bpf/selftests: Test for bpf_per_cpu_ptr() and bpf_this_cpu_ptr()

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.

Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200929235049.2533242-7-haoluo@google.com

1 files changed, 32 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
index 7dde2082131d..bb8ea9270f29 100644
--- a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
+++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
@@ -8,15 +8,47 @@
 __u64 out__runqueues_addr = -1;
 __u64 out__bpf_prog_active_addr = -1;
 
+__u32 out__rq_cpu = -1; /* percpu struct fields */
+int out__bpf_prog_active = -1; /* percpu int */
+
+__u32 out__this_rq_cpu = -1;
+int out__this_bpf_prog_active = -1;
+
+__u32 out__cpu_0_rq_cpu = -1; /* cpu_rq(0)->cpu */
+
 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_addr = (__u64)&runqueues;
 	out__bpf_prog_active_addr = (__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__bpf_prog_active = *active;
+
+	rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, 0);
+	if (rq) /* should always be valid, but we can't spare the check. */
+		out__cpu_0_rq_cpu = rq->cpu;
+
+	/* 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;
 }