Can someone help me understand Stack Frame

[unktehi]

I'm trying to understand the example that is given for how a stack frame works.  Here is the code of how they appear in the slies.  Can someone help me understand?

.data
sum DWORD ?
.code
   push 6    ; second argument
   push 5    ; first argument
   call AddTwo   ; EAX = sum
   mov  sum,eax   ; save the sum

AddTwo PROC
   push ebp
   mov  ebp,esp
   .
   .


Then the next slide goes on to 'recall the AddTwo PROC' (I'm not really sure if this is supposed to be a continuation of the first slide or what...maybe you understand better):

AddTwo PROC,
   val1:DWORD, val2:DWORD

   mov eax,val1
   add eax,val2

   ret
AddTwo ENDP


The next slide shows this code as the code that MASM actually generates when AddTwo is assembled:

AddTwo PROC,
val1:DWORD, val2:DWORD
   push ebp
   mov  ebp, esp
   
   mov  eax,val1
   add  eax,val2
   
   leave
   ret  8
AddTwo ENDP

[tenkey]

Commented out the PROC and ENDP to show that the new code does not need them any more.
Added simple label to complete the translation of PROC.

Added translation of argument addresses, assuming they are illustrating STDCALL calling convention:

Code Select Expand

;;; AddTwo PROC, val1:DWORD, val2:DWORD
AddTwo:
   push ebp
   mov  ebp, esp
   
   mov  eax,[ebp+4]   ;;; val1
   add  eax,[ebp+8]   ;;; val2
   
   leave
   ret  8
;;; AddTwo ENDP


[Mark Jones]

About the stack frame, please see  \masm32\help\asmintro.chm  under "The Stack." Great info there.

Also see:
http://www.masm32.com/board/index.php?topic=5160.0
http://www.masm32.com/board/index.php?topic=7597.0
http://www.masm32.com/board/index.php?topic=8743.0

Those were found by typing "help stack frame" into the Search: box at the top of the page.

[RuiLoureiro]

;;; AddTwo PROC, val1:DWORD, val2:DWORD
AddTwo:
   push ebp
   mov  ebp, esp
   
   mov  eax,[ebp+4]   ;;; val1
   add  eax,[ebp+8]   ;;; val2
   
   leave
   ret  8
;;; AddTwo ENDP

Hi tenkey,
              ebp+4 and ebp+8 are incorrect.
              AddTwo should be (we dont need to comment AddTwo proc):

AddTwo      proc
            push ebp
            mov  ebp, esp
   
            mov  eax,[ebp+8]      ; val1
            add  eax,[ebp+12]     ; val2
   
            leave
            ret  8
AddTwo      endp

When we  «push  Val2» then ESP points to Val2
when we  «push  Val1» then ESP points to Val1
when we «call  AddTwo» then ESP points to «ret address» and we go to AddTwo
when we «push ebp» then ESP points to EBP
when we mov  ebp, esp then EBP points to EBP
now, in this prog point, the stack frame is

                                       EBP                 <- [ebp + 0]   points to here
                                       ret address       <- [ebp + 4]   points to here
                                       Val1                 <- [ebp + 8]  points here to Val1
                                       Val2                 <- [ebp + 12] points here to Val2

Rui