Commit f8b299bc authored by Menglong Dong's avatar Menglong Dong Committed by Andrii Nakryiko
Browse files

libbpf: Add support to set kprobe/uprobe attach mode 



By default, libbpf will attach the kprobe/uprobe BPF program in the
latest mode that supported by kernel. In this patch, we add the support
to let users manually attach kprobe/uprobe in legacy or perf mode.

There are 3 mode that supported by the kernel to attach kprobe/uprobe:

  LEGACY: create perf event in legacy way and don't use bpf_link
  PERF: create perf event with perf_event_open() and don't use bpf_link

Signed-off-by: default avatarMenglong Dong <imagedong@tencent.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarBiao Jiang <benbjiang@tencent.com>
Link: create perf event with perf_event_open() and use bpf_link
Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/
Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com

Users now can manually choose the mode with
bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
parent fd4cb29f

tools/lib/bpf/libbpf.c

+47 −1
Original line number Diff line number Diff line
@@ -9724,6 +9724,7 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p 
	char errmsg[STRERR_BUFSIZE];

	struct bpf_link_perf *link;

	int prog_fd, link_fd = -1, err;

	bool force_ioctl_attach;



	if (!OPTS_VALID(opts, bpf_perf_event_opts))

		return libbpf_err_ptr(-EINVAL);
@@ -9747,7 +9748,8 @@ struct bpf_link *bpf_program__attach_perf_event_opts(const struct bpf_program *p 
	link->link.dealloc = &bpf_link_perf_dealloc;

	link->perf_event_fd = pfd;



	if (kernel_supports(prog->obj, FEAT_PERF_LINK)) {

	force_ioctl_attach = OPTS_GET(opts, force_ioctl_attach, false);

	if (kernel_supports(prog->obj, FEAT_PERF_LINK) && !force_ioctl_attach) {

		DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_opts,

			.perf_event.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0));
@@ -10106,6 +10108,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, 
				const struct bpf_kprobe_opts *opts)

{

	DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);

	enum probe_attach_mode attach_mode;

	char errmsg[STRERR_BUFSIZE];

	char *legacy_probe = NULL;

	struct bpf_link *link;
@@ -10116,11 +10119,32 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, 
	if (!OPTS_VALID(opts, bpf_kprobe_opts))

		return libbpf_err_ptr(-EINVAL);



	attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);

	retprobe = OPTS_GET(opts, retprobe, false);

	offset = OPTS_GET(opts, offset, 0);

	pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);



	legacy = determine_kprobe_perf_type() < 0;

	switch (attach_mode) {

	case PROBE_ATTACH_MODE_LEGACY:

		legacy = true;

		pe_opts.force_ioctl_attach = true;

		break;

	case PROBE_ATTACH_MODE_PERF:

		if (legacy)

			return libbpf_err_ptr(-ENOTSUP);

		pe_opts.force_ioctl_attach = true;

		break;

	case PROBE_ATTACH_MODE_LINK:

		if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))

			return libbpf_err_ptr(-ENOTSUP);

		break;

	case PROBE_ATTACH_MODE_DEFAULT:

		break;

	default:

		return libbpf_err_ptr(-EINVAL);

	}



	if (!legacy) {

		pfd = perf_event_open_probe(false /* uprobe */, retprobe,

					    func_name, offset,
@@ -10852,6 +10876,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, 
	const char *archive_path = NULL, *archive_sep = NULL;

	char errmsg[STRERR_BUFSIZE], *legacy_probe = NULL;

	DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts);

	enum probe_attach_mode attach_mode;

	char full_path[PATH_MAX];

	struct bpf_link *link;

	size_t ref_ctr_off;
@@ -10862,6 +10887,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, 
	if (!OPTS_VALID(opts, bpf_uprobe_opts))

		return libbpf_err_ptr(-EINVAL);



	attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT);

	retprobe = OPTS_GET(opts, retprobe, false);

	ref_ctr_off = OPTS_GET(opts, ref_ctr_offset, 0);

	pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
@@ -10903,6 +10929,26 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid, 
	}



	legacy = determine_uprobe_perf_type() < 0;

	switch (attach_mode) {

	case PROBE_ATTACH_MODE_LEGACY:

		legacy = true;

		pe_opts.force_ioctl_attach = true;

		break;

	case PROBE_ATTACH_MODE_PERF:

		if (legacy)

			return libbpf_err_ptr(-ENOTSUP);

		pe_opts.force_ioctl_attach = true;

		break;

	case PROBE_ATTACH_MODE_LINK:

		if (legacy || !kernel_supports(prog->obj, FEAT_PERF_LINK))

			return libbpf_err_ptr(-ENOTSUP);

		break;

	case PROBE_ATTACH_MODE_DEFAULT:

		break;

	default:

		return libbpf_err_ptr(-EINVAL);

