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Date: Thu, 14 Dec 2023 18:44:09 -0800
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Subject: Re: [PATCH bpf-next v13 07/14] bpf: pass attached BTF to the
 bpf_struct_ops subsystem
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To: thinker.li@gmail.com
Cc: sinquersw@gmail.com, kuifeng@meta.com, bpf@vger.kernel.org,
 ast@kernel.org, song@kernel.org, kernel-team@meta.com, andrii@kernel.org,
 drosen@google.com
References: <20231209002709.535966-1-thinker.li@gmail.com>
 <20231209002709.535966-8-thinker.li@gmail.com>
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From: Martin KaFai Lau <martin.lau@linux.dev>
In-Reply-To: <20231209002709.535966-8-thinker.li@gmail.com>
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On 12/8/23 4:27 PM, thinker.li@gmail.com wrote:
> @@ -681,15 +682,30 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
>   	struct bpf_struct_ops_map *st_map;
>   	const struct btf_type *t, *vt;
>   	struct bpf_map *map;
> +	struct btf *btf;
>   	int ret;
>   
> -	st_ops_desc = bpf_struct_ops_find_value(btf_vmlinux, attr->btf_vmlinux_value_type_id);
> -	if (!st_ops_desc)
> -		return ERR_PTR(-ENOTSUPP);
> +	if (attr->value_type_btf_obj_fd) {
> +		/* The map holds btf for its whole life time. */
> +		btf = btf_get_by_fd(attr->value_type_btf_obj_fd);
> +		if (IS_ERR(btf))
> +			return ERR_PTR(PTR_ERR(btf));

			return ERR_CAST(btf);

It needs to check for btf_is_module:

		if (!btf_is_module(btf)) {
			btf_put(btf);
			return ERR_PTR(-EINVAL);
		}

> +	} else {
> +		btf = btf_vmlinux;
> +		btf_get(btf);

btf_vmlinux could be NULL or a ERR_PTR? Lets take this chance to use 
bpf_get_btf_vmlinux():
		btf = bpf_get_btf_vmlinux();
	        if (IS_ERR(btf))
         	        return ERR_CAST(btf);

Going back to patch 4. This should be the only case that btf will be NULL or 
ERR_PTR?

will continue the remaining review later tonight.

pw-bot: cr

> +	}
> +
> +	st_ops_desc = bpf_struct_ops_find_value(btf, attr->btf_vmlinux_value_type_id);
> +	if (!st_ops_desc) {
> +		ret = -ENOTSUPP;
> +		goto errout;
> +	}
>   
>   	vt = st_ops_desc->value_type;
> -	if (attr->value_size != vt->size)
> -		return ERR_PTR(-EINVAL);
> +	if (attr->value_size != vt->size) {
> +		ret = -EINVAL;
> +		goto errout;
> +	}
>   
>   	t = st_ops_desc->type;
>