Re: Unity - patching methods
pardeike <[email protected]>
| Newsgroups | gmane.comp.gnome.mono.devel |
|---|---|
| Message-ID | <[email protected]> |
Ivo Smits wrote > One thing I found out is that when using > Marshal.GetDelegateForFunctionPointer, you need to keep a (managed) > reference to the delegate used to construct the function pointer around > as well. Otherwise the GC may clean up the delegate and the function > pointer will become invalid - although I did get a message informing me > that the handle had been cleaned instead of an immediate crash. Yes, I am aware of this. I have spend the better part of my weekend to test different strategies. Currently, I copy over IL code from the original to a DynamicMethod, prerun it, add a delegate to it, anchor all parts to a static object[] and the do the ordinary detour() that everyone is doing on original.MethodHandle.GetFunctionPointer() and dynamicCopyDelegate.MethodHandle.GetFunctionPointer(). It works BUT and this is something I am trying to understand: I can patch original A fine, or original B fine but when I do A and B together, the second call just crashes. I suspect that the ordinary detour that basically writes a jump to B at the start of A is wrong. It probably points to a trampoline and when two methods are patched the end result is messed up. Interestingly, that approach works fine if both methods are from loaded assemblies (my B is always dynamic and adding a delegate or prerunning it did not help). I read about trampolines (type-0, specific, generic and magic) and are still not sure if I understand this correctly. It says that the original CALL in the method points to a trampoline that itself invokes more stuff and compiles the called method and then *replaces the address of the original CALL in the method body*. Saves one jump so fine, but I am not sure if this would mean that *all* CALLs in the application need to be patched too or if this process is done for every CALL later with either recompiling (unlikely) or just using a pointer to the compiled method (in the method table?). I get lazy compiling but the replacement of call addresses is confusing. Sorry for the rant, Andreas -- View this message in context: http://mono.1490590.n4.nabble.com/Unity-patching-methods-tp4669765p4669773.html Sent from the Mono - Dev mailing list archive at Nabble.com. _______________________________________________ Mono-devel-list mailing list [email protected] http://lists.dot.net/mailman/listinfo/mono-devel-list