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.
However I agree with you that the perf_link_type may disallow the
extensions for the big union. I will think about it.
