Reverse Engineering for Beginners

CHAPTER 21. STRUCTURES CHAPTER 21. STRUCTURES

mov eax, esi

and eax, 15

push eax

push OFFSET $SG15435 ; 'stepping=%d', 0aH, 00H

call _printf

mov ecx, esi

shr ecx, 4

and ecx, 15

push ecx

push OFFSET $SG15436 ; 'model=%d', 0aH, 00H

call _printf

mov edx, esi

shr edx, 8

and edx, 15

push edx

push OFFSET $SG15437 ; 'family_id=%d', 0aH, 00H

call _printf

mov eax, esi

shr eax, 12

and eax, 3

push eax

push OFFSET $SG15438 ; 'processor_type=%d', 0aH, 00H

call _printf

mov ecx, esi

shr ecx, 16

and ecx, 15

push ecx

push OFFSET $SG15439 ; 'extended_model_id=%d', 0aH, 00H

call _printf

shr esi, 20

and esi, 255

push esi

push OFFSET $SG15440 ; 'extended_family_id=%d', 0aH, 00H

call _printf

add esp, 48

pop esi

xor eax, eax

pop ebx

add esp, 16
ret 0
_main ENDP

TheSHRinstruction shifting the value inEAXby the number of bits that must beskipped, e.g., we ignore some bitsat the
right side.

TheANDinstruction clears the unneeded bitson the left, or, in other words, leaves only those bits in theEAXregister we
need.