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

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 <redacted>
Signed-off-by: Rafael David Tinoco <redacted>
Signed-off-by: Lorenzo Fontana <redacted>
Signed-off-by: Leonardo Di Donato <redacted>
---
 .../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