Nsryjdtyk

For malware analysis purpose, i need to log some variables by modifying smali codes. I thought it would be a good idea to write a static logger method and add it to every class where i want to log some variable and then calling it inside other methods. As i have to make sure that i don't modify caller's registers, i came up with two options to write such a logger method:

1. As methods usually use v0 to v15 registers, i can use registers vx where 15<x<256 by declaring .registers 256 in logger method but as stated here, some instructions can accept only first 16 registers. For example invoke-static uses 4 bits to encode each parameter register so i can not pass it registers like v50 or so. So i need to use invoke-static/range instead. I don't know where to look and find other instructions with such limitation. (Actually i read Dalvik instruction format but couldn't understand it)


2. In the beginning of the logger method, save first 16 registers inside some unused range such as v100-v115, do what i want with first 16 registers and at end of logger method, load back actual values of first 16 registers from that unused range.

Any comment on pros/cons of each option? Actually i prefer option 1 as it provides more registers and is easier to implement but i don't know if it can make problems with some instructions.