Merge branch 'Typeless/weak ksym for gen_loader + misc fixups'

Kumar Kartikeya says:

====================

Patches (1,2,3,6) add typeless and weak ksym support to gen_loader. It is follow
up for the recent kfunc from modules series.

The later patches (7,8) are misc fixes for selftests, and patch 4 for libbpf
where we try to be careful to not end up with fds == 0, as libbpf assumes in
various places that they are greater than 0. Patch 5 fixes up missing O_CLOEXEC
in libbpf.

Changelog:
----------
v4 -> v5
v4: https://lore.kernel.org/bpf/20211020191526.2306852-1-memxor@gmail.com

 * Address feedback from Andrii
   * Drop use of ensure_good_fd in unneeded call sites
   * Add sys_bpf_fd
   * Add _lskel suffix to all light skeletons and change all current selftests
   * Drop early break in close loop for sk_lookup
   * Fix other nits

v3 -> v4
v3: https://lore.kernel.org/bpf/20211014205644.1837280-1-memxor@gmail.com

 * Remove gpl_only = true from bpf_kallsyms_lookup_name (Alexei)
 * Add bpf_dump_raw_ok check to ensure kptr_restrict isn't bypassed (Alexei)

v2 -> v3
v2: https://lore.kernel.org/bpf/20211013073348.1611155-1-memxor@gmail.com

 * Address feedback from Song
   * Move ksym logging to separate helper to avoid code duplication
   * Move src_reg mask stuff to separate helper
   * Fix various other nits, add acks
     * __builtin_expect is used instead of likely to as skel_internal.h is
       included in isolation.

v1 -> v2
v1: https://lore.kernel.org/bpf/20211006002853.308945-1-memxor@gmail.com

 * Remove redundant OOM checks in emit_bpf_kallsyms_lookup_name
 * Use designated initializer for sk_lookup fd array (Jakub)
 * Do fd check for all fd returning low level APIs (Andrii, Alexei)
 * Make Fixes: tag quote commit message, use selftests/bpf prefix (Song, Andrii)
 * Split typeless and weak ksym support into separate patches, expand commit
   message (Song)
 * Fix duplication in selftests stemming from use of LSKELS_EXTRA (Song)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>