On 8/9/23 4:41 AM, Kumar Kartikeya Dwivedi wrote:
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d0f6c984272b..9d67d0633c59 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2457,6 +2457,73 @@ static int add_subprog(struct bpf_verifier_env *env, int off)
return env->subprog_cnt - 1;
}
+static int bpf_find_exception_callback_insn_off(struct bpf_verifier_env *env)
+{
+ struct bpf_prog_aux *aux = env->prog->aux;
+ struct btf *btf = aux->btf;
+ const struct btf_type *t;
+ const char *name;
+ u32 main_btf_id;
+ int ret, i, j;
+
+ /* Non-zero func_info_cnt implies valid btf */
+ if (!aux->func_info_cnt)
+ return 0;
+ main_btf_id = aux->func_info[0].type_id;
+
+ t = btf_type_by_id(btf, main_btf_id);
+ if (!t) {
+ verbose(env, "invalid btf id for main subprog in func_info\n");
+ return -EINVAL;
+ }
+
+ name = btf_find_decl_tag_value(btf, t, -1, "exception_callback:");
+ if (IS_ERR(name)) {
+ ret = PTR_ERR(name);
+ /* If there is no tag present, there is no exception callback */
+ if (ret == -ENOENT)
+ ret = 0;
+ else if (ret == -EEXIST)
+ verbose(env, "multiple exception callback tags for main subprog\n");
+ return ret;
+ }
+
+ ret = -ENOENT;
+ for (i = 0; i < btf_nr_types(btf); i++) {
+ t = btf_type_by_id(btf, i);
+ if (!btf_type_is_func(t))
+ continue;
+ if (strcmp(name, btf_name_by_offset(btf, t->name_off)))
+ continue;
nit. btf_find_by_name_kind() could be used here.
+ if (btf_func_linkage(t) != BTF_FUNC_GLOBAL) {
+ verbose(env, "exception callback '%s' must have global linkage\n", name);
+ return -EINVAL;
+ } > +
+ ret = 0;
+ for (j = 0; j < aux->func_info_cnt; j++) {
+ if (aux->func_info[j].type_id != i)
+ continue;
+ ret = aux->func_info[j].insn_off;
+ /* Further func_info and subprog checks will also happen
+ * later, so assume this is the right insn_off for now.
+ */
+ if (!ret) {
+ verbose(env, "invalid exception callback insn_off in func_info: 0\n");
+ ret = -EINVAL;
+ }
+ }
+ if (!ret) {
+ verbose(env, "exception callback type id not found in func_info\n");
+ ret = -EINVAL;
+ }
+ break;
+ }
+ if (ret == -ENOENT)
+ verbose(env, "exception callback '%s' could not be found in BTF\n", name);
+ return ret;
+}
