From 8a4654a9243deb3db759ca071debdacc64e1e2db Mon Sep 17 00:00:00 2001
From: Idan Horowitz <idan.horowitz@gmail.com>
Date: Tue, 11 Jan 2022 21:50:12 +0200
Subject: [PATCH] Kernel: Make PerformanceEventBuffer::add_process fallible
 with ErrorOr

---
 Kernel/PerformanceEventBuffer.cpp | 21 +++++++++++++--------
 Kernel/PerformanceEventBuffer.h   |  2 +-
 Kernel/PerformanceManager.h       |  4 ++--
 Kernel/Process.cpp                | 11 ++++++-----
 4 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
index 9a339c5f04..0b87a8b317 100644
--- a/Kernel/PerformanceEventBuffer.cpp
+++ b/Kernel/PerformanceEventBuffer.cpp
@@ -313,29 +313,34 @@ OwnPtr<PerformanceEventBuffer> PerformanceEventBuffer::try_create_with_size(size
     return adopt_own_if_nonnull(new (nothrow) PerformanceEventBuffer(buffer_or_error.release_value()));
 }
 
-void PerformanceEventBuffer::add_process(const Process& process, ProcessEventType event_type)
+ErrorOr<void> PerformanceEventBuffer::add_process(const Process& process, ProcessEventType event_type)
 {
     SpinlockLocker locker(process.address_space().get_lock());
 
     OwnPtr<KString> executable;
     if (process.executable())
-        executable = MUST(process.executable()->try_serialize_absolute_path());
+        executable = TRY(process.executable()->try_serialize_absolute_path());
     else
-        executable = MUST(KString::formatted("<{}>", process.name()));
+        executable = TRY(KString::formatted("<{}>", process.name()));
 
-    [[maybe_unused]] auto rc = append_with_ip_and_bp(process.pid(), 0, 0, 0,
+    TRY(append_with_ip_and_bp(process.pid(), 0, 0, 0,
         event_type == ProcessEventType::Create ? PERF_EVENT_PROCESS_CREATE : PERF_EVENT_PROCESS_EXEC,
-        0, process.pid().value(), 0, executable->view());
+        0, process.pid().value(), 0, executable->view()));
 
+    ErrorOr<void> result;
     process.for_each_thread([&](auto& thread) {
-        [[maybe_unused]] auto rc = append_with_ip_and_bp(process.pid(), thread.tid().value(),
+        result = append_with_ip_and_bp(process.pid(), thread.tid().value(),
             0, 0, PERF_EVENT_THREAD_CREATE, 0, 0, 0, nullptr);
+        return result.is_error() ? IterationDecision::Break : IterationDecision::Continue;
     });
+    TRY(result);
 
     for (auto const& region : process.address_space().regions()) {
-        [[maybe_unused]] auto rc = append_with_ip_and_bp(process.pid(), 0,
-            0, 0, PERF_EVENT_MMAP, 0, region->range().base().get(), region->range().size(), region->name());
+        TRY(append_with_ip_and_bp(process.pid(), 0,
+            0, 0, PERF_EVENT_MMAP, 0, region->range().base().get(), region->range().size(), region->name()));
     }
+
+    return {};
 }
 
 ErrorOr<FlatPtr> PerformanceEventBuffer::register_string(NonnullOwnPtr<KString> string)
diff --git a/Kernel/PerformanceEventBuffer.h b/Kernel/PerformanceEventBuffer.h
index aa5a21bcb0..e07ca5ce1b 100644
--- a/Kernel/PerformanceEventBuffer.h
+++ b/Kernel/PerformanceEventBuffer.h
@@ -121,7 +121,7 @@ public:
 
     ErrorOr<void> to_json(KBufferBuilder&) const;
 
-    void add_process(const Process&, ProcessEventType event_type);
+    ErrorOr<void> add_process(const Process&, ProcessEventType event_type);
 
     ErrorOr<FlatPtr> register_string(NonnullOwnPtr<KString>);
 
diff --git a/Kernel/PerformanceManager.h b/Kernel/PerformanceManager.h
index 99ac5af73a..aba2e199b0 100644
--- a/Kernel/PerformanceManager.h
+++ b/Kernel/PerformanceManager.h
@@ -18,14 +18,14 @@ public:
     {
         if (g_profiling_all_threads) {
             VERIFY(g_global_perf_events);
-            g_global_perf_events->add_process(process, ProcessEventType::Create);
+            (void)g_global_perf_events->add_process(process, ProcessEventType::Create);
         }
     }
 
     inline static void add_process_exec_event(Process& process)
     {
         if (auto* event_buffer = process.current_perf_events_buffer()) {
-            event_buffer->add_process(process, ProcessEventType::Exec);
+            (void)event_buffer->add_process(process, ProcessEventType::Exec);
         }
     }
 
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index de1f395742..1c29c14249 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -788,11 +788,12 @@ void Process::tracer_trap(Thread& thread, const RegisterState& regs)
 
 bool Process::create_perf_events_buffer_if_needed()
 {
-    if (!m_perf_event_buffer) {
-        m_perf_event_buffer = PerformanceEventBuffer::try_create_with_size(4 * MiB);
-        m_perf_event_buffer->add_process(*this, ProcessEventType::Create);
-    }
-    return !!m_perf_event_buffer;
+    if (m_perf_event_buffer)
+        return true;
+    m_perf_event_buffer = PerformanceEventBuffer::try_create_with_size(4 * MiB);
+    if (!m_perf_event_buffer)
+        return false;
+    return !m_perf_event_buffer->add_process(*this, ProcessEventType::Create).is_error();
 }
 
 void Process::delete_perf_events_buffer()