On Sun, May 28, 2023 at 02:20:20PM +0000, Yafang Shao wrote:
> Currently, there is no way to check which functions are attached to a
> kprobe_multi link, causing confusion for users. It is important that we
> provide a means to expose these functions. The expected result is as follows,
>
> $ cat /proc/10936/fdinfo/9
> pos: 0
> flags: 02000000
> mnt_id: 15
> ino: 2094
> link_type: kprobe_multi
> link_id: 2
> prog_tag: a04f5eef06a7f555
> prog_id: 11
> func_count: 4
> func_addrs: ffffffffaad475c0
> ffffffffaad47600
> ffffffffaad47640
> ffffffffaad47680
I like the idea of exposing this through the link_info syscall,
but I'm bit concerned of potentially dumping thousands of addresses
through fdinfo file, because I always thought of fdinfo as brief
file info, but that might be just my problem ;-)
jirka
>
> $ cat /proc/10936/fdinfo/9 | grep "func_addrs" -A 4 | \
> awk '{ if (NR ==1) {print $2} else {print $1}}' | \
> 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
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> kernel/trace/bpf_trace.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 2bc41e6..0d84a7a 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -2548,9 +2548,26 @@ static void bpf_kprobe_multi_link_dealloc(struct bpf_link *link)
> kfree(kmulti_link);
> }
>
> +static void bpf_kprobe_multi_link_show_fdinfo(const struct bpf_link *link,
> + struct seq_file *seq)
> +{
> + struct bpf_kprobe_multi_link *kmulti_link;
> + int i;
> +
> + kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
> + seq_printf(seq, "func_count:\t%d\n", kmulti_link->cnt);
> + for (i = 0; i < kmulti_link->cnt; i++) {
> + if (i == 0)
> + seq_printf(seq, "func_addrs:\t%lx\n", kmulti_link->addrs[i]);
> + else
> + seq_printf(seq, " \t%lx\n", kmulti_link->addrs[i]);
> + }
> +}
> +
> static const struct bpf_link_ops bpf_kprobe_multi_link_lops = {
> .release = bpf_kprobe_multi_link_release,
> .dealloc = bpf_kprobe_multi_link_dealloc,
> + .show_fdinfo = bpf_kprobe_multi_link_show_fdinfo,
> };
>
> static void bpf_kprobe_multi_cookie_swap(void *a, void *b, int size, const void *priv)
> --
> 1.8.3.1
>
