On Wed, Sep 23, 2020 at 6:46 PM Song Liu <songliubraving@xxxxxx> wrote:
>
> Add .test_run for raw_tracepoint. Also, introduce a new feature that runs
> the target program on a specific CPU. This is achieved by a new flag in
> bpf_attr.test, BPF_F_TEST_RUN_ON_CPU. When this flag is set, the program
> is triggered on cpu with id bpf_attr.test.cpu. This feature is needed for
> BPF programs that handle perf_event and other percpu resources, as the
> program can access these resource locally.
>
> Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
> include/linux/bpf.h | 3 ++
> include/uapi/linux/bpf.h | 7 +++
> kernel/bpf/syscall.c | 2 +-
> kernel/trace/bpf_trace.c | 1 +
> net/bpf/test_run.c | 89 ++++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 7 +++
> 6 files changed, 108 insertions(+), 1 deletion(-)
>
[...]
> +int bpf_prog_test_run_raw_tp(struct bpf_prog *prog,
> + const union bpf_attr *kattr,
> + union bpf_attr __user *uattr)
> +{
> + void __user *ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
> + __u32 ctx_size_in = kattr->test.ctx_size_in;
> + struct bpf_raw_tp_test_run_info info;
> + int cpu, err = 0;
> +
> + /* doesn't support data_in/out, ctx_out, duration, or repeat */
> + if (kattr->test.data_in || kattr->test.data_out ||
> + kattr->test.ctx_out || kattr->test.duration ||
> + kattr->test.repeat)
duration and repeat sound generally useful (benchmarking raw_tp
programs), so it's a pity you haven't implemented them. But it can be
added later, so not a deal breaker.
> + return -EINVAL;
> +
> + if (ctx_size_in < prog->aux->max_ctx_offset)
> + return -EINVAL;
> +
> + if (ctx_size_in) {
> + info.ctx = kzalloc(ctx_size_in, GFP_USER);
> + if (!info.ctx)
> + return -ENOMEM;
> + if (copy_from_user(info.ctx, ctx_in, ctx_size_in)) {
> + err = -EFAULT;
> + goto out;
> + }
> + } else {
> + info.ctx = NULL;
> + }
> +
> + info.prog = prog;
> + cpu = kattr->test.cpu;
> +
> + if ((kattr->test.flags & BPF_F_TEST_RUN_ON_CPU) == 0 ||
> + cpu == smp_processor_id()) {
should we enforce that cpu == 0 if BPF_F_TEST_RUN_ON_CPU is not set?
> + __bpf_prog_test_run_raw_tp(&info);
> + } else {
> + /* smp_call_function_single() also checks cpu_online()
> + * after csd_lock(). However, since cpu_plus is from user
cpu_plus leftover in a comment
> + * space, let's do an extra quick check to filter out
> + * invalid value before smp_call_function_single().
> + */
> + if (!cpu_online(cpu)) {
briefly looking at cpu_online() code, it seems like it's not checking
that cpu is < NR_CPUS. Should we add a selftest that validates that
passing unreasonable cpu index doesn't generate warning or invalid
memory access?
> + err = -ENXIO;
> + goto out;
> + }
> +
> + err = smp_call_function_single(cpu, __bpf_prog_test_run_raw_tp,
> + &info, 1);
> + if (err)
> + goto out;
> + }
> +
[...]
