Is my understanding about PE's File Alignment correct?

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uu

Joined: 20 Jul 2024
Posts: 44

uu 13 Aug 2024, 10:24

This is more related to creating tiny PE by adjusting the size of File Alignment setting.

If my understanding is correct, then my newly drawn diagrams are all set.

Normally the default value of File Alignment is 512, and let's say I have two sections with each 300 bytes and 200 bytes, that would make the total EXE size 1536 bytes.
If I reduce it by halve to 256, only code section cannot fit single section, so there's need for multiple of 256. Correct?

If I further set the File Alignment to 4 or 16, it would make sure no unused null padded bytes. Question

Description:	256 File Alignment
Filesize:	31.09 KB
Viewed:	452 Time(s)

Description:	512 File Alignment
Filesize:	26.77 KB
Viewed:	452 Time(s)

13 Aug 2024, 10:24

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20340
Location: In your JS exploiting you and your system

revolution 13 Aug 2024, 10:53

The Windows loader has some restrictions that you need to comply with.

You are correct that the formal PE spec can accommodate different alignments, but the standard Windows loader doesn't accept all of those configurations.

13 Aug 2024, 10:53

uu

Joined: 20 Jul 2024
Posts: 44

uu 13 Aug 2024, 11:09

revolution wrote:

The Windows loader has some restrictions that you need to comply with.

You are correct that the formal PE spec can accommodate different alignments, but the standard Windows loader doesn't accept all of those configurations.

Thank you for the answer, I will only take my chance during size coding competition. Laughing

13 Aug 2024, 11:09

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20340
Location: In your JS exploiting you and your system

revolution 14 Aug 2024, 02:08

There is also the native PE format.

Code:

~ cat test.asm
format pe TYPE
entry $
ret

~ fasm -d TYPE=native test.asm
flat assembler  version 1.73.31  (16384 kilobytes memory)
1 passes, 448 bytes.

~ fasm -d TYPE=gui test.asm
flat assembler  version 1.73.31  (16384 kilobytes memory)
1 passes, 1024 bytes.

~ fasm -d TYPE=console test.asm
flat assembler  version 1.73.31  (16384 kilobytes memory)
1 passes, 1024 bytes.

~

14 Aug 2024, 02:08

uu

Joined: 20 Jul 2024
Posts: 44

uu 14 Aug 2024, 05:11

revolution wrote:

There is also the native PE format.

Small, but native is generating .SYS file, which is driver I think. Rolling Eyes

14 Aug 2024, 05:11

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20340
Location: In your JS exploiting you and your system

revolution 14 Aug 2024, 05:35

Tell the competition organiser to run your code as a kernel mode driver. Twisted Evil

Nothing can possibly go wrong.

14 Aug 2024, 05:35

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