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SubjectRe: [PATCH bpf-next v1 8/8] bpf/selftests: Test for bpf_per_cpu_ptr()
On Wed, Aug 19, 2020 at 3:42 PM Hao Luo <haoluo@google.com> wrote:
>
> Test bpf_per_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>
> ---

Acked-by: Andrii Nakryiko <andriin@fb.com>

> .../testing/selftests/bpf/prog_tests/ksyms_btf.c | 4 ++++
> .../testing/selftests/bpf/progs/test_ksyms_btf.c | 15 ++++++++++++++-
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> index 1dad61ba7e99..bdedd4a76b42 100644
> --- a/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_btf.c
> @@ -71,6 +71,10 @@ void test_ksyms_btf(void)
> "got %llu, exp %llu\n", data->out__runqueues, runqueues_addr);
> 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 %u\n", data->out__rq_cpu, 1);
> + CHECK(data->out__process_counts == -1, "process_counts",
> + "got %lu, exp != -1", data->out__process_counts);
>
> 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..78cf1ebb753d 100644
> --- a/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> +++ b/tools/testing/selftests/bpf/progs/test_ksyms_btf.c
> @@ -7,16 +7,29 @@
>
> __u64 out__runqueues = -1;
> __u64 out__bpf_prog_active = -1;
> +__u32 out__rq_cpu = -1;
> +unsigned long out__process_counts = -1;

try to not use long for variables, it is 32-bit integer in user-space
but always 64-bit in BPF. This causes problems when using skeleton on
32-bit architecture.

>
> -extern const struct rq runqueues __ksym; /* struct type global var. */
> +extern const struct rq runqueues __ksym; /* struct type percpu var. */
> extern const int bpf_prog_active __ksym; /* int type global var. */
> +extern const unsigned long process_counts __ksym; /* int type percpu var. */
>
> SEC("raw_tp/sys_enter")
> int handler(const void *ctx)
> {
> + struct rq *rq;
> + unsigned long *count;
> +
> out__runqueues = (__u64)&runqueues;
> out__bpf_prog_active = (__u64)&bpf_prog_active;
>
> + rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, 1);
> + if (rq)
> + out__rq_cpu = rq->cpu;

this is awesome!

Are there any per-cpu variables that are arrays? Would be nice to test
those too.


> + count = (unsigned long *)bpf_per_cpu_ptr(&process_counts, 1);
> + if (count)
> + out__process_counts = *count;
> +
> return 0;
> }
>
> --
> 2.28.0.220.ged08abb693-goog
>

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