Issue: when I run # the command prompt >tasm HelloWorld.asm and BTW I am using TAB in entering the file name HelloWorld.asm so there is no typo. I get this fatal command line error:
Turbo Assembler Version 4.1 Copyright (c) 1988, 1996 Borland
International
Assembling file: HelloWorld.asm
Fatal Command line: Can't locate file: HelloWorld.asm
Error messages: 1
Warning messages: None Passes: 1
Remaining memory: 452k
Here is my HelloWorld.asm:
.model small
.stack 100h
.data
;variablename type value or default initialization
dexter db "Hello World"
.code
start:
mov ax, #data
mov ds, ax
mov ah, 09h
mov dx, offeset dexter
int 21h
mov ah, 4ch
int 21h
end start
Request your kind help to know why I am getting this error?
I was facing a similar problem and found that keeping names less than 6-7 characters helps!
.model tiny
.stack
.data
Message db "hola mundo$"
.code
start:
mov dx,OFFSET Message
mov ax, SEG Message
mov ds,ax
mov ah,9
int 21h
mov ax,4C00h
int 21h
END start
Related
I'm new to assembly, and am consequently also learning to play around with GDB.
I've got a simple program I'm trying to test GDB with:
global _main
SECTION .data ;ro = read only
txt DB 0x41, 0x0A, 0x00 ;db = define byte
.len EQU $ - txt ;Assembler constant definition: Make len (current memory position start of line ($$ is start of current section) - position of txt)
SECTION .text ;Code
_main:
;Write message
MOV rax, 0x02000004 ;sys_write
MOV rdi, 1 ;File descriptor stdout
MOV rdx, txt.len ;Message length
MOV rcx, txt ;Message to write
SYSCALL ;Return value stored in rax
;Exit
MOV rdi, rax ;Copy return value to rdi as exit code
MOV rax, 0x02000001 ;Exit syscall number
SYSCALL
After setting breakpoints (e.g. b 18 -- before the program exits) and running the program via r, GDB announces that it is running the program on a new thread and my prompt is indefinitely taken away. ^C does nothing, and all I can do to stop the process is kill it.
I barely know what I'm doing, so probably something dumb, but how do I get my prompt to return so I can interact with GDB?
I am trying to learn me making GUI programs in assembly. I downloaded Flat Assembler and started to read the example programs. There I found this code.
This is 64 bit code in assembly (fasm) for Windows. It makes empty window. But there was very few comments in It, so It's hard for me to understand what's going on. I commented here which parts I don't understand.
format PE64 GUI 5.0
entry start
include 'win64a.inc'
section '.idata' import data readable writeable
library kernel32,'KERNEL32.DLL',\
user32,'USER32.DLL'
include 'api\kernel32.inc'
include 'api\user32.inc'
section '.data' data readable writeable
_title TCHAR 'Win64 program template',0
_class TCHAR 'FASMWIN64',0
_error TCHAR 'Startup failed.',0
wc WNDCLASSEX sizeof.WNDCLASSEX,0,WindowProc,0,0,NULL,NULL,NULL,COLOR_BTNFACE+1,NULL,_class,NULL
msg MSG
section '.text' code readable executable
start:
sub rsp,8 ; Make stack dqword aligned
invoke GetModuleHandle,0 ;GetModuleHandle,0?
mov [wc.hInstance],rax ;wc.hInstance?
invoke LoadIcon,0,IDI_APPLICATION ;LoadIcon,0,IDI_APPLICATION?
mov [wc.hIcon],rax ;wc.hIcon?
mov [wc.hIconSm],rax ;ec.hIconSm?
invoke LoadCursor,0,IDC_ARROW ;LoadCursor,0,IDC_ARROW?
mov [wc.hCursor],rax ;wc.hCursor?
invoke RegisterClassEx,wc ;RegisterClassEx,wc?
test rax,rax ;test?
jz error
invoke CreateWindowEx,0,_class,_title,WS_VISIBLE+WS_DLGFRAME+WS_SYSMENU,128,128,256,192,NULL,NULL,[wc.hInstance],NULL
test rax,rax
jz error
msg_loop: ;What does this function?
invoke GetMessage,msg,NULL,0,0
cmp eax,1
jb end_loop
jne msg_loop
invoke TranslateMessage,msg
invoke DispatchMessage,msg
jmp msg_loop
error:
invoke MessageBox,NULL,_error,NULL,MB_ICONERROR+MB_OK
end_loop:
invoke ExitProcess,[msg.wParam]
proc WindowProc uses rbx rsi rdi, hwnd,wmsg,wparam,lparam ;?
