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[2a01:cb08:8160:fc00:8902:d35:9cf3:dd66]) by smtp.gmail.com with ESMTPSA id d2sm3606309wrw.26.2021.12.17.05.52.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Dec 2021 05:52:05 -0800 (PST) Date: Fri, 17 Dec 2021 14:52:04 +0100 From: Paul Chaignon To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: bpf@vger.kernel.org, Quentin Monnet Subject: [PATCH bpf-next v2 1/2] libbpf: Probe for bounded loop support Message-ID: <7dfdf3f93467c619c14c40e957c54b87bb734294.1639748569.git.paul@isovalent.com> MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net This patch introduces a new probe to check whether the verifier supports bounded loops as introduced in commit 2589726d12a1 ("bpf: introduce bounded loops"). This patch will allow BPF users such as Cilium to probe for loop support on startup and only unconditionally unroll loops on older kernels. Reviewed-by: Quentin Monnet Signed-off-by: Paul Chaignon --- Changes in v2: - Resending to fix a format error. I had the good idea of saving the patch in Gmail as a draft before sending with mutt, which caused Gmail to remove the trailing space in the Git version signature. That then caused pathwork to generate an incorrect mbox file. tools/lib/bpf/libbpf.h | 1 + tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_probes.c | 20 ++++++++++++++++++++ 3 files changed, 22 insertions(+) diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 42b2f36fd9f0..3621aaaff67c 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -1058,6 +1058,7 @@ LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex); LIBBPF_API bool bpf_probe_helper(enum bpf_func_id id, enum bpf_prog_type prog_type, __u32 ifindex); LIBBPF_API bool bpf_probe_large_insn_limit(__u32 ifindex); +LIBBPF_API bool bpf_probe_bounded_loops(__u32 ifindex); /* * Get bpf_prog_info in continuous memory diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index b3938b3f8fc9..059d168452d7 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -423,6 +423,7 @@ LIBBPF_0.6.0 { LIBBPF_0.7.0 { global: bpf_btf_load; + bpf_probe_bounded_loops; bpf_program__log_buf; bpf_program__log_level; bpf_program__set_log_buf; diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c index 4bdec69523a7..e5bd691059e4 100644 --- a/tools/lib/bpf/libbpf_probes.c +++ b/tools/lib/bpf/libbpf_probes.c @@ -356,3 +356,23 @@ bool bpf_probe_large_insn_limit(__u32 ifindex) return errno != E2BIG && errno != EINVAL; } + +/* + * Probe for bounded loop support introduced in commit 2589726d12a1 + * ("bpf: introduce bounded loops"). + */ +bool bpf_probe_bounded_loops(__u32 ifindex) +{ + struct bpf_insn insns[4] = { + BPF_MOV64_IMM(BPF_REG_0, 10), + BPF_ALU64_IMM(BPF_SUB, BPF_REG_0, 1), + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, -2), + BPF_EXIT_INSN() + }; + + errno = 0; + probe_load(BPF_PROG_TYPE_SOCKET_FILTER, insns, ARRAY_SIZE(insns), NULL, + 0, ifindex); + + return !errno; +}