On 3/6/20 4:22 PM, John Fastabend wrote:
John Fastabend wrote:
It is not possible for the current verifier to track u32 alu ops and jmps
correctly. This can result in the verifier aborting with errors even though
the program should be verifiable. Cilium code base has hit this but worked
around it by changing int variables to u64 variables and marking a few
things volatile. It would be better to avoid these tricks.
Quick bit of clarification, originally I tried to just track u32 hence
the title and above u32 reference. After runnning some programs I realized
this wasn't really enough to handle all cases so I added the signed 32-bit
bounds tracker. If I missed some spots in the descriptions that was just
because I missed it in the proof reading here. u32 above should be 32-bit
subreg.
I also forgot to give Yonhong credit. Sorry Yonghong! The original alu ops
tracking patch came from him.
John, thanks for working on this! Hopefully this will resolve tricky
32bit subreg tracking issues. I will look at the RFC in the next couple
of days!
