netdev - Re: [PATCH bpf-next v3 3/4] bpf: add dummy BPF STRUCT

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Date:   Fri, 22 Oct 2021 17:35:30 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Hou Tao <houtao1@...wei.com>
CC:     Alexei Starovoitov <ast@...nel.org>, Yonghong Song <yhs@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 3/4] bpf: add dummy BPF STRUCT_OPS for test
  purpose

On Fri, Oct 22, 2021 at 03:55:10PM +0800, Hou Tao wrote:
> --- /dev/null
> +++ b/net/bpf/bpf_dummy_struct_ops.c
> @@ -0,0 +1,203 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2021. Huawei Technologies Co., Ltd
> + */
> +#include <linux/kernel.h>
> +#include <linux/bpf_verifier.h>
> +#include <linux/bpf.h>
> +#include <linux/btf.h>
> +
> +extern struct bpf_struct_ops bpf_bpf_dummy_ops;
> +
> +/* A common type for test_N with return value in bpf_dummy_ops */
> +typedef int (*dummy_ops_test_ret_fn)(struct bpf_dummy_ops_state *state, ...);
> +
> +struct bpf_dummy_ops_test_args {
> +	u64 args[MAX_BPF_FUNC_ARGS];
> +	struct bpf_dummy_ops_state state;
> +};
> +
> +static struct bpf_dummy_ops_test_args *
> +dummy_ops_init_args(const union bpf_attr *kattr, unsigned int nr)
> +{
> +	__u32 size_in;
> +	struct bpf_dummy_ops_test_args *args;
> +	void __user *ctx_in;
> +	void __user *u_state;
> +
> +	if (!nr || nr > MAX_BPF_FUNC_ARGS)
These checks are unnecessary and can be removed.  They had already been
checked by the verifier during the bpf prog load time.

Others lgtm.

Acked-by: Martin KaFai Lau <kafai@...com>

> +		return ERR_PTR(-EINVAL);
> +
> +	size_in = kattr->test.ctx_size_in;
> +	if (size_in != sizeof(u64) * nr)
> +		return ERR_PTR(-EINVAL);
> +
> +	args = kzalloc(sizeof(*args), GFP_KERNEL);
> +	if (!args)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ctx_in = u64_to_user_ptr(kattr->test.ctx_in);
> +	if (copy_from_user(args->args, ctx_in, size_in))
> +		goto out;
> +
> +	/* args[0] is 0 means state argument of test_N will be NULL */
> +	u_state = u64_to_user_ptr(args->args[0]);
> +	if (u_state && copy_from_user(&args->state, u_state,
> +				      sizeof(args->state)))
> +		goto out;
> +
> +	return args;
> +out:
> +	kfree(args);
> +	return ERR_PTR(-EFAULT);
> +}

[ ... ]

> +int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
> +			    union bpf_attr __user *uattr)
> +{
> +	const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
> +	const struct btf_type *func_proto;
> +	struct bpf_dummy_ops_test_args *args;
> +	struct bpf_tramp_progs *tprogs;
> +	void *image = NULL;
> +	unsigned int op_idx;
> +	int prog_ret;
> +	int err;
> +
> +	if (prog->aux->attach_btf_id != st_ops->type_id)
> +		return -EOPNOTSUPP;
> +
> +	func_proto = prog->aux->attach_func_proto;
> +	args = dummy_ops_init_args(kattr, btf_type_vlen(func_proto));
> +	if (IS_ERR(args))
> +		return PTR_ERR(args);