Commit b8c54ea4 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

libbpf: Add support to attach to fentry/fexit tracing progs 



Teach libbpf to recognize tracing programs types and attach them to
fentry/fexit.

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>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-7-ast@kernel.org
parent 1442e287

tools/include/uapi/linux/bpf.h

+2 −0
Original line number Diff line number Diff line
@@ -201,6 +201,8 @@ enum bpf_attach_type { 
	BPF_CGROUP_GETSOCKOPT,

	BPF_CGROUP_SETSOCKOPT,

	BPF_TRACE_RAW_TP,

	BPF_TRACE_FENTRY,

	BPF_TRACE_FEXIT,

	__MAX_BPF_ATTACH_TYPE

};

tools/lib/bpf/libbpf.c

+74 −25
Original line number Diff line number Diff line
@@ -3856,7 +3856,8 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level) 
	return 0;

}



static int libbpf_attach_btf_id_by_name(const char *name, __u32 *btf_id);

static int libbpf_attach_btf_id_by_name(const char *name,

					enum bpf_attach_type attach_type);



static struct bpf_object *

__bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
@@ -3910,7 +3911,6 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, 
	bpf_object__for_each_program(prog, obj) {

		enum bpf_prog_type prog_type;

		enum bpf_attach_type attach_type;

		__u32 btf_id;



		err = libbpf_prog_type_by_name(prog->section_name, &prog_type,

					       &attach_type);
@@ -3923,10 +3923,11 @@ __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, &btf_id);

			if (err)

			err = libbpf_attach_btf_id_by_name(prog->section_name,

							   attach_type);

			if (err <= 0)

				goto out;

			prog->attach_btf_id = btf_id;

			prog->attach_btf_id = err;

		}

	}
@@ -4935,6 +4936,10 @@ static const struct { 
	BPF_PROG_SEC("raw_tp/",			BPF_PROG_TYPE_RAW_TRACEPOINT),

	BPF_PROG_BTF("tp_btf/",			BPF_PROG_TYPE_TRACING,

						BPF_TRACE_RAW_TP),

	BPF_PROG_BTF("fentry/",			BPF_PROG_TYPE_TRACING,

						BPF_TRACE_FENTRY),

	BPF_PROG_BTF("fexit/",			BPF_PROG_TYPE_TRACING,

						BPF_TRACE_FEXIT),

	BPF_PROG_SEC("xdp",			BPF_PROG_TYPE_XDP),

	BPF_PROG_SEC("perf_event",		BPF_PROG_TYPE_PERF_EVENT),

	BPF_PROG_SEC("lwt_in",			BPF_PROG_TYPE_LWT_IN),
@@ -5052,43 +5057,56 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type, 
}



#define BTF_PREFIX "btf_trace_"

static int libbpf_attach_btf_id_by_name(const char *name, __u32 *btf_id)

int libbpf_find_vmlinux_btf_id(const char *name,

			       enum bpf_attach_type attach_type)

{

	struct btf *btf = bpf_core_find_kernel_btf();

	char raw_tp_btf_name[128] = BTF_PREFIX;

	char *dst = raw_tp_btf_name + sizeof(BTF_PREFIX) - 1;

	int ret, i, err = -EINVAL;

	char raw_tp_btf[128] = BTF_PREFIX;

	char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;

	const char *btf_name;

	int err = -EINVAL;

	u32 kind;



	if (IS_ERR(btf)) {

		pr_warn("vmlinux BTF is not found\n");

		return -EINVAL;

	}



	if (attach_type == BPF_TRACE_RAW_TP) {

		/* prepend "btf_trace_" prefix per kernel convention */

		strncat(dst, name, sizeof(raw_tp_btf) - sizeof(BTF_PREFIX));

		btf_name = raw_tp_btf;

		kind = BTF_KIND_TYPEDEF;

	} else {

		btf_name = name;

		kind = BTF_KIND_FUNC;

