is this a compiler thing? or its just me?

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Nameless

Joined: 30 Apr 2010
Posts: 95

Nameless 06 May 2010, 05:14

when i tried to put 'lpResource db 'SETTINGS',0' right before .code section, like this

Code:

lpResource    db      'SETTINGS',0
.code
 Start:

the output is 424+ kb :S

when i put it the same line, in the same app, but anywhere else (at the very top of the .data section for example) the output is the normal size
am i missing something here?
i can show anyone on teamviewer, just drop me a pm

06 May 2010, 05:14

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20303
Location: In your JS exploiting you and your system

revolution 06 May 2010, 05:40

Mixing initialised data with uninitialised data.

Code:

.data
rb 1000000 ;uninitialised
db 'X' ;initialised

Code:

.data
db 'X' ;initialised
rb 1000000 ;uninitialised

One section is 1 byte long and the other is 1000001 bytes long. The PE format can store implicit zeros at the end of a section but not at the beginning. You should either put all initialised data into a separate section, or put all initialised data together at the start of a section.

06 May 2010, 05:40

baldr

Joined: 19 Mar 2008
Posts: 1651

baldr 06 May 2010, 05:46

revolution wrote:

One section is 1 byte long and the other is 1000001 bytes long.

This can be misleading: both sections are 1000001 bytes long, they differ only in their representation in PE. Wink

06 May 2010, 05:46

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20303
Location: In your JS exploiting you and your system

revolution 06 May 2010, 08:29

Yes, baldr is correct. When the exe is loaded into memory the section sizes will be the same. But on disk the stored section sizes differ greatly.

06 May 2010, 08:29

Nameless

Joined: 30 Apr 2010
Posts: 95

Nameless 06 May 2010, 09:38

oh
ok, thanks for the info, also sorry for the mis-understanding

06 May 2010, 09:38

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