I was asked today if it was possible to use invoke to call a function that you get the address of from GetProcAddress .. after a bit of rummaging in the MASM manuals I found something that seems to work, and thought I would post a little example :U.
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Hi Jibz,
Nice work :U
Here is my method with an invoke macro simulation:
.386
.model flat,stdcall
option casemap:none
include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include invoke.inc
includelib \masm32\lib\kernel32.lib
.data
kernel db "user32.dll",0
func db "MessageBoxA",0
message db "Calling MessageBox through eax",0
caption db "Indirect Invoke Example",0
.code
start:
invoke LoadLibrary,ADDR kernel
invoke GetProcAddress,eax,ADDR func
_invoke eax,0,ADDR message,ADDR caption,MB_OK ; macro simulating invoke
invoke ExitProcess,0
END start
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Jibz,
I have not looked at your example yet but there is a prototype macro in the masm32 macro file called DDPROTO that does just that. Its useful for addresses obtained in a numer of ways, GetProcAddress, vtable addresses and procedure addresses passed to a DLL or similar for a callback. Here is a quick example of how its done using the DDPROTO macro.
LATER : Jibz, nice clear way to demonstrate how the indirect call is coded. :U
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.486 ; create 32 bit code
.model flat, stdcall ; 32 bit memory model
option casemap :none ; case sensitive
include \masm32\include\windows.inc
include \masm32\include\masm32.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
include \masm32\macros\macros.asm
includelib \masm32\lib\masm32.lib
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
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NewMsgBox DDPROTO (hProc,4) ; prototype a procedure address
.data?
hProc dd ?
hLib dd ?
.code
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start:
main proc
mov hLib, rv(LoadLibrary,"user32.dll")
mov hProc, rv(GetProcAddress,hLib,"MessageBoxA")
invoke NewMsgBox,0,chr$("MessageBoxA API call"),chr$("Invoke call to address"),MB_OK
exit
ret
main endp
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end start
Hutch,
Fr some reason, that code refuses to compile on my machine. Fist it complains about the commas in the two lines containing the RV syntax. If I remove the commas, it then complains that RV cannot be found.
Paul
Jibz,
Quote...I found something that seems to work, and thought I would post a little example
Or you can run naked (without the parameter counting and red tape that PROTO includes), by using an INVOKE wannabe. Ratch
; invoke F4PTR PTR eax, 0, addr szMsg1, addr szCapt, MB_OK
INVOKIT eax, 0, @ szMsg1, @ szCapt, MB_OK
00000022 6A 00 4 PUSH MB_OK
00000024 68 00000000 R 4 PUSH OFFSET szCapt
00000029 68 00000018 R 4 PUSH OFFSET szMsg1
0000002E 6A 00 4 PUSH 0
00000030 FF D0 1 CALL eax
Hi Paul,
Did you download the latest version of macros.asm?
Vortex,
Thanks for the heads up, it is working now. Somehow I missed Hutch's posting.
Paul
Sorry about that Paul,
I can always claim senile decay for think that everyone had the current macros but I do have a valid excuse, the Win2k install and a 4 HDD. 2 CD/DVD machine do not sleep together well and it has wasted some days setting it all back up. I installed Office 2000 last weekend and the shell would not start any longer. There is some virtue in large multipartition machines though, apart from the boot partition that I only keep the OS and related installations on, I lost nothing at all. This in part makes up for Win2k badly messing up the partition order that I had to manually set for 18 drives.
Hutch,
That's okay, it's my fault for not being observant. BTW: Offtopic: I would like to somehow help you with the windows.inc project. It is always easy to be critical of another person's work, I choose to try to help. I believe it needs to be finalized once and for all, just as you do.
Paul