n-gram coverage discrepancy

[adrianherrera]

Hi Jinghan Wang and afl-sensitive authors,

We are currently having a discussion here regarding a possible discrepancy between the paper's description of the n-gram coverage calculation and implementation.

In summary, the paper describes n-gram coverage as left-shifting the prev_block_trans, while this shift is missing in the implementation. Are you able to shed any light on this?

Thanks!

[StarGazerM]

I am not the author but I guess shift is done here:

https://github.com/bitsecurerlab/afl-sensitive/blob/elf_and_lava/afl-n4/qemu_mode/patches/afl-qemu-cpu-inl.h#L259

and cur val generate here is assign to gram array's end position.

[vanhauser-thc]

@StarGazerM what you point out is a right shift, whereas the paper describes a left shift.