Re: [PATCH bpf-next 1/4] bpf: introduce verifier internal test flag

[Song Liu <liu.song.a23@gmail.com>]

On Fri, Aug 23, 2019 at 2:59 AM Alexei Starovoitov <ast@kernel.org> wrote:
>
> Introduce BPF_F_TEST_STATE_FREQ flag to stress test parentage chain
> and state pruning.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
>  include/linux/bpf_verifier.h | 1 +
>  include/uapi/linux/bpf.h     | 3 +++
>  kernel/bpf/syscall.c         | 1 +
>  kernel/bpf/verifier.c        | 5 ++++-
>  4 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 5fe99f322b1c..26a6d58ca78c 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -355,6 +355,7 @@ struct bpf_verifier_env {
>         struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
>         int stack_size;                 /* number of states to be processed */
>         bool strict_alignment;          /* perform strict pointer alignment checks */
> +       bool test_state_freq;           /* test verifier with different pruning frequency */
>         struct bpf_verifier_state *cur_state; /* current verifier state */
>         struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
>         struct bpf_verifier_state_list *free_list;
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index b5889257cc33..5d2fb183ee2d 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -285,6 +285,9 @@ enum bpf_attach_type {
>   */
>  #define BPF_F_TEST_RND_HI32    (1U << 2)
>
> +/* The verifier internal test flag. Behavior is undefined */
> +#define BPF_F_TEST_STATE_FREQ  (1U << 3)
> +
>  /* When BPF ldimm64's insn[0].src_reg != 0 then this can have
>   * two extensions:
>   *
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index c0f62fd67c6b..ca60eafa6922 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1629,6 +1629,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
>
>         if (attr->prog_flags & ~(BPF_F_STRICT_ALIGNMENT |
>                                  BPF_F_ANY_ALIGNMENT |
> +                                BPF_F_TEST_STATE_FREQ |
>                                  BPF_F_TEST_RND_HI32))
>                 return -EINVAL;
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 16d66bd7af09..3fb50757e812 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -7223,7 +7223,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
>         struct bpf_verifier_state_list *sl, **pprev;
>         struct bpf_verifier_state *cur = env->cur_state, *new;
>         int i, j, err, states_cnt = 0;
> -       bool add_new_state = false;
> +       bool add_new_state = env->test_state_freq ? true : false;
>
>         cur->last_insn_idx = env->prev_insn_idx;
>         if (!env->insn_aux_data[insn_idx].prune_point)
> @@ -9263,6 +9263,9 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
>
>         env->allow_ptr_leaks = is_priv;
>
> +       if (is_priv)
> +               env->test_state_freq = attr->prog_flags & BPF_F_TEST_STATE_FREQ;
> +
>         ret = replace_map_fd_with_map_ptr(env);
>         if (ret < 0)
>                 goto skip_full_check;
> --
> 2.20.0
>