[PATCH bpf-next RFC v1 8/8] bpf, selftests: Add basic test for module kfunc call

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

This has to drop light skeleton generation and instead use libbpf
skeleton support, as loader program does not support kfunc module calls,
yet. This also tests support for invalid kfunc calls we added in prior
changes, such that verifier handles invalid call as long as it is
removed by code elimination pass (before fixup_kfunc_call).

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/btf.h                           |  1 +
 kernel/bpf/btf.c                              |  1 +
 kernel/trace/bpf_trace.c                      |  1 +
 tools/testing/selftests/bpf/Makefile          |  3 ++-
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   | 23 ++++++++++++++++++-
 .../selftests/bpf/prog_tests/ksyms_module.c   | 10 ++++----
 .../selftests/bpf/progs/test_ksyms_module.c   |  9 ++++++++
 7 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 8c0f29ed2af9..6e704981c475 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -254,5 +254,6 @@ struct kfunc_btf_set {
 	struct kfunc_btf_set name = { LIST_HEAD_INIT(name.list), (set) }
 
 DECLARE_KFUNC_BTF_SET_REG(bpf_tcp_ca);
+DECLARE_KFUNC_BTF_SET_REG(raw_tp);
 
 #endif
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index cc12470a55f9..85a0c2737ea1 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6251,3 +6251,4 @@ BTF_ID_LIST_GLOBAL_SINGLE(btf_task_struct_ids, struct, task_struct)
 	EXPORT_SYMBOL_GPL(unregister_##type##_kfunc_btf_set)
 
 DEFINE_KFUNC_BTF_SET_REG(bpf_tcp_ca);
+DEFINE_KFUNC_BTF_SET_REG(raw_tp);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 8e2eb950aa82..02fe14b5d005 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1599,6 +1599,7 @@ int __weak bpf_prog_test_run_tracing(struct bpf_prog *prog,
 const struct bpf_verifier_ops raw_tracepoint_verifier_ops = {
 	.get_func_proto  = raw_tp_prog_func_proto,
 	.is_valid_access = raw_tp_prog_is_valid_access,
+	.check_kfunc_call = __bpf_check_raw_tp_kfunc_call,
 };
 
 const struct bpf_prog_ops raw_tracepoint_prog_ops = {
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 866531c08e4f..1a4aa71e88f4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -174,6 +174,7 @@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_tes
 	$(Q)$(RM) bpf_testmod/bpf_testmod.ko # force re-compilation
 	$(Q)$(MAKE) $(submake_extras) -C bpf_testmod
 	$(Q)cp bpf_testmod/bpf_testmod.ko $@
+	$(Q)$(RESOLVE_BTFIDS) -s ../../../../vmlinux bpf_testmod.ko
 
 $(OUTPUT)/test_stub.o: test_stub.c $(BPFOBJ)
 	$(call msg,CC,,$@)
@@ -315,7 +316,7 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h		\
 		linked_vars.skel.h linked_maps.skel.h
 
 LSKELS := kfunc_call_test.c fentry_test.c fexit_test.c fexit_sleep.c \
-	test_ksyms_module.c test_ringbuf.c atomics.c trace_printk.c
+	  test_ringbuf.c atomics.c trace_printk.c
 SKEL_BLACKLIST += $$(LSKELS)
 
 test_static_linked.skel.h-deps := test_static_linked1.o test_static_linked2.o
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 141d8da687d2..8242f2bb50b4 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2020 Facebook */
 #include <linux/error-injection.h>
+#include <linux/btf.h>
+#include <linux/btf_ids.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/percpu-defs.h>
@@ -13,6 +15,12 @@
 
 DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123;
 
+noinline void
+bpf_testmod_test_mod_kfunc(int i)
+{
+	pr_info("mod kfunc i=%d\n", i);
+}
+
 noinline ssize_t
 bpf_testmod_test_read(struct file *file, struct kobject *kobj,
 		      struct bin_attribute *bin_attr,
@@ -55,13 +63,26 @@ static struct bin_attribute bin_attr_bpf_testmod_file __ro_after_init = {
 	.write = bpf_testmod_test_write,
 };
 
+BTF_SET_START(bpf_testmod_kfunc_ids)
+BTF_ID(func, bpf_testmod_test_mod_kfunc)
+BTF_SET_END(bpf_testmod_kfunc_ids)
+
+static DEFINE_KFUNC_BTF_SET(&bpf_testmod_kfunc_ids, bpf_testmod_kfunc_btf_set);
+
 static int bpf_testmod_init(void)
 {
-	return sysfs_create_bin_file(kernel_kobj, &bin_attr_bpf_testmod_file);
+	int ret;
+
+	ret = sysfs_create_bin_file(kernel_kobj, &bin_attr_bpf_testmod_file);
+	if (ret)
+		return ret;
+	register_raw_tp_kfunc_btf_set(&bpf_testmod_kfunc_btf_set);
+	return 0;
 }
 
 static void bpf_testmod_exit(void)
 {
+	unregister_raw_tp_kfunc_btf_set(&bpf_testmod_kfunc_btf_set);
 	return sysfs_remove_bin_file(kernel_kobj, &bin_attr_bpf_testmod_file);
 }
 
diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
index 2cd5cded543f..d3b0adc2a495 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_module.c
@@ -4,21 +4,19 @@
 #include <test_progs.h>
 #include <bpf/libbpf.h>
 #include <bpf/btf.h>
-#include "test_ksyms_module.lskel.h"
-
-static int duration;
+#include "test_ksyms_module.skel.h"
 
 void test_ksyms_module(void)
 {
-	struct test_ksyms_module* skel;
+	struct test_ksyms_module *skel;
 	int err;
 
 	skel = test_ksyms_module__open_and_load();
-	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+	if (!ASSERT_OK_PTR(skel, "test_ksyms_module__open_and_load"))
 		return;
 
 	err = test_ksyms_module__attach(skel);
-	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+	if (!ASSERT_OK(err, "test_ksyms_module__attach"))
 		goto cleanup;
 
 	usleep(1);
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_module.c b/tools/testing/selftests/bpf/progs/test_ksyms_module.c
index d6a0b3086b90..81f8790cb99d 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms_module.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_module.c
@@ -6,8 +6,11 @@
 #include <bpf/bpf_helpers.h>
 
 extern const int bpf_testmod_ksym_percpu __ksym;
+extern void bpf_testmod_test_mod_kfunc(int i) __ksym;
+extern void bpf_testmod_invalid_mod_kfunc(void) __ksym;
 
 int out_mod_ksym_global = 0;
+const volatile int x = 0;
 bool triggered = false;
 
 SEC("raw_tp/sys_enter")
@@ -16,6 +19,12 @@ int handler(const void *ctx)
 	int *val;
 	__u32 cpu;
 
+	/* This should be preserved by clang, but DCE'd by verifier, and still
+	 * allow loading the raw_tp prog
+	 */
+	if (x)
+		bpf_testmod_invalid_mod_kfunc();
+	bpf_testmod_test_mod_kfunc(42);
 	val = (int *)bpf_this_cpu_ptr(&bpf_testmod_ksym_percpu);
 	out_mod_ksym_global = *val;
 	triggered = true;
-- 
2.33.0