How to print eax value with Radare2?












2















I am solving a crack me challenge but I am stuck. The challenge executes several jne tests. The first test is the simpliest but I don't arrive to print the eax value to know the content of cmp instruction. According to this block of code :



|    ; DATA XREF from sym.main (0x804848e)

|    0x08048497      b88a55ea8b     mov eax, 0x8bea558a

|    0x0804849c      45             inc ebp

|    0x0804849d      f4             hlt

|    0x0804849e      83c004         add eax, 4

|    0x080484a1      8a00           mov al, byte [eax]

|    0x080484a3      38c2           cmp dl, al

|,=< 0x080484a5      753d           jne 0x80484e4


How can I print the eax value to understand what are compared in the instruction ?



0x080484a1 8a00 mov al, byte [eax]



According to this question, I tried the 0x080484a1 but when I enter the command pxr 1 @ eax+0x4, nothing appears. If I enter the command pxr @ eax+0x4, this code appears :



0x080c288c  0x6f6c6165  ealo ascii

0x080c2890  0x00796768  hgy. ascii


The ascii printed is linked with the string compared ksuiealohgy.






debugging radare2 debuggers







share|improve this question



























    2















    I am solving a crack me challenge but I am stuck. The challenge executes several jne tests. The first test is the simpliest but I don't arrive to print the eax value to know the content of cmp instruction. According to this block of code :



    |    ; DATA XREF from sym.main (0x804848e)
    
|    0x08048497      b88a55ea8b     mov eax, 0x8bea558a
    
|    0x0804849c      45             inc ebp
    
|    0x0804849d      f4             hlt
    
|    0x0804849e      83c004         add eax, 4
    
|    0x080484a1      8a00           mov al, byte [eax]
    
|    0x080484a3      38c2           cmp dl, al
    
|,=< 0x080484a5      753d           jne 0x80484e4


    How can I print the eax value to understand what are compared in the instruction ?



    0x080484a1 8a00 mov al, byte [eax]



    According to this question, I tried the 0x080484a1 but when I enter the command pxr 1 @ eax+0x4, nothing appears. If I enter the command pxr @ eax+0x4, this code appears :



    0x080c288c  0x6f6c6165  ealo ascii
    
0x080c2890  0x00796768  hgy. ascii


    The ascii printed is linked with the string compared ksuiealohgy.






    debugging radare2 debuggers







    share|improve this question

























      2












      2








      2








      I am solving a crack me challenge but I am stuck. The challenge executes several jne tests. The first test is the simpliest but I don't arrive to print the eax value to know the content of cmp instruction. According to this block of code :



      |    ; DATA XREF from sym.main (0x804848e)
      
|    0x08048497      b88a55ea8b     mov eax, 0x8bea558a
      
|    0x0804849c      45             inc ebp
      
|    0x0804849d      f4             hlt
      
|    0x0804849e      83c004         add eax, 4
      
|    0x080484a1      8a00           mov al, byte [eax]
      
|    0x080484a3      38c2           cmp dl, al
      
|,=< 0x080484a5      753d           jne 0x80484e4


      How can I print the eax value to understand what are compared in the instruction ?



      0x080484a1 8a00 mov al, byte [eax]



      According to this question, I tried the 0x080484a1 but when I enter the command pxr 1 @ eax+0x4, nothing appears. If I enter the command pxr @ eax+0x4, this code appears :



      0x080c288c  0x6f6c6165  ealo ascii
      
0x080c2890  0x00796768  hgy. ascii


      The ascii printed is linked with the string compared ksuiealohgy.






      debugging radare2 debuggers







      share|improve this question














      I am solving a crack me challenge but I am stuck. The challenge executes several jne tests. The first test is the simpliest but I don't arrive to print the eax value to know the content of cmp instruction. According to this block of code :



      |    ; DATA XREF from sym.main (0x804848e)
      
|    0x08048497      b88a55ea8b     mov eax, 0x8bea558a
      
|    0x0804849c      45             inc ebp
      
|    0x0804849d      f4             hlt
      
|    0x0804849e      83c004         add eax, 4
      
|    0x080484a1      8a00           mov al, byte [eax]
      
|    0x080484a3      38c2           cmp dl, al
      
|,=< 0x080484a5      753d           jne 0x80484e4


      How can I print the eax value to understand what are compared in the instruction ?



      0x080484a1 8a00 mov al, byte [eax]



      According to this question, I tried the 0x080484a1 but when I enter the command pxr 1 @ eax+0x4, nothing appears. If I enter the command pxr @ eax+0x4, this code appears :



      0x080c288c  0x6f6c6165  ealo ascii
      
0x080c2890  0x00796768  hgy. ascii


      The ascii printed is linked with the string compared ksuiealohgy.






      debugging radare2 debuggers




      debugging radare2 debuggers






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










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          Not sure why you used pxr as you could get the output with px 1 @ eax+0x4. But another options would be that you could run this opcode and then read the register value of al to get that. But in order to do that you need to use debugger commands instead (of course you need to be in debugging mode):



          [0x7f5953803e90]> dr?
          
Usage: dr   Registers commands
          
| dr                     Show 'gpr' registers
          
<snip>


          So to get the value of al execute during debugging session:



          [0x7f5953803e90]> dr al
          
0x00000090





          share|improve this answer























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            Not sure why you used pxr as you could get the output with px 1 @ eax+0x4. But another options would be that you could run this opcode and then read the register value of al to get that. But in order to do that you need to use debugger commands instead (of course you need to be in debugging mode):



            [0x7f5953803e90]> dr?
            
Usage: dr   Registers commands
            
| dr                     Show 'gpr' registers
            
<snip>


            So to get the value of al execute during debugging session:



            [0x7f5953803e90]> dr al
            
0x00000090





            share|improve this answer




























              2














              Not sure why you used pxr as you could get the output with px 1 @ eax+0x4. But another options would be that you could run this opcode and then read the register value of al to get that. But in order to do that you need to use debugger commands instead (of course you need to be in debugging mode):



              [0x7f5953803e90]> dr?
              
Usage: dr   Registers commands
              
| dr                     Show 'gpr' registers
              
<snip>


              So to get the value of al execute during debugging session:



              [0x7f5953803e90]> dr al
              
0x00000090





              share|improve this answer


























                2












                2








                2







                Not sure why you used pxr as you could get the output with px 1 @ eax+0x4. But another options would be that you could run this opcode and then read the register value of al to get that. But in order to do that you need to use debugger commands instead (of course you need to be in debugging mode):



                [0x7f5953803e90]> dr?
                
Usage: dr   Registers commands
                
| dr                     Show 'gpr' registers
                
<snip>


                So to get the value of al execute during debugging session:



                [0x7f5953803e90]> dr al
                
0x00000090





                share|improve this answer













                Not sure why you used pxr as you could get the output with px 1 @ eax+0x4. But another options would be that you could run this opcode and then read the register value of al to get that. But in order to do that you need to use debugger commands instead (of course you need to be in debugging mode):



                [0x7f5953803e90]> dr?
                
Usage: dr   Registers commands
                
| dr                     Show 'gpr' registers
                
<snip>


                So to get the value of al execute during debugging session:



                [0x7f5953803e90]> dr al
                
0x00000090






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered 7 hours ago









                Paweł ŁukasikPaweł Łukasik

                2,4461520




                2,4461520






























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