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Index > Windows > non default section.Characteristics

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sometimes



Joined: 12 Jul 2014
Posts: 5
Location: Russia
sometimes
hello, I want see in the compiled file section with IMAGE_SCN_CNT_UNINITIALIZED_DATA characteristics, but fasm support only 'code' and 'data' (IMAGE_SCN_CNT_CODE and IMAGE_SCN_CNT_INITIALIZED_DATA). So i need to modify fasm source, but I could not understand how. Can anyone help me?)
Post 12 Jul 2014, 07:25
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7725
Location: Kraków, Poland
Tomasz Grysztar
fasm automatically sets this flag when you put only the uninitialized data into your section, i.e. the definitions like "rb 100", "db ?", etc.
Post 12 Jul 2014, 08:12
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sometimes



Joined: 12 Jul 2014
Posts: 5
Location: Russia
sometimes
thx for answer
but I can not manage sections directly, simply by writing the desired value in Hex (like 0C0000040h)

more controllability is good idea Smile
Post 12 Jul 2014, 08:15
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DOS386



Joined: 08 Dec 2006
Posts: 1901
DOS386
> more controllability is good idea

use format binary for ultimate controllability (check out 2014 files)
Post 12 Jul 2014, 09:29
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sometimes



Joined: 12 Jul 2014
Posts: 5
Location: Russia
sometimes
DOS386, it's a really good idea, thank you.

But I'm still interested to understand the FASM source code, could you show where is FASM writing IMAGE_SECTION_HEDER.Characteristics?
I think that somewhere inside FORMATS.INC Wink
Post 12 Jul 2014, 09:55
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DOS386



Joined: 08 Dec 2006
Posts: 1901
DOS386
> I think that somewhere inside FORMATS.INC

YES

Code:
      pe_entry_init_ok:
        and     [number_of_sections],0
        movzx   ebx,word [edx+14h]
        lea     ebx,[edx+18h+ebx]
        mov     [current_section],ebx
        mov     dword [ebx],'.fla'
        mov     dword [ebx+4],'t'
        mov     [ebx+14h],edi
        mov     [ebx+0Ch],eax
        mov     dword [ebx+24h],0E0000060h ; <<<--- HERE
    


Poke in hardcoded value and later patch it as needed :-\
Post 12 Jul 2014, 10:10
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sometimes



Joined: 12 Jul 2014
Posts: 5
Location: Russia
sometimes
No, I plan normal modes, without repeated FASM rebuilding, and add some commands to the parser

Code:
mov     dword [ebx+24h],0E0001060h    


Аnd as I understand it's about ".flat" section only, it is not suitable if I write..

Code:
section 'some' code executable writeable    
Post 12 Jul 2014, 10:18
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Tomasz Grysztar



Joined: 16 Jun 2003
Posts: 7725
Location: Kraków, Poland
Tomasz Grysztar
In TABLES.INC, in the symbols data structure you can find entries for "code" and "data" flags:
Code:
 db 'code',19h,5    

Code:
 db 'data',19h,6    

The byte 19h is fasm's internal code for PE section flags, the second byte is the number of bit corresponding to the flag.
So you could define the new "udata" flag by inserting this new line into "symbols_5" table:
Code:
 db 'udata',19h,7    
Note that the table has to be sorted alphabetically, so you'd need to insert it between "tword" and "use16".
Post 12 Jul 2014, 12:21
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sometimes



Joined: 12 Jul 2014
Posts: 5
Location: Russia
sometimes
Tomasz Grysztar, this is what I need. thx twice
Post 12 Jul 2014, 13:52
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SokilOff



Joined: 20 Sep 2010
Posts: 15
SokilOff
Tomasz Grysztar wrote:
So you could define the new "udata" flag by inserting this new line into "symbols_5" table:
Code:
 db 'udata',19h,7    
Note that the table has to be sorted alphabetically, so you'd need to insert it between "tword" and "use16".
Thanks ! Some time ago I had ran into the same problem but decided that one can live without it :)
Maybe it's even worth to be added in the next FASM version.
Post 13 Jul 2014, 01:01
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