linux-kernel - Re: [PATCH v2 net-next 1/4] libbpf: add ability to guess program type based on section name

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Message-ID: <927054d8-94ea-dbd1-b9f7-213639006969@netronome.com>
Date:   Fri, 8 Dec 2017 10:33:34 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Roman Gushchin <guro@...com>, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, ast@...nel.org,
        daniel@...earbox.net, jakub.kicinski@...ronome.com, kafai@...com,
        David Ahern <dsahern@...il.com>
Subject: Re: [PATCH v2 net-next 1/4] libbpf: add ability to guess program type
 based on section name

2017-12-07 18:39 UTC+0000 ~ Roman Gushchin <guro@...com>
> The bpf_prog_load() function will guess program type if it's not
> specified explicitly. This functionality will be used to implement
> loading of different programs without asking a user to specify
> the program type. In first order it will be used by bpftool.
> 
> Signed-off-by: Roman Gushchin <guro@...com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Cc: Martin KaFai Lau <kafai@...com>
> Cc: Quentin Monnet <quentin.monnet@...ronome.com>
> Cc: David Ahern <dsahern@...il.com>
> ---
>  tools/lib/bpf/libbpf.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 51 insertions(+)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 5aa45f89da93..205b7822fa0a 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -1721,6 +1721,45 @@ BPF_PROG_TYPE_FNS(tracepoint, BPF_PROG_TYPE_TRACEPOINT);
>  BPF_PROG_TYPE_FNS(xdp, BPF_PROG_TYPE_XDP);
>  BPF_PROG_TYPE_FNS(perf_event, BPF_PROG_TYPE_PERF_EVENT);
>  
> +#define BPF_PROG_SEC(string, type) { string, sizeof(string), type }
> +static const struct {
> +	const char *sec;
> +	size_t len;
> +	enum bpf_prog_type prog_type;
> +} section_names[] = {
> +	BPF_PROG_SEC("socket",		BPF_PROG_TYPE_SOCKET_FILTER),
> +	BPF_PROG_SEC("kprobe/",		BPF_PROG_TYPE_KPROBE),
> +	BPF_PROG_SEC("kretprobe/",	BPF_PROG_TYPE_KPROBE),
> +	BPF_PROG_SEC("tracepoint/",	BPF_PROG_TYPE_TRACEPOINT),
> +	BPF_PROG_SEC("xdp",		BPF_PROG_TYPE_XDP),
> +	BPF_PROG_SEC("perf_event",	BPF_PROG_TYPE_PERF_EVENT),
> +	BPF_PROG_SEC("cgroup/skb",	BPF_PROG_TYPE_CGROUP_SKB),
> +	BPF_PROG_SEC("cgroup/sock",	BPF_PROG_TYPE_CGROUP_SOCK),
> +	BPF_PROG_SEC("cgroup/dev",	BPF_PROG_TYPE_CGROUP_DEVICE),
> +	BPF_PROG_SEC("sockops",		BPF_PROG_TYPE_SOCK_OPS),
> +	BPF_PROG_SEC("sk_skb",		BPF_PROG_TYPE_SK_SKB),
> +};
> +#undef BPF_PROG_SEC
> +
> +static enum bpf_prog_type bpf_program__guess_type(struct bpf_program *prog)
> +{
> +	int i;
> +
> +	if (!prog->section_name)
> +		goto err;
> +
> +	for (i = 0; i < ARRAY_SIZE(section_names); i++)
> +		if (strncmp(prog->section_name, section_names[i].sec,
> +			    section_names[i].len) == 0)
> +			return section_names[i].prog_type;
> +
> +err:
> +	pr_warning("failed to guess program type based on section name %s\n",
> +		   prog->section_name);
> +
> +	return BPF_PROG_TYPE_UNSPEC;
> +}
> +
>  int bpf_map__fd(struct bpf_map *map)
>  {
>  	return map ? map->fd : -EINVAL;
> @@ -1832,6 +1871,18 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
>  		return -ENOENT;
>  	}
>  
> +	/*
> +	 * If type is not specified, try to guess it based on
> +	 * section name.
> +	 */
> +	if (type == BPF_PROG_TYPE_UNSPEC) {
> +		type = bpf_program__guess_type(prog);
> +		if (type == BPF_PROG_TYPE_UNSPEC) {
> +			bpf_object__close(obj);
> +			return -EINVAL;
> +		}
> +	}
> +
>  	bpf_program__set_type(prog, type);
>  	err = bpf_object__load(obj);
>  	if (err) {
> 

Looks good to me, nice to avoid the hard-coded string lengths :). Thanks
for the changes!

Quentin