netdev - [PATCH bpf 0/2] Limit tail calls to 33 in all JIT compilers

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Message-ID: <cover.1575916815.git.paul.chaignon@gmail.com>
Date:   Mon, 9 Dec 2019 19:51:52 +0100
From:   Paul Chaignon <paul.chaignon@...nge.com>
To:     Paul Burton <paulburton@...nel.org>,
        Björn Töpel <bjorn.topel@...il.com>
Cc:     Mahshid Khezri <khezri.mahshid@...il.com>, paul.chaignon@...il.com,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf 0/2] Limit tail calls to 33 in all JIT compilers

The BPF interpreter and all JIT compilers, except RISC-V's and MIPS',
enforce a 33-tail calls limit at runtime.  Because of this discrepancy, a
BPF program can have a different behavior and output depending on whether
it is interpreted or JIT compiled, or depending on the underlying
architecture.

This patchset changes the RISC-V and MIPS JIT compilers to limit tail
calls to 33 instead of 32.  I have checked other BPF JIT compilers for the
same discrepancy.

Paul Chaignon (2):
  bpf, riscv: limit to 33 tail calls
  bpf, mips: limit to 33 tail calls

 arch/mips/net/ebpf_jit.c      | 9 +++++----
 arch/riscv/net/bpf_jit_comp.c | 4 ++--
 2 files changed, 7 insertions(+), 6 deletions(-)

-- 
2.17.1