From: Paul Chaignon <paul@isovalent.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org, Quentin Monnet <quentin@isovalent.com>
Subject: [PATCH bpf-next 1/2] libbpf: Probe for bounded loop support
Date: Fri, 17 Dec 2021 13:12:19 +0100 [thread overview]
Message-ID: <CAHMuVOB16tif6TRjdNVN9YjGc-UpOOwuo35SM+vY7Bf5=1+oiQ@mail.gmail.com> (raw)
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 <quentin@isovalent.com>
Signed-off-by: Paul Chaignon <paul@isovalent.com>
---
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;
+}
--
2.25.1
next reply other threads:[~2021-12-17 12:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 12:12 Paul Chaignon [this message]
2021-12-17 16:12 ` [PATCH bpf-next 1/2] libbpf: Probe for bounded loop support Andrii Nakryiko
2021-12-17 19:22 ` Paul Chaignon
2021-12-17 19:41 ` Andrii Nakryiko
2021-12-17 21:11 ` Paul Chaignon
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