On Tue, May 30, 2023 at 7:16 PM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote:
>
> 2023-05-28 14:20 UTC+0000 ~ Yafang Shao <laoar.shao@xxxxxxxxx>
> > Show the already expose kprobe_multi link info in bpftool. The result as
> > follows,
> >
> > $ bpftool link show
> > 2: kprobe_multi prog 11
> > func_cnt 4 addrs ffffffffaad475c0 ffffffffaad47600
> > ffffffffaad47640 ffffffffaad47680
> > pids trace(10936)
> >
> > $ bpftool link show -j
> > [{"id":1,"type":"perf_event","prog_id":5,"bpf_cookie":0,"pids":[{"pid":10658,"comm":"trace"}]},{"id":2,"type":"kprobe_multi","prog_id":11,"func_cnt":4,"addrs":[18446744072280634816,18446744072280634880,18446744072280634944,18446744072280635008],"pids":[{"pid":10936,"comm":"trace"}]},{"id":120,"type":"iter","prog_id":266,"target_name":"bpf_map"},{"id":121,"type":"iter","prog_id":267,"target_name":"bpf_prog"}]
> >
> > $ bpftool link show | grep -A 1 "func_cnt" | \
> > awk '{if (NR == 1) {print $4; print $5;} else {print $1; print $2} }' | \
> > awk '{"grep " $1 " /proc/kallsyms" | getline f; print f;}'
> > ffffffffaad475c0 T schedule_timeout_interruptible
> > ffffffffaad47600 T schedule_timeout_killable
> > ffffffffaad47640 T schedule_timeout_uninterruptible
> > ffffffffaad47680 T schedule_timeout_idle
>
> Looks nice, thank you!
>
> The address is a useful addition, but I feel like most of the time, this
> is the actual function name that we'd like to see. We could maybe print
> it directly in bpftool, what do you think? We already parse
> /proc/kallsyms elsewhere (to get the address of __bpf_call_base()). If
> we can parse the file only once for all func_cnt function, the overhead
> is maybe acceptable?
>
Thanks for your suggestion. Will change it.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > ---
> > tools/bpf/bpftool/link.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 50 insertions(+)
> >
> > diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
> > index 2d78607..76f1bb2 100644
> > --- a/tools/bpf/bpftool/link.c
> > +++ b/tools/bpf/bpftool/link.c
> > @@ -218,6 +218,20 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
> > jsonw_uint_field(json_wtr, "map_id",
> > info->struct_ops.map_id);
> > break;
> > + case BPF_LINK_TYPE_KPROBE_MULTI:
> > + const __u64 *addrs;
> > + __u32 i;
> > +
> > + jsonw_uint_field(json_wtr, "func_cnt", info->kprobe_multi.count);
> > + if (!info->kprobe_multi.count)
> > + break;
>
> I'd as well avoid having conditional entries in the JSON output. Let's
> just keep 0 and empty array in this case?
>
Will do it.
> > + jsonw_name(json_wtr, "addrs");
> > + jsonw_start_array(json_wtr);
> > + addrs = (const __u64 *)u64_to_ptr(info->kprobe_multi.addrs);
> > + for (i = 0; i < info->kprobe_multi.count; i++)
> > + jsonw_lluint(json_wtr, addrs[i]);
> > + jsonw_end_array(json_wtr);
> > + break;
> > default:
> > break;
> > }
> > @@ -396,6 +410,24 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
> > case BPF_LINK_TYPE_NETFILTER:
> > netfilter_dump_plain(info);
> > break;
> > + case BPF_LINK_TYPE_KPROBE_MULTI:
> > + __u32 indent, cnt, i;
> > + const __u64 *addrs;
> > +
> > + cnt = info->kprobe_multi.count;
> > + if (!cnt)
> > + break;
> > + printf("\n\tfunc_cnt %d addrs", cnt);
> > + for (i = 0; cnt; i++)
> > + cnt /= 10;
> > + indent = strlen("func_cnt ") + i + strlen(" addrs");
> > + addrs = (const __u64 *)u64_to_ptr(info->kprobe_multi.addrs);
> > + for (i = 0; i < info->kprobe_multi.count; i++) {
> > + if (i && !(i & 0x1))
> > + printf("\n\t%*s", indent, "");
> > + printf(" %0*llx", 16, addrs[i]);
> > + }
> > + break;
> > default:
> > break;
> > }
> > @@ -417,7 +449,9 @@ static int do_show_link(int fd)
> > {
> > struct bpf_link_info info;
> > __u32 len = sizeof(info);
> > + __u64 *addrs = NULL;
> > char buf[256];
> > + int count;
> > int err;
> >
> > memset(&info, 0, sizeof(info));
> > @@ -441,12 +475,28 @@ static int do_show_link(int fd)
> > info.iter.target_name_len = sizeof(buf);
> > goto again;
> > }
> > + if (info.type == BPF_LINK_TYPE_KPROBE_MULTI &&
> > + !info.kprobe_multi.addrs) {
> > + count = info.kprobe_multi.count;
> > + if (count) {
> > + addrs = malloc(count * sizeof(__u64));
>
> Nit: calloc() instead?
Good point. Will do it.
>
> > + if (!addrs) {
> > + p_err("mem alloc failed");
> > + close(fd);
> > + return -1;
> > + }
> > + info.kprobe_multi.addrs = (unsigned long)addrs;
> > + goto again;
> > + }
> > + }
> >
> > if (json_output)
> > show_link_close_json(fd, &info);
> > else
> > show_link_close_plain(fd, &info);
> >
> > + if (addrs)
> > + free(addrs);
> > close(fd);
> > return 0;
> > }
>
> The other bpftool patch (perf_event link) looks good to me.
>
Thanks for your review.
--
Regards
Yafang
