Messages in this thread | | | Subject | Re: [PATCH bpf-next 1/2] libbpf: Add probe for large INSN limit | From | Daniel Borkmann <> | Date | Mon, 6 Jan 2020 23:52:17 +0100 |
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On 12/27/19 12:06 PM, Michal Rostecki wrote: > Introduce a new probe which checks whether kernel has large maximum > program size (1M) which was increased in commit c04c0d2b968a ("bpf: > increase complexity limit and maximum program size"). > > Based on the similar check in Cilium[0], authored by Daniel Borkmann. > > [0] https://github.com/cilium/cilium/commit/657d0f585afd26232cfa5d4e70b6f64d2ea91596 > > Co-authored-by: Daniel Borkmann <daniel@iogearbox.net> > Signed-off-by: Michal Rostecki <mrostecki@suse.de> > --- > tools/lib/bpf/libbpf.h | 1 + > tools/lib/bpf/libbpf.map | 1 + > tools/lib/bpf/libbpf_probes.c | 23 +++++++++++++++++++++++ > 3 files changed, 25 insertions(+) > > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h > index fe592ef48f1b..26bf539f1b3c 100644 > --- a/tools/lib/bpf/libbpf.h > +++ b/tools/lib/bpf/libbpf.h > @@ -521,6 +521,7 @@ LIBBPF_API bool bpf_probe_prog_type(enum bpf_prog_type prog_type, > 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); > > /* > * Get bpf_prog_info in continuous memory > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map > index e9713a574243..b300d74c921a 100644 > --- a/tools/lib/bpf/libbpf.map > +++ b/tools/lib/bpf/libbpf.map > @@ -219,6 +219,7 @@ LIBBPF_0.0.7 { > bpf_object__detach_skeleton; > bpf_object__load_skeleton; > bpf_object__open_skeleton; > + bpf_probe_large_insn_limit; > bpf_prog_attach_xattr; > bpf_program__attach; > bpf_program__name; > diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c > index a9eb8b322671..925f95106a52 100644 > --- a/tools/lib/bpf/libbpf_probes.c > +++ b/tools/lib/bpf/libbpf_probes.c > @@ -17,6 +17,8 @@ > #include "libbpf.h" > #include "libbpf_internal.h" > > +#define INSN_REPEAT 4128 > + > static bool grep(const char *buffer, const char *pattern) > { > return !!strstr(buffer, pattern); > @@ -321,3 +323,24 @@ bool bpf_probe_helper(enum bpf_func_id id, enum bpf_prog_type prog_type, > > return res; > } > + > +/* > + * Probe for availability of kernel commit (5.3): > + * > + * c04c0d2b968a ("bpf: increase complexity limit and maximum program size") > + */ > +bool bpf_probe_large_insn_limit(__u32 ifindex) > +{ > + struct bpf_insn insns[INSN_REPEAT + 1]; > + int i;
Looks good, but lets test for 'BPF_MAXINSNS + 1' number of total insns, less arbitrary than 4128.
> + for (i = 0; i < INSN_REPEAT; i++) > + insns[i] = BPF_MOV64_IMM(BPF_REG_0, 1); > + insns[INSN_REPEAT] = BPF_EXIT_INSN(); > + > + errno = 0; > + probe_load(BPF_PROG_TYPE_SCHED_CLS, insns, ARRAY_SIZE(insns), NULL, 0, > + ifindex); > + > + return errno != E2BIG && errno != EINVAL; > +} >
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