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Index > DOS > P mode descriptors

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matefkr



Joined: 02 Sep 2007
Posts: 1291
Location: Ukraine, Beregovo
matefkr
What does it mean confirming (or not confirming) code segment? So what do the bit confirming if i have code segment?
Post 10 Jan 2008, 14:31
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System86



Joined: 15 Aug 2007
Posts: 77
System86
If a code segment is conforming, that means that less privileged code is able to jump to or call addresses in this segment. I'm not talking about call gates or interrupts here, I mean using far jmp or far call to directly jump to a memory address anywhere in the segment. An OS normally leaves this flag disabled (clear).
Post 11 Jan 2008, 00:15
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edfed



Joined: 20 Feb 2006
Posts: 4240
Location: 2018
edfed
thank you, me too i didn't understood this trick
Post 11 Jan 2008, 00:18
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matefkr



Joined: 02 Sep 2007
Posts: 1291
Location: Ukraine, Beregovo
matefkr
Thanks. And one more thing: If i load a selector of a code descriptor into a data segment register, (and first bit of type is set (read/write [read/noread if code]), could i write to that segment without any problem?
Post 11 Jan 2008, 12:13
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edfed



Joined: 20 Feb 2006
Posts: 4240
Location: 2018
edfed
i think it is impossible, as segment protection is done to avoid this possibility.
Post 11 Jan 2008, 13:03
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matefkr



Joined: 02 Sep 2007
Posts: 1291
Location: Ukraine, Beregovo
matefkr
I've inserted a simple selfmodifier code in an executable, and i've changed the .code section parameters (windows) to read, write code segment from read only code segment. Also it used ds to rewrite the code. But i just want it to know if it is worked because of usage of other segment register then cs.
Post 11 Jan 2008, 18:30
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