assembly - Assembler stuck in sys_read loop -

-

i've written piece of code takes number in ascii characters prompt, converts decimal number , stores in 'dnumber'. conversion has been checked , goes well. goes wrong @ prompt. seems stuck in infinite loop while asking user ascii character number. want program stop asking input when user presses enter, termination value never seems reached though think i've set way.

i've asked 2 related questions on forum lately , showed don't understand system calls properly. i've read documentation on 'http://www.tutorialspoint.com/assembly_programming', 'http://cs.lmu.edu/~ray/notes/nasmtutorial/' , of 'http://www.x86-64.org/documentation/abi.pdf' , apparently i'm still not getting it. can show me light.

here compiler info:

nasm -f elf64 convinput.asm  ld -s -o convinput convinput.o

here prompt:

$ ./convinput enter number , press enter:  123  123 123

as can see i've pressed enter twice, prompt still asks input.

here code:

section     .text  global _start  _start:      mov     eax, 4     mov     ebx, 1     mov     edx, lenmsg1     mov     ecx, msg1     int     80h      xor     eax, eax     xor     ebx, ebx     xor     edx, edx     mov     esi, data     call    input      mov     esi, data     movzx   ecx, byte [dignum]     xor     ebx,ebx    ; clear ebx      call    string_to_int      mov     dword [dnumber], eax      mov     eax, 1     mov     ebx, 0     int     80h  input:     mov  eax, 3     mov  ebx, 0     mov  ecx, esi     mov  edx, 1     int  80h      inc  byte [dignum]     cmp  byte [esi], 13     inc  esi     jne  input     ret  string_to_int:   xor   ebx,ebx   movzx eax, byte [esi]   inc   esi   sub   al,'0'    ; convert ascii number4   mov   ebx, 10   mul   ebx   add   ebx,eax   ; ebx = ebx*10 + eax     dec   byte [dignum]   cmp   byte [dignum], 0   jne   string_to_int   mov   eax,ebx   ret   section .bss      dignum  resb 1     data    resb 1000     dnumber resd 1 section .data     msg1 db 'enter number , press enter: ', 10, 0     lenmsg1 equ $ -msg1      ; esi = pointer string convert     ; ecx = number of digits in string (must > 0)     ; output:     ; eax = integer valu

judging values put eax using 32-bit syscall table, on linux different 64-bit one.

you can see syscalls (and arguments) called running program under strace.


Comments

Post a Comment

Popular posts from this blog

ruby - Trying to change last to "x"s to 23 -

-
i have been playing around irb , have string looks this: irb(main):072:0> puts ["[\"4354 5432 5432 xxxxx\", \"6547 6547 8543 xxxxx\", \"2344 6543 6674 xxxxx\", \"2346 6236 7543 xxxxx\", \"1273 5585 5587 xxxxx\"]"] => nil irb(main):073:0> what want gsub last 2 "x" s of each 17 digit combination, 23 . what i've tried far (i've been using rubular): a.gsub(/\d[x]/,"23") <= grabs "x" s i'm close a.gsub(/\w[x{2}]/,"23") <= grabs "x" s grabs two digits each combination. is there easier way i'm not understanding? a.gsub(/\d{4} \d{4} \d{4} xxx\kxx/, '23') \d{4} = 4 digits what \k drop matched far. can use don't replace entire number, still able validate have in desired format.
Read more

jquery - Clone last and append item to closest class -

-
this bare-bones code on page: <div class="list-container"> <div class="single-list-item"> <button>remove</button> </div> <div class="single-list-item"> <button>remove</button> </div> <div class="single-list-item"> <button>remove</button> </div> </div> <p><button class="add-list-item">add</button></p> <div class="list-container"> <div class="single-list-item"> <button>remove</button> </div> <div class="single-list-item"> <button>remove</button> </div> <div class="single-list-item"> <button>remove</button> </div> </div> <p><button class="add-list-item">add</button></p> <di
Read more

c - Unrecognised emulation mode: elf_i386 on MinGW32 -

-
i'm trying make kernel, , cannot link c output assembly. ld . i'm getting error: unrecognized emulation mode: elf_i386 i'm using windows 10 professional mingw32 , msys. code using: link.ld /* * link.ld */ output_format(elf32-i386) entry(start) sections { . = 0x100000; .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss) } } kernel.c /* * kernel.c */ void kmain(void) { const char *str = "my first kernel"; char *vidptr = (char*)0xb8000; //video mem begins here. unsigned int = 0; unsigned int j = 0; /* loops clears screen * there 25 lines each of 80 columns; each element takes 2 bytes */ while(j < 80 * 25 * 2) { /* blank character */ vidptr[j] = ' '; /* attribute-byte - light grey on black screen */ vidptr[j+1] = 0x07; j = j + 2; } j = 0; /* loop writes string video memory */ while(str[j] != '\0') { /
Read more