大会的64位NASM [英] Assembly 64-bit NASM

问题描述

我在做一个凸出。在64位的NASM。我要十进制转换为二进制和二进制到十进制。

I am doing a proj. in 64-bit NASM. I have to convert decimal to binary and binary to decimal.

我不断收到分段错误，当我调用printf调试后。

I keep getting segmentation fault after debugging when i call printf.

    extern printf

section .bss
decsave:    resd    2   ; stores dec->bin conversion
binsave:    resd    1  

section .data       ; preset constants, writeable
dec1:    db '1','2','4','.','3','7','5',0
bin1:    dq  01010110110101B ; 10101101.10101 note where binary point should be
ten:     dq     10
debug:  db "debug 124 is %ld", 10, 0

section .text       ; instructions, code segment
    global   main       ; for gcc standard linking
main:               ; label
    push    rbp             ; save rbp

;parse and convert integer portion of dec->bin     
        mov     rax,0       ; accumulate value here
        mov     al,[dec1]   ; get first ASCII digit
        sub     al,48       ; convert ASCII digit to binary
        mov     rbx,0           ; clear register (upper part)
        mov     bl,[dec1+1]     ; get next ASCII digit
        sub     rbx,48          ; convert ASCII digit to binary
        imul    rax,10          ; ignore rdx
        add     rax,rbx         ; increment accumulator
    mov rbx,0
    mov bl,[dec1+2]
    sub rbx,48
    imul    rax,10
    add rax,rbx
    mov [decsave],rax   ; save decimal portion

        mov rdi, debug
    mov rsi, [decsave]
    mov rax,0
    call    printf  

    ; return using c-style pops to return stack to correct position 
; and registers to correct content

        pop     rbp
    mov rax,0       
        ret                     ; return





; print the bits in decsave:
        section .bss
abits:  resb    17              ; 16 characters & zero terminator

    section .data
fmts:   db      "%s",0


section .text
; shift decimal portion into abits as ascii
        mov     rax,[decsave]   ; restore rax to dec. portion
        mov     rcx,8           ; for printing 1st 8 bits
loop3: mov     rdx,0           ; clear rdx ready for a bit
        shld    rdx,rax,1       ; top bit of rax into rdx
        add     rdx,48          ; make it ASCII
        mov     [abits+rcx-1],dl ; store character
        ror     rax,1           ; next bit into top of rax
        loop    loop3          ; decrement rcx, jump non zero

        mov     byte [abits+7],'.' ; end of dec. portion string
        mov     byte [abits+8],0   ; end of "C" string
        push    qword abits     ; string to print
        push    qword fmts      ; "%s"
        call    printf
        add     rsp,8

    mov     rax,[decsave+16]     ; increment to fractional portion
    mov     rcx,16       ; for printing 3 bits as required in the directions


loop4: mov     rdx,0           ; clear rdx ready for a bit
        shld    rdx,rax,1       ; top bit of rax into rdx
        add     rdx,48          ; make it ASCII
        mov     [abits+rcx-1],dl ; store character
        ror     rax,1           ; next bit into top of rax
        loop    loop4          ; decrement rcx, jump non zero

        mov     byte [abits+3],10 ; end of "C" string at 3 places
        mov     byte [abits+4],0 ; end of "C" string
        push    qword abits     ; string to print
        push    qword fmts      ; "%s"
        call    printf
        add     rsp,8

有没有任何其他的方法来解决它？

Is there a any other way to get around it?

感谢你。

推荐答案

随着小丑指出，如果可变参数的功能没有使用SSE，然后人必须是零。还有一个更大的问题在这里：

As Jester pointed out, if the vararg function is not using sse, then al must be zero. There is a bigger issue here:

随着X86-64调用约定，参数不栈上传递的，因为他们是32位的，但通过寄存器，而不是通过。哪些寄存器都取决于何种操作系统您的程序书面。

With the x86-64 calling convention, parameters are not passed on the stack as they are for 32bit, but instead passed through registers. Which registers all depend on what OS your program is written for.

的x86调用约定

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