libbpf: Skip bpf_object__probe_loading for light skeleton

mainline inclusion
from mainline-5.14-rc1
commit f9bceaa5
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f9bceaa59c5c47a8a08f48e19cbe887e500a1978

-------------------------------------------------

I'm getting the following error when running 'gen skeleton -L' as
regular user:

libbpf: Error in bpf_object__probe_loading():Operation not permitted(1).
Couldn't load trivial BPF program. Make sure your kernel supports BPF
(CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is set to big enough
value.

Fixes: 67234743 ("libbpf: Generate loader program out of BPF ELF file.")
Signed-off-by: NStanislav Fomichev <sdf@google.com>
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210521030653.2626513-1-sdf@google.com
(cherry picked from commit f9bceaa5)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/libbpf.c

@@ -4013,6 +4013,9 @@ bpf_object__probe_loading(struct bpf_object *obj)
 	};
 	int ret;
 
+	if (obj->gen_loader)
+		return 0;
+
 	/* make sure basic loading works */
 
 	memset(&attr, 0, sizeof(attr));