[PATCH v7 05/13] user_events: Add basic perf and eBPF support

Beau Belgrave
2021-12-09T22:32:27Z

Adds support to write out user_event data to perf_probe/perf files as
well as to any attached eBPF program.

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
kernel/trace/trace_events_user.c | 63 ++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index ae3ceaaa9098..807db0af74fb 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -541,6 +541,50 @@ static void user_event_ftrace(struct user_event *user, void *data, u32 datalen,
trace_event_buffer_commit(&event_buffer);
}

+#ifdef CONFIG_PERF_EVENTS
+/*
+ * Writes the user supplied payload out to perf ring buffer or eBPF program.
+ */
+static void user_event_perf(struct user_event *user, void *data, u32 datalen,
+ void *tpdata)
+{
+ struct hlist_head *perf_head;
+
+ if (bpf_prog_array_valid(&user->call)) {
+ struct user_bpf_context context = {0};
+
+ context.data_len = datalen;
+ context.data_type = USER_BPF_DATA_KERNEL;
+ context.kdata = data;
+
+ trace_call_bpf(&user->call, &context);
+ }
+
+ perf_head = this_cpu_ptr(user->call.perf_events);
+
+ if (perf_head && !hlist_empty(perf_head)) {
+ struct trace_entry *perf_entry;
+ struct pt_regs *regs;
+ size_t size = sizeof(*perf_entry) + datalen;
+ int context;
+
+ perf_entry = perf_trace_buf_alloc(ALIGN(size, 8),
+ &regs, &context);
+
+ if (unlikely(!perf_entry))
+ return;
+
+ perf_fetch_caller_regs(regs);
+
+ memcpy(perf_entry + 1, data, datalen);
+
+ perf_trace_buf_submit(perf_entry, size, context,
+ user->call.event.type, 1, regs,
+ perf_head, NULL);
+ }
+}
+#endif
+
/*
* Update the register page that is shared between user processes.
*/
@@ -563,6 +607,10 @@ static void update_reg_page_for(struct user_event *user)

if (probe_func == user_event_ftrace)
status |= EVENT_STATUS_FTRACE;
+#ifdef CONFIG_PERF_EVENTS
+ else if (probe_func == user_event_perf)
+ status |= EVENT_STATUS_PERF;
+#endif
else
status |= EVENT_STATUS_OTHER;
} while ((++probe_func_ptr)->func);
@@ -604,7 +652,19 @@ static int user_event_reg(struct trace_event_call *call,

#ifdef CONFIG_PERF_EVENTS
case TRACE_REG_PERF_REGISTER:
+ ret = tracepoint_probe_register(call->tp,
+ call->class->perf_probe,
+ data);
+ if (!ret)
+ goto inc;
+ break;
+
case TRACE_REG_PERF_UNREGISTER:
+ tracepoint_probe_unregister(call->tp,
+ call->class->perf_probe,
+ data);
+ goto dec;
+
case TRACE_REG_PERF_OPEN:
case TRACE_REG_PERF_CLOSE:
case TRACE_REG_PERF_ADD:
@@ -862,6 +922,9 @@ static int user_event_parse(char *name, char *args, char *flags,
user->class.get_fields = user_event_get_fields;
user->class.reg = user_event_reg;
user->class.probe = user_event_ftrace;
+#ifdef CONFIG_PERF_EVENTS
+ user->class.perf_probe = user_event_perf;
+#endif

mutex_lock(&event_mutex);
ret = user_event_trace_register(user);
--
2.17.1