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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 09/16] libbpf: Support for fd_idx
Date: Mon, 26 Apr 2021 10:14:45 -0700	[thread overview]
Message-ID: <CAEf4BzZ5CJmF45_aBWBHt2jYeLjs2o5VXEA3zfLDvTncW_hjZg@mail.gmail.com> (raw)
In-Reply-To: <20210423002646.35043-10-alexei.starovoitov@gmail.com>

On Thu, Apr 22, 2021 at 5:27 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.org>
>
> Add support for FD_IDX make libbpf prefer that approach to loading programs.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>  tools/lib/bpf/bpf.c             |  1 +
>  tools/lib/bpf/libbpf.c          | 70 +++++++++++++++++++++++++++++----
>  tools/lib/bpf/libbpf_internal.h |  1 +
>  3 files changed, 65 insertions(+), 7 deletions(-)
>

[...]

> +static int probe_kern_fd_idx(void)
> +{
> +       struct bpf_load_program_attr attr;
> +       struct bpf_insn insns[] = {
> +               BPF_LD_IMM64_RAW(BPF_REG_0, BPF_PSEUDO_MAP_IDX, 0),
> +               BPF_EXIT_INSN(),
> +       };
> +
> +       memset(&attr, 0, sizeof(attr));
> +       attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
> +       attr.insns = insns;
> +       attr.insns_cnt = ARRAY_SIZE(insns);
> +       attr.license = "GPL";
> +
> +       probe_fd(bpf_load_program_xattr(&attr, NULL, 0));

probe_fd() calls close(fd) internally, which technically can interfere
with errno, though close() shouldn't be called because syscall has to
fail on correct kernels... So this should work, but I feel like
open-coding that logic is better than ignoring probe_fd() result.

> +       return errno == EPROTO;
> +}
> +

[...]

> @@ -7239,6 +7279,8 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
>         struct bpf_program *prog;
>         size_t i;
>         int err;
> +       struct bpf_map *map;
> +       int *fd_array = NULL;
>
>         for (i = 0; i < obj->nr_programs; i++) {
>                 prog = &obj->programs[i];
> @@ -7247,6 +7289,16 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
>                         return err;
>         }
>
> +       if (kernel_supports(FEAT_FD_IDX) && obj->nr_maps) {
> +               fd_array = malloc(sizeof(int) * obj->nr_maps);
> +               if (!fd_array)
> +                       return -ENOMEM;
> +               for (i = 0; i < obj->nr_maps; i++) {
> +                       map = &obj->maps[i];
> +                       fd_array[i] = map->fd;

nit: obj->maps[i].fd will keep it a single line

> +               }
> +       }
> +
>         for (i = 0; i < obj->nr_programs; i++) {
>                 prog = &obj->programs[i];
>                 if (prog_is_subprog(obj, prog))
> @@ -7256,10 +7308,14 @@ bpf_object__load_progs(struct bpf_object *obj, int log_level)
>                         continue;
>                 }
>                 prog->log_level |= log_level;
> +               prog->fd_array = fd_array;

you are not freeing this memory on success, as far as I can see. And
given multiple programs are sharing fd_array, it's a bit problematic
for prog to have fd_array. This is per-object properly, so let's add
it at bpf_object level and clean it up on bpf_object__close()? And by
assigning to obj->fd_array at malloc() site, you won't need to do all
the error-handling free()s below.

>                 err = bpf_program__load(prog, obj->license, obj->kern_version);
> -               if (err)
> +               if (err) {
> +                       free(fd_array);
>                         return err;
> +               }
>         }
> +       free(fd_array);
>         return 0;
>  }
>
> diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> index 6017902c687e..9114c7085f2a 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -204,6 +204,7 @@ struct bpf_prog_load_params {
>         __u32 log_level;
>         char *log_buf;
>         size_t log_buf_sz;
> +       int *fd_array;
>  };
>
>  int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr);
> --
> 2.30.2
>

  reply	other threads:[~2021-04-26 17:15 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-23  0:26 [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, light skeleton Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 01/16] bpf: Introduce bpf_sys_bpf() helper and program type Alexei Starovoitov
2021-04-23 18:15   ` Yonghong Song
2021-04-23 18:28     ` Alexei Starovoitov
2021-04-23 19:32       ` Yonghong Song
2021-04-26 16:51   ` Andrii Nakryiko
2021-04-27 18:45   ` John Fastabend
2021-04-23  0:26 ` [PATCH v2 bpf-next 02/16] bpf: Introduce bpfptr_t user/kernel pointer Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 03/16] bpf: Prepare bpf syscall to be used from kernel and user space Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 04/16] libbpf: Support for syscall program type Alexei Starovoitov
2021-04-26 22:24   ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 05/16] selftests/bpf: Test " Alexei Starovoitov
2021-04-26 17:02   ` Andrii Nakryiko
2021-04-27  2:43     ` Alexei Starovoitov
2021-04-27 16:28       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 06/16] bpf: Make btf_load command to be bpfptr_t compatible Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 07/16] selftests/bpf: Test for btf_load command Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 08/16] bpf: Introduce fd_idx Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 09/16] libbpf: Support for fd_idx Alexei Starovoitov
2021-04-26 17:14   ` Andrii Nakryiko [this message]
2021-04-27  2:53     ` Alexei Starovoitov
2021-04-27 16:36       ` Andrii Nakryiko
2021-04-28  1:32         ` Alexei Starovoitov
2021-04-28 18:40           ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 10/16] bpf: Add bpf_btf_find_by_name_kind() helper Alexei Starovoitov
2021-04-26 22:46   ` Andrii Nakryiko
2021-04-27  3:37     ` Alexei Starovoitov
2021-04-27 17:45       ` Andrii Nakryiko
2021-04-28  1:55         ` Alexei Starovoitov
2021-04-28 18:44           ` Andrii Nakryiko
2021-04-27 21:00   ` John Fastabend
2021-04-27 21:05     ` John Fastabend
2021-04-28  2:10     ` Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 11/16] bpf: Add bpf_sys_close() helper Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 12/16] libbpf: Change the order of data and text relocations Alexei Starovoitov
2021-04-26 17:29   ` Andrii Nakryiko
2021-04-27  3:00     ` Alexei Starovoitov
2021-04-27 16:47       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 13/16] libbpf: Add bpf_object pointer to kernel_supports() Alexei Starovoitov
2021-04-26 17:30   ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 14/16] libbpf: Generate loader program out of BPF ELF file Alexei Starovoitov
2021-04-26 22:22   ` Andrii Nakryiko
2021-04-27  3:25     ` Alexei Starovoitov
2021-04-27 17:34       ` Andrii Nakryiko
2021-04-28  1:42         ` Alexei Starovoitov
2021-04-23  0:26 ` [PATCH v2 bpf-next 15/16] bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command Alexei Starovoitov
2021-04-26 22:35   ` Andrii Nakryiko
2021-04-27  3:28     ` Alexei Starovoitov
2021-04-27 17:38       ` Andrii Nakryiko
2021-04-23  0:26 ` [PATCH v2 bpf-next 16/16] selftests/bpf: Convert few tests to light skeleton Alexei Starovoitov
2021-04-23 21:36 ` [PATCH v2 bpf-next 00/16] bpf: syscall program, FD array, loader program, " Yonghong Song
2021-04-23 23:16   ` Alexei Starovoitov

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