netdev - [PATCH bpf-next 4/4] selftests/bpf: Add light skeleton test for kfunc detection.

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Date:   Mon, 20 Mar 2023 22:19:51 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, andrii@...nel.org, martin.lau@...nel.org,
        void@...ifault.com, davemarchevsky@...a.com, tj@...nel.org,
        memxor@...il.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
        kernel-team@...com
Subject: [PATCH bpf-next 4/4] selftests/bpf: Add light skeleton test for kfunc detection.

From: Alexei Starovoitov <ast@...nel.org>

Add light skeleton test for kfunc detection.

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 .../testing/selftests/bpf/progs/test_ksyms_weak.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
index 7003eef0c192..d00268c91e19 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
@@ -20,6 +20,8 @@ __u64 out__non_existent_typed = -1;
 /* test existing weak symbols can be resolved. */
 extern const struct rq runqueues __ksym __weak; /* typed */
 extern const void bpf_prog_active __ksym __weak; /* typeless */
+struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym __weak;
+void bpf_testmod_test_mod_kfunc(int i) __ksym __weak;
 
 
 /* non-existent weak symbols. */
@@ -29,6 +31,7 @@ extern const void bpf_link_fops1 __ksym __weak;
 
 /* typed symbols, default to zero. */
 extern const int bpf_link_fops2 __ksym __weak;
+void invalid_kfunc(void) __ksym __weak;
 
 SEC("raw_tp/sys_enter")
 int pass_handler(const void *ctx)
@@ -50,6 +53,18 @@ int pass_handler(const void *ctx)
 	if (&bpf_link_fops2) /* can't happen */
 		out__non_existent_typed = (__u64)bpf_per_cpu_ptr(&bpf_link_fops2, 0);
 
+	if (!bpf_ksym_exists(bpf_task_acquire))
+		/* dead code won't be seen by the verifier */
+		bpf_task_acquire(0);
+
+	if (!bpf_ksym_exists(bpf_testmod_test_mod_kfunc))
+		/* dead code won't be seen by the verifier */
+		bpf_testmod_test_mod_kfunc(0);
+
+	if (bpf_ksym_exists(invalid_kfunc))
+		/* dead code won't be seen by the verifier */
+		invalid_kfunc();
+
 	return 0;
 }
 
-- 
2.34.1