; Note that first four parameters are passed in registers,
; while names given in the declaration of procedure refer to the stack
; space reserved for them - you may store them there to be later accessible
; if the contents of registers gets destroyed. This may look like:
; mov [hwnd],rcx
; mov [wmsg],edx
; mov [wparam],r8
; mov [lparam],r9
cmp edx,WM_DESTROY
je .wmdestroy
.defwndproc: ;What does this?
invoke DefWindowProc,rcx,rdx,r8,r9
jmp .finish
.wmdestroy:
invoke PostQuitMessage,0
xor eax,eax
.finish:
ret
endp
I have the following code:
%include "io.inc"
section .data
msg db 'Hello World...$'
section .text
global CMAIN
CMAIN:
;write your code here
mov ah,09
mov dx,OFFSET msg
int 21h
xor eax, eax
xor dx,dx
ret
and it gets the next error:
[19:28:32] Warning! Errors have occurred in the build:
C:/Users/user/AppData/Local/Temp/SASM/program.asm:12: error: comma, colon, decorator or end of line expected after operand
gcc.exe: error: C:/Users/user/AppData/Local/Temp/SASM/program.o: No such file or directory
What is the problem? i'm using sasm ide.
This is TASM/MASM syntax:
mov dx,OFFSET msg
When using NASM you'd simply write:
mov dx,msg
So I have a simple C program that loops through the args passed to main then returns:
#include <stdio.h>
int main(int argc, char *argv[])
{
int i;
for(i = 0; i < argc; ++i) {
fprintf(stdout, "%s\n", argv[i]);
}
return 0;
}
I wanted to see how gcc wrote out the assembly in NASM format. I was looking over the output in the .asm file and noticed that the syntax was TASM. Below is the make file and the output from gcc. Am I doing something wrong or is it that gcc does not output true NASM syntax?
all: main
main: main.o
ld -o main main.o
main.o : main.c
gcc -S -masm=intel -o main.asm main.c
nasm -f elf -g -F stabs main.asm -l main.lst
AND
.file "main.c"
.intel_syntax noprefix
.section .rodata
.LC0:
.string "%s\n"
.text
.globl main
.type main, #function
main:
push ebp
mov ebp, esp
and esp, -16
sub esp, 32
mov DWORD PTR [esp+28], 0
jmp .L2
.L3:
mov eax, DWORD PTR [esp+28]
sal eax, 2
add eax, DWORD PTR [ebp+12]
mov ecx, DWORD PTR [eax]
mov edx, OFFSET FLAT:.LC0
mov eax, DWORD PTR stdout
mov DWORD PTR [esp+8], ecx
mov DWORD PTR [esp+4], edx
mov DWORD PTR [esp], eax
call fprintf
add DWORD PTR [esp+28], 1
.L2:
mov eax, DWORD PTR [esp+28]
cmp eax, DWORD PTR [ebp+8]
jl .L3
mov eax, 0
leave
ret
.size main, .-main
.ident "GCC: (GNU) 4.5.1 20100924 (Red Hat 4.5.1-4)"
.section .note.GNU-stack,"",#progbits
The errors on the command line are:
[mehoggan#fedora sandbox-print_args]$ make
gcc -S -masm=intel -o main.asm main.c
nasm -f elf -g -F stabs main.asm -l main.lst
main.asm:1: error: attempt to define a local label before any non-local labels
main.asm:1: error: parser: instruction expected
main.asm:2: error: attempt to define a local label before any non-local labels
main.asm:2: error: parser: instruction expected
main.asm:3: error: attempt to define a local label before any non-local labels
main.asm:3: error: parser: instruction expected
main.asm:4: error: attempt to define a local label before any non-local labels
main.asm:5: error: attempt to define a local label before any non-local labels
main.asm:5: error: parser: instruction expected
main.asm:6: error: attempt to define a local label before any non-local labels
main.asm:7: error: attempt to define a local label before any non-local labels
main.asm:7: error: parser: instruction expected
main.asm:8: error: attempt to define a local label before any non-local labels
main.asm:8: error: parser: instruction expected
main.asm:14: error: comma, colon or end of line expected
