How to print eax value with Radare2?
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
asked Mar 3 at 20:01
AnonymeAnonyme
464
add a comment |
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
asked Mar 3 at 20:01
AnonymeAnonyme
464
does the execution reach that place ? there is a hlt instruction before i dont think your execution will reach this point if the flow was linear en.wikipedia.org/wiki/HLT_(x86_instruction)
– blabb
Mar 4 at 4:31
Yes it reach that place.The problem is solved, thanks for your contribution.
– Anonyme
Mar 4 at 12:31
add a comment |
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
asked Mar 3 at 20:01
AnonymeAnonyme
464
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
asked Mar 3 at 20:01
AnonymeAnonyme
464
asked Mar 3 at 20:01
AnonymeAnonyme
464
asked Mar 3 at 20:01
AnonymeAnonyme
464
asked Mar 3 at 20:01
AnonymeAnonyme
464
asked Mar 3 at 20:01
AnonymeAnonyme
464
464
does the execution reach that place ? there is a hlt instruction before i dont think your execution will reach this point if the flow was linear en.wikipedia.org/wiki/HLT_(x86_instruction)
– blabb
Mar 4 at 4:31
Yes it reach that place.The problem is solved, thanks for your contribution.
– Anonyme
Mar 4 at 12:31
add a comment |
does the execution reach that place ? there is a hlt instruction before i dont think your execution will reach this point if the flow was linear en.wikipedia.org/wiki/HLT_(x86_instruction)
– blabb
Mar 4 at 4:31
Yes it reach that place.The problem is solved, thanks for your contribution.
– Anonyme
Mar 4 at 12:31
does the execution reach that place ? there is a hlt instruction before i dont think your execution will reach this point if the flow was linear en.wikipedia.org/wiki/HLT_(x86_instruction)
– blabb
Mar 4 at 4:31
does the execution reach that place ? there is a hlt instruction before i dont think your execution will reach this point if the flow was linear en.wikipedia.org/wiki/HLT_(x86_instruction)
– blabb
Mar 4 at 4:31
Yes it reach that place.The problem is solved, thanks for your contribution.
– Anonyme
Mar 4 at 12:31
Yes it reach that place.The problem is solved, thanks for your contribution.
– Anonyme
Mar 4 at 12:31
add a comment |
1 Answer
1
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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
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
add a comment |
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votes
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
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
add a comment |
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
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
add a comment |
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
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
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
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
answered Mar 3 at 21:05
Paweł ŁukasikPaweł Łukasik
2,4811520
2,4811520
add a comment |
add a comment |
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does the execution reach that place ? there is a hlt instruction before i dont think your execution will reach this point if the flow was linear en.wikipedia.org/wiki/HLT_(x86_instruction)
– blabb
Mar 4 at 4:31
Yes it reach that place.The problem is solved, thanks for your contribution.
– Anonyme
Mar 4 at 12:31