Reverse Engineering for Beginners

CHAPTER 24. 64-BIT VALUES IN 32-BIT ENVIRONMENT CHAPTER 24. 64-BIT VALUES IN 32-BIT ENVIRONMENT

24.1.3 MIPS.

A 64-bit value is returned in the V0-V1 ($2-$3) register pair (V0 ($2) is for the high part and V1 ($3) for the low part):

Listing 24.3: Optimizing GCC 4.4.5 (assembly listing)

li $3,-1867841536 # 0xffffffff90ab0000

li $2,305397760 # 0x12340000

ori $3,$3,0xcdef

j $31

ori $2,$2,0x5678

Listing 24.4: Optimizing GCC 4.4.5 (IDA)

lui $v1, 0x90AB

lui $v0, 0x1234

li $v1, 0x90ABCDEF

jr $ra

li $v0, 0x12345678

24.2 Arguments passing, addition, subtraction

#include <stdint.h>

uint64_t f_add (uint64_t a, uint64_t b)
{
return a+b;
};

void f_add_test ()
{
#ifdef GNUC
printf ("%lld\n", f_add(12345678901234, 23456789012345));
#else
printf ("%I64d\n", f_add(12345678901234, 23456789012345));
#endif
};

uint64_t f_sub (uint64_t a, uint64_t b)
{
return a-b;
};

24.2.1 x86

Listing 24.5: Optimizing MSVC 2012 /Ob1

_a$ = 8 ; size = 8
_b$ = 16 ; size = 8
_f_add PROC
mov eax, DWORD PTR _a$[esp-4]
add eax, DWORD PTR _b$[esp-4]
mov edx, DWORD PTR _a$[esp]
adc edx, DWORD PTR _b$[esp]
ret 0
_f_add ENDP

_f_add_test PROC
push 5461 ; 00001555H
push 1972608889 ; 75939f79H
push 2874 ; 00000b3aH
push 1942892530 ; 73ce2ff_subH
call _f_add
push edx
push eax