Tutorial How To Convert "Non-Convertable" Instructions on ARMConverter.com!

Rook · February 9, 2017

Today I'll be showing you guys and girls how you can convert some instructions which ARMConverter.com cannot convert. We'll still be using ARM Converter website to convert these instructions. This isn't really new as I wrote on the website the instructions you can follow but many didn't.

The most common instructions people want to convert are:

VLDR Sx, =xy.xy -> VLDR S0, =30.0
VSTR Sx, =xy.xy -> VSTR S0, =10.0
VCMP Sx, =xy.xy

etc.

The example we'll be using in this Tutorial is VLDR S16, =38.0 which controls the Zoom/FOV in-game and in order to modify that, we need to change the "38.0" but we cannot since ARM Converter doesn't recognise the instruction. BUT here's the workaround!

1. First of all, open IDA and get the hex value of that instruction.
9F ED 0F 8A = VLDR S16, =38.0

2. Now, open http://armconverter.com/hextoarm/ and enter the hex bytes then select whether it's a Thumb/ARM/ARM64 instruction and convert!

3. Hex To ARM Converter will display the same exact instruction in the output box, but "simplified" so that ARM Converter can read and convert it. This is because ARM To Hex and Hex To ARM are using different backends.

9F ED 0F 8A = VLDR S16, [PC, #0x3C]

Example: http://i.imgur.com/ScwmEhC.png

4. Now grab the instruction you got from Hex To ARM, modify if to your liking and then convert it back to hex using the ARM To Hex Converter.

In our case, we found out that "VLDR S16, [PC, #20]" was a good value for zooming in on the game. You need to modify the instruction a bit until you get what you need.

VLDR S16, [PC, #20] = 9F ED 05 8A

Example: http://i.imgur.com/JWnoL6b.png

5. Enter the new hex back into your binary/tweak and test.

That's it!