Commit 7e1b4681 authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

libbpf: Add uprobe multi link detection 



Adding uprobe-multi link detection. It will be used later in
bpf_program__attach_usdt function to check and use uprobe_multi
link over standard uprobe links.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230809083440.3209381-17-jolsa@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 5bfdd32d

tools/lib/bpf/libbpf.c

+36 −0
Original line number Diff line number Diff line
@@ -4829,6 +4829,39 @@ static int probe_perf_link(void) 
	return link_fd < 0 && err == -EBADF;

}



static int probe_uprobe_multi_link(void)

{

	LIBBPF_OPTS(bpf_prog_load_opts, load_opts,

		.expected_attach_type = BPF_TRACE_UPROBE_MULTI,

	);

	LIBBPF_OPTS(bpf_link_create_opts, link_opts);

	struct bpf_insn insns[] = {

		BPF_MOV64_IMM(BPF_REG_0, 0),

		BPF_EXIT_INSN(),

	};

	int prog_fd, link_fd, err;

	unsigned long offset = 0;



	prog_fd = bpf_prog_load(BPF_PROG_TYPE_KPROBE, NULL, "GPL",

				insns, ARRAY_SIZE(insns), &load_opts);

	if (prog_fd < 0)

		return -errno;



	/* Creating uprobe in '/' binary should fail with -EBADF. */

	link_opts.uprobe_multi.path = "/";

	link_opts.uprobe_multi.offsets = &offset;

	link_opts.uprobe_multi.cnt = 1;



	link_fd = bpf_link_create(prog_fd, -1, BPF_TRACE_UPROBE_MULTI, &link_opts);

	err = -errno; /* close() can clobber errno */



	if (link_fd >= 0)

		close(link_fd);

	close(prog_fd);



	return link_fd < 0 && err == -EBADF;

}



static int probe_kern_bpf_cookie(void)

{

	struct bpf_insn insns[] = {
@@ -4925,6 +4958,9 @@ static struct kern_feature_desc { 
	[FEAT_SYSCALL_WRAPPER] = {

		"Kernel using syscall wrapper", probe_kern_syscall_wrapper,

	},

	[FEAT_UPROBE_MULTI_LINK] = {

		"BPF multi-uprobe link support", probe_uprobe_multi_link,

	},

};



bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)

tools/lib/bpf/libbpf_internal.h

+2 −0
Original line number Diff line number Diff line
@@ -355,6 +355,8 @@ enum kern_feature_id { 
	FEAT_BTF_ENUM64,

	/* Kernel uses syscall wrapper (CONFIG_ARCH_HAS_SYSCALL_WRAPPER) */

	FEAT_SYSCALL_WRAPPER,

	/* BPF multi-uprobe link support */

	FEAT_UPROBE_MULTI_LINK,

	__FEAT_CNT,

};