Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200421002804.5118-1-luke.r.nels@gmail.com>
In-Reply-To: <20200421002804.5118-1-luke.r.nels@gmail.com>
From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Wed, 22 Apr 2020 22:29:04 -0700
Message-ID: <CAADnVQ+taVOr+Zr44eGgOoHXD6y-T-KBKco4KbFZ26jAOsa90A@mail.gmail.com>
Subject: Re: [PATCH bpf] bpf, riscv: Fix tail call count off by one in RV32
 BPF JIT
To:     Luke Nelson <lukenels@cs.washington.edu>
Cc:     bpf <bpf@vger.kernel.org>, Luke Nelson <luke.r.nels@gmail.com>,
        Xi Wang <xi.wang@gmail.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@gmail.com>,
        Network Development <netdev@vger.kernel.org>,
        linux-riscv@lists.infradead.org,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Apr 20, 2020 at 5:28 PM Luke Nelson <lukenels@cs.washington.edu> wrote:
>
> This patch fixes an off by one error in the RV32 JIT handling for BPF
> tail call. Currently, the code decrements TCC before checking if it
> is less than zero. This limits the maximum number of tail calls to 32
> instead of 33 as in other JITs. The fix is to instead check the old
> value of TCC before decrementing.
>
> Fixes: 5f316b65e99f ("riscv, bpf: Add RV32G eBPF JIT")
> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>

Applied. Thanks