non default section.Characteristics

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sometimes

Joined: 12 Jul 2014
Posts: 5
Location: Russia

sometimes 12 Jul 2014, 07:25

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?)

12 Jul 2014, 07:25

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8356
Location: Kraków, Poland

Tomasz Grysztar 12 Jul 2014, 08:12

fasm automatically sets this flag when you put only the uninitialized data into your section, i.e. the definitions like "rb 100", "db ?", etc.

12 Jul 2014, 08:12

sometimes

Joined: 12 Jul 2014
Posts: 5
Location: Russia

sometimes 12 Jul 2014, 08:15

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

12 Jul 2014, 08:15

DOS386

Joined: 08 Dec 2006
Posts: 1903

DOS386 12 Jul 2014, 09:29

> more controllability is good idea

use format binary for ultimate controllability (check out 2014 files)

12 Jul 2014, 09:29

sometimes

Joined: 12 Jul 2014
Posts: 5
Location: Russia

sometimes 12 Jul 2014, 09:55

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

12 Jul 2014, 09:55

DOS386

Joined: 08 Dec 2006
Posts: 1903

DOS386 12 Jul 2014, 10:10

> 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 :-\

12 Jul 2014, 10:10

sometimes

Joined: 12 Jul 2014
Posts: 5
Location: Russia

sometimes 12 Jul 2014, 10:18

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

12 Jul 2014, 10:18

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8356
Location: Kraków, Poland

Tomasz Grysztar 12 Jul 2014, 12:21

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".

12 Jul 2014, 12:21

sometimes

Joined: 12 Jul 2014
Posts: 5
Location: Russia

sometimes 12 Jul 2014, 13:52

Tomasz Grysztar, this is what I need. thx twice

12 Jul 2014, 13:52

SokilOff

Joined: 20 Sep 2010
Posts: 15

SokilOff 13 Jul 2014, 01:01

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.

13 Jul 2014, 01:01

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