Quick introduction to reverse engineering for beginners

};
printf ("stepping=%d\n", tmp->stepping);
printf ("model=%d\n", tmp->model);
printf ("family_id=%d\n", tmp->family_id);
printf ("processor_type=%d\n", tmp->processor_type);
printf ("extended_model_id=%d\n", tmp->extended_model_id);
printf ("extended_family_id=%d\n", tmp->extended_family_id);
return 0;
After CPUID will fill EAX/EBX/ECX/EDX, these registers will be reflected in b[] array. Then, we have a
pointer to CPUID_1_EAX structure and we point it to EAX value from b[] array.
In other words, we treat 32-bit int value as a structure.
Then we read from the stucture.
Let’s compile it in MSVC 2008 with /Ox option:
_b$ = -16 ; size = 16
_main PROC
sub esp, 16 ; 00000010H
push ebx
xor ecx, ecx
mov eax, 1
cpuid
push esi
lea esi, DWORD PTR _b$[esp+24]
mov DWORD PTR [esi], eax
mov DWORD PTR [esi+4], ebx
mov DWORD PTR [esi+8], ecx
mov DWORD PTR [esi+12], edx
mov esi, DWORD PTR _b$[esp+24]
mov eax, esi
and eax, 15 ; 0000000fH
push eax
push OFFSET $SG15435 ; ’stepping=%d’, 0aH, 00H
call _printf
mov ecx, esi
shr ecx, 4
and ecx, 15 ; 0000000fH
push ecx
push OFFSET $SG15436 ; ’model=%d’, 0aH, 00H
call _printf
mov edx, esi
shr edx, 8
and edx, 15 ; 0000000fH
push edx
push OFFSET $SG15437 ; ’family_id=%d’, 0aH, 00H
call _printf
mov eax, esi
shr eax, 12 ; 0000000cH
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