Patches for Resident Evil 2/3 audio issues

These games are erroneously zeroing buffers before they can be fully copied to ARAM by DMA. The responsible memset() calls are followed by a call to DVDRead() which issues dcbi instructions that effectively cancel the memset() on real hardware. Because Dolphin lacks dcache emulation, the effects of the memset() calls are observed, which causes missing audio.

In a comment on the original bug, phire noted that the issue can be corrected by simply nop'ing out the offending memset() calls. Because the games dynamically load different .rel executables based on the character and/or language, the addresses of these calls can vary.

To deal generally with the problem of dynamic code being loaded to fixed, known addresses, the patch engine is extended to support conditional patches which require a match against a known value. This sort of thing is already achievable with Action Replay codes, but their use depends on enabling cheats globally in Dolphin, which is not a prerequisite shared by patches.

Patches are included for every region, character, and language combination.

The end result is an approximation of the games' behavior on real hardware without the associated complexity of proper dcache emulation.

https://bugs.dolphin-emu.org/issues/9840

Data/Sys/GameSettings/GHAE08.ini

@@ -0,0 +1,11 @@
+# GHAE08 - Resident Evil 2 / Biohazard 2
+
+[OnFrame]
+# Skip memset call that is followed by dcbi, simulating dcache behavior
+$Fix audio issues
+# main.dol
+0x800339E4:dword:0x60000000
+# leon.rel
+0x8055ACBC:dword:0x60000000:0x4BAA8445
+# claire.rel
+0x8055AB54:dword:0x60000000:0x4BAA85AD

Data/Sys/GameSettings/GHAJ08.ini

@@ -0,0 +1,11 @@
+# GHAJ08 - Biohazard 2
+
+[OnFrame]
+# Skip memset call that is followed by dcbi, simulating dcache behavior
+$Fix audio issues
+# main.dol
+0x80065FFC:dword:0x60000000
+# leon.rel
+0x805C5CC4:dword:0x60000000:0x4BA3D43D
+# claire.rel
+0x805C5BFC:dword:0x60000000:0x4BA3D505

Data/Sys/GameSettings/GHAP08.ini

@@ -0,0 +1,27 @@
+# GHAP08 - Resident Evil 2 / Biohazard 2
+
+[OnFrame]
+# Skip memset call that is followed by dcbi, simulating dcache behavior
+$Fix audio issues
+# main.dol
+0x80033D60:dword:0x60000000
+# leon.rel
+0x8055C5F8:dword:0x60000000:0x4BAA6B09
+# claire.rel
+0x8055C490:dword:0x60000000:0x4BAA6C71
+# leon_g.rel
+0x8055C3B8:dword:0x60000000:0x4BAA6D49
+# claire_g.rel
+0x8055C328:dword:0x60000000:0x4BAA6DD9
+# leon_f.rel
+0x8055D188:dword:0x60000000:0x4BAA5F79
+# claire_f.rel
+0x8055D068:dword:0x60000000:0x4BAA6099
+# leon_s.rel
+0x8055D100:dword:0x60000000:0x4BAA6001
+# claire_s.rel
+0x8055D064:dword:0x60000000:0x4BAA609D
+# leon_i.rel
+0x8055CFDC:dword:0x60000000:0x4BAA6125
+# claire_i.rel
+0x8055CEBC:dword:0x60000000:0x4BAA6245

Data/Sys/GameSettings/GLEE08.ini

@@ -0,0 +1,7 @@
+# GLEE08 - Resident Evil 3: Nemesis
+
+[OnFrame]
+# Skip memset call that is followed by dcbi, simulating dcache behavior
+$Fix audio issues
+# main.dol
+0x80150E94:dword:0x60000000

Data/Sys/GameSettings/GLEJ08.ini

@@ -0,0 +1,7 @@
+# GLEJ08 - BioHazard 3: Last Escape
+
+[OnFrame]
+# Skip memset call that is followed by dcbi, simulating dcache behavior
+$Fix audio issues
+# main.dol
+0x8015110C:dword:0x60000000

Data/Sys/GameSettings/GLEP08.ini

@@ -0,0 +1,15 @@
+# GLEP08 - Resident Evil 3: Nemesis
+
+[OnFrame]
+# Skip memset call that is followed by dcbi, simulating dcache behavior
+$Fix audio issues
+# eng.rel
+0x8058C174:dword:0x60000000:0x4BA76F8D
+# ger.rel
+0x8058CE40:dword:0x60000000:0x4BA762C1
+# fra.rel
+0x8058D03C:dword:0x60000000:0x4BA760C5
+# spa.rel
+0x8058D024:dword:0x60000000:0x4BA760DD
+# ita.rel
+0x8058CEA4:dword:0x60000000:0x4BA7625D

Source/Core/Core/PatchEngine.cpp

@@ -105,6 +105,11 @@ void LoadPatchSection(const std::string& section, std::vector<Patch>& patches, I
           bool success = true;
           success &= TryParse(items[0], &pE.address);
           success &= TryParse(items[2], &pE.value);
+          if (items.size() >= 4)
+          {
+            success &= TryParse(items[3], &pE.comparand);
+            pE.conditional = true;
+          }
 
           const auto iter =
               std::find(s_patch_type_strings.begin(), s_patch_type_strings.end(), items[1]);
@@ -191,15 +196,37 @@ static void ApplyPatches(const std::vector<Patch>& patches)
       {
         u32 addr = entry.address;
         u32 value = entry.value;
+        u32 comparand = entry.comparand;
         switch (entry.type)
         {
         case PatchType::Patch8Bit:
+          if (entry.conditional)
+          {
+            if (PowerPC::HostRead_U8(addr) != static_cast<u8>(comparand))
+            {
+              break;
+            }
+          }
           PowerPC::HostWrite_U8(static_cast<u8>(value), addr);
           break;
         case PatchType::Patch16Bit:
+          if (entry.conditional)
+          {
+            if (PowerPC::HostRead_U16(addr) != static_cast<u16>(comparand))
+            {
+              break;
+            }
+          }
           PowerPC::HostWrite_U16(static_cast<u16>(value), addr);
           break;
         case PatchType::Patch32Bit:
+          if (entry.conditional)
+          {
+            if (PowerPC::HostRead_U32(addr) != comparand)
+            {
+              break;
+            }
+          }
           PowerPC::HostWrite_U32(value, addr);
           break;
         default:

