Merge pull request #4220 from Sonicadvance1/expose_faultsafe

Linux/FaultSafeUserMemAccess: Break out fault safe handler
FEX-Emu · Dec 16, 2024 · 57178ab · 57178ab
2 parents 527752c + 73ca4f8
commit 57178ab
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Showing 2 changed files with 15 additions and 12 deletions.
diff --git a/Source/Tools/LinuxEmulation/LinuxSyscalls/SignalDelegator.cpp b/Source/Tools/LinuxEmulation/LinuxSyscalls/SignalDelegator.cpp
@@ -578,18 +578,8 @@ void SignalDelegator::HandleGuestSignal(FEX::HLE::ThreadStateObject* ThreadObjec
         ERROR_AND_DIE_FMT("X86 shouldn't hit this InterruptFaultPage");
 #endif
       }
-    } else if (Signal == SIGSEGV && (SigInfo.si_code == SEGV_MAPERR || SigInfo.si_code == SEGV_ACCERR) &&
-               FaultSafeUserMemAccess::IsFaultLocation(ArchHelpers::Context::GetPc(UContext))) {
-      // If you want to emulate EFAULT behaviour then enable this if-statement.
-      // Do this once we find an application that depends on this.
-      if constexpr (false) {
-        // Return from the subroutine, returning EFAULT.
-        ArchHelpers::Context::SetArmReg(UContext, 0, EFAULT);
-        ArchHelpers::Context::SetPc(UContext, ArchHelpers::Context::GetArmReg(UContext, 30));
-        return;
-      } else {
-        ERROR_AND_DIE_FMT("Received invalid data to syscall. Crashing now!");
-      }
+    } else if (FaultSafeUserMemAccess::TryHandleSafeFault(Signal, SigInfo, UContext)) {
+      ERROR_AND_DIE_FMT("Received invalid data to syscall. Crashing now!");
     } else {
       if (IsAsyncSignal(&SigInfo, Signal) && MustDeferSignal) {
         // If the signal is asynchronous (as determined by si_code) and FEX is in a state of needing

diff --git a/Source/Tools/LinuxEmulation/LinuxSyscalls/Syscalls.h b/Source/Tools/LinuxEmulation/LinuxSyscalls/Syscalls.h
@@ -12,6 +12,7 @@ desc: Glue logic, STRACE magic
 #include "LinuxSyscalls/LinuxAllocator.h"
 #include "LinuxSyscalls/ThreadManager.h"
 #include "LinuxSyscalls/Seccomp/SeccompEmulator.h"
+#include "ArchHelpers/MContext.h"
 
 #include <FEXCore/Config/Config.h>
 #include <FEXCore/Core/Thunks.h>
@@ -674,6 +675,18 @@ namespace FaultSafeUserMemAccess {
   }
 #endif
   bool IsFaultLocation(uint64_t PC);
+
+  static inline bool TryHandleSafeFault(int Signal, const siginfo_t& SigInfo, void* UContext) {
+    if (Signal == SIGSEGV && (SigInfo.si_code == SEGV_MAPERR || SigInfo.si_code == SEGV_ACCERR) &&
+        FaultSafeUserMemAccess::IsFaultLocation(ArchHelpers::Context::GetPc(UContext))) {
+      // Return from the subroutine, returning EFAULT.
+      ArchHelpers::Context::SetArmReg(UContext, 0, EFAULT);
+      ArchHelpers::Context::SetPc(UContext, ArchHelpers::Context::GetArmReg(UContext, 30));
+      return true;
+    }
+
+    return false;
+  }
 } // namespace FaultSafeUserMemAccess
 
 } // namespace FEX::HLE