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Message-ID: <CAMsOgNDumbU7EWmOpwUoXdM5QWZ8h=W5nG3_JTFU5Tju-ofg_A@mail.gmail.com> Date: Wed, 1 May 2019 15:59:22 +0100 From: Jiong Wang <jiong.wang@...ronome.com> To: Alexei Starovoitov <alexei.starovoitov@...il.com> Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Networking <netdev@...r.kernel.org>, bpf@...r.kernel.org, Jakub Kicinski <jakub.kicinski@...ronome.com>, "oss-drivers@...ronome.com" <oss-drivers@...ronome.com> Subject: Re: 32-bit zext time complexity (Was Re: [PATCH bpf-next] selftests/bpf: two scale tests) > > if you can craft a test that shows patch_insn issue before your set, > > then it's ok to hack bpf_fill_scale1 to use alu64. > > As described above, does the test_verifier 732 + jit blinding looks convincing? > > > I would also prefer to go with option 2 (new zext insn) for JITs. > > Got it. I followed option 2 and have sent out v5 with latests changes/fixes: The major changes are: - introduced BPF_ZEXT, even though it doesn't resolve insn patch in-efficient, but could let JIT back-ends do optimal code-gen, and the change is small, so perhap just better to support it in this set. - while look insn patch code, I feel patched-insn need to be conservatiely marked if any insn inside patch buffer define sub-register. - Also fixed helper function return value handling bug. I am thinking helper function should have accurate return value type description, otherwise there could be bug. For example arm32 back-end just executes the native helper functions and doesn't do anything special on the return value. So a function returns u32 would only set native reg r0, not r1 in the pair. Then if the outside eBPF insn is casting it into u64, there needs to be zext. - adjusted test_verifier to make sure it could pass on hosts w and w/o hw zext. For more info, please see the cover letter and patch description at v5. Thanks. Regards, Jiong
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