Source/Core/Core/PatchEngine.h

@@ -27,6 +27,8 @@ struct PatchEntry
   PatchType type = PatchType::Patch8Bit;
   u32 address = 0;
   u32 value = 0;
+  u32 comparand = 0;
+  bool conditional = false;
 };
 
 struct Patch

Source/Core/DolphinQt/Config/NewPatchDialog.cpp

@@ -4,6 +4,7 @@
 
 #include "DolphinQt/Config/NewPatchDialog.h"
 
+#include <QCheckBox>
 #include <QDialogButtonBox>
 #include <QGridLayout>
 #include <QGroupBox>
@@ -95,6 +96,12 @@ static bool PatchEq(const PatchEngine::PatchEntry& a, const PatchEngine::PatchEn
   if (a.value != b.value)
     return false;
 
+  if (a.comparand != b.comparand)
+    return false;
+
+  if (a.conditional != b.conditional)
+    return false;
+
   return true;
 }
 
@@ -117,17 +124,25 @@ QGroupBox* NewPatchDialog::CreateEntry(PatchEngine::PatchEntry& entry)
 
   auto* offset = new QLineEdit;
   auto* value = new QLineEdit;
+  auto* comparand = new QLineEdit;
 
   m_edits.push_back(offset);
   m_edits.push_back(value);
+  m_edits.push_back(comparand);
+
+  auto* conditional = new QCheckBox(tr("Conditional"));
+  auto* comparand_label = new QLabel(tr("Comparand:"));
 
   auto* layout = new QGridLayout;
   layout->addWidget(type, 0, 0, 1, -1);
   layout->addWidget(new QLabel(tr("Offset:")), 1, 0);
   layout->addWidget(offset, 1, 1);
   layout->addWidget(new QLabel(tr("Value:")), 2, 0);
   layout->addWidget(value, 2, 1);
-  layout->addWidget(remove, 3, 0, 1, -1);
+  layout->addWidget(conditional, 3, 0, 1, -1);
+  layout->addWidget(comparand_label, 4, 0);
+  layout->addWidget(comparand, 4, 1);
+  layout->addWidget(remove, 5, 0, 1, -1);
   box->setLayout(layout);
 
   connect(offset, qOverload<const QString&>(&QLineEdit::textEdited),
@@ -164,6 +179,23 @@ QGroupBox* NewPatchDialog::CreateEntry(PatchEngine::PatchEntry& entry)
             value->setPalette(palette);
           });
 
+  connect(comparand, qOverload<const QString&>(&QLineEdit::textEdited),
+          [&entry, comparand](const QString& text) {
+            bool okay;
+            entry.comparand = text.toUInt(&okay, 16);
+
+            QFont font;
+            QPalette palette;
+
+            font.setBold(!okay);
+
+            if (!okay)
+              palette.setColor(QPalette::Text, Qt::red);
+
+            comparand->setFont(font);
+            comparand->setPalette(palette);
+          });
+
   connect(remove, &QPushButton::clicked, [this, box, entry] {
     if (m_patch.entries.size() > 1)
     {
@@ -195,8 +227,19 @@ QGroupBox* NewPatchDialog::CreateEntry(PatchEngine::PatchEntry& entry)
   word->setChecked(entry.type == PatchEngine::PatchType::Patch16Bit);
   dword->setChecked(entry.type == PatchEngine::PatchType::Patch32Bit);
 
+  connect(conditional, &QCheckBox::toggled, [&entry, comparand_label, comparand](bool checked) {
+    entry.conditional = checked;
+    comparand_label->setVisible(checked);
+    comparand->setVisible(checked);
+  });
+
+  conditional->setChecked(entry.conditional);
+  comparand_label->setVisible(entry.conditional);
+  comparand->setVisible(entry.conditional);
+
   offset->setText(QStringLiteral("%1").arg(entry.address, 8, 16, QLatin1Char('0')));
   value->setText(QStringLiteral("%1").arg(entry.value, 8, 16, QLatin1Char('0')));
+  comparand->setText(QStringLiteral("%1").arg(entry.comparand, 8, 16, QLatin1Char('0')));
 
   return box;
 }

Source/Core/DolphinQt/Config/PatchesWidget.cpp

@@ -142,8 +142,17 @@ void PatchesWidget::SavePatches()
 
     for (const auto& entry : patch.entries)
     {
-      lines.push_back(StringFromFormat("0x%08X:%s:0x%08X", entry.address,
-                                       PatchEngine::PatchTypeAsString(entry.type), entry.value));
+      if (!entry.conditional)
+      {
+        lines.push_back(StringFromFormat("0x%08X:%s:0x%08X", entry.address,
+                                         PatchEngine::PatchTypeAsString(entry.type), entry.value));
+      }
+      else
+      {
+        lines.push_back(StringFromFormat("0x%08X:%s:0x%08X:0x%08X", entry.address,
+                                         PatchEngine::PatchTypeAsString(entry.type), entry.value,
+                                         entry.comparand));
+      }
     }
   }