Merge branch 'fix-libbpf-s-bpf_object-and-bpf-subskel-interoperability'

Andrii Nakryiko says:

====================
Fix libbpf's bpf_object and BPF subskel interoperability

Fix libbpf's global data map mmap()'ing logic to make BPF objects loaded
through generic bpf_object__load() API interoperable with BPF subskeleton
instantiated from such BPF object. The issue is in re-mmap()'ing of global
data maps after BPF object is loaded into kernel, which is currently done in
BPF skeleton-specific code, and should instead be done in generic and common
bpf_object_load() logic.

See patch #2 for the fix, patch #3 for the selftests.  Patch #1 is preliminary
fix for existing spin_lock selftests which currently works by accident.
====================

Link: https://lore.kernel.org/r/20241023043908.3834423-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 77 insertions, 3 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/subskeleton.c b/tools/testing/selftests/bpf/prog_tests/subskeleton.c
index 9c31b7004f9c..fdf13ed0152a 100644
--- a/tools/testing/selftests/bpf/prog_tests/subskeleton.c
+++ b/tools/testing/selftests/bpf/prog_tests/subskeleton.c
@@ -46,7 +46,8 @@ static int subskeleton_lib_subresult(struct bpf_object *obj)
 	return result;
 }
 
-void test_subskeleton(void)
+/* initialize and load through skeleton, then instantiate subskeleton out of it */
+static void subtest_skel_subskeleton(void)
 {
 	int err, result;
 	struct test_subskeleton *skel;
@@ -76,3 +77,76 @@ void test_subskeleton(void)
 cleanup:
 	test_subskeleton__destroy(skel);
 }
+
+/* initialize and load through generic bpf_object API, then instantiate subskeleton out of it */
+static void subtest_obj_subskeleton(void)
+{
+	int err, result;
+	const void *elf_bytes;
+	size_t elf_bytes_sz = 0, rodata_sz = 0, bss_sz = 0;
+	struct bpf_object *obj;
+	const struct bpf_map *map;
+	const struct bpf_program *prog;
+	struct bpf_link *link = NULL;
+	struct test_subskeleton__rodata *rodata;
+	struct test_subskeleton__bss *bss;
+
+	elf_bytes = test_subskeleton__elf_bytes(&elf_bytes_sz);
+	if (!ASSERT_OK_PTR(elf_bytes, "elf_bytes"))
+		return;
+
+	obj = bpf_object__open_mem(elf_bytes, elf_bytes_sz, NULL);
+	if (!ASSERT_OK_PTR(obj, "obj_open_mem"))
+		return;
+
+	map = bpf_object__find_map_by_name(obj, ".rodata");
+	if (!ASSERT_OK_PTR(map, "rodata_map_by_name"))
+		goto cleanup;
+
+	rodata = bpf_map__initial_value(map, &rodata_sz);
+	if (!ASSERT_OK_PTR(rodata, "rodata_get"))
+		goto cleanup;
+
+	rodata->rovar1 = 10;
+	rodata->var1 = 1;
+	subskeleton_lib_setup(obj);
+
+	err = bpf_object__load(obj);
+	if (!ASSERT_OK(err, "obj_load"))
+		goto cleanup;
+
+	prog = bpf_object__find_program_by_name(obj, "handler1");
+	if (!ASSERT_OK_PTR(prog, "prog_by_name"))
+		goto cleanup;
+
+	link = bpf_program__attach(prog);
+	if (!ASSERT_OK_PTR(link, "prog_attach"))
+		goto cleanup;
+
+	/* trigger tracepoint */
+	usleep(1);
+
+	map = bpf_object__find_map_by_name(obj, ".bss");
+	if (!ASSERT_OK_PTR(map, "bss_map_by_name"))
+		goto cleanup;
+
+	bss = bpf_map__initial_value(map, &bss_sz);
+	if (!ASSERT_OK_PTR(rodata, "rodata_get"))
+		goto cleanup;
+
+	result = subskeleton_lib_subresult(obj) * 10;
+	ASSERT_EQ(bss->out1, result, "out1");
+
+cleanup:
+	bpf_link__destroy(link);
+	bpf_object__close(obj);
+}
+
+
+void test_subskeleton(void)
+{
+	if (test__start_subtest("skel_subskel"))
+		subtest_skel_subskeleton();
+	if (test__start_subtest("obj_subskel"))
+		subtest_obj_subskeleton();
+}
diff --git a/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c b/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
index 43f40c4fe241..1c8b678e2e9a 100644
--- a/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
+++ b/tools/testing/selftests/bpf/progs/test_spin_lock_fail.c
@@ -28,8 +28,8 @@ struct {
 	},
 };
 
-SEC(".data.A") struct bpf_spin_lock lockA;
-SEC(".data.B") struct bpf_spin_lock lockB;
+static struct bpf_spin_lock lockA SEC(".data.A");
+static struct bpf_spin_lock lockB SEC(".data.B");
 
 SEC("?tc")
 int lock_id_kptr_preserve(void *ctx)