relocationhandler.asm

pe exe packer (must use vc2005 to compile)

; Author:   Brandon LaCombe
; Date:     February 3, 2006
; License:  Public Domain
.386
.model flat, stdcall
option casemap:none

include     windows.inc
include     LoaderStructs.inc

.code
ExportRelocationHandler proc pdwRelocationHandlerSize:dword
    mov eax, pdwRelocationHandlerSize
    .if eax
        mov dword ptr[eax], relocation_handler_end - relocation_handler_start
    .endif
    mov eax, relocation_handler_start
    ret
ExportRelocationHandler endp

relocation_handler_start:
    mov ecx, (LOADER_STRUCT ptr[ebx]).dwImageDelta               ; ecx = image delta
    .if ecx                                                      ; only process if relocated
        mov edi, (LOADER_STRUCT ptr[ebx]).pRelocations           ; edi = reloc tbl ptr
        jmp enter_relocation_procedure                           ; enter reloc proc
relocation_loop:
        xor eax, eax                                             ; zero high word
        lodsw                                                    ; load reloc entry
        .if eax                                                  ; only process valid entries
            and ah, 00Fh                                         ; remove reloc type specifier
            add eax, (LOADER_STRUCT ptr[ebx]).dwImageBase        ; eax = address of reloc
            add [eax + edx], ecx                                 ; add delta to reloc
        .endif
enter_relocation_loop:
        cmp esi, edi                                             ; loop while we have reloc data
        jne relocation_loop                                      ; process next reloc entry
enter_relocation_procedure:
        mov edx, (IMAGE_BASE_RELOCATION ptr[edi]).VirtualAddress ; edx = reloc sec start rva
        lea esi, [edi + IMAGE_SIZEOF_BASE_RELOCATION]            ; esi = reloc data ptr
        add edi, (IMAGE_BASE_RELOCATION ptr[edi]).SizeOfBlock    ; edi = next reloc tbl
        test edx, edx                                            ; only process if we have an rva
        jnz enter_relocation_loop                                ; start processing reloc tbl
    .endif
relocation_handler_end:

end