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From: Luke Nelson <lukenels@cs.washington.edu>
To: "Björn Töpel" <bjorn.topel@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Netdev <netdev@vger.kernel.org>,
	linux-riscv@lists.infradead.org, bpf <bpf@vger.kernel.org>,
	Xi Wang <xi.wang@gmail.com>
Subject: Re: [PATCH bpf-next 2/8] riscv, bpf: add support for far branching
Date: Mon, 9 Dec 2019 13:08:34 -0800	[thread overview]
Message-ID: <CADasFoDOyJA0nDVCyA6EY78dHSSxxV+EXS=xUyLDW4_VhJvBkQ@mail.gmail.com> (raw)
In-Reply-To: <20191209173136.29615-3-bjorn.topel@gmail.com>

On Mon, Dec 9, 2019 at 9:32 AM Björn Töpel <bjorn.topel@gmail.com> 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@gmail.com>

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@cs.washington.edu>
Cc: Xi Wang <xi.wang@gmail.com>

  reply	other threads:[~2019-12-09 21:08 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-09 17:31 [PATCH bpf-next 0/8] riscv: BPF JIT fix, optimizations and far jumps support Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 1/8] riscv, bpf: fix broken BPF tail calls Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 2/8] riscv, bpf: add support for far branching Björn Töpel
2019-12-09 21:08   ` Luke Nelson [this message]
2019-12-09 21:27     ` Daniel Borkmann
2019-12-10  7:02       ` Luke Nelson
2019-12-10  5:32     ` Björn Töpel
2019-12-10  5:31   ` Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 3/8] riscv, bpf: add support for far jumps and exits Björn Töpel
2019-12-09 21:15   ` Luke Nelson
2019-12-09 17:31 ` [PATCH bpf-next 4/8] riscv, bpf: optimize BPF tail calls Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 5/8] riscv, bpf: provide RISC-V specific JIT image alloc/free Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 6/8] riscv, bpf: optimize calls Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 7/8] riscv, bpf: add missing uapi header for BPF_PROG_TYPE_PERF_EVENT programs Björn Töpel
2019-12-09 17:31 ` [PATCH bpf-next 8/8] riscv, perf: add arch specific perf_arch_bpf_user_pt_regs Björn Töpel

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