Kernel: Add PerformanceManager static class, move perf event APIs there

The current method of emitting performance events requires a bit of
boiler plate at every invocation, as well as having to ignore the
return code which isn't used outside of the perf event syscall. This
change attempts to clean that up by exposing high level API's that
can be used around the code base.

Kernel/PerformanceEventBuffer.cpp

@@ -20,12 +20,11 @@ PerformanceEventBuffer::PerformanceEventBuffer(NonnullOwnPtr<KBuffer> buffer)
 {
 }
 
-NEVER_INLINE KResult PerformanceEventBuffer::append(int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3)
+NEVER_INLINE KResult PerformanceEventBuffer::append(int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3, Thread* current_thread)
 {
     FlatPtr ebp;
     asm volatile("movl %%ebp, %%eax"
                  : "=a"(ebp));
-    auto current_thread = Thread::current();
     return append_with_eip_and_ebp(current_thread->pid(), current_thread->tid(), 0, ebp, type, arg1, arg2, arg3);
 }
 

Kernel/PerformanceEventBuffer.h

@@ -75,7 +75,7 @@ class PerformanceEventBuffer {
 public:
     static OwnPtr<PerformanceEventBuffer> try_create_with_size(size_t buffer_size);
 
-    KResult append(int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3);
+    KResult append(int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3, Thread* current_thread = Thread::current());
     KResult append_with_eip_and_ebp(ProcessID pid, ThreadID tid, u32 eip, u32 ebp,
         int type, FlatPtr arg1, FlatPtr arg2, const StringView& arg3);
 

Kernel/PerformanceManager.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2021, Brian Gianforcaro <bgianf@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/PerformanceEventBuffer.h>
+#include <Kernel/Process.h>
+#include <Kernel/Thread.h>
+
+namespace Kernel {
+
+class PerformanceManager {
+
+public:
+    inline static void add_thread_created_event(Thread& thread)
+    {
+        if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
+            [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_CREATE, thread.tid().value(), 0, nullptr, &thread);
+        }
+    }
+
+    inline static void add_thread_exit_event(Thread& thread)
+    {
+        if (auto* event_buffer = thread.process().current_perf_events_buffer()) {
+            [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_EXIT, thread.tid().value(), 0, nullptr, &thread);
+        }
+    }
+
+    inline static void add_mmap_perf_event(Process& current_process, Region const& region)
+    {
+        if (auto* event_buffer = current_process.current_perf_events_buffer()) {
+            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MMAP, region.vaddr().get(), region.size(), region.name());
+        }
+    }
+
+    inline static void add_unmap_perf_event(Process& current_process, Range const& region)
+    {
+        if (auto* event_buffer = current_process.current_perf_events_buffer()) {
+            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MUNMAP, region.base().get(), region.size(), nullptr);
+        }
+    }
+};
+
+}

Kernel/Process.h

@@ -492,6 +492,7 @@ private:
     friend class MemoryManager;
     friend class Scheduler;
     friend class Region;
+    friend class PerformanceManager;
 
     bool add_thread(Thread&);
     bool remove_thread(Thread&);

Kernel/Syscalls/exit.cpp

@@ -5,7 +5,7 @@
  */
 
 #include <Kernel/KSyms.h>
-#include <Kernel/PerformanceEventBuffer.h>
+#include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 
 namespace Kernel {
@@ -18,12 +18,11 @@ void Process::sys$exit(int status)
         m_termination_signal = 0;
     }
 
-    if (auto* event_buffer = current_perf_events_buffer()) {
+    auto* current_thread = Thread::current();
-        [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_EXIT, Thread::current()->tid().value(), 0, nullptr);
+    PerformanceManager::add_thread_exit_event(*current_thread);
-    }
 
     die();
-    Thread::current()->die_if_needed();
+    current_thread->die_if_needed();
     VERIFY_NOT_REACHED();
 }
 

Kernel/Syscalls/mmap.cpp

@@ -5,10 +5,10 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <AK/WeakPtr.h>
 #include <Kernel/Arch/x86/SmapDisabler.h>
 #include <Kernel/FileSystem/FileDescription.h>
 #include <Kernel/PerformanceEventBuffer.h>
+#include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/PageDirectory.h>
@@ -248,11 +248,6 @@ KResultOr<FlatPtr> Process::sys$mmap(Userspace<const Syscall::SC_mmap_params*> u
     if (!region)
         return ENOMEM;
 
