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.

Alexei Starovoitov committed 5 years ago

Commit 3d784171 parent 387544b5 files · +79 −0Browse files

Unified · Split

5 files

include/linux/bpf.h +1 −0
include/uapi/linux/bpf.h +7 −0
kernel/bpf/btf.c +62 −0
kernel/bpf/syscall.c +2 −0
tools/include/uapi/linux/bpf.h +7 −0

include/linux/bpf.h+1−0

@@ -1974,6 +1974,7 @@ extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto; · 1973 unmodified lines
1974	1974	extern const struct bpf_func_proto bpf_task_storage_get_proto;
1975	1975	extern const struct bpf_func_proto bpf_task_storage_delete_proto;
1976	1976	extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
	1977	+extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
1977	1978
1978	1979	const struct bpf_func_proto *bpf_tracing_func_proto(
1979	1980	enum bpf_func_id func_id, const struct bpf_prog *prog);

include/uapi/linux/bpf.h+7−0

@@ -4748,6 +4748,12 @@ union bpf_attr { · 4747 unmodified lines
4748	4748	* Execute bpf syscall with given arguments.
4749	4749	* Return
4750	4750	* A syscall result.
	4751	+ *
	4752	+ * long bpf_btf_find_by_name_kind(char *name, int name_sz, u32 kind, int flags)
	4753	+ * Description
	4754	+ * Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.
	4755	+ * Return
	4756	+ * Returns btf_id and btf_obj_fd in lower and upper 32 bits.
4751	4757	*/
4752	4758	#define __BPF_FUNC_MAPPER(FN) \
4753	4759	FN(unspec), \
@@ -4917,6 +4923,7 @@ union bpf_attr { · 163 unmodified lines
4917	4923	FN(for_each_map_elem), \
4918	4924	FN(snprintf), \
4919	4925	FN(sys_bpf), \
	4926	+ FN(btf_find_by_name_kind), \
4920	4927	/* */
4921	4928
4922	4929	/* integer value in 'imm' field of BPF_CALL instruction selects which helper

kernel/bpf/btf.c+62−0

@@ -6085,3 +6085,65 @@ struct module btf_try_get_module(const struct btf btf) · 6084 unmodified lines
6085	6085
6086	6086	return res;
6087	6087	}
	6088	+
	6089	+BPF_CALL_4(bpf_btf_find_by_name_kind, char *, name, int, name_sz, u32, kind, int, flags)
	6090	+{
	6091	+ struct btf *btf;
	6092	+ long ret;
	6093	+
	6094	+ if (flags)
	6095	+ return -EINVAL;
	6096	+
	6097	+ if (name_sz <= 1 \|\| name[name_sz - 1])
	6098	+ return -EINVAL;
	6099	+
	6100	+ btf = bpf_get_btf_vmlinux();
	6101	+ if (IS_ERR(btf))
	6102	+ return PTR_ERR(btf);
	6103	+
	6104	+ ret = btf_find_by_name_kind(btf, name, kind);
	6105	+ /* ret is never zero, since btf_find_by_name_kind returns
	6106	+ * positive btf_id or negative error.
	6107	+ */
	6108	+ if (ret < 0) {
	6109	+ struct btf *mod_btf;
	6110	+ int id;
	6111	+
	6112	+ /* If name is not found in vmlinux's BTF then search in module's BTFs */
	6113	+ spin_lock_bh(&btf_idr_lock);
	6114	+ idr_for_each_entry(&btf_idr, mod_btf, id) {
	6115	+ if (!btf_is_module(mod_btf))
	6116	+ continue;
	6117	+ /* linear search could be slow hence unlock/lock
	6118	+ * the IDR to avoiding holding it for too long
	6119	+ */
	6120	+ btf_get(mod_btf);
	6121	+ spin_unlock_bh(&btf_idr_lock);
	6122	+ ret = btf_find_by_name_kind(mod_btf, name, kind);
	6123	+ if (ret > 0) {
	6124	+ int btf_obj_fd;
	6125	+
	6126	+ btf_obj_fd = __btf_new_fd(mod_btf);
	6127	+ if (btf_obj_fd < 0) {
	6128	+ btf_put(mod_btf);
	6129	+ return btf_obj_fd;
	6130	+ }
	6131	+ return ret \| (((u64)btf_obj_fd) << 32);
	6132	+ }
	6133	+ spin_lock_bh(&btf_idr_lock);
	6134	+ btf_put(mod_btf);
	6135	+ }
	6136	+ spin_unlock_bh(&btf_idr_lock);
	6137	+ }
	6138	+ return ret;
	6139	+}
	6140	+
	6141	+const struct bpf_func_proto bpf_btf_find_by_name_kind_proto = {
	6142	+ .func = bpf_btf_find_by_name_kind,
	6143	+ .gpl_only = false,
	6144	+ .ret_type = RET_INTEGER,
	6145	+ .arg1_type = ARG_PTR_TO_MEM,
	6146	+ .arg2_type = ARG_CONST_SIZE,
	6147	+ .arg3_type = ARG_ANYTHING,
	6148	+ .arg4_type = ARG_ANYTHING,
	6149	+};

kernel/bpf/syscall.c+2−0

@@ -4584,6 +4584,8 @@ syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) · 4583 unmodified lines
4584	4584	switch (func_id) {
4585	4585	case BPF_FUNC_sys_bpf:
4586	4586	return &bpf_sys_bpf_proto;
	4587	+ case BPF_FUNC_btf_find_by_name_kind:
	4588	+ return &bpf_btf_find_by_name_kind_proto;
4587	4589	default:
4588	4590	return tracing_prog_func_proto(func_id, prog);
4589	4591	}

tools/include/uapi/linux/bpf.h+7−0

@@ -4748,6 +4748,12 @@ union bpf_attr { · 4747 unmodified lines
4748	4748	* Execute bpf syscall with given arguments.
4749	4749	* Return
4750	4750	* A syscall result.
	4751	+ *
	4752	+ * long bpf_btf_find_by_name_kind(char *name, int name_sz, u32 kind, int flags)
	4753	+ * Description
	4754	+ * Find BTF type with given name and kind in vmlinux BTF or in module's BTFs.
	4755	+ * Return
	4756	+ * Returns btf_id and btf_obj_fd in lower and upper 32 bits.
4751	4757	*/
4752	4758	#define __BPF_FUNC_MAPPER(FN) \
4753	4759	FN(unspec), \
@@ -4917,6 +4923,7 @@ union bpf_attr { · 163 unmodified lines
4917	4923	FN(for_each_map_elem), \
4918	4924	FN(snprintf), \
4919	4925	FN(sys_bpf), \
	4926	+ FN(btf_find_by_name_kind), \
4920	4927	/* */
4921	4928
4922	4929	/* integer value in 'imm' field of BPF_CALL instruction selects which helper