From d01d754b83a03beb372046e5db24644289341516 Mon Sep 17 00:00:00 2001
From: Jakub Berkop <jakub.berkop@gmail.com>
Date: Sat, 26 Feb 2022 22:59:26 +0100
Subject: [PATCH] Kernel: Fixed behavior of repeated calls to register_string

Previously register_string would return incorrect values when
called multiple times with the same input. This patch makes this
function return the same index, identical strings. This change was
required, as this functionality is now being used with read syscall
profiling, (#12465), which uses 'register_string' to registers file
path on every read syscall.
---
 Kernel/PerformanceEventBuffer.cpp | 24 +++++++++++++++++++-----
 Kernel/PerformanceEventBuffer.h   |  2 +-
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/Kernel/PerformanceEventBuffer.cpp b/Kernel/PerformanceEventBuffer.cpp
index 8ef21aad18..98c155fd58 100644
--- a/Kernel/PerformanceEventBuffer.cpp
+++ b/Kernel/PerformanceEventBuffer.cpp
@@ -199,8 +199,17 @@ ErrorOr<void> PerformanceEventBuffer::to_json_impl(Serializer& object) const
 {
     {
         auto strings = TRY(object.add_array("strings"));
-        for (auto const& it : m_strings)
-            TRY(strings.add(it->view()));
+        Vector<KString*> strings_sorted_by_index;
+        TRY(strings_sorted_by_index.try_resize(m_strings.size()));
+
+        for (auto& entry : m_strings) {
+            strings_sorted_by_index[entry.value] = const_cast<Kernel::KString*>(entry.key.ptr());
+        }
+
+        for (size_t i = 0; i < m_strings.size(); i++) {
+            TRY(strings.add(strings_sorted_by_index[i]->view()));
+        }
+
         TRY(strings.finish());
     }
 
@@ -361,9 +370,14 @@ ErrorOr<void> PerformanceEventBuffer::add_process(const Process& process, Proces
 
 ErrorOr<FlatPtr> PerformanceEventBuffer::register_string(NonnullOwnPtr<KString> string)
 {
-    FlatPtr string_id = m_strings.size();
-    TRY(m_strings.try_set(move(string)));
-    return string_id;
+    auto it = m_strings.find(string);
+    if (it != m_strings.end()) {
+        return it->value;
+    }
+
+    auto new_index = m_strings.size();
+    TRY(m_strings.try_set(move(string), move(new_index)));
+    return new_index;
 }
 
 }
diff --git a/Kernel/PerformanceEventBuffer.h b/Kernel/PerformanceEventBuffer.h
index 41d36a16cf..7570dd136b 100644
--- a/Kernel/PerformanceEventBuffer.h
+++ b/Kernel/PerformanceEventBuffer.h
@@ -145,7 +145,7 @@ private:
     size_t m_count { 0 };
     NonnullOwnPtr<KBuffer> m_buffer;
 
-    HashTable<NonnullOwnPtr<KString>> m_strings;
+    HashMap<NonnullOwnPtr<KString>, size_t> m_strings;
 };
 
 extern bool g_profiling_all_threads;