[PATCH v2 bpf-next 11/11] selftests/bpf: add multi-file statically linked BPF object file test

[Andrii Nakryiko <andrii@kernel.org>]

Add Makefile infra to specify multi-file BPF object files (and derivative
skeletons). Add first selftest validating BPF static linker can merge together
successfully two independent BPF object files and resulting object and
skeleton are correct and usable.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/testing/selftests/bpf/Makefile          | 12 ++++++
 .../selftests/bpf/prog_tests/static_linked.c  | 40 +++++++++++++++++++
 .../selftests/bpf/progs/test_static_linked1.c | 30 ++++++++++++++
 .../selftests/bpf/progs/test_static_linked2.c | 31 ++++++++++++++
 4 files changed, 113 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/static_linked.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_static_linked1.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_static_linked2.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 7ed5690be237..ed45565c1f70 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -303,6 +303,10 @@ endef
 
 SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
 
+LINKED_SKELS := test_static_linked.skel.h
+
+test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o
+
 # Set up extra TRUNNER_XXX "temporary" variables in the environment (relies on
 # $eval()) and pass control to DEFINE_TEST_RUNNER_RULES.
 # Parameters:
@@ -323,6 +327,7 @@ TRUNNER_BPF_OBJS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.o, $$(TRUNNER_BPF_SRCS)
 TRUNNER_BPF_SKELS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.skel.h,	\
 				 $$(filter-out $(SKEL_BLACKLIST),	\
 					       $$(TRUNNER_BPF_SRCS)))
+TRUNNER_BPF_SKELS_LINKED := $$(addprefix $$(TRUNNER_OUTPUT)/,$(LINKED_SKELS))
 TEST_GEN_FILES += $$(TRUNNER_BPF_OBJS)
 
 # Evaluate rules now with extra TRUNNER_XXX variables above already defined
@@ -359,6 +364,12 @@ $(TRUNNER_BPF_SKELS): %.skel.h: %.o $(BPFTOOL) | $(TRUNNER_OUTPUT)
 	$$(call msg,GEN-SKEL,$(TRUNNER_BINARY),$$@)
 	$(Q)$$(BPFTOOL) gen object $$(<:.o=.bpfo) $$<
 	$(Q)$$(BPFTOOL) gen skeleton $$(<:.o=.bpfo) > $$@
+
+$(TRUNNER_BPF_SKELS_LINKED): $(TRUNNER_BPF_OBJS) $(BPFTOOL) | $(TRUNNER_OUTPUT)
+	$$(call msg,LINK-BPF,$(TRUNNER_BINARY),$$(@:.skel.h=.bpfo))
+	$(Q)$$(BPFTOOL) gen object $$(@:.skel.h=.bpfo) $$(addprefix $(TRUNNER_OUTPUT)/,$$($$(@F)-deps))
+	$$(call msg,GEN-SKEL,$(TRUNNER_BINARY),$$@)
+	$(Q)$$(BPFTOOL) gen skeleton $$(@:.skel.h=.bpfo) > $$@
 endif
 
 # ensure we set up tests.h header generation rule just once
@@ -380,6 +391,7 @@ $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o:			\
 		      $(TRUNNER_EXTRA_HDRS)				\
 		      $(TRUNNER_BPF_OBJS)				\
 		      $(TRUNNER_BPF_SKELS)				\
+		      $(TRUNNER_BPF_SKELS_LINKED)			\
 		      $$(BPFOBJ) | $(TRUNNER_OUTPUT)
 	$$(call msg,TEST-OBJ,$(TRUNNER_BINARY),$$@)
 	$(Q)cd $$(@D) && $$(CC) -I. $$(CFLAGS) -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
diff --git a/tools/testing/selftests/bpf/prog_tests/static_linked.c b/tools/testing/selftests/bpf/prog_tests/static_linked.c
new file mode 100644
index 000000000000..46556976dccc
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/static_linked.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+
+#include <test_progs.h>
+#include "test_static_linked.skel.h"
+
+void test_static_linked(void)
+{
+	int err;
+	struct test_static_linked* skel;
+
+	skel = test_static_linked__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	skel->rodata->rovar1 = 1;
+	skel->bss->static_var1 = 2;
+	skel->bss->static_var11 = 3;
+
+	skel->rodata->rovar2 = 4;
+	skel->bss->static_var2 = 5;
+	skel->bss->static_var22 = 6;
+
+	err = test_static_linked__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	err = test_static_linked__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger */
+	usleep(1);
+
+	ASSERT_EQ(skel->bss->var1, 1 * 2 + 2 + 3, "var1");
+	ASSERT_EQ(skel->bss->var2, 4 * 3 + 5 + 6, "var2");
+
+cleanup:
+	test_static_linked__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_static_linked1.c b/tools/testing/selftests/bpf/progs/test_static_linked1.c
new file mode 100644
index 000000000000..ea1a6c4c7172
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_static_linked1.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+/* 8-byte aligned .bss */
+static volatile long static_var1;
+static volatile int static_var11;
+int var1 = 0;
+/* 4-byte aligned .rodata */
+const volatile int rovar1;
+
+/* same "subprog" name in both files */
+static __noinline int subprog(int x)
+{
+	/* but different formula */
+	return x * 2;
+}
+
+SEC("raw_tp/sys_enter")
+int handler1(const void *ctx)
+{
+	var1 = subprog(rovar1) + static_var1 + static_var11;
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";
+int VERSION SEC("version") = 1;
diff --git a/tools/testing/selftests/bpf/progs/test_static_linked2.c b/tools/testing/selftests/bpf/progs/test_static_linked2.c
new file mode 100644
index 000000000000..54d8d1ab577c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_static_linked2.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+/* 4-byte aligned .bss */
+static volatile int static_var2;
+static volatile int static_var22;
+int var2 = 0;
+/* 8-byte aligned .rodata */
+const volatile long rovar2;
+
+/* same "subprog" name in both files */
+static __noinline int subprog(int x)
+{
+	/* but different formula */
+	return x * 3;
+}
+
+SEC("raw_tp/sys_enter")
+int handler2(const void *ctx)
+{
+	var2 = subprog(rovar2) + static_var2 + static_var22;
+
+	return 0;
+}
+
+/* different name and/or type of the variable doesn't matter */
+char _license[] SEC("license") = "GPL";
+int _version SEC("version") = 1;
-- 
2.24.1