Commit cc7d8f2c authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
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libbpf: Support target-less SEC() definitions for BTF-backed programs 



Similar to previous patch, support target-less definitions like
SEC("fentry"), SEC("freplace"), etc. For such BTF-backed program types
it is expected that user will specify BTF target programmatically at
runtime using bpf_program__set_attach_target() *before* load phase. If
not, libbpf will report this as an error.

Aslo use SEC_ATTACH_BTF flag instead of explicitly listing a set of
types that are expected to require attach_btf_id. This was an accidental
omission during custom SEC() support refactoring.

Signed-off-by: default avatarAndrii Nakryiko <andrii@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/20220428185349.3799599-3-andrii@kernel.org
parent 9af8efc4

tools/lib/bpf/libbpf.c

+32 −17
Original line number Original line Diff line number Diff line
@@ -6682,17 +6682,32 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog, 
	if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_FRAGS))

	if (prog->type == BPF_PROG_TYPE_XDP && (def & SEC_XDP_FRAGS))

		opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;

		opts->prog_flags |= BPF_F_XDP_HAS_FRAGS;





	if (def & SEC_DEPRECATED)

	if (def & SEC_DEPRECATED) {

		pr_warn("SEC(\"%s\") is deprecated, please see https://github.com/libbpf/libbpf/wiki/Libbpf-1.0-migration-guide#bpf-program-sec-annotation-deprecations for details\n",

		pr_warn("SEC(\"%s\") is deprecated, please see https://github.com/libbpf/libbpf/wiki/Libbpf-1.0-migration-guide#bpf-program-sec-annotation-deprecations for details\n",

			prog->sec_name);

			prog->sec_name);

	}





	if ((prog->type == BPF_PROG_TYPE_TRACING ||

	if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {

	     prog->type == BPF_PROG_TYPE_LSM ||

	     prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {

		int btf_obj_fd = 0, btf_type_id = 0, err;

		int btf_obj_fd = 0, btf_type_id = 0, err;

		const char *attach_name;

		const char *attach_name;





		attach_name = strchr(prog->sec_name, '/') + 1;

		attach_name = strchr(prog->sec_name, '/');

		if (!attach_name) {

			/* if BPF program is annotated with just SEC("fentry")

			 * (or similar) without declaratively specifying

			 * target, then it is expected that target will be

			 * specified with bpf_program__set_attach_target() at

			 * runtime before BPF object load step. If not, then

			 * there is nothing to load into the kernel as BPF

			 * verifier won't be able to validate BPF program

			 * correctness anyways.

			 */

			pr_warn("prog '%s': no BTF-based attach target is specified, use bpf_program__set_attach_target()\n",

				prog->name);

			return -EINVAL;

		}

		attach_name++; /* skip over / */



		err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);

		err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);

		if (err)

		if (err)

			return err;

			return err;
@@ -8869,18 +8884,18 @@ static const struct bpf_sec_def section_defs[] = { 
	SEC_DEF("raw_tp+",		RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tp+",		RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tracepoint.w+",	RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tracepoint.w+",	RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tp.w+",		RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("raw_tp.w+",		RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),

	SEC_DEF("tp_btf/",		TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("tp_btf+",		TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fentry/",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fentry+",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fmod_ret/",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fmod_ret+",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fexit/",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fexit+",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("fentry.s/",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),

	SEC_DEF("fentry.s+",		TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),

	SEC_DEF("fmod_ret.s/",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),

	SEC_DEF("fmod_ret.s+",		TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),

	SEC_DEF("fexit.s/",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),

	SEC_DEF("fexit.s+",		TRACING, BPF_TRACE_FEXIT, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_trace),

	SEC_DEF("freplace/",		EXT, 0, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("freplace+",		EXT, 0, SEC_ATTACH_BTF, attach_trace),

	SEC_DEF("lsm/",			LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),

	SEC_DEF("lsm+",			LSM, BPF_LSM_MAC, SEC_ATTACH_BTF, attach_lsm),

	SEC_DEF("lsm.s/",		LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),

	SEC_DEF("lsm.s+",		LSM, BPF_LSM_MAC, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_lsm),

	SEC_DEF("iter/",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),

	SEC_DEF("iter+",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF, attach_iter),

	SEC_DEF("iter.s/",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_iter),

	SEC_DEF("iter.s+",		TRACING, BPF_TRACE_ITER, SEC_ATTACH_BTF | SEC_SLEEPABLE, attach_iter),

	SEC_DEF("syscall",		SYSCALL, 0, SEC_SLEEPABLE),

	SEC_DEF("syscall",		SYSCALL, 0, SEC_SLEEPABLE),

	SEC_DEF("xdp.frags/devmap",	XDP, BPF_XDP_DEVMAP, SEC_XDP_FRAGS),

	SEC_DEF("xdp.frags/devmap",	XDP, BPF_XDP_DEVMAP, SEC_XDP_FRAGS),

	SEC_DEF("xdp/devmap",		XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),

	SEC_DEF("xdp/devmap",		XDP, BPF_XDP_DEVMAP, SEC_ATTACHABLE),