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Index > Windows > When I see a call 0xDE.... in a deubgger what does it mean?

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halivingston



Joined: 04 Aug 2015
Posts: 2
halivingston
I just found out that the E8 opcode for x86 near call is pc-relative. Yes, I'm new to assembly.

So now my world is thoroughly shaken. If the instruction is pc-relative, how is it that in Visual Studio's disassembly window, I see call 0xDEADBEEF ... that to me is a memory address.

In fact, if I had to generate some code, like a call instruction, I'm almost positive I've previously done it by putting near call's opcode and then a memory location. How does that work?
Post 04 Aug 2015, 20:31
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17248
Location: In your JS exploiting you and your system
revolution
The debugger just needs to add the IP of the next instruction to the offset encoded in the instruction and that will give the absolute address.
Code:
org 0x12345678
call @f ;e8 00 00 00 00  <--- IP of next instruction = 0x1234567D, offset = 0x00000000
@@: ;<--- address 0x1234567D    
Post 05 Aug 2015, 01:23
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