Commit e7bf94db authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
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libbpf: Add support for attaching BPF programs to other BPF programs 



Extend libbpf api to pass attach_prog_fd into bpf_object__open.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-19-ast@kernel.org
parent 5b92a28a

tools/include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -425,6 +425,7 @@ union bpf_attr { 
		__aligned_u64	line_info;	/* line info */

		__u32		line_info_cnt;	/* number of bpf_line_info records */

		__u32		attach_btf_id;	/* in-kernel BTF type id to attach to */

		__u32		attach_prog_fd; /* 0 to attach to vmlinux */

	};



	struct { /* anonymous struct used by BPF_OBJ_* commands */

tools/lib/bpf/bpf.c

+5 −3
Original line number Diff line number Diff line
@@ -228,10 +228,13 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr, 
	memset(&attr, 0, sizeof(attr));

	attr.prog_type = load_attr->prog_type;

	attr.expected_attach_type = load_attr->expected_attach_type;

	if (attr.prog_type == BPF_PROG_TYPE_TRACING)

	if (attr.prog_type == BPF_PROG_TYPE_TRACING) {

		attr.attach_btf_id = load_attr->attach_btf_id;

	else

		attr.attach_prog_fd = load_attr->attach_prog_fd;

	} else {

		attr.prog_ifindex = load_attr->prog_ifindex;

		attr.kern_version = load_attr->kern_version;

	}

	attr.insn_cnt = (__u32)load_attr->insns_cnt;

	attr.insns = ptr_to_u64(load_attr->insns);

	attr.license = ptr_to_u64(load_attr->license);
@@ -245,7 +248,6 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr, 
		attr.log_size = 0;

	}



	attr.kern_version = load_attr->kern_version;

	attr.prog_btf_fd = load_attr->prog_btf_fd;

	attr.func_info_rec_size = load_attr->func_info_rec_size;

	attr.func_info_cnt = load_attr->func_info_cnt;

tools/lib/bpf/bpf.h

+4 −1
Original line number Diff line number Diff line
@@ -77,7 +77,10 @@ struct bpf_load_program_attr { 
	const struct bpf_insn *insns;

	size_t insns_cnt;

	const char *license;

	union {

		__u32 kern_version;

		__u32 attach_prog_fd;

	};

	union {

		__u32 prog_ifindex;

		__u32 attach_btf_id;

tools/lib/bpf/libbpf.c

+59 −12
Original line number Diff line number Diff line
@@ -189,6 +189,7 @@ struct bpf_program { 


	enum bpf_attach_type expected_attach_type;

	__u32 attach_btf_id;

	__u32 attach_prog_fd;

	void *func_info;

	__u32 func_info_rec_size;

	__u32 func_info_cnt;
@@ -3683,8 +3684,13 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, 
	load_attr.insns = insns;

	load_attr.insns_cnt = insns_cnt;

	load_attr.license = license;

	if (prog->type == BPF_PROG_TYPE_TRACING) {

		load_attr.attach_prog_fd = prog->attach_prog_fd;

		load_attr.attach_btf_id = prog->attach_btf_id;

	} else {

		load_attr.kern_version = kern_version;

		load_attr.prog_ifindex = prog->prog_ifindex;

	}

	/* if .BTF.ext was loaded, kernel supports associated BTF for prog */

	if (prog->obj->btf_ext)

		btf_fd = bpf_object__btf_fd(prog->obj);
@@ -3699,7 +3705,6 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, 
	load_attr.line_info_cnt = prog->line_info_cnt;

	load_attr.log_level = prog->log_level;

	load_attr.prog_flags = prog->prog_flags;

	load_attr.attach_btf_id = prog->attach_btf_id;



retry_load:

	log_buf = malloc(log_buf_size);
@@ -3856,9 +3861,9 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level) 
	return 0;

