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How to print eax value with Radare2?


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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.










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.










    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.










      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






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked 8 hours ago









      AnonymeAnonyme

      414




      414






















          1 Answer
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          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























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            1 Answer
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            oldest

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            active

            oldest

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            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














              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 6 hours ago









                Paweł ŁukasikPaweł Łukasik

                2,4461520




                2,4461520






























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