On Tue, Jul 6, 2021 at 10:24 AM Martynas Pumputis <m@xxxxxxxxx> wrote: > > When loading a BPF program with a pinned map, the loader checks whether > the pinned map can be reused, i.e. their properties match. To derive > such of the pinned map, the loader invokes BPF_OBJ_GET_INFO_BY_FD and > then does the comparison. > > Unfortunately, on < 4.12 kernels the BPF_OBJ_GET_INFO_BY_FD is not > available, so loading the program fails with the following error: > > libbpf: failed to get map info for map FD 5: Invalid argument > libbpf: couldn't reuse pinned map at > '/sys/fs/bpf/tc/globals/cilium_call_policy': parameter > mismatch" > libbpf: map 'cilium_call_policy': error reusing pinned map > libbpf: map 'cilium_call_policy': failed to create: > Invalid argument(-22) > libbpf: failed to load object 'bpf_overlay.o' > > To fix this, probe the kernel for BPF_OBJ_GET_INFO_BY_FD support. If it > doesn't support, then fallback to derivation of the map properties via > /proc/$PID/fdinfo/$MAP_FD. > > Signed-off-by: Martynas Pumputis <m@xxxxxxxxx> The code looks good to me. Except a checkpatch CHECK: CHECK: Comparison to NULL could be written "!obj" #96: FILE: tools/lib/bpf/libbpf.c:3943: + if (obj == NULL || kernel_supports(obj, FEAT_OBJ_GET_INFO_BY_FD)) Also, I think this should target bpf-next tree? Thanks, Song
