Re: [PATCH v2 bpf-next 16/17] selftests/bpf: add global variables linking selftest

---
  tools/testing/selftests/bpf/Makefile          |  3 +-
  .../selftests/bpf/prog_tests/linked_vars.c    | 43 +++++++++++++++
  .../selftests/bpf/progs/linked_vars1.c        | 54 ++++++++++++++++++
  .../selftests/bpf/progs/linked_vars2.c        | 55 +++++++++++++++++++
  4 files changed, 154 insertions(+), 1 deletion(-)
  create mode 100644 tools/testing/selftests/bpf/prog_tests/linked_vars.c
  create mode 100644 tools/testing/selftests/bpf/progs/linked_vars1.c
  create mode 100644 tools/testing/selftests/bpf/progs/linked_vars2.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 427ccfec1a6a..d8f176b55c01 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile

@@ -308,10 +308,11 @@ endef
  
  SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
  
-LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h
+LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h linked_vars.skel.h
  
  test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o
  linked_funcs.skel.h-deps := linked_funcs1.o linked_funcs2.o
+linked_vars.skel.h-deps := linked_vars1.o linked_vars2.o
  
  LINKED_BPF_SRCS := $(patsubst %.o,%.c,$(foreach skel,$(LINKED_SKELS),$($(skel)-deps)))
  

diff --git a/tools/testing/selftests/bpf/prog_tests/linked_vars.c b/tools/testing/selftests/bpf/prog_tests/linked_vars.c
new file mode 100644
index 000000000000..f3d6ba31ef99
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/linked_vars.c

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <test_progs.h>
+#include <sys/syscall.h>
+#include "linked_vars.skel.h"
+
+void test_linked_vars(void)
+{
+	int err;
+	struct linked_vars *skel;
+
+	skel = linked_vars__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	skel->bss->input_bss1 = 1000;
+	skel->bss->input_bss2 = 2000;
+	skel->bss->input_bss_weak = 3000;
+
+	err = linked_vars__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	err = linked_vars__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger */
+	syscall(SYS_getpgid);
+
+	ASSERT_EQ(skel->bss->output_bss1, 1000 + 2000 + 3000, "output_bss1");
+	ASSERT_EQ(skel->bss->output_bss2, 1000 + 2000 + 3000, "output_bss2");
+	/* 10 comes from "winner" input_data_weak in first obj file */
+	ASSERT_EQ(skel->bss->output_data1, 1 + 2 + 10, "output_bss1");
+	ASSERT_EQ(skel->bss->output_data2, 1 + 2 + 10, "output_bss2");
+	/* 10 comes from "winner" input_rodata_weak in first obj file */

+	ASSERT_EQ(skel->bss->output_rodata1, 11 + 22 + 100, "output_weak1");
+	ASSERT_EQ(skel->bss->output_rodata2, 11 + 22 + 100, "output_weak2");
+
+cleanup:
+	linked_vars__destroy(skel);
+}

diff --git a/tools/testing/selftests/bpf/progs/linked_vars1.c b/tools/testing/selftests/bpf/progs/linked_vars1.c
new file mode 100644
index 000000000000..bc96eff9b8c1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/linked_vars1.c

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+extern int LINUX_KERNEL_VERSION __kconfig;
+/* this weak extern will be strict due to the other file's strong extern */
+extern bool CONFIG_BPF_SYSCALL __kconfig __weak;
+extern const void bpf_link_fops __ksym __weak;
+
+int input_bss1 = 0;
+int input_data1 = 1;
+const volatile int input_rodata1 = 11;
+
+int input_bss_weak __weak = 0;
+/* these two definitions should win */
+int input_data_weak __weak = 10;
+const volatile int input_rodata_weak __weak = 100;
+