The Shed is going Social! Join us on FaceBook and Twitter and chime in on the conversation.
|
 |
|
Dev Shed Forums
> Programming Languages - More
> Other Programming Languages
|
NASM assmebly language, addition of 2 arrays, and store into 3rd
Discuss NASM assmebly language, addition of 2 arrays, and store into 3rd in the Other Programming Languages forum on Dev Shed.
NASM assmebly language, addition of 2 arrays, and store into 3rd A place for discussing programming languages not covered in specific forums such as Assembler, COBOL, etc. - you get the idea.
|
|
 |
|
|
|
|
Dev Shed Forums Sponsor:
|
|
|
February 21st, 2011, 12:03 PM
|
|
Registered User
|
|
Join Date: Feb 2011
Posts: 2
Time spent in forums: 15 m 58 sec
Reputation Power: 0
|
|
|
NASM assmebly language, addition of 2 arrays, and store into 3rd
my program needs some tweaking,
so far it reads in 6 values then stores them into array1, then reads in another 6 and stores them into array 2
then i initialiaze array3 to store the sums of array1 and array2,
but i get a segmentation fault in my add function i believe
any suggestions guys?
I know my esp+XX values are off, but i've gone through every number up to 100, and none of them hold any values from array 1 and array2?
ideas?
Code:
%include "asm_io.asm"
segment .bss
array1 resd 6
array2 resd 6
array3 resd 6
segment .data
prompt1 db "Enter your number(if done enter: 0 ) : ", 0
aprompt1 db "Array1 Contents: ", 0
aprompt2 db "Array2 Contents: ", 0
aprompt3 db "Maximum Array Entries Reached: " , 0
dprompt db "Goodbye ! ", 0
segment .text
extern puts, _printf, scanf, dump_line
global asm_main
asm_main:
enter 0,0
pushad
;Declare Array1
push 6 ;declares max size of array1
push 0 ;indicates number of elements in array1
push array1 ;declares starting address of array1
mov ecx, 0
mov eax, prompt1
call print_string
call print_nl
call read_sarray32 ;begin reading values into array
call print_sarray32 ;print out values of array1
pop edx ;popped to keep balanced stack
pop edx ;popped to keep balanced stack
pop edx ;popped to keep balanced stack
popad
;Declare Array2
pusha
push 6 ;declares max size of array2
push 0 ;indicates number of elements in array2
push array2 ;declares starting address of array2
mov eax, prompt1
call print_string
call print_nl
call read_sarray32
call print_sarray32
pop edx ;popped to keep balanced stack
pop edx ;popped to keep balanced stack
pop edx ;popped to keep balanced stack
popad
;Declare Array3
pushad
push 6
;push 0
push array2
push array1
push array3
call add_arrays
call print_sarray32
mov eax, dprompt ;print out Goodbye Message
call print_string
pop ebx ;popped to keep balanced stack
pop edx ;popped to keep balanced stack
pop ecx ;popped to keep balanced stack
pop eax ;popped to keep balanced stack
;pop edx ;popped to keep balanced stack
popad
leave
ret
read_sarray32:
;enter 0,0
pushad
;mov ebx, 0 ;initialize ebx at 0
mov ebx, [esp+36] ;array starting position
mov edx, [esp+44] ;array max size
mov ecx, 0
read_loop:
mov eax, prompt1
call print_string
call read_int
inc ecx ;increment counter
cmp eax, 0
jz Done
jmp continue_loop
continue_loop:
mov [ebx], eax ;move value into memory slot ebx
add ebx, 4 ;move to next location for db words
cmp ecx, 6 ; did i reach maximum values of array size?
