x86 parity flag

pf.asm

; nasm -f macho -o pf.o
; ld pf.o
; ./a.out
;
; this probably works on linuxes too, i think exit and write should be the same.
;
; should produce:
;     tears (2)
; 00000246 <-- eax = 0, xor by 0
; 00000206 <-- xor ax, 0x0100
; 00000246 <-- eax = 0, xor by 0
; 00000202 <-- xor ah, 0x01. Parity flag cleared. :)

section .text

global start

start:
    mov eax, 0
    xor eax, 0
    pushfd
    call print_reg

    xor ax, 0x0100
    pushfd
    call print_reg

    mov eax, 0
    xor eax, 0
    pushfd
    call print_reg
    xor ah, 0x01
    pushfd
    call print_reg

    jmp end

print_reg:
    push eax
    mov eax, [esp + 0x8]
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4
    call print_high
    shl eax, 4

    push dword 1
    push dword newln
    push dword 1
    sub esp, 0x04
    mov eax, 0x04
    int 0x80
    add esp, 0x10

    pop eax
    ret

end:
skip:
    mov eax, 1
    push 0
    sub esp, 12
    int 0x80

print_high:
    push eax
    push ebx

    mov ebx, eax
    shr ebx, 28
    and ebx, 0x0f
    add ebx, hexdigits

    push dword 1
    push dword ebx
    push dword 1
    sub esp, 0x04

    mov eax, 0x04
    int 0x80

    add esp, 0x10
    pop ebx
    pop eax
    ret


section .data
newln db 0x0A
hexdigits db "0123456789abcdef"