Code:
; tiny.asm
BITS 32
;
; MZ header
;
; The only two fields that matter are e_magic and e_lfanew
mzhdr:
dw "MZ" ; e_magic
dw 0 ; e_cblp UNUSED
;
; PE signature
;
pesig:
dd "PE" ; e_cp, e_crlc UNUSED ; PE signature
;
; PE header
;
pehdr:
dw 0x014C ; e_cparhdr UNUSED ; Machine (Intel 386)
dw 1 ; e_minalloc UNUSED ; NumberOfSections
; dd 0xC3582A6A ; e_maxalloc, e_ss UNUSED ; TimeDateStamp UNUSED
; Entry point
start:
push byte 42
pop eax
ret
codesize equ $ - start
dd 0 ; e_sp, e_csum UNUSED ; PointerToSymbolTable UNUSED
dd 0 ; e_ip, e_cs UNUSED ; NumberOfSymbols UNUSED
dw sections-opthdr ; e_lsarlc UNUSED ; SizeOfOptionalHeader
dw 0x103 ; e_ovno UNUSED ; Characteristics
;
; PE optional header
;
; The debug directory size at offset 0x94 from here must be 0
filealign equ 4
sectalign equ 4 ; must be 4 because of e_lfanew
%define round(n, r) (((n+(r-1))/r)*r)
opthdr:
dw 0x10B ; e_res UNUSED ; Magic (PE32)
db 8 ; MajorLinkerVersion UNUSED
db 0 ; MinorLinkerVersion UNUSED
;
; PE code section
;
sections:
dd round(codesize, filealign) ; SizeOfCode UNUSED ; Name UNUSED
dd 0 ; e_oemid, e_oeminfo UNUSED ; SizeOfInitializedData UNUSED
dd codesize ; e_res2 UNUSED ; SizeOfUninitializedData UNUSED ; VirtualSize
dd start ; AddressOfEntryPoint ; VirtualAddress
dd codesize ; BaseOfCode UNUSED ; SizeOfRawData
dd start ; BaseOfData UNUSED ; PointerToRawData
dd 0x400000 ; ImageBase ; PointerToRelocations UNUSED
dd sectalign ; e_lfanew ; SectionAlignment ; PointerToLinenumbers UNUSED
dd filealign ; FileAlignment ; NumberOfRelocations, NumberOfLinenumbers UNUSED
dw 4 ; MajorOperatingSystemVersion UNUSED ; Characteristics UNUSED
dw 0 ; MinorOperatingSystemVersion UNUSED
dw 0 ; MajorImageVersion UNUSED
dw 0 ; MinorImageVersion UNUSED
dw 4 ; MajorSubsystemVersion
dw 0 ; MinorSubsystemVersion UNUSED
dd 0 ; Win32VersionValue UNUSED
dd round(hdrsize, sectalign)+round(codesize,sectalign) ; SizeOfImage
dd round(hdrsize, filealign) ; SizeOfHeaders
dd 0 ; CheckSum UNUSED
db 2 ; Subsystem (Win32 GUI)
hdrsize equ $ - $$
filesize equ $ - $$