Help/Support Arm to hex conversion then back to arm instruction seems weird

i0s_tweak3r · July 3, 2017

I'm trying to hack the number of saves in a game so it doesn't increment. It appears I found the right instruction, which originally read,

ADDS R0, #1 at text: 000520FA

I wanted to get offset, original value, and hacked value, so I highlighted entire instruction, hit "patch program/change word" in IDA, and it gave me offset, original value, then I entered my hacked hex that armconverter gave me when I entered

ADDS R0, #0 (Trying to add value of zero into Register 0 instead of incrementing 1)

Armconverter gave me the hex:

0xE2911000 for that instruction

After entering that change, the resulting instruction in IDA (The ASRS that's highlighted) is totally different. Any help would be greatly appreciated.

Edited to add: I'm using an arm64 binary, IDA x64, but used the 32 bit segment of armconverter because it's a 32 bit instruction.

Updated July 3, 2017 by i0s_tweak3r
img

Rook · July 3, 2017

Is that a thumb or arm binary?

i0s_tweak3r · July 3, 2017

37 minutes ago, DiDA said:

Is that a thumb or arm binary?

I think I see where I messed up. The thumb hex output is 0x0030, which is closer to original value. It's thumb-2 I guess. That changes instruction to

MOVS R0, R6

If whatever's in R6=0, or the same value as before incrementing, it may be correct.

To answer question,

When I loaded binary it said it had both arm and thumb instructions. I thought maybe since the game was old that's why it didn't look like a typical arm64 binary.

Also when trying to thin binary it gave "must be fat file" error typical of apps I download and crack on my arm64 device.

Going to test binary patch to see if it works...

Updated July 3, 2017 by i0s_tweak3r
Answering question better

xiaov · July 3, 2017

Arm64 must use arm64 armconveter, imposibble armv7

But to r0, it is armv7 register..

i0s_tweak3r · July 3, 2017

Instead of trying to change instruction to ADDS R0, #0 would it be better to just NOP it? I prolly should've done that in the first place... (Since the instruction is telling it to do something I don't want to happen, and it should keep the R0 at same value then.)

xiaov · July 3, 2017

1 hour ago, i0s_tweak3r said:

Instead of trying to change instruction to ADDS R0, #0 would it be better to just NOP it? I prolly should've done that in the first place... (Since the instruction is telling it to do something I don't want to happen, and it should keep the R0 at same value then.)

Mov r0,#0 = 0020

nop = c046