On Sun, May 28, 2023 at 02:20:26PM +0000, Yafang Shao wrote:
> By adding support for ->fill_link_info to the perf_event link, users will
> be able to inspect it using `bpftool link show`. While users can currently
> access this information via `bpftool perf show`, consolidating the link
> information for all link types in one place would be more convenient.
>
> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ---
> include/uapi/linux/bpf.h | 6 ++++++
> kernel/bpf/syscall.c | 46 ++++++++++++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 6 ++++++
> 3 files changed, 58 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 6be9b1d..1f2be1d 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6438,6 +6438,12 @@ struct bpf_link_info {
> __aligned_u64 addrs;
> __u32 count;
> } kprobe_multi;
> + struct {
> + __aligned_u64 name;
> + __aligned_u64 addr;
__aligned_u64 ? what is the reason?
> + __u32 name_len;
> + __u32 offset;
> + } perf_event;
> };
> } __attribute__((aligned(8)));
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 33a72ec..b12707e 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3329,10 +3329,56 @@ static void bpf_perf_link_show_fdinfo(const struct bpf_link *link,
> seq_printf(seq, "offset:\t%llu\n", probe_offset);
> }
>
> +static int bpf_perf_link_fill_link_info(const struct bpf_link *link,
> + struct bpf_link_info *info)
> +{
> + struct bpf_perf_link *perf_link = container_of(link, struct bpf_perf_link, link);
> + char __user *ubuf = u64_to_user_ptr(info->perf_event.name);
> + u32 ulen = info->perf_event.name_len;
> + const struct perf_event *event;
> + u64 probe_offset, probe_addr;
> + u32 prog_id, fd_type;
> + const char *buf;
> + size_t len;
> + int err;
> +
> + if (!ulen ^ !ubuf)
> + return -EINVAL;
> + if (!ubuf)
> + return 0;
> +
> + event = perf_get_event(perf_link->perf_file);
> + if (IS_ERR(event))
> + return PTR_ERR(event);
> +
> + err = bpf_get_perf_event_info(event, &prog_id, &fd_type,
> + &buf, &probe_offset,
> + &probe_addr);
> + if (err)
> + return err;
> +
> + len = strlen(buf);
> + info->perf_event.name_len = len + 1;
this use of name_len contradicts with patch 8.
Is it 'in' or 'out' field?
> + if (buf) {
> + err = bpf_copy_to_user(ubuf, buf, ulen, len);
> + if (err)
> + return err;
> + } else {
> + char zero = '\0';
> +
> + if (put_user(zero, ubuf))
> + return -EFAULT;
> + }
> + info->perf_event.addr = probe_addr;
> + info->perf_event.offset = probe_offset;
> + return 0;
> +}
> +
> static const struct bpf_link_ops bpf_perf_link_lops = {
> .release = bpf_perf_link_release,
> .dealloc = bpf_perf_link_dealloc,
> .show_fdinfo = bpf_perf_link_show_fdinfo,
> + .fill_link_info = bpf_perf_link_fill_link_info,
> };
>
> static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 6be9b1d..1f2be1d 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -6438,6 +6438,12 @@ struct bpf_link_info {
> __aligned_u64 addrs;
> __u32 count;
> } kprobe_multi;
> + struct {
> + __aligned_u64 name;
> + __aligned_u64 addr;
> + __u32 name_len;
> + __u32 offset;
> + } perf_event;
> };
> } __attribute__((aligned(8)));
>
> --
> 1.8.3.1
>
