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Gi@nnis Cheater Reputation: 1
Joined: 26 Oct 2013 Posts: 32 Location: Greece
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Posted: Fri Apr 07, 2017 5:05 pm Post subject: Mono - call static method from assembly [SOLVED] |
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I can't figure out what am I doing wrong.
I am trying to call a c# method from this code:
Code: |
usemono()
define(GGetAddress, "G:get") // static int get(string name);
define(GSetAddress, "G:set") // static void set(string name, int value);
define(GIncreaseAddress, "G:inc") // static void inc(string name, int value);
alloc(CallGet,512)
alloc(CallSet,512)
alloc(CallIncrease,512)
registerSymbol(CallGet)
registerSymbol(CallSet)
registerSymbol(CallIncrease)
alloc(VarName, 256)
registerSymbol(VarName)
alloc(VarValue, 4)
registerSymbol(VarValue)
CallGet:
push VarName // push the pointer to the address of the string
// variable name
call GGetAddress // call the get function
add esp, 4 // clean-up the stuck
mov dword ptr [VarValue], eax // store the return value
ret // return
CallSet:
push [VarValue] // push the integer value
push VarName // push the pointer to the address of the string
// variable name
call GSetAddress // call the get function
add esp, 8 // clean-up the stuck
ret // return
CallIncrease:
push [VarValue] // push the integer value
push VarName // push the pointer to the address of the string
// variable name
call GIncreaseAddress // call the get function
add esp, 8 // clean-up the stuck
ret // return
VarName:
// type etc ... (copied from real string)
db A4 85 1C 04 00 00 00 00
// length
dd 5
// the string
db 6D 00 6F 00 6E 00 65 00 79 00
dq 0
VarValue:
dd 0
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The other two methods are working fine, but the get method leads to crash. I am calling them from LUA via: Code: | autoAssemble("createThread(CallGet)") |
The main differences between the functions that I've manage to figure out so far is that the get method first of all returns a value, and that the get method has none-static method calls.
Note that I am not a programmer, so don't go too deep with the explanation because I'll, probably, not understand it.
Any help will be greatly appreciated, thanks in advance.
Last edited by Gi@nnis on Mon Apr 10, 2017 6:52 am; edited 1 time in total |
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Dark Byte Site Admin Reputation: 457
Joined: 09 May 2003 Posts: 25252 Location: The netherlands
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Posted: Fri Apr 07, 2017 5:14 pm Post subject: |
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either call that code from a codecave you know is getting executed from a mono thread, or let your thread first attach to mono
e.g something like this:
Code: |
alloc(self,4)
call mono.mono_get_root_domain //eax contains the root domain
push eax //give it as parameter to mono_thread_attach
call mono.mono_thread_attach
sub esp,4 //undo the push because cdecl
mov [self],eax
call CallGet
push [self]
call mono.mono_thread_detach
sub esp,4
ret 4
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(and make sure the first 4 bytes of VarName are correct. It looks like a vtable address for a String class object, so that can change between runs)
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Gi@nnis Cheater Reputation: 1
Joined: 26 Oct 2013 Posts: 32 Location: Greece
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Posted: Sat Apr 08, 2017 5:09 am Post subject: Thanks, it works!:D |
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It works!
Replaced call CallGet code with:
Code: |
mov eax,eax
call mono.mono_get_root_domain //eax contains the root domain
push eax //give it as parameter to mono_thread_attach
call mono.mono_thread_attach
sub esp,4 //undo the push because cdecl
mov [self],eax
push VarName // push the pointer that points to the address
// of the string variable name
call GGetAddress // call the get method
mov dword ptr [VarValue], eax // store the return value
push [self]
call mono.mono_thread_detach
add esp,10 // clean the stack
ret
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and it works as intended.
Thanks! As always, you're a life savior.
And thanks for the example, without it it would be very hard for me to understand what you're saying.
You're right about the string; that is a problem that I am aware of, the way I plan on dealing with it is to copy the bytes from a known string literal.(G:get+offset there is a pointer to a string (always))
If I may, I wanted to ask another question. I feel like creating a thread each time I click a button is a bit wasteful. I have another version where I created an infinite loop (with a kill switch) where it sleeps and checks for
a switch every second like:
Code: |
cmp byte ptr [switchesGet],1
jne _exit
cmp byte ptr [switchesGet+1],1
jne _sleep
_callGet:
blah blah ...
_sleep:
push #1000
call KERNEL32.sleep
jmp main
_exit:
ret
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Is there a real advantage to one of the two methods? Should I even worry about it, or it’s an insignificant problem and creating a few dozens of threads in a course of an hour or two doesn't create a problem?
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Gi@nnis Cheater Reputation: 1
Joined: 26 Oct 2013 Posts: 32 Location: Greece
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Posted: Mon Apr 10, 2017 6:52 am Post subject: Closing Post |
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I assume that my last question is either idiotic, or too hard to answer, either way I'd like to report that I am using the new thread method and it works fine so far, for several hours of straight gaming.
Also the initial c# string bytes do not actually affect the results of the functions. So, I left them 0 (didn't bother to implement the solution that I had in mind) and everything works fine.
Thanks again for the help Dark-Byte, I wouldn't be able to find the solution on my own.
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