Commit 1162f844 authored by Hechao Li's avatar Hechao Li Committed by Daniel Borkmann
Browse files

bpf: Print error message for bpftool cgroup show 



Currently, when bpftool cgroup show <path> has an error, no error
message is printed. This is confusing because the user may think the
result is empty.

Before the change:

$ bpftool cgroup show /sys/fs/cgroup
ID       AttachType      AttachFlags     Name
$ echo $?
255

After the change:
$ ./bpftool cgroup show /sys/fs/cgroup
Error: can't query bpf programs attached to /sys/fs/cgroup: Operation
not permitted

v2: Rename check_query_cgroup_progs to cgroup_has_attached_progs

Signed-off-by: default avatarHechao Li <hechaol@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191224011742.3714301-1-hechaol@fb.com
parent 8ab9da57

tools/bpf/bpftool/cgroup.c

+39 −17
Original line number Diff line number Diff line
@@ -117,6 +117,25 @@ static int count_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type) 
	return prog_cnt;

}



static int cgroup_has_attached_progs(int cgroup_fd)

{

	enum bpf_attach_type type;

	bool no_prog = true;



	for (type = 0; type < __MAX_BPF_ATTACH_TYPE; type++) {

		int count = count_attached_bpf_progs(cgroup_fd, type);



		if (count < 0 && errno != EINVAL)

			return -1;



		if (count > 0) {

			no_prog = false;

			break;

		}

	}



	return no_prog ? 0 : 1;

}

static int show_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type,

				   int level)

{
@@ -161,6 +180,7 @@ static int show_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type, 
static int do_show(int argc, char **argv)

{

	enum bpf_attach_type type;

	int has_attached_progs;

	const char *path;

	int cgroup_fd;

	int ret = -1;
@@ -192,6 +212,16 @@ static int do_show(int argc, char **argv) 
		goto exit;

	}



	has_attached_progs = cgroup_has_attached_progs(cgroup_fd);

	if (has_attached_progs < 0) {

		p_err("can't query bpf programs attached to %s: %s",

		      path, strerror(errno));

		goto exit_cgroup;

	} else if (!has_attached_progs) {

		ret = 0;

		goto exit_cgroup;

	}



	if (json_output)

		jsonw_start_array(json_wtr);

	else
@@ -212,6 +242,7 @@ static int do_show(int argc, char **argv) 
	if (json_output)

		jsonw_end_array(json_wtr);



exit_cgroup:

	close(cgroup_fd);

exit:

	return ret;
@@ -228,7 +259,7 @@ static int do_show_tree_fn(const char *fpath, const struct stat *sb, 
			   int typeflag, struct FTW *ftw)

{

	enum bpf_attach_type type;

	bool skip = true;

	int has_attached_progs;

	int cgroup_fd;



	if (typeflag != FTW_D)
@@ -240,22 +271,13 @@ static int do_show_tree_fn(const char *fpath, const struct stat *sb, 
		return SHOW_TREE_FN_ERR;

	}



	for (type = 0; type < __MAX_BPF_ATTACH_TYPE; type++) {

		int count = count_attached_bpf_progs(cgroup_fd, type);



		if (count < 0 && errno != EINVAL) {

	has_attached_progs = cgroup_has_attached_progs(cgroup_fd);

	if (has_attached_progs < 0) {

		p_err("can't query bpf programs attached to %s: %s",

		      fpath, strerror(errno));

		close(cgroup_fd);

		return SHOW_TREE_FN_ERR;

		}

		if (count > 0) {

			skip = false;

			break;

		}

	}



	if (skip) {

	} else if (!has_attached_progs) {

		close(cgroup_fd);

		return 0;

	}

CRA Git | Maintained and supported by SUSTech CRA and CCSE