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libbpf: Add probe for large INSN limit 

Introduce a new probe which checks whether kernel has large maximum
program size which was increased in the following commit:

c04c0d2b96 ("bpf: increase complexity limit and maximum program size")

Based on the similar check in Cilium[0], authored by Daniel Borkmann.

  [0] 657d0f585a

Co-authored-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Michal Rostecki <mrostecki@opensuse.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Link: https://lore.kernel.org/bpf/20200108162428.25014-2-mrostecki@opensuse.org
This commit is contained in:
Michal Rostecki 2020-01-08 17:23:52 +01:00 committed by Daniel Borkmann
parent 1ece2fbe9b
commit 5ff0512003
3 changed files with 23 additions and 0 deletions
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1
tools/lib/bpf/libbpf.h
View File

@ -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

1
tools/lib/bpf/libbpf.map
View File

@ -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;

21
tools/lib/bpf/libbpf_probes.c
View File

@ -321,3 +321,24 @@ 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[BPF_MAXINSNS + 1];
int i;
for (i = 0; i < BPF_MAXINSNS; i++)
insns[i] = BPF_MOV64_IMM(BPF_REG_0, 1);
insns[BPF_MAXINSNS] = BPF_EXIT_INSN();
errno = 0;
probe_load(BPF_PROG_TYPE_SCHED_CLS, insns, ARRAY_SIZE(insns), NULL, 0,
ifindex);
return errno != E2BIG && errno != EINVAL;
}