Commit 4e1ea332 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

bpftool: Support dumping a map with btf_vmlinux_value_type_id 



This patch makes bpftool support dumping a map's value properly
when the map's value type is a type of the running kernel's btf.
(i.e. map_info.btf_vmlinux_value_type_id is set instead of
map_info.btf_value_type_id).  The first usecase is for the
BPF_MAP_TYPE_STRUCT_OPS.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200115230044.1103008-1-kafai@fb.com
parent 84c72cee

tools/bpf/bpftool/map.c

+50 −11
Original line number Diff line number Diff line
@@ -252,6 +252,7 @@ static int do_dump_btf(const struct btf_dumper *d, 
		       struct bpf_map_info *map_info, void *key,

		       void *value)

{

	__u32 value_id;

	int ret;



	/* start of key-value pair */
@@ -265,9 +266,12 @@ static int do_dump_btf(const struct btf_dumper *d, 
			goto err_end_obj;

	}



	value_id = map_info->btf_vmlinux_value_type_id ?

		: map_info->btf_value_type_id;



	if (!map_is_per_cpu(map_info->type)) {

		jsonw_name(d->jw, "value");

		ret = btf_dumper_type(d, map_info->btf_value_type_id, value);

		ret = btf_dumper_type(d, value_id, value);

	} else {

		unsigned int i, n, step;
@@ -279,8 +283,7 @@ static int do_dump_btf(const struct btf_dumper *d, 
			jsonw_start_object(d->jw);

			jsonw_int_field(d->jw, "cpu", i);

			jsonw_name(d->jw, "value");

			ret = btf_dumper_type(d, map_info->btf_value_type_id,

					      value + i * step);

			ret = btf_dumper_type(d, value_id, value + i * step);

			jsonw_end_object(d->jw);

			if (ret)

				break;
@@ -932,6 +935,44 @@ static int maps_have_btf(int *fds, int nb_fds) 
	return 1;

}



static struct btf *btf_vmlinux;



static struct btf *get_map_kv_btf(const struct bpf_map_info *info)

{

	struct btf *btf = NULL;



	if (info->btf_vmlinux_value_type_id) {

		if (!btf_vmlinux) {

			btf_vmlinux = libbpf_find_kernel_btf();

			if (IS_ERR(btf_vmlinux))

				p_err("failed to get kernel btf");

		}

		return btf_vmlinux;

	} else if (info->btf_value_type_id) {

		int err;



		err = btf__get_from_id(info->btf_id, &btf);

		if (err || !btf) {

			p_err("failed to get btf");

			btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);

		}

	}



	return btf;

}



static void free_map_kv_btf(struct btf *btf)

{

	if (!IS_ERR(btf) && btf != btf_vmlinux)

		btf__free(btf);

}



static void free_btf_vmlinux(void)

{

	if (!IS_ERR(btf_vmlinux))

		btf__free(btf_vmlinux);

}



static int

map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,

	 bool show_header)
@@ -952,14 +993,11 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr, 
	prev_key = NULL;



	if (wtr) {

		if (info->btf_id) {

			err = btf__get_from_id(info->btf_id, &btf);

			if (err || !btf) {

				err = err ? : -ESRCH;

				p_err("failed to get btf");

		btf = get_map_kv_btf(info);

		if (IS_ERR(btf)) {

			err = PTR_ERR(btf);

			goto exit_free;

		}

		}



		if (show_header) {

			jsonw_start_object(wtr);	/* map object */
@@ -999,7 +1037,7 @@ exit_free: 
	free(key);

	free(value);

	close(fd);

	btf__free(btf);

	free_map_kv_btf(btf);



	return err;

}
@@ -1067,6 +1105,7 @@ exit_close: 
		close(fds[i]);

exit_free:

	free(fds);

	free_btf_vmlinux();

	return err;

}

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