IOS LLE: optional IPC request/reply metadata trace (StarletOS phase 11 L2)

With DOLPHIN_IPC_TRACE=1 and the original IOS on the emulated Starlet, log
each request Broadway posts (X1: command, descriptor, argument words, an
OPEN's path) and each reply Starlet posts (Y1: original command, result).
Buffer contents are never read; nothing changes without the variable.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

Source/Core/Core/HW/WII_IPC.cpp

@@ -3,6 +3,9 @@
 
 #include "Core/HW/WII_IPC.h"
 
+#include <cstdlib>
+#include <string>
+
 #include "Common/ChunkFile.h"
 #include "Common/CommonTypes.h"
 #include "Common/Logging/Log.h"
@@ -10,6 +13,7 @@
 #include "Core/CoreTiming.h"
 #include "Core/HW/DVD/DVDInterface.h"
 #include "Core/HW/MMIO.h"
+#include "Core/HW/Memmap.h"
 #include "Core/HW/ProcessorInterface.h"
 #include "Core/IOS/IOS.h"
 #include "Core/IOS/Starlet/Starlet.h"
@@ -142,6 +146,55 @@ void WiiIPC::Shutdown()
 {
 }
 
+namespace
+{
+// StarletOS phase 11 (proposal L2): with DOLPHIN_IPC_TRACE=1 while the original IOS runs on the
+// emulated Starlet, each IPC request Broadway posts (X1) and each reply Starlet posts (Y1) is
+// logged with its metadata only: the command, the descriptor and the five argument words (an
+// OPEN's path), then the reply's result. Buffer contents are never read.
+bool IPCTraceEnabled()
+{
+  static const bool enabled = [] {
+    const char* value = std::getenv("DOLPHIN_IPC_TRACE");
+    return value != nullptr && value[0] == '1';
+  }();
+  return enabled;
+}
+
+void TraceIPCRequest(Core::System& system, u32 address)
+{
+  auto& memory = system.GetMemory();
+  if (memory.GetPointerForRange(address, 0x20) == nullptr)
+  {
+    NOTICE_LOG_FMT(WII_IPC, "IPCTRACE RQ {:08x} unreadable", address);
+    return;
+  }
+  const u32 command = memory.Read_U32(address);
+  const u32 fd = memory.Read_U32(address + 8);
+  u32 arg[5];
+  for (u32 i = 0; i < 5; ++i)
+    arg[i] = memory.Read_U32(address + 0xc + 4 * i);
+  std::string path;
+  if (command == 1 && memory.GetPointerForRange(arg[0], 64) != nullptr)
+    path = " P " + memory.GetString(arg[0], 64);
+  NOTICE_LOG_FMT(WII_IPC, "IPCTRACE RQ {:08x} C {} FD {} A {:08x} {:08x} {:08x} {:08x} {:08x}{}",
+                 address, command, static_cast<s32>(fd), arg[0], arg[1], arg[2], arg[3], arg[4],
+                 path);
+}
+
+void TraceIPCReply(Core::System& system, u32 address)
+{
+  auto& memory = system.GetMemory();
+  if (memory.GetPointerForRange(address, 0x10) == nullptr)
+  {
+    NOTICE_LOG_FMT(WII_IPC, "IPCTRACE RP {:08x} unreadable", address);
+    return;
+  }
+  NOTICE_LOG_FMT(WII_IPC, "IPCTRACE RP {:08x} C {} RC {}", address, memory.Read_U32(address + 8),
+                 static_cast<s32>(memory.Read_U32(address + 4)));
+}
+}  // namespace
+
 void WiiIPC::RegisterMMIO(MMIO::Mapping* mmio, u32 base)
 {
   // Both IPC message registers are general-purpose read/write registers on
@@ -168,6 +221,8 @@ void WiiIPC::RegisterMMIO(MMIO::Mapping* mmio, u32 base)
                      wii_ipc.m_ppc_irq_flags |= INT_CAUSE_IPC_BROADWAY;
                    if (wii_ipc.m_ctrl.X1)
                    {
+                     if (system.GetStarlet() && IPCTraceEnabled() && (val >> 0 & 1))
+                       TraceIPCRequest(system, wii_ipc.m_ppc_msg);
                      if (system.GetStarlet())
                        wii_ipc.m_arm_irq_flags |= INT_CAUSE_IPC_STARLET;
                      else if (system.GetIOS())
@@ -386,6 +441,9 @@ void WiiIPC::WriteStarletRegister(u32 offset, u32 value)
     break;
   case IPC_ARMCTRL:
     m_ctrl.arm(value);
+    // StarletOS phase 11: Y1 (bit 0) posts the reply whose pointer is in ARMMSG.
+    if (IPCTraceEnabled() && (value & 1))
+      TraceIPCReply(m_system, m_arm_msg);
     break;
   case PPC_IRQFLAG:
     m_ppc_irq_flags &= ~value;