Commit 3ec84f4b authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: Add bpf_cookie support to bpf_link_create() API 



Add ability to specify bpf_cookie value when creating BPF perf link with
bpf_link_create() low-level API.

Given BPF_LINK_CREATE command is growing and keeps getting new fields that are
specific to the type of BPF_LINK, extend libbpf side of bpf_link_create() API
and corresponding OPTS struct to accomodate such changes. Add extra checks to
prevent using incompatible/unexpected combinations of fields.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210815070609.987780-11-andrii@kernel.org
parent 668ace0e

tools/lib/bpf/bpf.c

+25 −7
Original line number Diff line number Diff line
@@ -684,8 +684,13 @@ int bpf_link_create(int prog_fd, int target_fd, 
	iter_info_len = OPTS_GET(opts, iter_info_len, 0);

	target_btf_id = OPTS_GET(opts, target_btf_id, 0);



	/* validate we don't have unexpected combinations of non-zero fields */

	if (iter_info_len || target_btf_id) {

		if (iter_info_len && target_btf_id)

			return libbpf_err(-EINVAL);

		if (!OPTS_ZEROED(opts, target_btf_id))

			return libbpf_err(-EINVAL);

	}



	memset(&attr, 0, sizeof(attr));

	attr.link_create.prog_fd = prog_fd;
@@ -693,14 +698,27 @@ int bpf_link_create(int prog_fd, int target_fd, 
	attr.link_create.attach_type = attach_type;

	attr.link_create.flags = OPTS_GET(opts, flags, 0);



	if (iter_info_len) {

		attr.link_create.iter_info =

			ptr_to_u64(OPTS_GET(opts, iter_info, (void *)0));

		attr.link_create.iter_info_len = iter_info_len;

	} else if (target_btf_id) {

	if (target_btf_id) {

		attr.link_create.target_btf_id = target_btf_id;

		goto proceed;

	}



	switch (attach_type) {

	case BPF_TRACE_ITER:

		attr.link_create.iter_info = ptr_to_u64(OPTS_GET(opts, iter_info, (void *)0));

		attr.link_create.iter_info_len = iter_info_len;

		break;

	case BPF_PERF_EVENT:

		attr.link_create.perf_event.bpf_cookie = OPTS_GET(opts, perf_event.bpf_cookie, 0);

		if (!OPTS_ZEROED(opts, perf_event))

			return libbpf_err(-EINVAL);

		break;

	default:

		if (!OPTS_ZEROED(opts, flags))

			return libbpf_err(-EINVAL);

		break;

	}

proceed:

	fd = sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr));

	return libbpf_err_errno(fd);

}

tools/lib/bpf/bpf.h

+7 −1
Original line number Diff line number Diff line
@@ -177,8 +177,14 @@ struct bpf_link_create_opts { 
	union bpf_iter_link_info *iter_info;

	__u32 iter_info_len;

	__u32 target_btf_id;

	union {

		struct {

			__u64 bpf_cookie;

		} perf_event;

	};

	size_t :0;

};

#define bpf_link_create_opts__last_field target_btf_id

#define bpf_link_create_opts__last_field perf_event



LIBBPF_API int bpf_link_create(int prog_fd, int target_fd,

			       enum bpf_attach_type attach_type,

tools/lib/bpf/libbpf_internal.h

+22 −10
Original line number Diff line number Diff line
@@ -196,6 +196,17 @@ void *libbpf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz, 
		     size_t cur_cnt, size_t max_cnt, size_t add_cnt);

int libbpf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt);



static inline bool libbpf_is_mem_zeroed(const char *p, ssize_t len)

{

	while (len > 0) {

		if (*p)

			return false;

		p++;

		len--;

	}

	return true;

}



static inline bool libbpf_validate_opts(const char *opts,

					size_t opts_sz, size_t user_sz,

					const char *type_name)
@@ -204,17 +215,10 @@ static inline bool libbpf_validate_opts(const char *opts, 
		pr_warn("%s size (%zu) is too small\n", type_name, user_sz);

		return false;

	}

	if (user_sz > opts_sz) {

		size_t i;



		for (i = opts_sz; i < user_sz; i++) {

			if (opts[i]) {

				pr_warn("%s has non-zero extra bytes\n",

					type_name);

	if (!libbpf_is_mem_zeroed(opts + opts_sz, (ssize_t)user_sz - opts_sz)) {

		pr_warn("%s has non-zero extra bytes\n", type_name);

		return false;

	}

		}

	}

	return true;

}
@@ -233,6 +237,14 @@ static inline bool libbpf_validate_opts(const char *opts, 
			(opts)->field = value;	\

	} while (0)



#define OPTS_ZEROED(opts, last_nonzero_field)				      \

({									      \

	ssize_t __off = offsetofend(typeof(*(opts)), last_nonzero_field);     \

	!(opts) || libbpf_is_mem_zeroed((const void *)opts + __off,	      \

					(opts)->sz - __off);		      \

})





int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz);

int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz);

int libbpf__load_raw_btf(const char *raw_types, size_t types_len,