[es] - Read and print int u assembly (MIPS) programu

vidonk
Slobodan Vidovic
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Read and print int u assembly (MIPS) programu

^{28.03.2017. u 18:42 - pre 98 meseci}

Pokušavam da napišem program koji će da sačuva unesen cio broj i kasnije da ga "odštampa" u konzoli.
Prvi poblem sa kojim se susrećem jeste koji sistemski call da pozovem a koji je definisan u /usr/mips-linux-gnu/include/asm/unistd.h.

Code:
#ifndef _ASM_UNISTD_H
#define _ASM_UNISTD_H

#include <asm/sgidefs.h>

#if _MIPS_SIM == _MIPS_SIM_ABI32

/*
* Linux o32 style syscalls are in the range from 4000 to 4999.
*/
#define __NR_Linux            4000
#define __NR_syscall            (__NR_Linux +    0)
#define __NR_exit            (__NR_Linux +    1)
#define __NR_fork            (__NR_Linux +    2)
#define __NR_read            (__NR_Linux +    3)
#define __NR_write            (__NR_Linux +    4)
#define __NR_open            (__NR_Linux +    5)
#define __NR_close            (__NR_Linux +    6)

Mislim da je to __NR_read I stvarno nakon

Code:
#Raad the integer and save it in s0
    li    v0,__NR_read
    syscall
    move s0, v0

program čeka da se unese input, dobro ja unesem recimo proj 9 ali u registru v0 i s0 nalazi se 0x2 ?

EDIT:

Ovako našao sam ovo

Code:
asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count);

to su dake argumenti koje zahtjeva __NR_read, dobro ovu bi bila moja pitanja
1. prvi argument je fd znači za stdin je 0 ?
2. drugi argument je char __user *buf to znači da je pointer prema bufferu, pointer prema nekoj memorijskoj lokaciji ? Probao sam da stavim ovako

Code:
#Read the integer and save it in s0
    nop
    nop
    li    a0,0        # firs argument, for stdin is 0 ISTR, see "man 2 read"
    la    a1,(var1)    # second argument load adress of var1 in to a1
    li    a2,10     # third argument is count of byts
    li    v0,__NR_read
    syscall
    .data
    var1:       .space    12

ali dobijam SIGSEGV, Segmentation fault.
3. treći argument je size_t count znači neki broj ? ali čega ?

_{[Ovu poruku je menjao vidonk dana 29.03.2017. u 15:16 GMT+1]}

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Branimir Maksimovic

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Re: Read and print int u assembly (MIPS) programu

^{29.03.2017. u 03:01 - pre 98 meseci}

Mislim da treba da napravis da podaci budu u writeable .data sekciji. Kako to da uradis u ovom asembleru, ne znam, ali trazi u tom pravcu.

edit: wuick google mi je dao ovo:
.data # Tells assembler we're in the data segment
val: .word 10, -14, 30 # Three words placed in memory

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vidonk
Slobodan Vidovic
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Re: Read and print int u assembly (MIPS) programu

^{29.03.2017. u 14:24 - pre 98 meseci}

Citat:

Branimir Maksimovic: Mislim da treba da napravis da podaci budu u writeable .data sekciji. Kako to da uradis u ovom asembleru, ne znam, ali trazi u tom pravcu.

edit: wuick google mi je dao ovo:
.data # Tells assembler we're in the data segment
val: .word 10, -14, 30 # Three words placed in memory

Pozdrav Branimire,

pa stavio sam u writable data sekciju var1 .space20 koja zauzima 20 bajta, i probao da stavim memorijsku lokaciju od var1 kao drugi argument

Code:

la a1,0(var1)

ali dobijam Program received signal SIGSEGV, Segmentation fault. stvarno ne znam šta da stavim i kako kao drugi argument

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Branimir Maksimovic

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Re: Read and print int u assembly (MIPS) programu

^{29.03.2017. u 14:38 - pre 98 meseci}

Ah pa sta ide posle syscall? Moras da pozoves sys_exit.

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vidonk
Slobodan Vidovic
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Re: Read and print int u assembly (MIPS) programu

^{29.03.2017. u 21:48 - pre 98 meseci}

Riješio sam evo ga cio program, imao sam neke "zaostale" naredbe koje su prouzrokovale segm. fault

Code:
/*
* hello-1.2/Makefile
*
* This file is subject to the terms and conditions of the GNU General Public
* License.  See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1995, 1997 by Ralf Baechle
*/
#include <regdef.h>
#include <sys/asm.h>
#include <sys/syscall.h>

EXPORT(__start)

    .set    noreorder
    LEAF(main)

#Prompt for the integer to enter
    li    a0,1        # first argument fd 1 for iutput
    la    a1,prompt    # second argument memory location of hello string
    li    a2,20        # lenght of string to print
    li    v0,__NR_write    # syscall write,they are defined in unistd.h
    syscall

#Read the integer and save it in s0
    nop
    nop
    li    a0,0        # firs argument, for stdin is 0 ISTR, see "man 2 read"
    la    a1,(var1)    # second argument load adress of var1 into a1
    li    a2,12     # third argument is count of byts
    li    v0,__NR_read
    syscall
    move t0, v0

#Print the message
    li    a0,1        # first argument fd 1
    la    a1,output    # second argument memory location of hello string
    li    a2,256        # lenght of string to print
    li    v0,__NR_write    # syscall write,they are defined in unistd.h
    syscall

#Output the number
    nop
    nop

quit:            # label quit
    li    v0,__NR_exit    # load system call for exit in v0
    syscall

    nop

    END(main)

    .data

prompt:    .asciiz    "Enter an intriger: "
output:    .asciiz    "\nYou typed the number "
var1:       .space     256

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