global _start
section .data
var dq 12494F04A6344129h
msg db "The number of times 4 present in the given number"
len equ $-msg
novar db 00
section .bss
section .text
mov dl,0Ah
mov cl,10
_start :
mov rsi,var
up: mov al,byte ptr [rsi]
mov ah,00
div dl
cmp ah,04
je dn
jne dn1
dn: inc byte[novar]
dn1: inc rsi
dec cl
jne up
jmp exit
exit: mov eax,4
mov ebx,1
mov ecx,msg
mov edx,len
int 80h
mov eax,4
mov ebx,1
mov ecx,novar
mov edx,1
int 80h
mov eax,1
mov ebx,0
int 80h
Nasm doesn't use "ptr" - that won't even assemble.
The first two lines - above the _start: label - are never executed, so those registers are never initialized. That's probably what causes the exception. dl is probably zero!
len is fine - it's an equate, not a variable.
You probably want to add the character '0' to novar before printing it.
None of this looks useful to me. Are you sure this is the question you're trying to answer, #Shubham Satpute?
Related
When I run this program it says:
jdoodle.asm:9: error: invalid combination of opcode and operands
The problem is the AND al, ah. The rest of the code should be correct, I just need to know how to solve this problem because as it seems I can't do an AND between 2 registers.
section .text
global _start
_start:
call _input
mov al, input
mov ah, maschera
and al, ah
mov input, al
call _output
jmp _exit
_input:
mov eax, 3
mov ebx, 0
mov ecx, input
mov edx, 1
int 80h
ret
_output:
mov eax, 4
mov ebx, 1
mov ecx, input
mov edx, 1
int 80h
ret
_exit:
mov eax, 1
int 80h
section .data
maschera: db 11111111b
segment .bss
input resb 1
MASM/TASM/JWASM syntax is different from NASM. If you want to load/store data at an address you need to explicitly use square brackets. If you want to use the MOV instruction to place the address of a label in a variable you do not use square brackets. Square brackets are like a de-reference operator.
In 32-bit code you will want to ensure addresses are loaded into 32-bit registers. Any address above 255 won't fit in an 8 byte register, any address above 65535 won't fit in a 16-bit register.
The code you were probably looking for is:
section .text
global _start
_start:
call _input
mov al, [input]
mov ah, [maschera]
and al, ah
mov [input], al
call _output
jmp _exit
_input:
mov eax, 3
mov ebx, 0
mov ecx, input
mov edx, 1
int 80h
ret
_output:
mov eax, 4
mov ebx, 1
mov ecx, input
mov edx, 1
int 80h
ret
_exit:
mov eax, 1
int 80h
section .data
maschera: db 11111111b
segment .bss
input resb 1
At start I want to say that I'm a beginner in Assembly. I want to write a program which firstly adds two numbers and then divide the result by 2, so i want to get an average of two numbers. The problem is in section after dividing, but program without this section about dividing works well and prints the sum.
section .data
mess1 db 'Podaj pierwsza liczbe: '
len1 equ $- mess1
mess2 db 'Podaj druga liczbe: '
len2 equ $- mess2
mess3 db 'Wynik: '
len3 equ $- mess3
section .bss
zmienna1 resb 4
zmienna2 resb 4
wynik resb 8 ;result
section .text
global _start
_start:
mov eax,4
mov ebx,1
mov ecx,mess1
mov edx,len1
int 0x80
mov eax,3 ;sys_read to 3
mov ebx,0 ;stdin
mov ecx,zmienna1
mov edx,4 ;4 to rozmiar
int 0x80
mov eax,4
mov ebx,1
mov ecx,mess2
mov edx,len2
int 0x80
mov eax,3
mov ebx,0 ;sys_read i stdin
mov ecx,zmienna2
mov edx,4 ;4 rozmiar
int 0x80
mov eax,4
mov ebx,1
mov ecx,mess3
mov edx,len3
int 0x80
;Teraz wrzuc zmienna1 do eax, a zmienna2 do ebx
; odejmij ASCII-owe '0' aby przekonwertowac na dzisiejtne
mov eax,[zmienna1]
sub eax,'0'
mov ebx,[zmienna2]
sub ebx,'0'
add eax,ebx
add eax,'0' ;zamien na binarne z decymalnego
mov [wynik],eax
div wynik,'2'
add wynik,'0'
;pokaz sume
mov eax,4 ;
mov ebx,1
mov ecx,wynik
mov edx,8 ;8 to rozmiar tego wyniku z bss
int 0x80
exit:
mov eax,4
xor ebx,ebx
int 0x80
I'm trying to make a very simple assembly program run, however I seem to get segfaults whatever I do.
Here is my code (should print 'a' on a linux machine)
section .data
buffer times 50 db 97
pointer db 0
section .text
global _start
_start:
mov ECX , pointer
mov EDX , [buffer + ECX]
mov EAX , 4
mov EBX , 1
mov ECX , EDX
mov EDX , 1
int 0x80
It causes a segfault on the first MOV but it seems obvious to me that it should work.
