llvm dev - Apr 2012 - [LLVMdev] RE : RE : RE : Detect if a basicblock is part of a loop

This is my main.c (just a crappy test file):

#include <stdlib.h>

void foo() {
        foo();
}

int main(int argc,char** argv) {
        int a = 1;
        int b = 3;
        int c = a+b;

        int k;
        for(k=0;k<10;++k) {                          // The loop I'm
trying to detect
                int sdf = 123123;
                c++;
        }

        if(c - atoi(argv[1]) < 4)
                c = 0;
        else
                c = 1;

        return c;
}

The ir code corresponding to the loop:

; <label>:7                                       ; preds = %13, %0
  %8 = load i32* %k, align 4
  %9 = icmp slt i32 %8, 10
  br i1 %9, label %10, label %16

; <label>:10                                      ; preds = %7
  store i32 123123, i32* %sdf, align 4
  %11 = load i32* %c, align 4
  %12 = add nsw i32 %11, 1
  store i32 %12, i32* %c, align 4
  br label %13

; <label>:13                                      ; preds = %10
  %14 = load i32* %k, align 4
  %15 = add nsw i32 %14, 1
  store i32 %15, i32* %k, align 4
  br label %7
> is LLVMobfuscationTest.so your own pass? What does it do?
Yes it's my own lib... It contains some obfuscation's passes. The one
I'm trying to make now is making code flattening!

Cheers

ps: I tried Cristianno Martins solution, but it didn't work too :(

________________________________________
De : 陳韋任 [chenwj at iis.sinica.edu.tw]
Date d'envoi : vendredi 27 avril 2012 14:45
À : Rinaldini Julien
Cc: llvmdev at cs.uiuc.edu
Objet : Re: [LLVMdev] RE :  Detect if a basicblock is part of a loop
> Just as I said to Hal, nothing else than:
> $ clang -emit-llvm -S -o main.ll main.c
> $ ../build/Release/bin/opt -load
../build/Release/lib/LLVMobfuscationTest.so -flattening -S main.ll -o
main.opt.ll
  Then you might need to past your main.c. Besides, is LLVMobfuscationTest.so
your own pass? What does it do?

Regards,
chenwj

--
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

> Yes it's my own lib... It contains some obfuscation's passes. The
one I'm trying to make now is making code flattening!
                                                                                
^^^^^^^^^^^^^^^^^^^^^^
  What's the flattening effect? Maybe try NOT to flat it first?

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

It try to put all basicblock in a switch in a loop, like that for example:

int main() {
    if(something)
         somethingelse:
    else
          another;
}

become:

int main() {
    while(true) {
        switch(var) {
            case 0:
                 if(something)
                    var+=1;
                 else:
                     var+=2;
                  break;
              case1:
                    somethingelse;
                    var = MAX;
                    break;
               case2:
                     another;
                      var = MAX;
               case MAX:
                      exit();
           }
      }
}

But I'm trying that before any attempt of code flattening, just to see if I
can detect loop...

Cheers
________________________________________
De : 陳韋任 [chenwj at iis.sinica.edu.tw]
Date d'envoi : vendredi 27 avril 2012 15:05
À : Rinaldini Julien
Cc: llvmdev at cs.uiuc.edu
Objet : Re: [LLVMdev] RE :  RE :  Detect if a basicblock is part of a loop
> Yes it's my own lib... It contains some obfuscation's passes. The
one I'm trying to make now is making code flattening!
                                                                                
^^^^^^^^^^^^^^^^^^^^^^
  What's the flattening effect? Maybe try NOT to flat it first?

Regards,
chenwj

--
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj