On Tue, Apr 30, 2024 at 05:42:14PM GMT, Arnaldo Carvalho de Melo wrote:
> On Mon, Apr 29, 2024 at 04:46:00PM -0600, Daniel Xu wrote:
> > This commit teaches pahole to parse symbols in .BTF_ids section in
> > vmlinux and discover exported kfuncs. Pahole then takes the list of
> > kfuncs and injects a BTF_KIND_DECL_TAG for each kfunc.
> >
> > Example of encoding:
> >
> > $ bpftool btf dump file .tmp_vmlinux.btf | rg "DECL_TAG 'bpf_kfunc'" | wc -l
> > 121
> >
> > $ bpftool btf dump file .tmp_vmlinux.btf | rg 56337
> > [56337] FUNC 'bpf_ct_change_timeout' type_id=56336 linkage=static
> > [127861] DECL_TAG 'bpf_kfunc' type_id=56337 component_idx=-1
> >
> > This enables downstream users and tools to dynamically discover which
> > kfuncs are available on a system by parsing vmlinux or module BTF, both
> > available in /sys/kernel/btf.
> >
> > This feature is enabled with --btf_features=decl_tag,decl_tag_kfuncs.
>
> I'm trying this but:
>
> ⬢[acme@toolbox pahole]$ time pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
> btf_encoder__tag_kfuncs(cgroup_rstat_updated): found=0
> btf_encoder__tag_kfuncs(cgroup_rstat_flush): found=0
> btf_encoder__tag_kfuncs(security_file_permission): found=0
> btf_encoder__tag_kfuncs(security_inode_getattr): found=0
> btf_encoder__tag_kfuncs(security_file_open): found=0
> btf_encoder__tag_kfuncs(security_path_truncate): found=0
> btf_encoder__tag_kfuncs(vfs_truncate): found=0
> btf_encoder__tag_kfuncs(vfs_fallocate): found=0
> btf_encoder__tag_kfuncs(dentry_open): found=0
> btf_encoder__tag_kfuncs(vfs_getattr): found=0
> btf_encoder__tag_kfuncs(filp_close): found=0
> btf_encoder__tag_kfuncs(bpf_lookup_user_key): found=0
> btf_encoder__tag_kfuncs(bpf_lookup_system_key): found=0
> btf_encoder__tag_kfuncs(bpf_key_put): found=0
> btf_encoder__tag_kfuncs(bpf_verify_pkcs7_signature): found=0
> btf_encoder__tag_kfuncs(bpf_obj_new_impl): found=0
> <SNIP all with found=0>
>
> With:
>
> ⬢[acme@toolbox pahole]$ git diff -U16
> diff --git a/btf_encoder.c b/btf_encoder.c
> index c2df2bc7a374447b..27a16d6564381b60 100644
> --- a/btf_encoder.c
> +++ b/btf_encoder.c
> @@ -1689,32 +1689,35 @@ static int btf_encoder__tag_kfuncs(struct btf_encoder *encoder)
> func = get_func_name(name);
> if (!func)
> continue;
>
> /* Check if function belongs to a kfunc set */
> ranges = gobuffer__entries(&btf_kfunc_ranges);
> ranges_cnt = gobuffer__nr_entries(&btf_kfunc_ranges);
> found = false;
> for (j = 0; j < ranges_cnt; j++) {
> size_t addr = sym.st_value;
>
> if (ranges[j].start <= addr && addr < ranges[j].end) {
> found = true;
> break;
> }
> }
> +
> + printf("%s(%s): found=%d\n", __func__, func, found);
> +
> if (!found) {
> free(func);
> continue;
> }
>
> err = btf_encoder__tag_kfunc(encoder, &btf_funcs, func);
> if (err) {
> fprintf(stderr, "%s: failed to tag kfunc '%s'\n", __func__, func);
> free(func);
> goto out;
> }
> free(func);
> }
>
> err = 0;
> out:
>
> --------------
>
> The vmlinux I'm testing on has the kfuncs, etc, as we can see with:
>
> ⬢[acme@toolbox pahole]$ readelf -sW vmlinux | grep __BTF_ID__func__ | wc -l
> 517
> ⬢[acme@toolbox pahole]$ readelf -sW vmlinux | grep __BTF_ID__func__ | tail
> 97887: ffffffff83266bfc 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_cong_avoid__805493
> 97888: ffffffff83266c04 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_state__806494
> 97889: ffffffff83266c0c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_cwnd_event__807495
> 97890: ffffffff83266c14 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__cubictcp_acked__808496
> 98068: ffffffff83266c24 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_reno_ssthresh__773199
> 98069: ffffffff83266c2c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_reno_cong_avoid__774200
> 98070: ffffffff83266c34 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_reno_undo_cwnd__775201
> 98071: ffffffff83266c3c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_slow_start__776202
> 98072: ffffffff83266c44 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__tcp_cong_avoid_ai__777203
> 101522: ffffffff83266c5c 4 OBJECT LOCAL DEFAULT 15 __BTF_ID__func__update_socket_protocol__80024
> ⬢[acme@toolbox pahole]$
>
>
> So that btf_encoder__tag_kfuncs() isn't finding any?
>
> $ pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
> btf_encoder__tag_kfuncs(vmlinux)
>
> Yeah, getting the source filename, the right one.
>
> Then is_sym_kfunc_set() never returns true... But:
>
> ⬢[acme@toolbox pahole]$ time pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
> is_sym_kfunc_set(__BTF_ID__set8__bpf_rstat_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__key_sig_kfunc_set, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__generic_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__common_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_map_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__cpumask_kfunc_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_syscall_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_skb, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_xdp, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_sock_addr, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_sk_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__xdp_metadata_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_test_modify_return_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__test_sk_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__tcp_cubic_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_tcp_ca_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_mptcp_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__)
>
> real 0m5.586s
> user 0m29.707s
> sys 0m2.160s
> ⬢[acme@toolbox pahole]$
>
> And then:
>
> ⬢[acme@toolbox pahole]$ time pahole -j --btf_features=decl_tag,decl_tag_kfuncs --btf_encode_detached=vmlinux.btf.decl_tag,decl_tag_kfuncs vmlinux
> is_sym_kfunc_set(__BTF_ID__set8__bpf_rstat_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__key_sig_kfunc_set, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__generic_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__common_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_map_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__cpumask_kfunc_btf_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__hid_bpf_syscall_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_skb, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_xdp, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_kfunc_check_set_sock_addr, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_sk_iter_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__xdp_metadata_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_test_modify_return_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__test_sk_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__tcp_cubic_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_tcp_ca_check_kfunc_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
> is_sym_kfunc_set(__BTF_ID__set8__bpf_mptcp_fmodret_ids, BTF_ID_SET8_PFX=__BTF_ID__set8__, set->flags= 0, BTF_SET8_KFUNCS=1, ret=0)
set->flags=0 here is odd. I'd expect at least some of those to be
non-zero. Can you check if your tree has
https://github.com/torvalds/linux/commit/6f3189f38a3e995232e028a4c341164c4aca1b20
?
Thanks,
Daniel
