On Mon, 9 Dec 2019 at 22:08, Luke Nelson <lukenels@xxxxxxxxxxxxxxxxx> wrote: > > On Mon, Dec 9, 2019 at 9:32 AM Björn Töpel <bjorn.topel@xxxxxxxxx> wrote: > > > > This commit adds branch relaxation to the BPF JIT, and with that > > support for far (offset greater than 12b) branching. > > > > The branch relaxation requires more than two passes to converge. For > > most programs it is three passes, but for larger programs it can be > > more. > > > > Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx> > > We have been developing a formal verification tool for BPF JIT > compilers, which we have used in the past to find bugs in the RV64 > and x32 BPF JITs: > > https://unsat.cs.washington.edu/projects/serval/ > > Recently I added support for verifying the JIT for branch and jump > instructions, and thought it a good opportunity to verify these > patches that add support for far jumps and branching. > > I ported these patches to our tool and ran verification, which > didn't find any bugs according to our specification of BPF and > RISC-V. > > The tool and code are publicly available, and you can read a more > detailed writeup of the results here: > > https://github.com/uw-unsat/bpf-jit-verif/tree/far-jump-review > > Currently the tool works on a manually translated version of the > JIT from C to Rosette, but we are experimenting with ways of making > this process more automated. > > > Reviewed-by: Luke Nelson <lukenels@xxxxxxxxxxxxxxxxx> > Cc: Xi Wang <xi.wang@xxxxxxxxx> Wow! Very cool! Thanks a bunch for this!
