Re: [PATCH bpf-next v8 3/4] bpf: Create argument information for nullable arguments.

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Feb 08, 2024 at 06:37:49PM -0800, thinker.li@gmail.com wrote:

SNIP

>  enum bpf_struct_ops_state {
> @@ -1790,6 +1806,7 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
>  			     struct btf *btf,
>  			     struct bpf_verifier_log *log);
>  void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map);
> +void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc);
>  #else
>  #define register_bpf_struct_ops(st_ops, type) ({ (void *)(st_ops); 0; })
>  static inline bool bpf_try_module_get(const void *data, struct module *owner)
> @@ -1814,6 +1831,10 @@ static inline void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struc
>  {
>  }
>  
> +static inline void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc, int len)
> +{
> +}

extra len argument?

jirka


SNIP

> +/* Clean up the arg_info in a struct bpf_struct_ops_desc. */
> +void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc)
> +{
> +	struct bpf_struct_ops_arg_info *arg_info;
> +	int i;
> +
> +	arg_info = st_ops_desc->arg_info;
> +	if (!arg_info)
> +		return;
> +
> +	for (i = 0; i < btf_type_vlen(st_ops_desc->type); i++)
> +		kfree(arg_info[i].info);
> +
> +	kfree(arg_info);
> +}
> +
>  int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
>  			     struct btf *btf,
>  			     struct bpf_verifier_log *log)
>  {
>  	struct bpf_struct_ops *st_ops = st_ops_desc->st_ops;
> +	struct bpf_struct_ops_arg_info *arg_info;
>  	const struct btf_member *member;
>  	const struct btf_type *t;
>  	s32 type_id, value_id;
>  	char value_name[128];
>  	const char *mname;
> -	int i;
> +	int i, err;
>  
>  	if (strlen(st_ops->name) + VALUE_PREFIX_LEN >=
>  	    sizeof(value_name)) {
> @@ -160,6 +320,17 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
>  	if (!is_valid_value_type(btf, value_id, t, value_name))
>  		return -EINVAL;
>  
> +	arg_info = kcalloc(btf_type_vlen(t), sizeof(*arg_info),
> +			   GFP_KERNEL);
> +	if (!arg_info)
> +		return -ENOMEM;
> +
> +	st_ops_desc->arg_info = arg_info;
> +	st_ops_desc->type = t;
> +	st_ops_desc->type_id = type_id;
> +	st_ops_desc->value_id = value_id;
> +	st_ops_desc->value_type = btf_type_by_id(btf, value_id);
> +
>  	for_each_member(i, t, member) {
>  		const struct btf_type *func_proto;
>  
> @@ -167,40 +338,52 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
>  		if (!*mname) {
>  			pr_warn("anon member in struct %s is not supported\n",
>  				st_ops->name);
> -			return -EOPNOTSUPP;
> +			err = -EOPNOTSUPP;
> +			goto errout;
>  		}
>  
>  		if (__btf_member_bitfield_size(t, member)) {
>  			pr_warn("bit field member %s in struct %s is not supported\n",
>  				mname, st_ops->name);
> -			return -EOPNOTSUPP;
> +			err = -EOPNOTSUPP;
> +			goto errout;
>  		}
>  
>  		func_proto = btf_type_resolve_func_ptr(btf,
>  						       member->type,
>  						       NULL);
> -		if (func_proto &&
> -		    btf_distill_func_proto(log, btf,
> +		if (!func_proto)
> +			continue;
> +
> +		if (btf_distill_func_proto(log, btf,
>  					   func_proto, mname,
>  					   &st_ops->func_models[i])) {
>  			pr_warn("Error in parsing func ptr %s in struct %s\n",
>  				mname, st_ops->name);
> -			return -EINVAL;
> +			err = -EINVAL;
> +			goto errout;
>  		}
> +
> +		err = prepare_arg_info(btf, st_ops->name, mname,
> +				       func_proto,
> +				       arg_info + i);
> +		if (err)
> +			goto errout;
>  	}
>  
>  	if (st_ops->init(btf)) {
>  		pr_warn("Error in init bpf_struct_ops %s\n",
>  			st_ops->name);
> -		return -EINVAL;
> +		err = -EINVAL;
> +		goto errout;
>  	}
>  
> -	st_ops_desc->type_id = type_id;
> -	st_ops_desc->type = t;
> -	st_ops_desc->value_id = value_id;
> -	st_ops_desc->value_type = btf_type_by_id(btf, value_id);
> -
>  	return 0;
> +
> +errout:
> +	bpf_struct_ops_desc_release(st_ops_desc);
> +
> +	return err;
>  }
>  
>  static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index db53bb76387e..533f02b92c94 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -1699,6 +1699,13 @@ static void btf_free_struct_meta_tab(struct btf *btf)
>  static void btf_free_struct_ops_tab(struct btf *btf)
>  {
>  	struct btf_struct_ops_tab *tab = btf->struct_ops_tab;
> +	int i;
> +
> +	if (!tab)
> +		return;
> +
> +	for (i = 0; i < tab->cnt; i++)
> +		bpf_struct_ops_desc_release(&tab->ops[i]);
>  
>  	kfree(tab);
>  	btf->struct_ops_tab = NULL;
> @@ -6130,6 +6137,26 @@ static bool prog_args_trusted(const struct bpf_prog *prog)
>  	}
>  }
>  
> +int btf_ctx_arg_offset(struct btf *btf, const struct btf_type *func_proto,
> +		       u32 arg_no)
> +{
> +	const struct btf_param *args;
> +	const struct btf_type *t;
> +	int off = 0, i;
> +	u32 sz;
> +
> +	args = btf_params(func_proto);
> +	for (i = 0; i < arg_no; i++) {
> +		t = btf_type_by_id(btf, args[i].type);
> +		t = btf_resolve_size(btf, t, &sz);
> +		if (IS_ERR(t))
> +			return PTR_ERR(t);
> +		off += roundup(sz, 8);
> +	}
> +
> +	return off;
> +}
> +
>  bool btf_ctx_access(int off, int size, enum bpf_access_type type,
>  		    const struct bpf_prog *prog,
>  		    struct bpf_insn_access_aux *info)
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index c92d6af7d975..72ca27f49616 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -20419,6 +20419,12 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
>  		}
>  	}
>  
> +	/* btf_ctx_access() used this to provide argument type info */
> +	prog->aux->ctx_arg_info =
> +		st_ops_desc->arg_info[member_idx].info;
> +	prog->aux->ctx_arg_info_size =
> +		st_ops_desc->arg_info[member_idx].cnt;
> +
>  	prog->aux->attach_func_proto = func_proto;
>  	prog->aux->attach_func_name = mname;
>  	env->ops = st_ops->verifier_ops;
> -- 
> 2.34.1
> 
>