Commit 3d78417b authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

bpf: Add bpf_btf_find_by_name_kind() helper. 



Add new helper:
long bpf_btf_find_by_name_kind(char *name, int name_sz, u32 kind, int flags)
Description
	Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.
Return
	Returns btf_id and btf_obj_fd in lower and upper 32 bits.

It will be used by loader program to find btf_id to attach the program to
and to find btf_ids of ksyms.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-10-alexei.starovoitov@gmail.com
parent 387544bf

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -1974,6 +1974,7 @@ extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto; 
extern const struct bpf_func_proto bpf_task_storage_get_proto;

extern const struct bpf_func_proto bpf_task_storage_delete_proto;

extern const struct bpf_func_proto bpf_for_each_map_elem_proto;

extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;



const struct bpf_func_proto *bpf_tracing_func_proto(

	enum bpf_func_id func_id, const struct bpf_prog *prog);

include/uapi/linux/bpf.h

+7 −0
Original line number Diff line number Diff line
@@ -4748,6 +4748,12 @@ union bpf_attr { 
 * 		Execute bpf syscall with given arguments.

 * 	Return

 * 		A syscall result.

 *

 * long bpf_btf_find_by_name_kind(char *name, int name_sz, u32 kind, int flags)

 * 	Description

 * 		Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.

 * 	Return

 * 		Returns btf_id and btf_obj_fd in lower and upper 32 bits.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -4917,6 +4923,7 @@ union bpf_attr { 
	FN(for_each_map_elem),		\

	FN(snprintf),			\

	FN(sys_bpf),			\

	FN(btf_find_by_name_kind),	\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

kernel/bpf/btf.c

+62 −0
Original line number Diff line number Diff line
@@ -6085,3 +6085,65 @@ struct module *btf_try_get_module(const struct btf *btf) 


	return res;

}



BPF_CALL_4(bpf_btf_find_by_name_kind, char *, name, int, name_sz, u32, kind, int, flags)

{

	struct btf *btf;

	long ret;



	if (flags)

		return -EINVAL;



	if (name_sz <= 1 || name[name_sz - 1])

		return -EINVAL;



	btf = bpf_get_btf_vmlinux();

	if (IS_ERR(btf))

		return PTR_ERR(btf);



	ret = btf_find_by_name_kind(btf, name, kind);

	/* ret is never zero, since btf_find_by_name_kind returns

	 * positive btf_id or negative error.

	 */

	if (ret < 0) {

		struct btf *mod_btf;

		int id;



		/* If name is not found in vmlinux's BTF then search in module's BTFs */

		spin_lock_bh(&btf_idr_lock);

		idr_for_each_entry(&btf_idr, mod_btf, id) {

			if (!btf_is_module(mod_btf))

				continue;

			/* linear search could be slow hence unlock/lock

			 * the IDR to avoiding holding it for too long

			 */

			btf_get(mod_btf);

			spin_unlock_bh(&btf_idr_lock);

			ret = btf_find_by_name_kind(mod_btf, name, kind);

			if (ret > 0) {

				int btf_obj_fd;



				btf_obj_fd = __btf_new_fd(mod_btf);

				if (btf_obj_fd < 0) {

					btf_put(mod_btf);

					return btf_obj_fd;

				}

				return ret | (((u64)btf_obj_fd) << 32);

			}

			spin_lock_bh(&btf_idr_lock);

			btf_put(mod_btf);

		}

		spin_unlock_bh(&btf_idr_lock);

	}

	return ret;

}



const struct bpf_func_proto bpf_btf_find_by_name_kind_proto = {

	.func		= bpf_btf_find_by_name_kind,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_MEM,

	.arg2_type	= ARG_CONST_SIZE,

	.arg3_type	= ARG_ANYTHING,

	.arg4_type	= ARG_ANYTHING,

};

kernel/bpf/syscall.c

+2 −0
Original line number Diff line number Diff line
@@ -4584,6 +4584,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
	switch (func_id) {

	case BPF_FUNC_sys_bpf:

		return &bpf_sys_bpf_proto;

	case BPF_FUNC_btf_find_by_name_kind:

		return &bpf_btf_find_by_name_kind_proto;

	default:

		return tracing_prog_func_proto(func_id, prog);

	}

tools/include/uapi/linux/bpf.h

+7 −0
Original line number Diff line number Diff line
@@ -4748,6 +4748,12 @@ union bpf_attr { 
 * 		Execute bpf syscall with given arguments.

 * 	Return

 * 		A syscall result.

 *

 * long bpf_btf_find_by_name_kind(char *name, int name_sz, u32 kind, int flags)

 * 	Description

 * 		Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.

 * 	Return

 * 		Returns btf_id and btf_obj_fd in lower and upper 32 bits.

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -4917,6 +4923,7 @@ union bpf_attr { 
	FN(for_each_map_elem),		\

	FN(snprintf),			\

	FN(sys_bpf),			\

	FN(btf_find_by_name_kind),	\

	/* */



/* integer value in 'imm' field of BPF_CALL instruction selects which helper