;
; Was FASM example of writing simple EXE program using "format MZ" ,
; But now "MZ-header-$0200-BUG" test :
; File will have $0400 bytes, but header will say $0200,2 instead of 0,2 !!!
;

format MZ as "EXE"

stack $1000
heap 0

        push    cs
        pop     ds

        mov     ah,9
        mov     dx,txhello
        int     $21        ; Print to screen

        mov     ax,$4C00
        int     $21        ; Exit from EXE

txhello: db 'Hello world !',$0D,$0A,$24

        db 962 dup (0)
;END.
    

format PE GUI 4.0 DLL at 7000000h on 'stub.exe'    

format PE GUI 4.0 DLL at 7000000h ontop 'stub.exe'    

Related issue: when building a PE on the top of a MZ stub, FASM enhances the MZ header to $40 bytes. This is not always appreciated

But how can I store the PE header offset there otherwise?

; This follows a $20 bytes long MZ header
 
org 0 ; 2nd 

; [8086]

  ; Here starting from DOS: DS = ???/PSP | ES = (seg-addr) of PSP
 ; We have exactly 28 bytes left before 0,0,0,0

  mov    ax,$7202            ; 3   -> 3
    push   ax
   popf                       ; This is not 100% safe from "V86" , but sufficient here
       pushf
       pop    bx                  ; 4x1 -> 7
    cmp    ax,bx               ; 2   -> 9
    je     short llmover       ; 2   -> 11 | OK we have at least 80386
       call   ssprint+ccmoversize ; 3   -> 14 final size | !!!! "org" missmatch
       db "Need 80386",0
 jmp    near llabort+ccmoversize ; "org" issue again
       ;------------------------------

 if $<>28
        error "You have a 80386 size BUG !!!"
   end if

  db 0,0,0,0         ; PE position

llmover: ; This was "main" , here "org" is 32 = $20
  ; Here still DS = ???/PSP | ES = (seg-addr) of PSP
  ; Also CS = SS , because of our COOL MZ header 

; [80286]
     push  cs
    pop   ds
    cld                   ; !!!
         mov   dx,es           ; Save PSP in DX
      mov   ax,[es:2]       ; !!! PSP !!! | Top of memory | Absolute (seg-addr) ?
     sub   ax,vvlolodiv16  ; AX := top - lolospacetotal (in par)
     mov   es,ax           ; Dest of move
        mov   ss,ax
         ; SS is ^^^ now also (top-lolospacetotal)
   ; Switch ^^^ SS first / only, CS later, keep SP as-is
    

typedef struct _IMAGE_DOS_HEADER {  // DOS .EXE header
     USHORT e_magic;         // Magic number
     USHORT e_cblp;          // Bytes on last page of file
     USHORT e_cp;            // Pages in file
     USHORT e_crlc;          // Relocations
     USHORT e_cparhdr;       // Size of header in paragraphs
     USHORT e_minalloc;      // Minimum extra paragraphs needed
     USHORT e_maxalloc;      // Maximum extra paragraphs needed
     USHORT e_ss;            // Initial (relative) SS value
     USHORT e_sp;            // Initial SP value
     USHORT e_csum;          // Checksum
     USHORT e_ip;            // Initial IP value
     USHORT e_cs;            // Initial (relative) CS value
     USHORT e_lfarlc;        // File address of relocation table
     USHORT e_ovno;          // Overlay number
     USHORT e_res[4];        // Reserved words
     USHORT e_oemid;         // OEM identifier (for e_oeminfo)
     USHORT e_oeminfo;       // OEM information; e_oemid specific
     USHORT e_res2[10];      // Reserved words
     LONG   e_lfanew;        // File address of new exe header
   } IMAGE_DOS_HEADER, *PIMAGE_DOS_HEADER;    

I think you will find

that the pointer to the PE header must be at 0x3C.

If you put it at 0x1C then the OS won't see it.

        if $<>28
          error "You have a 80386 size BUG !!!"
        end if

        db 0,0,0,0         ; PE position    

Maybe I misunderstand your code

...at $3C (RTFS ^^^) ... or 0x3C for C guru's

> What does the value 28 mean there?

It's $1C - since org was set to 0 last time, at position $20 from file begin (RTFS - the top line)

Even if you put the offset at valid offset in file, it is not valid if it is outside the boundaries of header.

find the dollar ($) character to be very ugly. The 0x format is much clearer IMO.

your efforts to squeeze a few bytes out of the header by inserting code in there seems rather odd. Is there a particular purposes you have for this? Is your HDD too small to hold the extra data?

COOL. MASM-guru's append "h" at the end of the number, Quack-BASIC guru's prepend it with "&H", and GAS-guru's must use both "$" and "0x" when pressuring the compiler to accept a hex number

Tomasz Grysztar wrote:

Even if you put the offset at valid offset in file, it is not valid if it is outside the boundaries of header.

Evidence, please. It always worked for me like this. All PE loaders I've seen so far do ignore the MZ header and simply look at $3C.

Save 32 bytes here, save 50 bytes there, save some more space in ??? , at the end one will get a 1 MiB distro instead of a 10 GiB distro

Evidence, please. It always worked for me like this. All PE loaders I've seen so far do ignore the MZ header and simply look at $3C.

The fact that it works doesn't mean it is correct.

Tomasz Grysztar wrote:

The fact that it works doesn't mean it is correct.

Please point me to documentation saying that it's wrong.