Re: [PATCH bpf-next 3/5] selftests/bpf: add selftest for BPF_PROG_TYPE_USER

[Andrii Nakryiko]

On Sat, Aug 1, 2020 at 1:50 AM Song Liu <songliubraving@xxxxxx> wrote:
>
> This test checks the correctness of BPF_PROG_TYPE_USER program, including:
> running on the right cpu, passing in correct args, returning retval, and
> being able to call bpf_get_stack|stackid.
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
>  .../selftests/bpf/prog_tests/user_prog.c      | 52 +++++++++++++++++
>  tools/testing/selftests/bpf/progs/user_prog.c | 56 +++++++++++++++++++
>  2 files changed, 108 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/user_prog.c
>  create mode 100644 tools/testing/selftests/bpf/progs/user_prog.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/user_prog.c b/tools/testing/selftests/bpf/prog_tests/user_prog.c
> new file mode 100644
> index 0000000000000..416707b3bff01
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/user_prog.c
> @@ -0,0 +1,52 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Facebook */
> +#include <test_progs.h>
> +#include "user_prog.skel.h"
> +
> +static int duration;
> +
> +void test_user_prog(void)
> +{
> +       struct bpf_user_prog_args args = {{0, 1, 2, 3, 4}};
> +       struct bpf_prog_test_run_attr attr = {};
> +       struct user_prog *skel;
> +       int i, numcpu, ret;
> +
> +       skel = user_prog__open_and_load();
> +
> +       if (CHECK(!skel, "user_prog__open_and_load",
> +                 "skeleton open_and_laod failed\n"))
> +               return;
> +
> +       numcpu = libbpf_num_possible_cpus();

nit: possible doesn't mean online right now, so it will fail on
offline or non-present CPUs

> +
> +       attr.prog_fd = bpf_program__fd(skel->progs.user_func);
> +       attr.data_size_in = sizeof(args);
> +       attr.data_in = &args;
> +
> +       /* start from -1, so we test cpu_plus == 0 */
> +       for (i = -1; i < numcpu; i++) {
> +               args.args[0] = i + 1;
> +               attr.cpu_plus = i + 1;
> +               ret = bpf_prog_test_run_xattr(&attr);
> +               CHECK(ret, "bpf_prog_test_run_xattr", "returns error\n");
> +
> +               /* skip two tests for i == -1 */
> +               if (i == -1)
> +                       continue;
> +               CHECK(attr.retval != i + 2, "bpf_prog_test_run_xattr",
> +                     "doesn't get expected retval\n");
> +               CHECK(skel->data->sum != 11 + i, "user_prog_args_test",
> +                     "sum of args doesn't match\n");
> +       }
> +
> +       CHECK(skel->data->cpu_match == 0, "cpu_match_test", "failed\n");
> +       CHECK(skel->bss->get_stack_success != numcpu + 1, "test_bpf_get_stack",
> +             "failed on %d cores\n", numcpu - skel->bss->get_stack_success);
> +       CHECK(skel->bss->get_stackid_success != numcpu + 1,
> +             "test_bpf_get_stackid",
> +             "failed on %d cores\n",
> +             numcpu + 1 - skel->bss->get_stackid_success);
> +
> +       user_prog__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/user_prog.c b/tools/testing/selftests/bpf/progs/user_prog.c
> new file mode 100644
> index 0000000000000..cf320e97f107a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/user_prog.c
> @@ -0,0 +1,56 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Facebook */
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#ifndef PERF_MAX_STACK_DEPTH
> +#define PERF_MAX_STACK_DEPTH         127
> +#endif
> +
> +typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
> +
> +struct {
> +       __uint(type, BPF_MAP_TYPE_STACK_TRACE);
> +       __uint(max_entries, 16384);
> +       __uint(key_size, sizeof(__u32));
> +       __uint(value_size, sizeof(stack_trace_t));
> +} stackmap SEC(".maps");
> +
> +volatile int cpu_match = 1;
> +volatile __u64 sum = 1;
> +volatile int get_stack_success = 0;
> +volatile int get_stackid_success = 0;
> +volatile __u64 stacktrace[PERF_MAX_STACK_DEPTH];

nit: no need for volatile for non-static variables

> +
> +SEC("user")
> +int user_func(struct bpf_user_prog_ctx *ctx)

If you put args in bpf_user_prog_ctx as a first field, you should be
able to re-use the BPF_PROG macro to access those arguments in a more
user-friendly way.

> +{
> +       int cpu = bpf_get_smp_processor_id();
> +       __u32 key = cpu;
> +       long stackid, err;
> +
> +       /* check the program runs on the right cpu */
> +       if (ctx->args[0] && ctx->args[0] != cpu + 1)
> +               cpu_match = 0;
> +
> +       /* check the sum of arguments are correct */
> +       sum = ctx->args[0] + ctx->args[1] + ctx->args[2] +
> +               ctx->args[3] + ctx->args[4];
> +
> +       /* check bpf_get_stackid works */
> +       stackid = bpf_get_stackid(ctx, &stackmap, 0);
> +       if (stackid >= 0)
> +               get_stackid_success++;
> +
> +       /* check bpf_get_stack works */
> +       err = bpf_get_stack(ctx, (void *)stacktrace,
> +                           PERF_MAX_STACK_DEPTH * sizeof(__u64),
> +                           BPF_F_USER_STACK);
> +       if (err >= 0)
> +               get_stack_success++;
> +
> +       return cpu + 2;
> +}
> --
> 2.24.1
>