Reverse Engineering for Beginners

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

POP {r4,pc}

ENDP

||f_div|| PROC
PUSH {r4,lr}
BL __aeabi_uldivmod
POP {r4,pc}
ENDP

||f_rem|| PROC
PUSH {r4,lr}
BL __aeabi_uldivmod
MOV r0,r2
MOV r1,r3
POP {r4,pc}
ENDP

24.3.3 MIPS.

Optimizing GCC for MIPS can generate 64-bit multiplication code, but has to call a library routine for 64-bit division:

Listing 24.13: Optimizing GCC 4.4.5 (IDA)

f_mul:
mult $a2, $a1
mflo $v0
or $at, $zero ; NOP
or $at, $zero ; NOP
mult $a0, $a3
mflo $a0
addu $v0, $a0
or $at, $zero ; NOP
multu $a3, $a1
mfhi $a2
mflo $v1
jr $ra
addu $v0, $a2

f_div:

var_10 = -0x10
var_4 = -4

lui $gp, (__gnu_local_gp >> 16)

addiu $sp, -0x20

la $gp, (__gnu_local_gp & 0xFFFF)

sw $ra, 0x20+var_4($sp)

sw $gp, 0x20+var_10($sp)

lw $t9, (__udivdi3 & 0xFFFF)($gp)

or $at, $zero

jalr $t9

or $at, $zero

lw $ra, 0x20+var_4($sp)

or $at, $zero

jr $ra

addiu $sp, 0x20

f_rem:

var_10 = -0x10
var_4 = -4

lui $gp, (__gnu_local_gp >> 16)

addiu $sp, -0x20

la $gp, (__gnu_local_gp & 0xFFFF)

sw $ra, 0x20+var_4($sp)

sw $gp, 0x20+var_10($sp)

lw $t9, (__umoddi3 & 0xFFFF)($gp)

or $at, $zero