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Message-ID: <20181220175301.GO20955@mini-arch.hsd1.ca.comcast.net>
Date: Thu, 20 Dec 2018 09:53:01 -0800
From: Stanislav Fomichev <sdf@...ichev.me>
To: Quentin Monnet <quentin.monnet@...ronome.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
oss-drivers@...ronome.com,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Stanislav Fomichev <sdf@...gle.com>
Subject: Re: [RFC PATCH bpf-next v2 6/9] tools: bpftool: add probes for eBPF
helper functions
On 12/20, Quentin Monnet wrote:
> Similarly to what was done for program types and map types, add a set of
> probes to test the availability of the different eBPF helper functions
> on the current system.
>
> Each known helper is tested with all program types supported by the
> system, in order to establish a compatibility matrix. Output is provided
> as a list of compatible program types, for each helper.
>
> Sample output:
>
> # bpftool feature probe kernel
> ...
> Scanning eBPF helper functions...
> ...
> eBPF helper bpf_skb_change_head supported for program types: \
> lwt_xmit sk_skb
> eBPF helper bpf_xdp_adjust_head supported for program types: xdp
> eBPF helper bpf_probe_read_str supported for program types: \
> kprobe tracepoint perf_event raw_tracepoint
> ...
>
> # bpftool --json --pretty feature probe kernel
> {
> ...
> "helpers": {
> ...
> "bpf_skb_change_head_compat_list": ["lwt_xmit","sk_skb"
> ],
> "bpf_xdp_adjust_head_compat_list": ["xdp"
> ],
> "bpf_probe_read_str_compat_list": ["kprobe","tracepoint", \
> "perf_event","raw_tracepoint"
> ],
> ...
> }
> }
>
> v2:
> - Move probes from bpftool to libbpf.
> - Test all program types for each helper, print a list of working prog
> types for each helper.
> - Fall back on include/uapi/linux/bpf.h for names and ids of helpers.
> - Remove C-style macros output from this patch.
>
> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
> ---
> .../bpftool/Documentation/bpftool-feature.rst | 4 ++
> tools/bpf/bpftool/feature.c | 51 +++++++++++++++
> tools/lib/bpf/libbpf.h | 2 +
> tools/lib/bpf/libbpf.map | 1 +
> tools/lib/bpf/libbpf_probes.c | 63 +++++++++++++++++++
> 5 files changed, 121 insertions(+)
>
> diff --git a/tools/bpf/bpftool/Documentation/bpftool-feature.rst b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
> index 40ac13c0b782..255e3b3629a0 100644
> --- a/tools/bpf/bpftool/Documentation/bpftool-feature.rst
> +++ b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
> @@ -30,6 +30,10 @@ DESCRIPTION
>
> Keyword **kernel** can be omitted.
>
> + Note that when probed, some eBPF helpers (e.g.
> + **bpf_trace_printk**\ () or **bpf_probe_write_user**\ ()) may
> + print warnings to kernel logs.
> +
> **bpftool feature help**
> Print short help message.
>
> diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
> index 3c44953ded5a..bc483823014b 100644
> --- a/tools/bpf/bpftool/feature.c
> +++ b/tools/bpf/bpftool/feature.c
> @@ -25,6 +25,11 @@ enum probe_component {
> COMPONENT_KERNEL,
> };
>
> +#define BPF_HELPER_MAKE_ENTRY(name) [BPF_FUNC_ ## name] = "bpf_" # name
> +static const char * const helper_name[] = {
> + __BPF_FUNC_MAPPER(BPF_HELPER_MAKE_ENTRY)
> +};
> +
> /* Miscellaneous utility functions */
>
> static bool check_procfs(void)
> @@ -418,6 +423,45 @@ static void probe_map_type(enum bpf_map_type map_type)
> print_bool_feature(feat_name, plain_desc, res);
> }
>
> +static void
> +probe_helper(__u32 id, const char *name, int kernel_version,
> + bool *supported_types)
> +{
> + char feat_name[128], plain_desc[128];
> + unsigned int i;
> +
> + sprintf(feat_name, "%s_compat_list", name);
> + sprintf(plain_desc,
> + "eBPF helper %s supported for program types:",
> + name);
> +
> + if (json_output) {
> + jsonw_name(json_wtr, feat_name);
> + jsonw_start_array(json_wtr);
> + } else {
> + printf("%s", plain_desc);
> + }
> +
> + for (i = BPF_PROG_TYPE_UNSPEC + 1;
> + i < ARRAY_SIZE(prog_type_name); i++) {
> + if (!supported_types[i])