	}



	if (!legacy) {

		pfd = perf_event_open_probe(true /* uprobe */, retprobe, binary_path,

					    func_offset, pid, ref_ctr_off);

tools/lib/bpf/libbpf.h

+37 −13
Original line number Diff line number Diff line
@@ -447,12 +447,15 @@ LIBBPF_API struct bpf_link * 
bpf_program__attach(const struct bpf_program *prog);



struct bpf_perf_event_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

	/* custom user-provided value fetchable through bpf_get_attach_cookie() */

	__u64 bpf_cookie;

	/* don't use BPF link when attach BPF program */

	bool force_ioctl_attach;

	size_t :0;

};

#define bpf_perf_event_opts__last_field bpf_cookie

#define bpf_perf_event_opts__last_field force_ioctl_attach



LIBBPF_API struct bpf_link *

bpf_program__attach_perf_event(const struct bpf_program *prog, int pfd);
@@ -461,8 +464,25 @@ LIBBPF_API struct bpf_link * 
bpf_program__attach_perf_event_opts(const struct bpf_program *prog, int pfd,

				    const struct bpf_perf_event_opts *opts);



/**

 * enum probe_attach_mode - the mode to attach kprobe/uprobe

 *

 * force libbpf to attach kprobe/uprobe in specific mode, -ENOTSUP will

 * be returned if it is not supported by the kernel.

 */

enum probe_attach_mode {

	/* attach probe in latest supported mode by kernel */

	PROBE_ATTACH_MODE_DEFAULT = 0,

	/* attach probe in legacy mode, using debugfs/tracefs */

	PROBE_ATTACH_MODE_LEGACY,

	/* create perf event with perf_event_open() syscall */

	PROBE_ATTACH_MODE_PERF,

	/* attach probe with BPF link */

	PROBE_ATTACH_MODE_LINK,

};



struct bpf_kprobe_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

	/* custom user-provided value fetchable through bpf_get_attach_cookie() */

	__u64 bpf_cookie;
@@ -470,9 +490,11 @@ struct bpf_kprobe_opts { 
	size_t offset;

	/* kprobe is return probe */

	bool retprobe;

	/* kprobe attach mode */

	enum probe_attach_mode attach_mode;

	size_t :0;

};

#define bpf_kprobe_opts__last_field retprobe

#define bpf_kprobe_opts__last_field attach_mode



LIBBPF_API struct bpf_link *

bpf_program__attach_kprobe(const struct bpf_program *prog, bool retprobe,
@@ -506,7 +528,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog, 
				      const struct bpf_kprobe_multi_opts *opts);



struct bpf_ksyscall_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

	/* custom user-provided value fetchable through bpf_get_attach_cookie() */

	__u64 bpf_cookie;
@@ -552,7 +574,7 @@ bpf_program__attach_ksyscall(const struct bpf_program *prog, 
			     const struct bpf_ksyscall_opts *opts);



struct bpf_uprobe_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

	/* offset of kernel reference counted USDT semaphore, added in

	 * a6ca88b241d5 ("trace_uprobe: support reference counter in fd-based uprobe")
@@ -570,9 +592,11 @@ struct bpf_uprobe_opts { 
	 * binary_path.

	 */

	const char *func_name;

	/* uprobe attach mode */

	enum probe_attach_mode attach_mode;

	size_t :0;

};

#define bpf_uprobe_opts__last_field func_name

#define bpf_uprobe_opts__last_field attach_mode



/**

 * @brief **bpf_program__attach_uprobe()** attaches a BPF program
@@ -646,7 +670,7 @@ bpf_program__attach_usdt(const struct bpf_program *prog, 
			 const struct bpf_usdt_opts *opts);



struct bpf_tracepoint_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

	/* custom user-provided value fetchable through bpf_get_attach_cookie() */

	__u64 bpf_cookie;
@@ -1110,7 +1134,7 @@ struct user_ring_buffer; 
typedef int (*ring_buffer_sample_fn)(void *ctx, void *data, size_t size);



struct ring_buffer_opts {

	size_t sz; /* size of this struct, for forward/backward compatiblity */

	size_t sz; /* size of this struct, for forward/backward compatibility */

};



#define ring_buffer_opts__last_field sz
@@ -1475,7 +1499,7 @@ LIBBPF_API void 
bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s);



struct gen_loader_opts {

	size_t sz; /* size of this struct, for forward/backward compatiblity */

	size_t sz; /* size of this struct, for forward/backward compatibility */

	const char *data;

	const char *insns;

	__u32 data_sz;
@@ -1493,13 +1517,13 @@ enum libbpf_tristate { 
};



struct bpf_linker_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

};

#define bpf_linker_opts__last_field sz



struct bpf_linker_file_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

};

#define bpf_linker_file_opts__last_field sz
@@ -1542,7 +1566,7 @@ typedef int (*libbpf_prog_attach_fn_t)(const struct bpf_program *prog, long cook 
				       struct bpf_link **link);



struct libbpf_prog_handler_opts {

	/* size of this struct, for forward/backward compatiblity */

	/* size of this struct, for forward/backward compatibility */

	size_t sz;

	/* User-provided value that is passed to prog_setup_fn,

	 * prog_prepare_load_fn, and prog_attach_fn callbacks. Allows user to