[PATCH bpf-next v4 6/6] bpf/selftests: Test for bpf_per_cpu_ptr() and bpf_this_cpu_ptr()

Hao Luo
2020-09-29T23:51:19Z

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 | 18 +++++++++++
.../selftests/bpf/progs/test_ksyms_btf.c | 32 +++++++++++++++++++
2 files changed, 50 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
index c6ef06c0629a..28e26bd3e0ca 100644
--- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
+++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
@@ -11,6 +11,8 @@ static int duration;
void test_ksyms_btf(void)
{
__u64 runqueues_addr, bpf_prog_active_addr;
+ __u32 this_rq_cpu;
+ int this_bpf_prog_active;
struct test_ksyms_btf *skel = NULL;
struct test_ksyms_btf__data *data;
struct btf *btf;
@@ -64,6 +66,22 @@ void test_ksyms_btf(void)
(unsigned long long)data->out__bpf_prog_active_addr,
(unsigned long long)bpf_prog_active_addr);

+ CHECK(data->out__rq_cpu == -1, "rq_cpu",
+ "got %u, exp != -1\n", data->out__rq_cpu);
+ CHECK(data->out__bpf_prog_active < 0, "bpf_prog_active",
+ "got %d, exp >= 0\n", data->out__bpf_prog_active);
+ CHECK(data->out__cpu_0_rq_cpu != 0, "cpu_rq(0)->cpu",
+ "got %u, exp 0\n", data->out__cpu_0_rq_cpu);
+
+ this_rq_cpu = data->out__this_rq_cpu;
+ CHECK(this_rq_cpu != data->out__rq_cpu, "this_rq_cpu",
+ "got %u, exp %u\n", this_rq_cpu, data->out__rq_cpu);
+
+ this_bpf_prog_active = data->out__this_bpf_prog_active;
+ CHECK(this_bpf_prog_active != data->out__bpf_prog_active, "this_bpf_prog_active",
+ "got %d, exp %d\n", this_bpf_prog_active,
+ data->out__bpf_prog_active);
+
cleanup:
btf__free(btf);
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 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;
}

--
2.28.0.709.gb0816b6eb0-goog