Re: [PATCH bpf-next 6/8] bpftool: print local function pointer properly

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On Thu, Feb 4, 2021 at 5:53 PM Yonghong Song <yhs@xxxxxx> wrote:
>
> With later hashmap example, using bpftool xlated output may
> look like:
>   int dump_task(struct bpf_iter__task * ctx):
>   ; struct task_struct *task = ctx->task;
>      0: (79) r2 = *(u64 *)(r1 +8)
>   ; if (task == (void *)0 || called > 0)
>   ...
>     19: (18) r2 = subprog[+18]
>     30: (18) r2 = subprog[+26]
>   ...
>   36: (95) exit
>   __u64 check_hash_elem(struct bpf_map * map, __u32 * key, __u64 * val,
>                         struct callback_ctx * data):
>   ; struct bpf_iter__task *ctx = data->ctx;
>     37: (79) r5 = *(u64 *)(r4 +0)
>   ...
>     55: (95) exit
>   __u64 check_percpu_elem(struct bpf_map * map, __u32 * key,
>                           __u64 * val, void * unused):
>   ; check_percpu_elem(struct bpf_map *map, __u32 *key, __u64 *val, void *unused)
>     56: (bf) r6 = r3
>   ...
>     83: (18) r2 = subprog[+-46]

this +-46 looks very confusing...

>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
>  tools/bpf/bpftool/xlated_dumper.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/tools/bpf/bpftool/xlated_dumper.c b/tools/bpf/bpftool/xlated_dumper.c
> index 8608cd68cdd0..7bdd90503727 100644
> --- a/tools/bpf/bpftool/xlated_dumper.c
> +++ b/tools/bpf/bpftool/xlated_dumper.c
> @@ -196,6 +196,9 @@ static const char *print_imm(void *private_data,
>         else if (insn->src_reg == BPF_PSEUDO_MAP_VALUE)
>                 snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
>                          "map[id:%u][0]+%u", insn->imm, (insn + 1)->imm);
> +       else if (insn->src_reg == BPF_PSEUDO_FUNC)
> +               snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
> +                        "subprog[+%d]", insn->imm + 1);

why not `subprog[%+d]` instead (see above about confusing output)

>         else
>                 snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
>                          "0x%llx", (unsigned long long)full_imm);
> --
> 2.24.1
>



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