On Thu, Sep 3, 2020 at 3:35 PM Hao Luo <haoluo@xxxxxxxxxx> wrote:
>
> 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@xxxxxx>
> Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
> ---
> .../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);
see below for few suggestions to make these test more specific
out__this_bpf_prog_active it should always be > 0, no?
> +
> 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;
this is equivalent to using bpf_this_cpu_ptr(), so:
1. you can compare value with out__this_xxx in user-space
2. it's interesting to also test that you can read value from some
other CPU. Can you add another variable and get value from CPU #0
always? E.g., for out__cpu_0_rq_cpu it should always be zero, right?
> +
> + /* 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
>
