bpftool: Reimplement large insn size limit feature probing

Reimplement bpf_probe_large_insn_limit() in bpftool, as that libbpf API
is scheduled for deprecation in v0.8.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/bpf/20211217171202.3352835-4-andrii@kernel.org

diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index 5397077..6719b92 100644 (file)
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -642,12 +642,32 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
                printf("\n");
 }
 
-static void
-probe_large_insn_limit(const char *define_prefix, __u32 ifindex)
+/*
+ * Probe for availability of kernel commit (5.3):
+ *
+ * c04c0d2b968a ("bpf: increase complexity limit and maximum program size")
+ */
+static void probe_large_insn_limit(const char *define_prefix, __u32 ifindex)
 {
+       LIBBPF_OPTS(bpf_prog_load_opts, opts,
+               .prog_ifindex = ifindex,
+       );
+       struct bpf_insn insns[BPF_MAXINSNS + 1];
        bool res;
+       int i, fd;
+
+       for (i = 0; i < BPF_MAXINSNS; i++)
+               insns[i] = BPF_MOV64_IMM(BPF_REG_0, 1);
+       insns[BPF_MAXINSNS] = BPF_EXIT_INSN();
+
+       errno = 0;
+       fd = bpf_prog_load(BPF_PROG_TYPE_SCHED_CLS, NULL, "GPL",
+                          insns, ARRAY_SIZE(insns), &opts);
+       res = fd >= 0 || (errno != E2BIG && errno != EINVAL);
+
+       if (fd >= 0)
+               close(fd);
 
-       res = bpf_probe_large_insn_limit(ifindex);
        print_bool_feature("have_large_insn_limit",
                           "Large program size limit",
                           "LARGE_INSN_LIMIT",