libbpf: Use page size as max_entries when probing ring buffer map

Using page size as max_entries when probing ring buffer map, else the
probe may fail on host with 64KB page size (e.g., an ARM64 host).

After the fix, the output of "bpftool feature" on above host will be
correct.

Before :
    eBPF map_type ringbuf is NOT available
    eBPF map_type user_ringbuf is NOT available

After :
    eBPF map_type ringbuf is available
    eBPF map_type user_ringbuf is available

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221116072351.1168938-2-houtao@huaweicloud.com
This commit is contained in:
Hou Tao 2022-11-16 15:23:48 +08:00 committed by Andrii Nakryiko
parent 47df8a2f78
commit 689eb2f1ba

View File

@ -234,7 +234,7 @@ static int probe_map_create(enum bpf_map_type map_type)
case BPF_MAP_TYPE_USER_RINGBUF:
key_size = 0;
value_size = 0;
max_entries = 4096;
max_entries = sysconf(_SC_PAGE_SIZE);
break;
case BPF_MAP_TYPE_STRUCT_OPS:
/* we'll get -ENOTSUPP for invalid BTF type ID for struct_ops */