selftests/bpf: Add split BTF dedup selftests

Add selftests validating BTF deduplication for split BTF case. Add a helper
macro that allows to validate entire BTF with raw BTF dump, not just
type-by-type. This saves tons of code and complexity.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201105043402.2530976-11-andrii@kernel.org

tools/testing/selftests/bpf/btf_helpers.c

@@ -3,6 +3,8 @@
 #include <stdio.h>
 #include <errno.h>
 #include <bpf/btf.h>
+#include <bpf/libbpf.h>
+#include "test_progs.h"
 
 static const char * const btf_kind_str_mapping[] = {
 	[BTF_KIND_UNKN]		= "UNKNOWN",
@@ -198,3 +200,60 @@ const char *btf_type_raw_dump(const struct btf *btf, int type_id)
 
 	return buf;
 }
+
+int btf_validate_raw(struct btf *btf, int nr_types, const char *exp_types[])
+{
+	int i;
+	bool ok = true;
+
+	ASSERT_EQ(btf__get_nr_types(btf), nr_types, "btf_nr_types");
+
+	for (i = 1; i <= nr_types; i++) {
+		if (!ASSERT_STREQ(btf_type_raw_dump(btf, i), exp_types[i - 1], "raw_dump"))
+			ok = false;
+	}
+
+	return ok;
+}
+
+static void btf_dump_printf(void *ctx, const char *fmt, va_list args)
+{
+	vfprintf(ctx, fmt, args);
+}
+
+/* Print BTF-to-C dump into a local buffer and return string pointer back.
+ * Buffer *will* be overwritten by subsequent btf_type_raw_dump() calls
+ */
+const char *btf_type_c_dump(const struct btf *btf)
+{
+	static char buf[16 * 1024];
+	FILE *buf_file;
+	struct btf_dump *d = NULL;
+	struct btf_dump_opts opts = {};
+	int err, i;
+
+	buf_file = fmemopen(buf, sizeof(buf) - 1, "w");
+	if (!buf_file) {
+		fprintf(stderr, "Failed to open memstream: %d\n", errno);
+		return NULL;
+	}
+
+	opts.ctx = buf_file;
+	d = btf_dump__new(btf, NULL, &opts, btf_dump_printf);
+	if (libbpf_get_error(d)) {
+		fprintf(stderr, "Failed to create btf_dump instance: %ld\n", libbpf_get_error(d));
+		return NULL;
+	}
+
+	for (i = 1; i <= btf__get_nr_types(btf); i++) {
+		err = btf_dump__dump_type(d, i);
+		if (err) {
+			fprintf(stderr, "Failed to dump type [%d]: %d\n", i, err);
+			return NULL;
+		}
+	}
+
+	fflush(buf_file);
+	fclose(buf_file);
+	return buf;
+}

tools/testing/selftests/bpf/btf_helpers.h

@@ -8,5 +8,12 @@
 
 int fprintf_btf_type_raw(FILE *out, const struct btf *btf, __u32 id);
 const char *btf_type_raw_dump(const struct btf *btf, int type_id);
+int btf_validate_raw(struct btf *btf, int nr_types, const char *exp_types[]);
 
+#define VALIDATE_RAW_BTF(btf, raw_types...)				\
+	btf_validate_raw(btf,						\
+			 sizeof((const char *[]){raw_types})/sizeof(void *),\
+			 (const char *[]){raw_types})
+
+const char *btf_type_c_dump(const struct btf *btf);
 #endif