Linux assembly: Printing date and time

[bubu]

Hello, I'm trying to print date and time in linux usign GAS (GNU assembler). I started from a hello world code and I modified to show system date and time.

I'm stuck in two very basic errors I can't seem to find solution. Here's the code:

##############################################################################
## getdatetime.s															##
##																			##
## Compile with:															##
## as -o getdatetime.o getdatetime.s && ld -o getdatetime -O0 getdatetime.o	##
##																			##
##############################################################################
	.section .data
	.section .text
	.globl _start

_start:
	# call function to print date and time
	jmp		print_date_time

	## terminate program via _exit () system call 
	xorl	%eax,		%eax	# %eax = 0
	incl	%eax				# %eax = 1 system call _exit ()
	xorl	%ebx,		%ebx	# %ebx = 0 normal program return code
	int		$0x80				# execute system call _exit ()

## get system date and time and push it in stack: sec/min/hour/day/mon/year
print_date_time:
	movl	$78,		%eax	# getdatetime () system call
	int		$0x80				# execute system call getdatetime ()
	addl	$0x48,		%eax	# convert to ascii value
	mov		%al,		%ecx	# print %al to see if we have something interesting in it (sec, min, hour, day, mon, year) or something
	movl	$1,			%edx	# %edx = 1 = print length
	movl	$4,			%eax	# write () system call
	int $0x80					# execute write () system call
	ret

When I compile with

as -o getdatetime.o getdatetime.s && ld -o getdatetime -O0 getdatetime.o

It gives me an error:

getdatetime.s: Assembler messages:
getdatetime.s:27: Error: suffix or operands invalid for `mov'

Line 27 is:

mov		%al,		%ecx	# print %al to see if we have something interesting in it (sec, min, hour, day, mon, year) or something

Thanks for your attention.

[bubu]

I changed line 27 to use eax instead. Now it compiles. But I get segmentation fault when I run the program!

Code currently is:

    .section .data
    .section .text
    .globl _start

_start:
    # call function to print date and time
    jmp        print_date_time

    ## terminate program via _exit () system call 
    xorl    %eax,        %eax    # %eax = 0
    incl    %eax                # %eax = 1 system call _exit ()
    xorl    %ebx,        %ebx    # %ebx = 0 normal program return code
    int        $0x80                # execute system call _exit ()

## get system date and time and push it in stack: sec/min/hour/day/mon/year
print_date_time:
    movl    $0x78,        %eax    # getdatetime () system call
    int        $0x80                # execute system call getdatetime ()
    addl    $0x48,        %eax    # convert to ascii value
    movl    %eax,        %ecx    # print %eax to see if we have something interesting in it (sec, min, hour, day, mon, year) or something
    movl    $4,            %edx    # %edx = 1 = print length
    movl    $4,            %eax    # write () system call
    int $0x80                    # execute write () system call
    ret

[olivthill2]

mov is Intel syntax and movl is AT&T syntax
See http://asm.sourceforge.net/articles/linasm.html

With AT&T syntax, the fourth letter, just after mov can be b for a byte (8 bits), w for a word (16 bits), or l for a long word (32 bits).