Commit bfa92e0b authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'bpftool: fix feature output when helper probes fail' 

Milan Landaverde says:

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

Currently in bpftool's feature probe, we incorrectly tell the user that
all of the helper functions are supported for program types where helper
probing fails or is explicitly unsupported[1]:

$ bpftool feature probe
...
eBPF helpers supported for program type tracing:
	- bpf_map_lookup_elem
	- bpf_map_update_elem
	- bpf_map_delete_elem
	...
	- bpf_redirect_neigh
	- bpf_check_mtu
	- bpf_sys_bpf
	- bpf_sys_close

This patch adjusts bpftool to relay to the user when helper support
can't be determined:

$ bpftool feature probe
...
eBPF helpers supported for program type lirc_mode2:
    Program type not supported
eBPF helpers supported for program type tracing:
    Could not determine which helpers are available
eBPF helpers supported for program type struct_opts:
    Could not determine which helpers are available
eBPF helpers supported for program type ext:
    Could not determine which helpers are available

Rather than imply that no helpers are available for the program type, we
let the user know that helper function probing failed entirely.

[1] https://lore.kernel.org/bpf/20211217171202.3352835-2-andrii@kernel.org/


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

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents 7b3a0638 b06a92a1

tools/bpf/bpftool/feature.c

+17 −5
Original line number Diff line number Diff line
@@ -638,7 +638,7 @@ probe_map_type(enum bpf_map_type map_type, const char *define_prefix, 


		res = probe_map_type_ifindex(map_type, ifindex);

	} else {

		res = libbpf_probe_bpf_map_type(map_type, NULL);

		res = libbpf_probe_bpf_map_type(map_type, NULL) > 0;

	}



	/* Probe result depends on the success of map creation, no additional
@@ -690,7 +690,7 @@ probe_helper_ifindex(enum bpf_func_id id, enum bpf_prog_type prog_type, 
	return res;

}



static void

static bool

probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type,

			  const char *define_prefix, unsigned int id,

			  const char *ptype_name, __u32 ifindex)
@@ -701,7 +701,7 @@ probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 
		if (ifindex)

			res = probe_helper_ifindex(id, prog_type, ifindex);

		else

			res = libbpf_probe_bpf_helper(prog_type, id, NULL);

			res = libbpf_probe_bpf_helper(prog_type, id, NULL) > 0;

#ifdef USE_LIBCAP

		/* Probe may succeed even if program load fails, for

		 * unprivileged users check that we did not fail because of
@@ -723,6 +723,8 @@ probe_helper_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 
		if (res)

			printf("\n\t- %s", helper_name[id]);

	}



	return res;

}



static void
@@ -732,6 +734,7 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 
	const char *ptype_name = prog_type_name[prog_type];

	char feat_name[128];

	unsigned int id;

	bool probe_res = false;



	if (ifindex)

		/* Only test helpers for offload-able program types */
@@ -764,7 +767,7 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 
				continue;

			/* fallthrough */

		default:

			probe_helper_for_progtype(prog_type, supported_type,

			probe_res |= probe_helper_for_progtype(prog_type, supported_type,

						  define_prefix, id, ptype_name,

						  ifindex);

		}
@@ -772,8 +775,17 @@ probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type, 


	if (json_output)

		jsonw_end_array(json_wtr);

	else if (!define_prefix)

	else if (!define_prefix) {

		printf("\n");

		if (!probe_res) {

			if (!supported_type)

				printf("\tProgram type not supported\n");

			else

				printf("\tCould not determine which helpers are available\n");

		}

	}





}



static void