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Date: Mon, 21 Jan 2019 11:45:05 +0000
From: Quentin Monnet <quentin.monnet@...ronome.com>
To: Taeung Song <treeze.taeung@...il.com>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>
Cc: netdev@...r.kernel.org,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Andrey Ignatov <rdna@...com>
Subject: Re: [PATCH RESEND bpf-next v3] libbpf: Show supported ELF section
names on when failed to guess a prog/attach type
2019-01-21 16:25 UTC+0900 ~ Taeung Song <treeze.taeung@...il.com>
> We need to let users check their wrong ELF section name
> with proper ELF section names when failed to get a prog/attach type from it.
> Because users can't realize libbpf guess prog/attach types from
> given ELF section names.
> For example, when a 'cgroup' section name of a BPF program is used,
> show available ELF section names(types).
>
> Before:
>
> $ bpftool prog load bpf-prog.o /sys/fs/bpf/prog1
> Error: failed to guess program type based on ELF section name cgroup
>
> After:
>
> libbpf: failed to guess program type based on ELF section name 'cgroup'
> libbpf: supported section(type) names are: socket kprobe/ kretprobe/ classifier action tracepoint/ raw_tracepoint/ xdp perf_event lwt_in lwt_out lwt_xmit lwt_seg6local cgroup_skb/ingress cgroup_skb/egress cgroup/skb cgroup/sock cgroup/post_bind4 cgroup/post_bind6 cgroup/dev sockops sk_skb/stream_parser sk_skb/stream_verdict sk_skb sk_msg lirc_mode2 flow_dissector cgroup/bind4 cgroup/bind6 cgroup/connect4 cgroup/connect6 cgroup/sendmsg4 cgroup/sendmsg6
>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>
Please do not add "Reviewed-by" tags unless offered by the reviewers. I
cannot remember either Jakub or I giving the tag for this series so far.
Just in case, more details on the usage of this tag are available in
Documentation/process/submitting-patches.rst, in section
"Using Reported-by:, Tested-by:, Reviewed-by:, Suggested-by: and Fixes:"
> Cc: Andrey Ignatov <rdna@...com>
> Signed-off-by: Taeung Song <treeze.taeung@...il.com>
This version of the patch looks better, thanks! A few additional
comments below.
> ---
> tools/bpf/bpftool/prog.c | 10 ++----
> tools/lib/bpf/libbpf.c | 34 +++++++++++++++++--
> .../selftests/bpf/test_socket_cookie.c | 4 +--
> 3 files changed, 36 insertions(+), 12 deletions(-)
>
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 2d1bb7d6ff51..0640e9bc0ada 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -930,10 +930,9 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> err = libbpf_prog_type_by_name(type, &attr.prog_type,
> &expected_attach_type);
> free(type);
> - if (err < 0) {
> - p_err("unknown program type '%s'", *argv);
> + if (err < 0)
> goto err_free_reuse_maps;
> - }
> +
> NEXT_ARG();
> } else if (is_prefix(*argv, "map")) {
> void *new_map_replace;
> @@ -1028,11 +1027,8 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>
> err = libbpf_prog_type_by_name(sec_name, &prog_type,
> &expected_attach_type);
> - if (err < 0) {
> - p_err("failed to guess program type based on section name %s\n",
> - sec_name);
> + if (err < 0)
> goto err_close_obj;
> - }
> }
>
> bpf_program__set_ifindex(pos, ifindex);
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 169e347c76f6..ea44d7a05149 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2667,10 +2667,31 @@ static const struct {
> #undef BPF_EAPROG_SEC
> #undef BPF_APROG_COMPAT
>
> +#define MAX_TYPE_NAME_SIZE 32
> +
> +static char *libbpf_get_type_names(bool attach_type)
> +{
> + int i, len = ARRAY_SIZE(section_names) * MAX_TYPE_NAME_SIZE;
> + char *buf = malloc(len);
I'd rather have the malloc() on a line separate from variable
declaration, like this:
char *buf;
buf = malloc(len);
Also, can you please make sure that malloc() succeeds? (if (!buf) ...)
> +
> + buf[0] = '\0';
> + /* Forge string buf with all available names */
> + for (i = 0; i < ARRAY_SIZE(section_names); i++) {
Could you please add a check on "buf"'s length to make sure there is no
overflow? It seems very unlikely that we add a section name so long as
to make this happen, but just in case.
> + if (attach_type && !section_names[i].is_attachable)
> + continue;
> +
> + strcat(buf, " ");
> + strcat(buf, section_names[i].sec);
> + }
> +
> + return buf;
The code in this function uses a mix of tabs and spaces for indents.
Please stick to tabs.
> +}
> +
> int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
> enum bpf_attach_type *expected_attach_type)
> {
> int i;
> + char *type_names;
Please declare variables in reverse-Christmas-tree order.
>
> if (!name)
> return -EINVAL;
> @@ -2682,6 +2703,11 @@ int libbpf_prog_type_by_name(const char *name, enum bpf_prog_type *prog_type,
> *expected_attach_type = section_names[i].expected_attach_type;
> return 0;
> }
> + pr_warning("failed to guess program type based on ELF section name '%s'\n", name);
> + type_names = libbpf_get_type_names(false);
> + pr_info("supported section(type) names are:%s\n", type_names);
> + free(type_names);
> +
> return -EINVAL;
> }
>
> @@ -2689,6 +2715,7 @@ int libbpf_attach_type_by_name(const char *name,
> enum bpf_attach_type *attach_type)
> {
> int i;
> + char *type_names;
(same comment on variables' order)
>
> if (!name)
> return -EINVAL;
> @@ -2701,6 +2728,11 @@ int libbpf_attach_type_by_name(const char *name,
> *attach_type = section_names[i].attach_type;
> return 0;
> }
> + pr_warning("failed to guess attach type based on ELF section name '%s'\n", name);
> + type_names = libbpf_get_type_names(true);
> + pr_info("attachable section(type) names are:%s\n", type_names);
> + free(type_names);
> +
> return -EINVAL;
> }
>
> @@ -2907,8 +2939,6 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> err = bpf_program__identify_section(prog, &prog_type,
> &expected_attach_type);
> if (err < 0) {
> - pr_warning("failed to guess program type based on section name %s\n",
> - prog->section_name);
> bpf_object__close(obj);
> return -EINVAL;
> }
> diff --git a/tools/testing/selftests/bpf/test_socket_cookie.c b/tools/testing/selftests/bpf/test_socket_cookie.c
> index fc7832ee566b..e51d63786ff8 100644
> --- a/tools/testing/selftests/bpf/test_socket_cookie.c
> +++ b/tools/testing/selftests/bpf/test_socket_cookie.c
> @@ -158,10 +158,8 @@ static int run_test(int cgfd)
> bpf_object__for_each_program(prog, pobj) {
> prog_name = bpf_program__title(prog, /*needs_copy*/ false);
>
> - if (libbpf_attach_type_by_name(prog_name, &attach_type)) {
> - log_err("Unexpected prog: %s", prog_name);
> + if (libbpf_attach_type_by_name(prog_name, &attach_type))
> goto err;
> - }
>
> err = bpf_prog_attach(bpf_program__fd(prog), cgfd, attach_type,
> BPF_F_ALLOW_OVERRIDE);
>
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