Commit 63f2f5ee authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: add ability to attach/detach BPF program to perf event 



bpf_program__attach_perf_event allows to attach BPF program to existing
perf event hook, providing most generic and most low-level way to attach BPF
programs. It returns struct bpf_link, which should be passed to
bpf_link__destroy to detach and free resources, associated with a link.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Reviewed-by: default avatarStanislav Fomichev <sdf@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 1c2e9efc

tools/lib/bpf/libbpf.c

+63 −0
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include <linux/limits.h>

#include <linux/perf_event.h>

#include <linux/ring_buffer.h>

#include <sys/ioctl.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <sys/vfs.h>
@@ -3958,6 +3959,68 @@ int bpf_link__destroy(struct bpf_link *link) 
	return err;

}



struct bpf_link_fd {

	struct bpf_link link; /* has to be at the top of struct */

	int fd; /* hook FD */

};



static int bpf_link__destroy_perf_event(struct bpf_link *link)

{

	struct bpf_link_fd *l = (void *)link;

	int err;



	err = ioctl(l->fd, PERF_EVENT_IOC_DISABLE, 0);

	if (err)

		err = -errno;



	close(l->fd);

	return err;

}



struct bpf_link *bpf_program__attach_perf_event(struct bpf_program *prog,

						int pfd)

{

	char errmsg[STRERR_BUFSIZE];

	struct bpf_link_fd *link;

	int prog_fd, err;



	if (pfd < 0) {

		pr_warning("program '%s': invalid perf event FD %d\n",

			   bpf_program__title(prog, false), pfd);

		return ERR_PTR(-EINVAL);

	}

	prog_fd = bpf_program__fd(prog);

	if (prog_fd < 0) {

		pr_warning("program '%s': can't attach BPF program w/o FD (did you load it?)\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_perf_event;

	link->fd = pfd;



	if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, prog_fd) < 0) {

		err = -errno;

		free(link);

		pr_warning("program '%s': failed to attach to pfd %d: %s\n",

			   bpf_program__title(prog, false), pfd,

			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));

		return ERR_PTR(err);

	}

	if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {

		err = -errno;

		free(link);

		pr_warning("program '%s': failed to enable pfd %d: %s\n",

			   bpf_program__title(prog, false), pfd,

			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));

		return ERR_PTR(err);

	}

	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

+3 −0
Original line number Diff line number Diff line
@@ -169,6 +169,9 @@ struct bpf_link; 


LIBBPF_API int bpf_link__destroy(struct bpf_link *link);



LIBBPF_API struct bpf_link *

bpf_program__attach_perf_event(struct bpf_program *prog, int pfd);



struct bpf_insn;



/*

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ LIBBPF_0.0.4 { 
	global:

		bpf_link__destroy;

		bpf_object__load_xattr;

		bpf_program__attach_perf_event;

		btf_dump__dump_type;

		btf_dump__free;

		btf_dump__new;

CRA Git | Maintained and supported by SUSTech CRA and CCSE