-    if (auto* event_buffer = current_perf_events_buffer()) {
-        [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MMAP, region->vaddr().get(),
-            region->size(), name.is_null() ? region->name() : name);
-    }
-
     region->set_mmap(true);
     if (map_shared)
         region->set_shared(true);
@@ -260,6 +255,9 @@ KResultOr<FlatPtr> Process::sys$mmap(Userspace<const Syscall::SC_mmap_params*> u
         region->set_stack(true);
     if (!name.is_null())
         region->set_name(name);
+
+    PerformanceManager::add_mmap_perf_event(*this, *region);
+
     return region->vaddr().get();
 }
 
@@ -437,10 +435,10 @@ KResultOr<int> Process::sys$set_mmap_name(Userspace<const Syscall::SC_set_mmap_n
         return EINVAL;
     if (!region->is_mmap())
         return EPERM;
-    if (auto* event_buffer = current_perf_events_buffer()) {
+
-        [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MMAP, region->vaddr().get(), region->size(), name.characters());
-    }
     region->set_name(move(name));
+    PerformanceManager::add_mmap_perf_event(*this, *region);
+
     return 0;
 }
 
@@ -463,13 +461,11 @@ KResultOr<int> Process::sys$munmap(Userspace<void*> addr, size_t size)
     if (auto* whole_region = space().find_region_from_range(range_to_unmap)) {
         if (!whole_region->is_mmap())
             return EPERM;
-        auto base = whole_region->vaddr();
+
-        auto size = whole_region->size();
+        PerformanceManager::add_unmap_perf_event(*this, whole_region->range());
+
         bool success = space().deallocate_region(*whole_region);
         VERIFY(success);
-        if (auto* event_buffer = current_perf_events_buffer()) {
-            [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MUNMAP, base.get(), size, nullptr);
-        }
         return 0;
     }
 
@@ -542,9 +538,7 @@ KResultOr<int> Process::sys$munmap(Userspace<void*> addr, size_t size)
         new_region->map(space().page_directory());
     }
 
-    if (auto* event_buffer = current_perf_events_buffer()) {
+    PerformanceManager::add_unmap_perf_event(*this, range_to_unmap);
-        [[maybe_unused]] auto res = event_buffer->append(PERF_EVENT_MUNMAP, range_to_unmap.base().get(), range_to_unmap.size(), nullptr);
-    }
 
     return 0;
 }

Kernel/Syscalls/thread.cpp

@@ -8,7 +8,7 @@
 #include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/StringView.h>
-#include <Kernel/PerformanceEventBuffer.h>
+#include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/VM/MemoryManager.h>
 #include <Kernel/VM/PageDirectory.h>
@@ -70,9 +70,7 @@ KResultOr<int> Process::sys$create_thread(void* (*entry)(void*), Userspace<const
     if (tsr_result.is_error())
         return tsr_result.error();
 
-    if (m_perf_event_buffer) {
+    PerformanceManager::add_thread_created_event(*thread);
-        [[maybe_unused]] auto rc = m_perf_event_buffer->append(PERF_EVENT_THREAD_CREATE, thread->tid().value(), 0, nullptr);
-    }
 
     ScopedSpinLock lock(g_scheduler_lock);
     thread->set_priority(requested_thread_priority);
@@ -89,11 +87,10 @@ void Process::sys$exit_thread(Userspace<void*> exit_value)
         this->sys$exit(0);
     }
 
-    if (auto* event_buffer = current_perf_events_buffer()) {
+    auto current_thread = Thread::current();
-        [[maybe_unused]] auto rc = event_buffer->append(PERF_EVENT_THREAD_EXIT, 0, 0, nullptr);
+    PerformanceManager::add_thread_exit_event(*current_thread);
-    }
 
-    Thread::current()->exit(reinterpret_cast<void*>(exit_value.ptr()));
+    current_thread->exit(reinterpret_cast<void*>(exit_value.ptr()));
     VERIFY_NOT_REACHED();
 }