main.asm:17: error: comma, colon or end of line expected
main.asm:19: error: comma, colon or end of line expected
main.asm:20: error: comma, colon or end of line expected
main.asm:21: error: comma, colon or end of line expected
main.asm:22: error: comma, colon or end of line expected
main.asm:23: error: comma, colon or end of line expected
main.asm:24: error: comma, colon or end of line expected
main.asm:25: error: comma, colon or end of line expected
main.asm:27: error: comma, colon or end of line expected
main.asm:29: error: comma, colon or end of line expected
main.asm:30: error: comma, colon or end of line expected
main.asm:35: error: parser: instruction expected
main.asm:36: error: parser: instruction expected
main.asm:37: error: parser: instruction expected
make: *** [main.o] Error 1
What lead me to believe that this is TASM syntax was information posted at this link:
http://rs1.szif.hu/~tomcat/win32/intro.txt
TASM coders usually have lexical difficulties with NASM because it
lacks the "ptr" keyword used extensively in TASM.
TASM uses this:
mov al, byte ptr [ds:si] or mov ax, word ptr [ds:si] or mov eax,
dword ptr [ds:si]
For NASM This simply translates into:
mov al, byte [ds:si] or mov ax, word [ds:si] or mov eax, dword
[ds:si]
NASM allows these size keywords in many places, and thus gives you a
lot of control over the generated opcodes in a unifrom way, for
example These are all valid:
push dword 123 jmp [ds: word 1234] ; these both specify the size
of the offset jmp [ds: dword 1234] ; for tricky code when
interfacing 32bit and
; 16bit segments
it can get pretty hairy, but the important thing to remember is you
can have all the control you need, when you want it.
Intel syntax means Intel syntax, not NASM syntax. MASM and TASM syntaxes are based on Intel Syntax, NASM syntax gets inspiration from Intel syntax, but it is different.
What gcc outputs is actually gas syntax using Intel syntax for individual instructions, (Assembler directives, labels et al. use gas-specific syntax)
I really do not understand why this simple code works fine in the first attempt but when
putting it in a procedure an error shows:
NTVDM CPU has encountered an illegal instruction
CS:db22 IP:4de4 OP:f0 ff ff ff ff
The first code segment works just fine:
.model small
.stack 100h
.code
start:
mov ax,#data
mov ds,ax
mov es,ax
MOV AH,02H ;sets cursor up
MOV BH,00H
MOV DH,02
MOV DL,00
INT 10H
EXIT:
MOV AH,4CH
INT 21H
END
However This generates an error:
.model small
.stack 100h
.code
start:
mov ax,#data
mov ds,ax
mov es,ax
call set_cursor
PROC set_cursor near
MOV AH,02H ;sets cursor up
MOV BH,00H
MOV DH,02
MOV DL,00
INT 10H
RET
set_cursor ENDP
EXIT:
MOV AH,4CH
INT 21H
END
Note: Nothing is wrong with windows config. I have tried many sample codes that work fine
Thanks
You left out a JMP:
call set_cursor
jmp EXIT ; <== you forgot this part
PROC set_cursor near
What's happening is that after call set_cursor, you're then falling through to the proc and and executing it again, then when you hit the ret it pops the stack and you jump to, well, who knows?
Edit: As someone else pointed out, you're better off putting your PROC after your main code ends, instead of sticking it in the middle and jumping around it. But you've probably figured that out already :)
You should move the code of the procedure after the part where you exit the program (or follow egrunin's advice).
The reason for your segfault is that the code in the procedure is executed again after you first call it. During the second execution the code crashes on RET because there is no valid return address on the stack.