jz maximum_entries
jmp read_loop
maximum_entries:
mov eax, aprompt3
call print_string
jmp Done
Done:
mov [esp+40], ecx ;moves counter value back to stack
popad
;leave
ret
print_sarray32:
enter 0,0
pushad
mov ecx, 0 ;initialize counter to 0
mov ebx, [esp+40] ;move starting location to ebx
mov edx, [esp+44] ;move # items to edx
mov eax, aprompt1
call print_string
call print_nl
print_loop:
mov eax, [ebx] ;move value of index 0 of array to eax
call print_int ;print out number
call print_nl
add ebx, 4 ; moved ebx location to next slot
inc ecx ; counter is incremented by 1
cmp ecx, edx ; edx
jz print_sarrayDone
jmp print_loop
print_sarrayDone:
popad
leave
ret
add_arrays:
enter 0,0
pushad
mov ecx, 0 ;initialize counter to 0
mov ebx, [esp+52] ;moves starting location of array1 into ebx
mov ebp, [esp+54] ;moves starting locatino of array2 into ebp
mov esi, [esp+52] ;moves starting loaction of array3 into esi
mov eax, ebx
call print_int
call print_nl
mov eax, ebp
call print_int
call print_nl
add_loop:
inc ecx
mov eax, [ebx] ;moves value of ebx into eax
add eax,[edx] ;moves value of ebp into edx
mov [esi], eax ;move he sum of values stored in eax into esi
add esi, 4 ;increment location of pointer
add ebx, 4 ;increment location of pointer
add ebp, 4 ;increment location of pointer
cmp ecx, edx
jz add_done
jmp add_loop
add_done:
popad
leave
ret
|
February 21st, 2011, 03:15 PM
|
|
|
Usually you save the value in ESP at the beginning of your function call into EBP and then use EBP to reference the location of your arguments (saving you the trouble of figuring out how far your register saving and local variables move the stack pointer).
Code:
somefunction:
push ebp
mov ebp esp
; save space for locals
; push other registers that are used locally
; do some computation
; restore registers
mov esp ebp
pop ebp
ret
Which leaves your memory in this layout inside your function:
Code:
+-----------+
| |
| Caller's |
| |
| Registers |
| |
+-----------+
| Local Var | <-- EBP - 4
+-----------+
| Saved EBP | <-- EBP Points here
+-----------+
| Ret Addr | <-- EBP + 4
+-----------+
| Argument1 | <-- EBP + 8
+-----------+
| Argument2 | <-- EBP + 12
+-----------+
| . . . |
If you must do it via an offset from ESP, these are the questions you need to answer:
(1) What does PUSHAD place onto the stack?
(2) How much memory does this take up
(3) Where does ESP point at the start of the function?
__________________
sub{*{$::{$_}}{CODE}==$_[0]&& print for(%:: )}->(\&Meh);
|
February 21st, 2011, 04:58 PM
|
|
Registered User
|
|
Join Date: Feb 2011
Posts: 2
Time spent in forums: 15 m 58 sec
Reputation Power: 0
|
|
|
thanks for the reply
I figured out the memory addreses of the 3 arrays i pushed,
and i think it's adding correctly
but now when i go to print out array3, it's either giving me garbage, or it's giving me values of array2... i tried finding the location of array3 and can't figure it out...
also tried calling print inside the add function and no luck...
also you said to move the esp value into ebx, and i think i did that when i moved the 3 addresses into 3 different registers....if that's what you meant?
|
February 22nd, 2011, 07:29 PM
|
|
|
Quote: | Originally Posted by ilinan87 but now when i go to print out array3, it's either giving me garbage, or it's giving me values of array2... i tried finding the location of array3 and can't figure it out... |
Post your current code.
Quote: | Originally Posted by ilinan97 also you said to move the esp value into ebx, and i think i did that when i moved the 3 addresses into 3 different registers....if that's what you meant? |
No. I meant you use EBP (not the same as EBX) to store the address of the top of the stack (not a value stored on the stack) when your function starts. You then retrieve your arguments using an offset from EBP (which will stay constant regardless of what you push onto the stack later in the function).
|
Developer Shed Advertisers and Affiliates
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Rate This Thread |
 Linear Mode
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
|
Del.icio.us
Digg
Google
Spurl
Blink
Furl
Simpy
Y! MyWeb