}



static int libbpf_attach_btf_id_by_name(const char *name,

					enum bpf_attach_type attach_type);



static int libbpf_find_attach_btf_id(const char *name,

				     enum bpf_attach_type attach_type,

				     __u32 attach_prog_fd);

static struct bpf_object *

__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,

		   struct bpf_object_open_opts *opts)
@@ -3869,6 +3874,7 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, 
	const char *obj_name;

	char tmp_name[64];

	bool relaxed_maps;

	__u32 attach_prog_fd;

	int err;



	if (elf_version(EV_CURRENT) == EV_NONE) {
@@ -3899,6 +3905,7 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, 
	obj->relaxed_core_relocs = OPTS_GET(opts, relaxed_core_relocs, false);

	relaxed_maps = OPTS_GET(opts, relaxed_maps, false);

	pin_root_path = OPTS_GET(opts, pin_root_path, NULL);

	attach_prog_fd = OPTS_GET(opts, attach_prog_fd, 0);



	CHECK_ERR(bpf_object__elf_init(obj), err, out);

	CHECK_ERR(bpf_object__check_endianness(obj), err, out);
@@ -3923,11 +3930,13 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, 
		bpf_program__set_type(prog, prog_type);

		bpf_program__set_expected_attach_type(prog, attach_type);

		if (prog_type == BPF_PROG_TYPE_TRACING) {

			err = libbpf_attach_btf_id_by_name(prog->section_name,

							   attach_type);

			err = libbpf_find_attach_btf_id(prog->section_name,

							attach_type,

							attach_prog_fd);

			if (err <= 0)

				goto out;

			prog->attach_btf_id = err;

			prog->attach_prog_fd = attach_prog_fd;

		}

	}
@@ -5086,8 +5095,42 @@ int libbpf_find_vmlinux_btf_id(const char *name, 
	return err;

}



static int libbpf_attach_btf_id_by_name(const char *name,

					enum bpf_attach_type attach_type)

static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)

{

	struct bpf_prog_info_linear *info_linear;

	struct bpf_prog_info *info;

	struct btf *btf = NULL;

	int err = -EINVAL;



	info_linear = bpf_program__get_prog_info_linear(attach_prog_fd, 0);

	if (IS_ERR_OR_NULL(info_linear)) {

		pr_warn("failed get_prog_info_linear for FD %d\n",

			attach_prog_fd);

		return -EINVAL;

	}

	info = &info_linear->info;

	if (!info->btf_id) {

		pr_warn("The target program doesn't have BTF\n");

		goto out;

	}

	if (btf__get_from_id(info->btf_id, &btf)) {

		pr_warn("Failed to get BTF of the program\n");

		goto out;

	}

	err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);

	btf__free(btf);

	if (err <= 0) {

		pr_warn("%s is not found in prog's BTF\n", name);

		goto out;

	}

out:

	free(info_linear);

	return err;

}



static int libbpf_find_attach_btf_id(const char *name,

				     enum bpf_attach_type attach_type,

				     __u32 attach_prog_fd)

{

	int i, err;
@@ -5099,6 +5142,10 @@ static int libbpf_attach_btf_id_by_name(const char *name, 
			continue;

		if (strncmp(name, section_names[i].sec, section_names[i].len))

			continue;

		if (attach_prog_fd)

			err = libbpf_find_prog_btf_id(name + section_names[i].len,

						      attach_prog_fd);

		else

			err = libbpf_find_vmlinux_btf_id(name + section_names[i].len,

							 attach_type);

		if (err <= 0)

tools/lib/bpf/libbpf.h

+2 −1
Original line number Diff line number Diff line
@@ -108,8 +108,9 @@ struct bpf_object_open_opts { 
	 * auto-pinned to that path on load; defaults to "/sys/fs/bpf".

	 */

	const char *pin_root_path;

	__u32 attach_prog_fd;

};

#define bpf_object_open_opts__last_field pin_root_path

#define bpf_object_open_opts__last_field attach_prog_fd



LIBBPF_API struct bpf_object *bpf_object__open(const char *path);

LIBBPF_API struct bpf_object *