netdev - Re: [PATCH v3 3/4] libbpf: add bpf_prog_test_run

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Date:   Fri, 23 Nov 2018 23:25:11 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Lorenz Bauer <lmb@...udflare.com>, ast@...nel.org
Cc:     netdev@...r.kernel.org, linux-api@...r.kernel.org,
        ys114321@...il.com
Subject: Re: [PATCH v3 3/4] libbpf: add bpf_prog_test_run_xattr

On 11/22/2018 03:09 PM, Lorenz Bauer wrote:
> Add a new function, which encourages safe usage of the test interface.
> bpf_prog_test_run continues to work as before, but should be considered
> unsafe.
> 
> Signed-off-by: Lorenz Bauer <lmb@...udflare.com>

Set looks good to me, thanks! Three small things below:

> ---
>  tools/lib/bpf/bpf.c | 27 +++++++++++++++++++++++++++
>  tools/lib/bpf/bpf.h | 13 +++++++++++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
> index 961e1b9fc592..f8518bef6886 100644
> --- a/tools/lib/bpf/bpf.c
> +++ b/tools/lib/bpf/bpf.c
> @@ -424,6 +424,33 @@ int bpf_prog_test_run(int prog_fd, int repeat, void *data, __u32 size,
>  	return ret;
>  }
>  
> +int bpf_prog_test_run_xattr(const struct bpf_prog_test_run_attr *test_attr,
> +			    __u32 *size_out, __u32 *retval, __u32 *duration)
> +{
> +	union bpf_attr attr;
> +	int ret;
> +
> +	if (!test_attr->data_out && test_attr->size_out > 0)
> +		return -EINVAL;
> +
> +	bzero(&attr, sizeof(attr));
> +	attr.test.prog_fd = test_attr->prog_fd;
> +	attr.test.data_in = ptr_to_u64(test_attr->data);
> +	attr.test.data_out = ptr_to_u64(test_attr->data_out);
> +	attr.test.data_size_in = test_attr->size;
> +	attr.test.data_size_out = test_attr->size_out;
> +	attr.test.repeat = test_attr->repeat;
> +
> +	ret = sys_bpf(BPF_PROG_TEST_RUN, &attr, sizeof(attr));
> +	if (size_out)
> +		*size_out = attr.test.data_size_out;
> +	if (retval)
> +		*retval = attr.test.retval;
> +	if (duration)
> +		*duration = attr.test.duration;
> +	return ret;
> +}
> +
>  int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id)
>  {
>  	union bpf_attr attr;
> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
> index 26a51538213c..570f19f77f42 100644
> --- a/tools/lib/bpf/bpf.h
> +++ b/tools/lib/bpf/bpf.h
> @@ -110,6 +110,19 @@ LIBBPF_API int bpf_prog_attach(int prog_fd, int attachable_fd,
>  LIBBPF_API int bpf_prog_detach(int attachable_fd, enum bpf_attach_type type);
>  LIBBPF_API int bpf_prog_detach2(int prog_fd, int attachable_fd,
>  				enum bpf_attach_type type);
> +
> +struct bpf_prog_test_run_attr {
> +	int prog_fd;
> +	int repeat;
> +	const void *data;
> +	__u32 size;
> +	void *data_out; /* optional */
> +	__u32 size_out;

Small nit: could we name these data_{in,out} and data_size_{in,out} as
well, so it's analog to the ones from the bpf_attr?

> +};
> +
> +LIBBPF_API int bpf_prog_test_run_xattr(const struct bpf_prog_test_run_attr *test_attr,
> +				       __u32 *size_out, __u32 *retval,
> +				       __u32 *duration);
>  LIBBPF_API int bpf_prog_test_run(int prog_fd, int repeat, void *data,
>  				 __u32 size, void *data_out, __u32 *size_out,
>  				 __u32 *retval, __u32 *duration);

Could we add a comment into the header here stating that we discourage
bpf_prog_test_run()'s use?

It would probably also make sense since we go that route that we would
convert the 10 bpf_prog_test_run() instances under test_progs.c at the
same time so that people extending or looking at BPF kselftests don't
copy discouraged bpf_prog_test_run() api as examples from this point
onwards anymore.

Thanks,
Daniel