For an assignment I have to finish the code for a program that uses a loop to compare each array element to a target value that's provided through user input. So for example, when the program asks me to type a number and I type the number 6, it should give me the sixth number in this list. '7','3','2','1','0','5','6','4','8','9'
I typed what the comments told me to type but I keep getting this error when I try to compile it.
main.o: In function `getNextElement':
main.asm:(.text+0x92): relocation truncated to fit: R_386_8 against '.data'
Can anyone tell me what I'm doing wrong here?
;;;;;;;;;;;;;;;;;;;; MACRO DEFINITIONS ;;;;;;;;;;;;;;;;;;;;
; A macro with two parameters
; Implements the write system call
%macro writestring 2
mov eax, 4 ;sys_write system call number
mov ebx, 1 ;file descriptor std_out
mov ecx, %1 ;message to write from parameter 1
mov edx, %2 ;message length from parameter 2
int 0x80
%endmacro
; A macro with two parameters
; Implements the sys_read call
%macro read_string 2
mov eax, 3 ;sys_write system call number
mov ebx, 2 ;file descriptor std_in
mov ecx, %1 ;variable/array to hold data, pass by reference in param 1
mov edx, %2 ;number of bytes to read passed by value in param 2
int 0x80
%endmacro
;;;;;;;;;;;;;;;;;;;; DATA SEGMENT ;;;;;;;;;;;;;;;;;;;;
section .data
msg1 db 'Here are the elements: '
lenmsg1 equ $-msg1
msg2 db 'Enter a number to search for: '
lenmsg2 equ $-msg2
msg3 db 'The target value was found at index '
lenmsg3 equ $-msg3
msg4 db 'The target value was NOT found...',0x0a, 0x0d
lenmsg4 equ $-msg4
asciinums db '7','3','2','1','0','5','6','4','8','9'
lenasciinums equ $-asciinums
crlf db 0x0d, 0x0a
lencrlf equ $ - crlf
target db 0x00
targetlocation db 0x30
section .text
global _start
_start:
writestring msg1, lenmsg1
writestring asciinums, lenasciinums
writestring crlf, lencrlf
writestring msg2, lenmsg2
read_string target, 1
writestring crlf, lencrlf
mov eax, asciinums ;eax holds base address
mov ecx, 0 ;ecx is index register
getNextElement:
mov [eax+ecx], al ;copy value from asciinums into an 8-bit register
cmp al, target ;compare the 8-bit register to target value
je targetlocation ;jump if equal to the found label
inc ecx ;increment index register
cmp ecx, 10 ;compare index register to decimal 10
jne getNextElement ;if index register not equal to 10 go to getNextElement
writestring msg4, lenmsg4
jmp terminate
found:
add [targetlocation], ecx
writestring msg3, lenmsg3
writestring targetlocation, 1
writestring crlf, lencrlf
terminate:
mov eax, 1 ;terminate program
int 0x80
I also know that the problem is from this section of the code.
mov eax, asciinums ;eax holds base address
mov ecx, 0 ;ecx is index register
getNextElement:
mov [eax+ecx], al ;copy value from asciinums into an 8-bit register
cmp al, target ;compare the 8-bit register to target value
je targetlocation ;jump if equal to the found label
inc ecx ;increment index register
cmp ecx, 10 ;compare index register to decimal 10
jne getNextElement ;if index register not equal to 10 go to getNextElement
This is the website I used to compile. Any help would be greatly appreciated.
Assuming that you're writing code for x86 architecture the problem is je instruction in getNextElement. je instruction is a short jump, it expects relative address as a parameter only and it can't be used to make indirect jumps. Here you can look at the difference between je and jmp instructions:
http://x86.renejeschke.de/html/file_module_x86_id_146.html
http://x86.renejeschke.de/html/file_module_x86_id_147.html
Added:
mov [eax+ecx], al ;copy value from asciinums into an 8-bit register
Here you're moving al into memory and comment says the opposite. Fix it, use je found and try again.
Added:
And another one:
mov [eax+ecx], al ;copy value from asciinums into an 8-bit register
here you're ruining eax register by loading data into al. On the next loop you'll fetch garbage from memory.
Checked, after fixing all mentioned mistakes it works perfectly.
;;;;;;;;;;;;;;;;;;;; MACRO DEFINITIONS ;;;;;;;;;;;;;;;;;;;;
; A macro with two parameters
; Implements the write system call
%macro writestring 2
mov eax, 4 ;sys_write system call number
mov ebx, 1 ;file descriptor std_out
mov ecx, %1 ;message to write from parameter 1
mov edx, %2 ;message length from parameter 2
int 0x80
%endmacro
; A macro with two parameters
; Implements the sys_read call
%macro read_string 2
mov eax, 3 ;sys_write system call number
mov ebx, 2 ;file descriptor std_in
mov ecx, %1 ;variable/array to hold data, pass by reference in param 1
mov edx, %2 ;number of bytes to read passed by value in param 2
int 0x80
%endmacro
;;;;;;;;;;;;;;;;;;;; DATA SEGMENT ;;;;;;;;;;;;;;;;;;;;
section .data
msg1 db 'Here are the elements: '
lenmsg1 equ $-msg1
msg2 db 'Enter a number to search for: '
lenmsg2 equ $-msg2
msg3 db 'The target value was found at index '
lenmsg3 equ $-msg3
msg4 db 'The target value was NOT found...',0x0a, 0x0d
lenmsg4 equ $-msg4
asciinums db '7','3','2','1','0','5','6','4','8','9'
lenasciinums equ $-asciinums
crlf db 0x0d, 0x0a
lencrlf equ $ - crlf
target db 0x00
targetlocation db 0x30
section .text
global _start
_start:
writestring msg1, lenmsg1
writestring asciinums, lenasciinums
writestring crlf, lencrlf
writestring msg2, lenmsg2
read_string target, 1
writestring crlf, lencrlf
mov eax, asciinums ;eax holds base address
mov ecx, 0 ;ecx is index register
getNextElement:
mov bl, [eax+ecx] ;copy value from asciinums into an 8-bit register
cmp bl, [target] ;compare the 8-bit register to target value
je found ;jump if equal to the found label
inc ecx ;increment index register
cmp ecx, 10 ;compare index register to decimal 10
jne getNextElement ;if index register not equal to 10 go to getNextElement
writestring msg4, lenmsg4
jmp terminate
found:
add [targetlocation], ecx
writestring msg3, lenmsg3
writestring targetlocation, 1
writestring crlf, lencrlf
terminate:
mov eax, 1 ;terminate program
int 0x80