> + continue;
> +
> + if (!bpf_probe_helper(id, i, kernel_version, 0))
> + continue;
> +
> + if (json_output)
> + jsonw_string(json_wtr, prog_type_name[i]);
> + else
> + printf(" %s", prog_type_name[i]);
> + }
> +
> + if (json_output)
> + jsonw_end_array(json_wtr);
> + else
> + printf("\n");
> +}
> +
> static int do_probe(int argc, char **argv)
> {
> enum probe_component target = COMPONENT_UNSPEC;
> @@ -494,6 +538,13 @@ static int do_probe(int argc, char **argv)
> for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++)
> probe_map_type(i);
>
> + print_end_then_start_section("helpers",
> + "Scanning eBPF helper functions...");
> +
> + for (i = 1; i < ARRAY_SIZE(helper_name); i++)
> + probe_helper(i, helper_name[i], kernel_version,
> + supported_types);
> +
> exit_close_json:
> if (json_output) {
> /* End current "section" of probes */
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 202c1ee5c579..ab5b40af5fae 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -361,6 +361,8 @@ bpf_prog_linfo__lfind(const struct bpf_prog_linfo *prog_linfo,
> LIBBPF_API bool bpf_probe_prog_type(enum bpf_prog_type prog_type,
> int kernel_version, __u32 ifindex);
> LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex);
> +LIBBPF_API bool bpf_probe_helper(__u32 id, enum bpf_prog_type prog_type,
> + int kernel_version, __u32 ifindex);
>
> #ifdef __cplusplus
> } /* extern "C" */
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index c08f4c726e8e..67e51b2becec 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -56,6 +56,7 @@ LIBBPF_0.0.1 {
> bpf_object__unpin_maps;
> bpf_object__unpin_programs;
> bpf_perf_event_read_simple;
> + bpf_probe_helper;
> bpf_probe_map_type;
> bpf_probe_prog_type;
> bpf_prog_attach;
> diff --git a/tools/lib/bpf/libbpf_probes.c b/tools/lib/bpf/libbpf_probes.c
> index 796fe1e66169..19aa062f33b5 100644
> --- a/tools/lib/bpf/libbpf_probes.c
> +++ b/tools/lib/bpf/libbpf_probes.c
> @@ -3,7 +3,11 @@
> /* Copyright (c) 2018 Netronome Systems, Inc. */
>
> #include <errno.h>
> +#include <fcntl.h>
> +#include <string.h>
> +#include <stdlib.h>
> #include <unistd.h>
> +#include <net/if.h>
>
> #include <linux/filter.h>
> #include <linux/kernel.h>
> @@ -11,6 +15,37 @@
> #include "bpf.h"
> #include "libbpf.h"
>
> +static bool grep(const char *buffer, const char *pattern)
> +{
> + return !!strstr(buffer, pattern);
> +}
> +
> +static int get_vendor_id(int ifindex)
> +{
> + char ifname[IF_NAMESIZE], path[64], buf[8];
> + ssize_t len;
> + int fd;
> +
> + if (!if_indextoname(ifindex, ifname))
> + return -1;
> +
> + snprintf(path, sizeof(path), "/sys/class/net/%s/device/vendor", ifname);
> +
> + fd = open(path, O_RDONLY);
> + if (fd < 0)
> + return -1;
> +
> + len = read(fd, buf, sizeof(buf));
> + close(fd);
> + if (len < 0)
> + return -1;
> + if (len >= (ssize_t)sizeof(buf))
> + return -1;
> + buf[len] = '\0';
> +
> + return strtol(buf, NULL, 0);
> +}
> +
> static void
> prog_load(enum bpf_prog_type prog_type, const struct bpf_insn *insns,
> size_t insns_cnt, int kernel_version, char *buf, size_t buf_len,
> @@ -112,3 +147,31 @@ bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex)
>
> return fd >= 0;
> }
> +
> +bool bpf_probe_helper(__u32 id, enum bpf_prog_type prog_type,
> + int kernel_version, __u32 ifindex)
> +{
> + struct bpf_insn insns[2] = {
> + BPF_EMIT_CALL(id),
> + BPF_EXIT_INSN()
> + };
> + char buf[4096] = {};
> + bool res;
> +
> + prog_load(prog_type, insns, ARRAY_SIZE(insns), kernel_version,
> + buf, sizeof(buf), ifindex);
> + res = !grep(buf, "invalid func ") && !grep(buf, "unknown func ");
Why not look at errno directly?
> +
> + if (ifindex) {
> + switch (get_vendor_id(ifindex)) {
> + case 0x19ee: /* Netronome specific */
> + res = res && !grep(buf, "not supported by FW") &&
> + !grep(buf, "unsupported function id");
> + break;
> + default:
> + break;
> + }
> + }
> +
> + return res;
> +}
> --
> 2.17.1
>
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