[PATCH bpf-next v2 6/6] bpf/selftests: Test for bpf_per_cpu_ptr() and bpf_this_cpu_ptr()

[Hao Luo <haoluo@google.com>]

Test bpf_per_cpu_ptr() and bpf_this_cpu_ptr(). Test two paths in the
kernel. If the base pointer points to a struct, the returned reg is
of type PTR_TO_BTF_ID. Direct pointer dereference can be applied on
the returned variable. If the base pointer isn't a struct, the
returned reg is of type PTR_TO_MEM, which also supports direct pointer
dereference.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Hao Luo <haoluo@google.com>
---
 .../selftests/bpf/prog_tests/ksyms_btf.c      | 10 +++++++
 .../selftests/bpf/progs/test_ksyms_btf.c      | 26 +++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
index 7b6846342449..22cc642dbc0e 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -58,6 +58,16 @@ void test_ksyms_btf(void)
 	CHECK(data->out__bpf_prog_active != bpf_prog_active_addr, "bpf_prog_active",
 	      "got %llu, exp %llu\n", data->out__bpf_prog_active, bpf_prog_active_addr);
 
+	CHECK(data->out__rq_cpu == -1, "rq_cpu",
+	      "got %u, exp != -1\n", data->out__rq_cpu);
+	CHECK(data->out__percpu_bpf_prog_active == -1, "percpu_bpf_prog_active",
+	      "got %d, exp != -1\n", data->out__percpu_bpf_prog_active);
+
+	CHECK(data->out__this_rq_cpu == -1, "this_rq_cpu",
+	      "got %u, exp != -1\n", data->out__this_rq_cpu);
+	CHECK(data->out__this_bpf_prog_active == -1, "this_bpf_prog_active",
+	      "got %d, exp != -1\n", data->out__this_bpf_prog_active);
+
 cleanup:
 	test_ksyms_btf__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
index e04e31117f84..02d564349892 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
@@ -8,15 +8,41 @@
 __u64 out__runqueues = -1;
 __u64 out__bpf_prog_active = -1;
 
+__u32 out__rq_cpu = -1; /* percpu struct fields */
+int out__percpu_bpf_prog_active = -1; /* percpu int */
+
+__u32 out__this_rq_cpu = -1;
+int out__this_bpf_prog_active = -1;
+
 extern const struct rq runqueues __ksym; /* struct type global var. */
 extern const int bpf_prog_active __ksym; /* int type global var. */
 
 SEC("raw_tp/sys_enter")
 int handler(const void *ctx)
 {
+	struct rq *rq;
+	int *active;
+	__u32 cpu;
+
 	out__runqueues = (__u64)&runqueues;
 	out__bpf_prog_active = (__u64)&bpf_prog_active;
 
+	cpu = bpf_get_smp_processor_id();
+
+	/* test bpf_per_cpu_ptr() */
+	rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, cpu);
+	if (rq)
+		out__rq_cpu = rq->cpu;
+	active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu);
+	if (active)
+		out__percpu_bpf_prog_active = *active;
+
+	/* test bpf_this_cpu_ptr */
+	rq = (struct rq *)bpf_this_cpu_ptr(&runqueues);
+	out__this_rq_cpu = rq->cpu;
+	active = (int *)bpf_this_cpu_ptr(&bpf_prog_active);
+	out__this_bpf_prog_active = *active;
+
 	return 0;
 }
 
-- 
2.28.0.526.ge36021eeef-goog