	}

	err = btf__find_by_name_kind(btf, btf_name, kind);

	btf__free(btf);

	return err;

}



static int libbpf_attach_btf_id_by_name(const char *name,

					enum bpf_attach_type attach_type)

{

	int i, err;



	if (!name)

		goto out;

		return -EINVAL;



	for (i = 0; i < ARRAY_SIZE(section_names); i++) {

		if (!section_names[i].is_attach_btf)

			continue;

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

			continue;

		/* prepend "btf_trace_" prefix per kernel convention */

		strncat(dst, name + section_names[i].len,

			sizeof(raw_tp_btf_name) - sizeof(BTF_PREFIX));

		ret = btf__find_by_name(btf, raw_tp_btf_name);

		if (ret <= 0) {

			pr_warn("%s is not found in vmlinux BTF\n", dst);

			goto out;

		}

		*btf_id = ret;

		err = 0;

		goto out;

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

						 attach_type);

		if (err <= 0)

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

		return err;

	}

	pr_warn("failed to identify btf_id based on ELF section name '%s'\n", name);

	err = -ESRCH;

out:

	btf__free(btf);

	return err;

	return -ESRCH;

}



int libbpf_attach_type_by_name(const char *name,
@@ -5716,6 +5734,37 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(struct bpf_program *prog, 
	return (struct bpf_link *)link;

}



struct bpf_link *bpf_program__attach_trace(struct bpf_program *prog)

{

	char errmsg[STRERR_BUFSIZE];

	struct bpf_link_fd *link;

	int prog_fd, pfd;



	prog_fd = bpf_program__fd(prog);

	if (prog_fd < 0) {

		pr_warn("program '%s': can't attach before loaded\n",

			bpf_program__title(prog, false));

		return ERR_PTR(-EINVAL);

	}



	link = malloc(sizeof(*link));

	if (!link)

		return ERR_PTR(-ENOMEM);

	link->link.destroy = &bpf_link__destroy_fd;



	pfd = bpf_raw_tracepoint_open(NULL, prog_fd);

	if (pfd < 0) {

		pfd = -errno;

		free(link);

		pr_warn("program '%s': failed to attach to trace: %s\n",

			bpf_program__title(prog, false),

			libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));

		return ERR_PTR(pfd);

	}

	link->fd = pfd;

	return (struct bpf_link *)link;

}



enum bpf_perf_event_ret

bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,

			   void **copy_mem, size_t *copy_size,

tools/lib/bpf/libbpf.h

+4 −0
Original line number Diff line number Diff line
@@ -188,6 +188,8 @@ libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type, 
			 enum bpf_attach_type *expected_attach_type);

LIBBPF_API int libbpf_attach_type_by_name(const char *name,

					  enum bpf_attach_type *attach_type);

LIBBPF_API int libbpf_find_vmlinux_btf_id(const char *name,

					  enum bpf_attach_type attach_type);



/* Accessors of bpf_program */

struct bpf_program;
@@ -251,6 +253,8 @@ LIBBPF_API struct bpf_link * 
bpf_program__attach_raw_tracepoint(struct bpf_program *prog,

				   const char *tp_name);



LIBBPF_API struct bpf_link *

bpf_program__attach_trace(struct bpf_program *prog);

struct bpf_insn;



/*

tools/lib/bpf/libbpf.map

+2 −0
Original line number Diff line number Diff line
@@ -199,10 +199,12 @@ LIBBPF_0.0.6 { 
		bpf_map__set_pin_path;

		bpf_object__open_file;

		bpf_object__open_mem;

		bpf_program__attach_trace;

		bpf_program__get_expected_attach_type;

		bpf_program__get_type;

		bpf_program__is_tracing;

		bpf_program__set_tracing;

		bpf_program__size;

		btf__find_by_name_kind;

		libbpf_find_vmlinux_btf_id;

} LIBBPF_0.0.5;

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