termios in FASM

[ZeekyHBomb]

I wanted to get a bit into FASM. I already have some experience with another assembly-language, which would be for the myAVR micro-controller.

I tried getting unbuffered input from the standard-stream without using a library, but instead resorting to syscalls.
Apparently ioctl should do fine for this (I'm on Linux), though I seem to not get the termios-struct right.
Here's my code:

format elf executable

entry main

;syscalls
SYSCALL_EXIT	equ 1
SYSCALL_READ	equ 3
SYSCALL_IOCTL	equ 54

;standard I/O
STDIN	equ 0

;ioctl subfunctions
TCGETS	equ 0x5401
TCSETS	equ 0x5402

;struct termios
struc termios{
	.c_iflag rd 1 ;input mode flags
	.c_oflag rd 1 ;output mode flags
	.c_cflag rd 1 ;control mode flags
	.c_lflag rd 1 ;local mode flags
	.c_line rb 1 ;line discipline
	.c_cc rb 32 ;control characters
	.c_ispeed rd 1 ;input speed
	.c_ospeed rd 1 ;output speed
}

;termios flags
ICANON equ 2 ;Do erase and kill processing
ECHO equ 8 ;Enable echo

;static data
segment readable writable

oldtermios termios
newtermios termios

;--------
segment executable
main:
	;get old termios mode
	mov eax, SYSCALL_IOCTL
	mov ebx, STDIN
	mov ecx, TCGETS
	mov edx, oldtermios

	;copy termios
;	mov esi, oldtermios
;	mov edi, newtermios

;	mov ecx, 4
;	repz movs dword [edi], [esi]
;	mov ecx, 33
;	repz movs byte [edi], [esi]
;	mov ecx, 2
;	repz movs dword [edi], [esi]

	;set new termios
;	and dword [newtermios.c_lflag], not (ICANON or ECHO)
	mov eax, SYSCALL_IOCTL
	mov ebx, STDIN
	mov ecx, TCSETS
	mov edx, oldtermios ;newtermios
	int 0x80

	;get input
	mov eax, SYSCALL_READ
	mov ebx, STDIN
	mov ecx, esp
	mov edx, 1
	int 0x80

	;reset termios
	mov eax, SYSCALL_IOCTL
	mov ebx, STDIN
	mov ecx, TCSETS
	mov edx, oldtermios
;	int 0x80

	;exit
	mov eax, SYSCALL_EXIT
	mov ebx, 0
	int 0x80

I'm getting the termios and without modification setting it again, but input is broken after I assemble and run it. It also doesn't wait for any input upon launching.

Here's the struct as in /usr/include/bits/termios.h

typedef unsigned char	cc_t;
typedef unsigned int	speed_t;
typedef unsigned int	tcflag_t;

#define NCCS 32
struct termios
  {
    tcflag_t c_iflag;		/* input mode flags */
    tcflag_t c_oflag;		/* output mode flags */
    tcflag_t c_cflag;		/* control mode flags */
    tcflag_t c_lflag;		/* local mode flags */
    cc_t c_line;			/* line discipline */
    cc_t c_cc[NCCS];		/* control characters */
    speed_t c_ispeed;		/* input speed */
    speed_t c_ospeed;		/* output speed */
#define _HAVE_STRUCT_TERMIOS_C_ISPEED 1
#define _HAVE_STRUCT_TERMIOS_C_OSPEED 1
  };

And as a little side-question: is there a more convenient way of copying structs?

[ZeekyHBomb]

I don't have an account there, but since I have one here I thought I'd ask.
You're probably right though, there are not too many assembly-programmers (apart maybe from the Arduino guys; didn't follow their thread).

Copying the struct like this seems way too obvious. I guess I just was costumed to a C-way of thinking...
I will look into the struct macro,I just began FASM by looking at a NASM tutorial and getting some parts of the FASM manual ;)

[Agent766]

[QUOTE=ZeekyHBomb;22141906]You're probably right though, there are not too many assembly-programmers (apart maybe from the Arduino guys; didn't follow their thread).[/QUOTE]

Arduinos have a Wiring based language.

[turb_]

nasm supremacy

[jA_cOp]

If the struc and struct macros don't add alignment padding, try adding your own padding for the single-byte c_line field.

[ZeekyHBomb]

Nope. Tried adding 3 bytes before c_line, after, before the whole data and after the whole data.
I should try writing the contents of termios to file, write a C pendant and compare the two files.

[editline]07:55PM[/editline]

How do I access errno?
This code returns 1, though the file gets created

format elf executable

entry main

;syscalls
SYSCALL_EXIT	equ 1
SYSCALL_WRITE	equ 4
SYSCALL_CLOSE	equ 6
SYSCALL_CREAT	equ 8
SYSCALL_IOCTL	equ 54

;standard I/O
STDIN	equ 0

;open modes
S_IWUSR	equ 200 ;write permission
S_IRUSR equ 400 ;read permission

;ioctl subfunctions
TCGETS	equ 0x5401
TCSETS	equ 0x5402

;struct termios
struc termios{
	.c_iflag rd 1 ;input mode flags
	.c_oflag rd 1 ;output mode flags
	.c_cflag rd 1 ;control mode flags
	.c_lflag rd 1 ;local mode flags
	.c_line rb 1 ;line discipline
	.c_cc rb 32 ;control characters
	.c_ispeed rd 1 ;input speed
	.c_ospeed rd 1 ;output speed
	;.unused rb 3 ;3 byte padding
}

;termios flags
ICANON equ 2 ;Do erase and kill processing
ECHO equ 8 ;Enable echo

;static data
segment readable writeable

oldtermios termios
newtermios termios

filename db "termios.txt", 0
fd rd 1

;--------
segment executable
main:
	;open file
	mov eax, SYSCALL_CREAT
	mov ebx, filename
	mov ecx, S_IWUSR or S_IRUSR
	int 0x80
	mov ecx, 1 ;return code 1
	test eax, eax
	js exit
	mov [fd], eax

	;get old termios mode
	mov eax, SYSCALL_IOCTL
	mov ebx, STDIN
	mov ecx, TCGETS
	mov edx, oldtermios

	;write file
	mov eax, SYSCALL_WRITE
	mov ebx, fd
	mov ecx, oldtermios
	mov edx, 6 * 4 + 33
	int 0x80
	mov ecx, 1 ;return code 2
	test eax, 6 * 4 + 33
	jne exit
	mov ecx, 0 ;return code 0

exit:
	;close file
	mov eax, SYSCALL_CLOSE
	mov ebx, fd
	int 0x80

	;exit
	mov eax, SYSCALL_EXIT
	mov ebx, ecx
	int 0x80

[editline]10:56PM[/editline]

Okay, so I got around to the errno thanks to [url=http://www.lxhp.in-berlin.de/lhpsyscal.html]this page[/url]. The man-pages are only for C :(
It's stored (negated) in eax.
The fd after SYSCALL_WRITE shoulda been [fd].

So, now it writes 57 bytes, but all are 0.
There are indeed 3 bytes padding and after updating ... still all 0.
My C-version outputs a bunch of different bytes just fine.

[ZeekyHBomb]

Well, that was dumb. I was missing an int 0x80 after SYSCALL_IOCTL. In both assembly-files :P
Works fine now :D