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From:   =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
To:     Pu Lehui <pulehui@huaweicloud.com>, bpf@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Pu Lehui <pulehui@huawei.com>,
        Pu Lehui <pulehui@huaweicloud.com>
Subject: Re: [PATCH bpf v3] riscv, bpf: Emit fixed-length instructions for
 BPF_PSEUDO_FUNC
In-Reply-To: <20221206091410.1584784-1-pulehui@huaweicloud.com>
References: <20221206091410.1584784-1-pulehui@huaweicloud.com>
Date:   Tue, 06 Dec 2022 11:57:55 +0100
Message-ID: <87fsds240c.fsf@all.your.base.are.belong.to.us>
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Pu Lehui <pulehui@huaweicloud.com> writes:

> From: Pu Lehui <pulehui@huawei.com>
>
> For BPF_PSEUDO_FUNC instruction, verifier will refill imm with
> correct addresses of bpf_calls and then run last pass of JIT.
> Since the emit_imm of RV64 is variable-length, which will emit
> appropriate length instructions accorroding to the imm, it may
> broke ctx->offset, and lead to unpredictable problem, such as
> inaccurate jump. So let's fix it with fixed-length instructions.
>
> Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
> Signed-off-by: Pu Lehui <pulehui@huawei.com>
> Suggested-by: Bj=C3=B6rn T=C3=B6pel <bjorn@rivosinc.com>

Thank you!

Acked-by: Bj=C3=B6rn T=C3=B6pel <bjorn@kernel.org>
Reviewed-by: Bj=C3=B6rn T=C3=B6pel <bjorn@kernel.org>