Kernel: Start working on a syscall for logging performance events

This patch introduces sys$perf_event() with two event types:

- PERF_EVENT_MALLOC
- PERF_EVENT_FREE

After the first call to sys$perf_event(), a process will begin keeping
these events in a buffer. When the process dies, that buffer will be
written out to "perfcore" in the current directory unless that filename
is already taken.

This is probably not the best way to do this, but it's a start and will
make it possible to start doing memory allocation profiling. :^)

Kernel/Process.h

@@ -35,6 +35,7 @@
 #include <AK/Weakable.h>
 #include <Kernel/FileSystem/VirtualFileSystem.h>
 #include <Kernel/Lock.h>
+#include <Kernel/PerformanceEventBuffer.h>
 #include <Kernel/Syscall.h>
 #include <Kernel/TTY/TTY.h>
 #include <Kernel/Thread.h>
@@ -301,6 +302,7 @@ public:
     int sys$chroot(const char* path, size_t path_length, int mount_flags);
     int sys$pledge(const Syscall::SC_pledge_params*);
     int sys$unveil(const Syscall::SC_unveil_params*);
+    int sys$perf_event(int type, uintptr_t arg1, uintptr_t arg2);
 
     template<bool sockname, typename Params>
     int get_sock_or_peer_name(const Params&);
@@ -511,6 +513,8 @@ private:
 
     WaitQueue& futex_queue(i32*);
     HashMap<u32, OwnPtr<WaitQueue>> m_futex_queues;
+
+    OwnPtr<PerformanceEventBuffer> m_perf_event_buffer;
 };
 
 class ProcessInspectionHandle {