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Message-ID: <CAEf4BzasaZYD7y+4Po=K=jBq3Q7JSUMpJ_NSQv7B9=v6fieZ7g@mail.gmail.com>
Date: Thu, 5 Jun 2025 11:41:57 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Tao Chen <chen.dylane@...ux.dev>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
andrii@...nel.org, martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
yonghong.song@...ux.dev, kpsingh@...nel.org, sdf@...ichev.me,
haoluo@...gle.com, jolsa@...nel.org, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next] bpf: Add show_fdinfo for perf_event
On Wed, Jun 4, 2025 at 9:37 AM Tao Chen <chen.dylane@...ux.dev> wrote:
>
> After commit 1b715e1b0ec5 ("bpf: Support ->fill_link_info for perf_event") add
> perf_event info, we can also show the info with the method of cat /proc/[fd]/fdinfo.
>
> kprobe fdinfo:
> link_type: perf
> link_id: 2
> prog_tag: bcf7977d3b93787c
> prog_id: 18
> name: bpf_fentry_test1
> offset: 0
> missed: 0
> addr: ffffffffaea8d134
> event_type: 3
> cookie: 3735928559
>
> uprobe fdinfo:
> link_type: perf
> link_id: 6
> prog_tag: bcf7977d3b93787c
> prog_id: 7
> name: /proc/self/exe
> offset: 6507541
> event_type: 1
> cookie: 3735928559
>
> tracepoint fdinfo:
> link_type: perf
> link_id: 4
> prog_tag: bcf7977d3b93787c
> prog_id: 8
> tp_name: sched_switch
> event_type: 5
> cookie: 3735928559
>
> perf_event fdinfo:
> link_type: perf
> link_id: 5
> prog_tag: bcf7977d3b93787c
> prog_id: 9
> type: 1
> config: 2
> event_type: 6
> cookie: 3735928559
>
> Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
> ---
> kernel/bpf/syscall.c | 126 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 126 insertions(+)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 9794446bc8..9af54852eb 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3793,6 +3793,35 @@ static int bpf_perf_link_fill_kprobe(const struct perf_event *event,
> info->perf_event.kprobe.cookie = event->bpf_cookie;
> return 0;
> }
> +
> +static void bpf_perf_link_fdinfo_kprobe(const struct perf_event *event,
> + struct seq_file *seq)
> +{
> + const char *name;
> + int err;
> + u32 prog_id, type;
> + u64 offset, addr;
> + unsigned long missed;
> +
> + err = bpf_get_perf_event_info(event, &prog_id, &type, &name,
> + &offset, &addr, &missed);
> + if (err)
> + return;
> +
> + if (type == BPF_FD_TYPE_KRETPROBE)
> + type = BPF_PERF_EVENT_KRETPROBE;
> + else
> + type = BPF_PERF_EVENT_KPROBE;
maybe use "kretprobe" and "kprobe" strings?
> +
> + seq_printf(seq,
> + "name:\t%s\n"
> + "offset:\t%llu\n"
llx, hex makes most sense (we had similar discussion within the
context of bpftool reporting)
pw-bot: cr
> + "missed:\t%lu\n"
> + "addr:\t%llx\n"
ditto, address -> hex
> + "event_type:\t%u\n"
> + "cookie:\t%llu\n",
> + name, offset, missed, addr, type, event->bpf_cookie);
> +}
> #endif
>
> #ifdef CONFIG_UPROBE_EVENTS
> @@ -3820,6 +3849,34 @@ static int bpf_perf_link_fill_uprobe(const struct perf_event *event,
> info->perf_event.uprobe.cookie = event->bpf_cookie;
> return 0;
> }
> +
> +static void bpf_perf_link_fdinfo_uprobe(const struct perf_event *event,
> + struct seq_file *seq)
> +{
> + const char *name;
> + int err;
> + u32 prog_id, type;
> + u64 offset, addr;
> + unsigned long missed;
> +
> + err = bpf_get_perf_event_info(event, &prog_id, &type, &name,
> + &offset, &addr, &missed);
> + if (err)
> + return;
> +
> + if (type == BPF_FD_TYPE_URETPROBE)
> + type = BPF_PERF_EVENT_URETPROBE;
> + else
> + type = BPF_PERF_EVENT_UPROBE;
strings, just as above
> +
> + seq_printf(seq,
> + "name:\t%s\n"
> + "offset:\t%llu\n"
hex
> + "event_type:\t%u\n"
> + "cookie:\t%llu\n",
> + name, offset, type, event->bpf_cookie);
> +
> +}
> #endif
>
> static int bpf_perf_link_fill_probe(const struct perf_event *event,
> @@ -3888,10 +3945,79 @@ static int bpf_perf_link_fill_link_info(const struct bpf_link *link,
> }
> }
>
> +static void bpf_perf_event_link_show_fdinfo(const struct perf_event *event,
> + struct seq_file *seq)
> +{
> + seq_printf(seq,
> + "type:\t%u\n"
> + "config:\t%llu\n"
> + "event_type:\t%u\n"
string?
> + "cookie:\t%llu\n",
> + event->attr.type, event->attr.config,
> + BPF_PERF_EVENT_EVENT, event->bpf_cookie);
> +}
> +
> +static void bpf_tracepoint_link_show_fdinfo(const struct perf_event *event,
> + struct seq_file *seq)
> +{
> + int err;
> + const char *name;
> + u32 prog_id;
> +
> + err = bpf_get_perf_event_info(event, &prog_id, NULL, &name, NULL,
> + NULL, NULL);
> + if (err)
> + return;
> +
> + seq_printf(seq,
> + "tp_name:\t%s\n"
> + "event_type:\t%u\n"
string
> + "cookie:\t%llu\n",
> + name, BPF_PERF_EVENT_TRACEPOINT, event->bpf_cookie);
> +}
> +
> +static void bpf_probe_link_show_fdinfo(const struct perf_event *event,
> + struct seq_file *seq)
> +{
> +#ifdef CONFIG_KPROBE_EVENTS
> + if (event->tp_event->flags & TRACE_EVENT_FL_KPROBE)
> + return bpf_perf_link_fdinfo_kprobe(event, seq);
> +#endif
> +
> +#ifdef CONFIG_UPROBE_EVENTS
> + if (event->tp_event->flags & TRACE_EVENT_FL_UPROBE)
> + return bpf_perf_link_fdinfo_uprobe(event, seq);
> +#endif
> +}
> +
> +static void bpf_perf_link_show_fdinfo(const struct bpf_link *link,
> + struct seq_file *seq)
> +{
> + struct bpf_perf_link *perf_link;
> + const struct perf_event *event;
> +
> + perf_link = container_of(link, struct bpf_perf_link, link);
> + event = perf_get_event(perf_link->perf_file);
> + if (IS_ERR(event))
> + return;
> +
> + switch (event->prog->type) {
> + case BPF_PROG_TYPE_PERF_EVENT:
> + return bpf_perf_event_link_show_fdinfo(event, seq);
> + case BPF_PROG_TYPE_TRACEPOINT:
> + return bpf_tracepoint_link_show_fdinfo(event, seq);
> + case BPF_PROG_TYPE_KPROBE:
> + return bpf_probe_link_show_fdinfo(event, seq);
> + default:
> + return;
> + }
> +}
> +
> static const struct bpf_link_ops bpf_perf_link_lops = {
> .release = bpf_perf_link_release,
> .dealloc = bpf_perf_link_dealloc,
> .fill_link_info = bpf_perf_link_fill_link_info,
> + .show_fdinfo = bpf_perf_link_show_fdinfo,
> };
>
> static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> --
> 2.43.0
>
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