I reduced it to almost nothing and it still segfault.
section .data
msg db "hello"
section .text
global _start
_start:
mov EAX,1
I've run this succesfully:
section .text
global _start
_start:
mov ax, 0b
dec ax
sub ax, 11111111b
mov bx, 97
add ax, bx
mov [INVENTORY], ax ; put a in first inventory pos
mov eax, 4
mov ebx, 1
mov ecx, INVENTORY
mov edx, 1
int 0x80
mov ax, [INVENTORY]
add ax, 1
mov [INVENTORY + 1], ax ; put b in second inventory pos
mov [VAR], ax
mov eax, 4
mov ebx, 1
mov ecx, VAR
mov edx, 1
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, '\n'
mov edx, 1
int 0x80
mov eax,1
int 0x80
_newline:
section .data
VAR DW 0
INVENTORY TIMES 8 DW 0
Is it possible that it has to do with the symbols I use for newlines or tabs? I generate the assembly from java and I use \t for tabs and \n for new lines (and spaces so it doesn't look too bad.
I'm using NASM and I'm running it here:
https://www.tutorialspoint.com/compile_assembly_online.php
Thank you!
If you are just trying to print out a set of 'a's.
section .data
buffer times 50 db 97
len.buffer equ $-buffer
pointer db 0
section .text
global _start
_start:
; ssize_t write(int fd, const void *buf, size_t count);
; i386 ebx ecx edx esi edi ebp
mov EAX , 4 ; write syscall
mov EBX , 1 ; std out
lea ecx, [buffer] ; buffer
mov edx, len.buffer ; size
int 0x80
_exit:
mov eax, 1 ; exit syscall
int 0x80
output:
./yvon_001
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\ndavid#ubuntuserver00A:~/asm$ ./yvon_001
In the end #MichealPetch was right, I needed to add an EXIT syscall at the end of the code. The sample I tried still did a SEGFAULT because I was moving pointer instead of [pointer] in a registry.
Thanks for comments and answers!
I need to make a program that lets the user enter a string character by character and then print it in reverse. space means end of input (space should be entered by user.)
section .bss
c : resb 1
section .text
global _start
_start :
mov ecx, 0
mov edx, 0
saisie :
push ecx
push edx
mov eax,3
mov ebx,0
mov ecx,c
mov edx,1
int 80h
mov ecx,[c] ; put the entered value in ecx
cmp ecx,32 ; compare ecx with space.
je espace ;
pop edx
inc edx
pop ecx
jmp saisie
espace :
pop edx
cmp edx,0 ; if counter is 0 we exit if not we print what's in stack.
je fin
mov eax,4
mov ebx,1
pop ecx
int 80h
dec edx
jmp espace
fin :
mov eax, 1
mov ebx, 0
int 80h
When I enter characters and space at the end, the program just exits without error like it has done its job.
Can anyone explain this behavior and how I can correct it?
section .text
global _start ;must be declared for linker (ld)
_start:
mov eax,5
mov ebx,plname
mov ecx,0x202
mov edx,0700o
int 0x80
mov eax,4
mov ecx,plaintext
mov edx,256
int 0x80
xor eax,eax
inc eax
xor ebx,ebx
int 0x80
section .data
key db '123456passwordqwerty',0x0
keylen equ $ - key ;length of our dear string
plname db 'plname.bin',0x0
plaintext times 256 db 1
first part planned to create a file specified in plname, first time I'd tryed create it into /tmp/plname.bin and after fail, try to create at least into excuting directory.I've also tried create syscall and got the same results.
programm fails on open syscall, after excuting int 0x80 instruction, eax contains -2, programm ends normally, but doesn't create file.
here i got flags and mods
https://sourceware.org/gdb/onlinedocs/gdb/mode_005ft-Values.html#mode_005ft-Values
here is gdb output
Dump of assembler code for function _start:
0x08048080 <+0>: mov $0x8,%eax
0x08048085 <+5>: mov $0x80490c9,%ebx
0x0804808a <+10>: mov $0x700,%ecx
0x0804808f <+15>: int $0x80
0x08048091 <+17>: mov $0x4,%eax
0x08048096 <+22>: mov $0x80490e3,%ecx
0x0804809b <+27>: mov $0x100,%edx
0x080480a0 <+32>: int $0x80
0x080480a2 <+34>: xor %eax,%eax
0x080480a4 <+36>: inc %eax
0x080480a5 <+37>: xor %ebx,%ebx
0x080480a7 <+39>: int $0x80
End of assembler dump.
Breakpoint 1, 0x0804808f in _start ()
(gdb) i r eax
eax 0x5 5
(gdb) stepi
0x08048094 in _start ()
(gdb) i r eax
eax 0x5 5
(gdb) i r eax ebx ecx edx esi edi
eax 0x5 5
ebx 0x80490d1 134516945
ecx 0x202 514
edx 0x1c0 448
esi 0x0 0
edi 0x0 0
(gdb) stepi
0x08048096 in _start ()
(gdb) i r eax ebx ecx edx esi edi
eax 0xfffffffe -2
ebx 0x80490d1 134516945
ecx 0x202 514
edx 0x1c0 448
esi 0x0 0
edi 0x0 0
You used the wrong reference manual. What you linked to is the flags used in the gdb protocol, not the ones used by system calls.
O_CREAT is actually 0100 octal, so you should do mov ecx,0102o.
Also note you have forgotten to move the returned file descriptor from eax to ebx for the sys_write.
Working code:
section .text
global _start ;must be declared for linker (ld)
_start:
mov eax,5
mov ebx,plname
mov ecx,0102o
mov edx,0700o
int 0x80
mov ebx, eax
mov eax,4
mov ecx,plaintext
mov edx,256
int 0x80
xor eax,eax
inc eax
xor ebx,ebx
int 0x80
section .data
key db '123456passwordqwerty',0x0
keylen equ $ - key ;length of our dear string
plname db 'plname.bin',0x0
plaintext times 256 db 1