[PATCH bpf-next v6 7/7] selftests/bpf: Test "bpftool gen min_core_btf"

["Mauricio Vásquez" <mauricio@kinvolk.io>]

This commit reuses the core_reloc test to check if the BTF files
generated with "bpftool gen min_core_btf" are correct. This introduces
test_core_btfgen() that runs all the core_reloc tests, but this time
the source BTF files are generated by using "bpftool gen min_core_btf".

The goal of this test is to check that the generated files are usable,
and not to check if the algorithm is creating an optimized BTF file.

Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>
Signed-off-by: Rafael David Tinoco <rafael.tinoco@aquasec.com>
Signed-off-by: Lorenzo Fontana <lorenzo.fontana@elastic.co>
Signed-off-by: Leonardo Di Donato <leonardo.didonato@elastic.co>
---
 .../selftests/bpf/prog_tests/core_reloc.c     | 46 ++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
index b8bdd1c3efca..10a1d5fb788e 100644
--- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
+++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
@@ -2,6 +2,7 @@
 #include <test_progs.h>
 #include "progs/core_reloc_types.h"
 #include "bpf_testmod/bpf_testmod.h"
+#include <linux/limits.h>
 #include <sys/mman.h>
 #include <sys/syscall.h>
 #include <bpf/btf.h>
@@ -354,6 +355,8 @@ static int duration = 0;
 	.fails = true,							\
 }
 
+#define BTFGEN_BTF_PATH "/tmp/btfgen.btf"
+
 struct core_reloc_test_case;
 
 typedef int (*setup_test_fn)(struct core_reloc_test_case *test);
@@ -836,7 +839,21 @@ static size_t roundup_page(size_t sz)
 	return (sz + page_size - 1) / page_size * page_size;
 }
 
-void test_core_reloc(void)
+static int run_btfgen(const char *src_btf, const char *dst_btf, const char *objpath)
+{
+	char command[4096];
+	int n;
+
+	n = snprintf(command, sizeof(command),
+		     "./tools/build/bpftool/bpftool gen min_core_btf %s %s %s",
+		     src_btf, dst_btf, objpath);
+	if (n < 0 || n >= sizeof(command))
+		return -1;
+
+	return system(command);
+}
+
+static void _test_core_reloc(bool btfgen)
 {
 	const size_t mmap_sz = roundup_page(sizeof(struct data));
 	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, open_opts);
@@ -863,6 +880,22 @@ void test_core_reloc(void)
 			continue;
 		}
 
+		/* generate a "minimal" BTF file and use it as source */
+		if (btfgen) {
+			if (!test_case->btf_src_file || test_case->fails) {
+				test__skip();
+				continue;
+			}
+
+			unlink(BTFGEN_BTF_PATH);
+			err = run_btfgen(test_case->btf_src_file, BTFGEN_BTF_PATH,
+					 test_case->bpf_obj_file);
+			if (!ASSERT_OK(err, "run_btfgen"))
+				goto cleanup;
+
+			test_case->btf_src_file = BTFGEN_BTF_PATH;
+		}
+
 		if (test_case->setup) {
 			err = test_case->setup(test_case);
 			if (CHECK(err, "test_setup", "test #%d setup failed: %d\n", i, err))
@@ -954,8 +987,19 @@ void test_core_reloc(void)
 			CHECK_FAIL(munmap(mmap_data, mmap_sz));
 			mmap_data = NULL;
 		}
+		unlink(BTFGEN_BTF_PATH);
 		bpf_link__destroy(link);
 		link = NULL;
 		bpf_object__close(obj);
 	}
 }
+
+void test_core_reloc(void)
+{
+	_test_core_reloc(false);
+}
+
+void test_core_btfgen(void)
+{
+	_test_core_reloc(true);
+}
-- 
2.25.1