On Wed, Jun 14, 2023 at 10:34 AM Kui-Feng Lee <sinquersw@xxxxxxxxx> wrote:
>
>
>
> On 6/12/23 19:47, Yafang Shao wrote:
> > On Tue, Jun 13, 2023 at 1:36 AM Yonghong Song <yhs@xxxxxxxx> wrote:
> >>
> >>
> >>
> >> On 6/12/23 8:16 AM, Yafang Shao wrote:
> >>> By introducing support for ->fill_link_info to the perf_event link, users
> >>> gain the ability to inspect it using `bpftool link show`. While the current
> >>> approach involves accessing this information via `bpftool perf show`,
> >>> consolidating link information for all link types in one place offers
> >>> greater convenience. Additionally, this patch extends support to the
> >>> generic perf event, which is not currently accommodated by
> >>> `bpftool perf show`. While only the perf type and config are exposed to
> >>> userspace, other attributes such as sample_period and sample_freq are
> >>> ignored. It's important to note that if kptr_restrict is not permitted, the
> >>> probed address will not be exposed, maintaining security measures.
> >>>
> >>> A new enum bpf_link_perf_event_type is introduced to help the user
> >>> understand which struct is relevant.
> >>>
> >>> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> >>> ---
> >>> include/uapi/linux/bpf.h | 32 +++++++++++
> >>> kernel/bpf/syscall.c | 124 +++++++++++++++++++++++++++++++++++++++++
> >>> tools/include/uapi/linux/bpf.h | 32 +++++++++++
> >>> 3 files changed, 188 insertions(+)
> >>>
> >>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> >>> index 23691ea..8d4556e 100644
> >>> --- a/include/uapi/linux/bpf.h
> >>> +++ b/include/uapi/linux/bpf.h
> >>> @@ -1056,6 +1056,16 @@ enum bpf_link_type {
> >>> MAX_BPF_LINK_TYPE,
> >>> };
> >>>
> >>> +enum bpf_perf_link_type {
> >>> + BPF_PERF_LINK_UNSPEC = 0,
> >>> + BPF_PERF_LINK_UPROBE = 1,
> >>> + BPF_PERF_LINK_KPROBE = 2,
> >>> + BPF_PERF_LINK_TRACEPOINT = 3,
> >>> + BPF_PERF_LINK_PERF_EVENT = 4,
> >>> +
> >>> + MAX_BPF_LINK_PERF_EVENT_TYPE,
> >>> +};
> >>> +
> >>> /* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
> >>> *
> >>> * NONE(default): No further bpf programs allowed in the subtree.
> >>> @@ -6443,7 +6453,29 @@ struct bpf_link_info {
> >>> __u32 count;
> >>> __u32 flags;
> >>> } kprobe_multi;
> >>> + struct {
> >>> + __u64 config;
> >>> + __u32 type;
> >>> + } perf_event; /* BPF_LINK_PERF_EVENT_PERF_EVENT */
> >>> + struct {
> >>> + __aligned_u64 file_name; /* in/out: buff ptr */
> >>> + __u32 name_len;
> >>> + __u32 offset; /* offset from name */
> >>> + __u32 flags;
> >>> + } uprobe; /* BPF_LINK_PERF_EVENT_UPROBE */
> >>> + struct {
> >>> + __aligned_u64 func_name; /* in/out: buff ptr */
> >>> + __u32 name_len;
> >>> + __u32 offset; /* offset from name */
> >>> + __u64 addr;
> >>> + __u32 flags;
> >>> + } kprobe; /* BPF_LINK_PERF_EVENT_KPROBE */
> >>> + struct {
> >>> + __aligned_u64 tp_name; /* in/out: buff ptr */
> >>> + __u32 name_len;
> >>> + } tracepoint; /* BPF_LINK_PERF_EVENT_TRACEPOINT */
> >>> };
> >>> + __u32 perf_link_type; /* enum bpf_perf_link_type */
> >>
> >> I think put perf_link_type into each indivual struct is better.
> >> It won't increase the bpf_link_info struct size. It will allow
> >> extensions for all structs in the big union (raw_tracepoint,
> >> tracing, cgroup, iter, ..., kprobe_multi, ...) etc.
> >
> > If we put it into each individual struct, we have to choose one
> > specific struct to get the type before we use the real struct, for
> > example,
> > if (info.perf_event.type == BPF_PERF_LINK_PERF_EVENT)
> > goto out;
> > if (info.perf_event.type == BPF_PERF_LINK_TRACEPOINT &&
> > !info.tracepoint.tp_name) {
> > info.tracepoint.tp_name = (unsigned long)&buf;
> > info.tracepoint.name_len = sizeof(buf);
> > goto again;
> > }
> > ...
> >
> > That doesn't look perfect.
>
> How about adding a common struct?
>
> struct {
> __u32 type;
> } perf_common;
>
> Then you check info.perf_common.type.
I perfer below struct,
struct {
__u32 type; /* enum bpf_perf_link_type */
union {
struct {
__u64 config;
__u32 type;
} perf_event; /* BPF_PERF_LINK_PERF_EVENT */
struct {
__aligned_u64 file_name; /* in/out */
__u32 name_len;
__u32 offset;/* offset from file_name */
__u32 flags;
} uprobe; /* BPF_PERF_LINK_UPROBE */
struct {
__aligned_u64 func_name; /* in/out */
__u32 name_len;
__u32 offset;/* offset from func_name */
__u64 addr;
__u32 flags;
} kprobe; /* BPF_PERF_LINK_KPROBE */
struct {
__aligned_u64 tp_name; /* in/out */
__u32 name_len;
} tracepoint; /* BPF_PERF_LINK_TRACEPOINT */
};
} perf_link;
I think that would be more clear.
--
Regards
Yafang
