From 18e0fc7cfa3178e8ff11ccbb8f778b25a19fca4f Mon Sep 17 00:00:00 2001
From: galister <22305755+galister@users.noreply.github.com>
Date: Fri, 27 Jan 2023 03:52:37 +0100
Subject: [PATCH] use hooking logic from AngriestSCV's fork

---
 OpenVR-SpaceCalibratorDriver/Hooking.h        | 69 ++++++++++++-------
 .../InterfaceHookInjector.cpp                 |  6 +-
 2 files changed, 49 insertions(+), 26 deletions(-)

diff --git a/OpenVR-SpaceCalibratorDriver/Hooking.h b/OpenVR-SpaceCalibratorDriver/Hooking.h
index da116ca..7d7a773 100644
--- a/OpenVR-SpaceCalibratorDriver/Hooking.h
+++ b/OpenVR-SpaceCalibratorDriver/Hooking.h
@@ -4,6 +4,9 @@
 #include <map>
 #include <string>
 #include <sys/mman.h>
+#include <stdexcept>
+#include <vector>
+#include <unistd.h>
 
 class IHook
 {
@@ -24,46 +27,66 @@ class IHook
 	static std::map<std::string, IHook *> hooks;
 };
 
-template <typename R, typename... Args>
+template <typename FuncType>
 class Hook : public IHook
 {
+	void * obj = nullptr;
+	int offset = 0;
+
 public:
+	FuncType originalFunc = nullptr;
 	Hook(const std::string &name) : IHook(name) { }
-
-	bool CreateHookInObjectVTable(void *object, int vtableOffset, R(*detourFunction)(Args...))
+  
+  template<typename T>
+	bool CreateHookInObjectVTable(void *object, int vtableOffset, T* detourFunction)
 	{
-		// For virtual objects, VC++ adds a pointer to the vtable as the first member.
+    		long pageSize = sysconf(_SC_PAGESIZE);
+
+		obj = object;
+		offset = vtableOffset;
+   		// For virtual objects, VC++ (and from what I can tell gcc)  adds a pointer to the vtable as the first member.
 		// To access the vtable, we simply dereference the object.
-		vFunc = *((void ***)object) + vtableOffset;
+		void **vtable = *((void ***)object);
 
 		// The vtable itself is an array of pointers to member functions,
 		// in the order they were declared in.
-		originalFunc = reinterpret_cast<R(*)(Args...)>(*vFunc);
-		uintptr_t startPage = reinterpret_cast<uintptr_t >(vFunc) & ~0xFFF;
-		uintptr_t endPage = reinterpret_cast<uintptr_t >(vFunc + sizeof(detourFunction)) & ~0xFFF;
-		mprotect(reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(vFunc) & ~0xFFF), endPage - startPage + 4096, PROT_READ | PROT_WRITE | PROT_EXEC);
-		*vFunc = reinterpret_cast<void*>(detourFunction);
-		mprotect(reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(vFunc) & ~0xFFF), endPage - startPage + 4096, PROT_EXEC);
-		LOG("Enabled hook for %s", name.c_str());
+		originalFunc = (FuncType) vtable[vtableOffset];
+		targetFunc = (void*) vtable[vtableOffset];
+
+		if((uintptr_t) vtable % 8  != 0 )
+		{
+			obj = nullptr;
+			originalFunc = nullptr;
+			throw std::runtime_error("vtable entry not aligned to 8 byte pointer");
+		}
+
+		uintptr_t otherPage = (uintptr_t) vtable & ~(uintptr_t) (pageSize - 1);
+		int err = mprotect((void*) otherPage, pageSize, PROT_READ | PROT_WRITE | PROT_EXEC);
+		if(err){
+			LOG("Failed to set memory protection %d", err);
+		}
+		else {
+			//LOG("%s", "Setting vtable value");
+			vtable[vtableOffset] = (void*) detourFunction;
+			//LOG("%s", "Resetting permissions vtable value");
+			mprotect((void*) otherPage, pageSize, PROT_READ | PROT_EXEC);
+		}
+
+		LOG("Enabled Linux hook for %s", name.c_str());
 		enabled = true;
 		return true;
 	}
 
 	void Destroy()
 	{
-		if (enabled)
-		{
-			uintptr_t startPage = reinterpret_cast<uintptr_t >(vFunc) & ~0xFFF;
-			uintptr_t endPage = reinterpret_cast<uintptr_t >(vFunc + sizeof(originalFunc)) & ~0xFFF;
-			mprotect(reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(vFunc) & ~0xFFF), endPage - startPage + 4096, PROT_READ | PROT_WRITE | PROT_EXEC);
-			*vFunc = reinterpret_cast<void*>(originalFunc);
-			mprotect(reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(vFunc) & ~0xFFF), endPage - startPage + 4096, PROT_EXEC);
-			enabled = false;
-		}
+    
+		//redoing it is enough if it was done the first time.
+		if(obj && originalFunc) CreateHookInObjectVTable(obj, offset, originalFunc);
+		obj = nullptr;
+		originalFunc = nullptr;
 	}
-	R(*originalFunc)(Args...) = nullptr;
 
 private:
 	bool enabled = false;
-	void **vFunc;
+	void* targetFunc = nullptr;
 };
diff --git a/OpenVR-SpaceCalibratorDriver/InterfaceHookInjector.cpp b/OpenVR-SpaceCalibratorDriver/InterfaceHookInjector.cpp
index ee6988c..b74014d 100644
--- a/OpenVR-SpaceCalibratorDriver/InterfaceHookInjector.cpp
+++ b/OpenVR-SpaceCalibratorDriver/InterfaceHookInjector.cpp
@@ -5,13 +5,13 @@
 
 static ServerTrackedDeviceProvider *Driver = nullptr;
 
-static Hook<void*, vr::IVRDriverContext*, const char*, vr::EVRInitError*>
+static Hook<void*(*)(vr::IVRDriverContext *, const char *, vr::EVRInitError *)> 
 	GetGenericInterfaceHook("IVRDriverContext::GetGenericInterface");
 
-static Hook<void, vr::IVRServerDriverHost*, uint32_t, const vr::DriverPose_t&, uint32_t>
+static Hook<void(*)(vr::IVRServerDriverHost *, uint32_t, const vr::DriverPose_t &, uint32_t)>
 	TrackedDevicePoseUpdatedHook005("IVRServerDriverHost005::TrackedDevicePoseUpdated");
 
-static Hook<void, vr::IVRServerDriverHost*, uint32_t, const vr::DriverPose_t&, uint32_t>
+static Hook<void(*)(vr::IVRServerDriverHost *, uint32_t, const vr::DriverPose_t &, uint32_t)>
 	TrackedDevicePoseUpdatedHook006("IVRServerDriverHost006::TrackedDevicePoseUpdated");
 
 static void DetourTrackedDevicePoseUpdated005(vr::IVRServerDriverHost *_this, uint32_t unWhichDevice, const vr::DriverPose_t &newPose, uint32_t unPoseStructSize)