		return PTR_ERR(d);
+
+	for (id = 1; id <= type_cnt; id++) {
+		err = btf_dump__dump_type(d, id);
+		if (err)
+			goto done;
+	}
+
+done:
+	btf_dump__free(d);
+	return err;
+}
+
+int test_btf_dump_case(int n, struct btf_dump_test_case *test_case)
+{
+	char test_file[256], out_file[256], diff_cmd[1024];
+	struct btf *btf = NULL;
+	int err = 0, fd = -1;
+	FILE *f = NULL;
+
+	fprintf(stderr, "Test case #%d (%s): ", n, test_case->name);
+
+	snprintf(test_file, sizeof(test_file), "%s.o", test_case->name);
+
+	btf = btf__parse_elf(test_file, NULL);
+	if (CHECK(IS_ERR(btf),
+	    "failed to load test BTF: %ld\n", PTR_ERR(btf))) {
+		err = -PTR_ERR(btf);
+		btf = NULL;
+		goto done;
+	}
+
+	snprintf(out_file, sizeof(out_file),
+		 "/tmp/%s.output.XXXXXX", test_case->name);
+	fd = mkstemp(out_file);
+	if (CHECK(fd < 0, "failed to create temp output file: %d\n", fd)) {
+		err = fd;
+		goto done;
+	}
+	f = fdopen(fd, "w");
+	if (CHECK(f == NULL, "failed to open temp output file: %s(%d)\n",
+		  strerror(errno), errno)) {
+		close(fd);
+		goto done;
+	}
+
+	test_case->opts.ctx = f;
+	err = btf_dump_all_types(btf, &test_case->opts);
+	fclose(f);
+	close(fd);
+	if (CHECK(err, "failure during C dumping: %d\n", err)) {
+		goto done;
+	}
+
+	snprintf(test_file, sizeof(test_file), "progs/%s.c", test_case->name);
+	/*
+	 * Diff test output and expected test output, contained between
+	 * START-EXPECTED-OUTPUT and END-EXPECTED-OUTPUT lines in test case.
+	 * For expected output lines, everything before '*' is stripped out.
+	 * Also lines containing comment start and comment end markers are
+	 * ignored. 
+	 */
+	snprintf(diff_cmd, sizeof(diff_cmd),
+		 "awk '/START-EXPECTED-OUTPUT/{out=1;next} "
+		 "/END-EXPECTED-OUTPUT/{out=0} "
+		 "/\\/\\*|\\*\\//{next} " /* ignore comment start/end lines */
+		 "out {sub(/^[ \\t]*\\*/, \"\"); print}' '%s' | diff -u - '%s'",
+		 test_file, out_file);
+	err = system(diff_cmd);
+	if (CHECK(err,
+		  "differing test output, output=%s, err=%d, diff cmd:\n%s\n",
+		  out_file, err, diff_cmd))
+		goto done;
+
+	remove(out_file);
+	fprintf(stderr, "OK\n");
+
+done:
+	btf__free(btf);
+	return err;
+}
+
+int main() {
+	int test_case_cnt, i, err, failed = 0;
+
+	test_case_cnt = sizeof(btf_dump_test_cases) /
+			sizeof(btf_dump_test_cases[0]);
+
+	for (i = 0; i < test_case_cnt; i++) {
+		err = test_btf_dump_case(i, &btf_dump_test_cases[i]);
+		if (err)
+			failed++;
+	}
+
+	fprintf(stderr, "%d tests succeeded, %d tests failed.\n",
+		test_case_cnt - failed, failed);
+
+	return failed;
+}