Hot-patching?

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l4m2

Joined: 15 Jan 2015
Posts: 670

l4m2 21 Feb 2015, 15:00

debugging INT 21 it is

Code:

90     NOP
90     NOP
E8**** CALL ****

I guessed it must be hot patching, but the 5 bytes before aren't

Code:

90 90 90 90 90

.So are they still hooken code?[/code]

21 Feb 2015, 15:00

nop

Joined: 01 Sep 2008
Posts: 165
Location: right here left there

nop 21 Feb 2015, 23:11

are you sugesting microsoft would use self modifying code inside a dos interupt Question

you maybe right and the 2 nops could be replaced by a near jmp to bypass the subroutine call

21 Feb 2015, 23:11

l4m2

Joined: 15 Jan 2015
Posts: 670

l4m2 22 Feb 2015, 06:21

nop wrote:

are you sugesting microsoft would use self modifying code inside a dos interupt you maybe right and the 2 nops could be replaced by a near jmp to bypass the subroutine call

I know the one in Windows which is just after 5 nops and is

Code:

Mov edi, edi

22 Feb 2015, 06:21

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 22 Feb 2015, 09:00

l4m2,

That could be alignment due to linker involved.

22 Feb 2015, 09:00

l4m2

Joined: 15 Jan 2015
Posts: 670

l4m2 22 Feb 2015, 09:38

baldr wrote:

l4m2,

That could be alignment due to linker involved.

so why not directly go to the third command

22 Feb 2015, 09:38

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 22 Feb 2015, 09:45

l4m2,

It seems to me that you didn't understand neither 'alignment' nor 'linker'.

22 Feb 2015, 09:45

sinsi

Joined: 10 Aug 2007
Posts: 794
Location: Adelaide

sinsi 22 Feb 2015, 19:18

l4m2 wrote:

debugging INT 21 it is
Code:
90     NOP
90     NOP
E8**** CALL ****    
I guessed it must be hot patching, but the 5 bytes before aren't
Code:
90 90 90 90 90    
.So are they still hooken code?[/code]

I think that code is when DOS is loaded high, it calls himem's a20 enable then jumps to FDxx:xxxx, if not high the two nops become a short jump past the E8

22 Feb 2015, 19:18

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