Kernel+LibC: Add PERF_EVENT_SIGNPOST

This event will be used by userspace programs wanting to mark
interesting high-level events in the profile. :^)

Kernel/PerformanceEventBuffer.cpp

@@ -137,6 +137,10 @@ KResult PerformanceEventBuffer::append_with_ip_and_bp(ProcessID pid, ThreadID ti
         break;
     case PERF_EVENT_SYSCALL:
         break;
+    case PERF_EVENT_SIGNPOST:
+        event.data.signpost.arg1 = arg1;
+        event.data.signpost.arg2 = arg2;
+        break;
     default:
         return EINVAL;
     }
@@ -231,6 +235,11 @@ bool PerformanceEventBuffer::to_json_impl(Serializer& object) const
         case PERF_EVENT_SYSCALL:
             event_object.add("type", "syscall");
             break;
+        case PERF_EVENT_SIGNPOST:
+            event_object.add("type"sv, "signpost"sv);
+            event_object.add("arg1"sv, event.data.signpost.arg1);
+            event_object.add("arg2"sv, event.data.signpost.arg2);
+            break;
         }
         event_object.add("pid", event.pid);
         event_object.add("tid", event.tid);

Kernel/PerformanceEventBuffer.h

@@ -62,6 +62,11 @@ struct [[gnu::packed]] KFreePerformanceEvent {
     FlatPtr ptr;
 };
 
+struct [[gnu::packed]] SignpostPerformanceEvent {
+    FlatPtr arg1;
+    FlatPtr arg2;
+};
+
 struct [[gnu::packed]] PerformanceEvent {
     u16 type { 0 };
     u8 stack_size { 0 };
@@ -80,6 +85,7 @@ struct [[gnu::packed]] PerformanceEvent {
         ContextSwitchPerformanceEvent context_switch;
         KMallocPerformanceEvent kmalloc;
         KFreePerformanceEvent kfree;
+        SignpostPerformanceEvent signpost;
     } data;
     static constexpr size_t max_stack_frame_count = 64;
     FlatPtr stack[max_stack_frame_count];

Kernel/UnixTypes.h

@@ -63,6 +63,7 @@ enum {
     PERF_EVENT_KFREE = 4096,
     PERF_EVENT_PAGE_FAULT = 8192,
     PERF_EVENT_SYSCALL = 16384,
+    PERF_EVENT_SIGNPOST = 32768,
 };
 
 #define WNOHANG 1

Userland/Libraries/LibC/serenity.h

@@ -113,6 +113,7 @@ enum {
     PERF_EVENT_KFREE = 4096,
     PERF_EVENT_PAGE_FAULT = 8192,
     PERF_EVENT_SYSCALL = 16384,
+    PERF_EVENT_SIGNPOST = 32768,
 };
 
 #define PERF_EVENT_MASK_ALL (~0ull)