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: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-10-alexei.starovoitov@gmail.com

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7fd5338..9dc44ba 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -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);

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index de58a71..3cc0735 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -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

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index fbf6c06..8571632 100644 (file)
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -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,
+};

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index da7dc24..f93ff2e 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -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);
        }

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index de58a71..3cc0735 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -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