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Date: Thu, 25 Apr 2019 20:20:55 +0100
From: Quentin Monnet <quentin.monnet@...ronome.com>
To: Andrii Nakryiko <andriin@...com>, andrii.nakryiko@...il.com,
kernel-team@...com, netdev@...r.kernel.org, bpf@...r.kernel.org,
ast@...com, daniel@...earbox.net, yhs@...com,
songliubraving@...com, kafai@...com, acme@...nel.org
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH v3 bpf-next 2/4] bpftool/docs: add btf sub-command
documentation
2019-04-25 09:55 UTC-0700 ~ Andrii Nakryiko <andriin@...com>
> Document usage and sample output format for `btf dump` sub-command.
>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Alexei Starovoitov <ast@...com>
> Cc: Yonghong Song <yhs@...com>
> Cc: Martin KaFai Lau <kafai@...com>
> Cc: Song Liu <songliubraving@...com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Acked-by: Yonghong Song <yhs@...com>
> Signed-off-by: Andrii Nakryiko <andriin@...com>
> ---
> .../bpf/bpftool/Documentation/bpftool-btf.rst | 205 ++++++++++++++++++
> .../bpftool/Documentation/bpftool-cgroup.rst | 3 +-
> .../bpftool/Documentation/bpftool-feature.rst | 3 +-
> .../bpf/bpftool/Documentation/bpftool-map.rst | 3 +-
> .../bpf/bpftool/Documentation/bpftool-net.rst | 3 +-
> .../bpftool/Documentation/bpftool-perf.rst | 3 +-
> .../bpftool/Documentation/bpftool-prog.rst | 3 +-
> tools/bpf/bpftool/Documentation/bpftool.rst | 3 +-
> 8 files changed, 219 insertions(+), 7 deletions(-)
> create mode 100644 tools/bpf/bpftool/Documentation/bpftool-btf.rst
>
> diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> new file mode 100644
> index 000000000000..d37d782a1cfb
> --- /dev/null
> +++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> @@ -0,0 +1,205 @@
> +================
> +bpftool-btf
> +================
> +-------------------------------------------------------------------------------
> +tool for inspection of BTF data
> +-------------------------------------------------------------------------------
> +
> +:Manual section: 8
> +
> +SYNOPSIS
> +========
> +
> + **bpftool** [*OPTIONS*] **btf** *COMMAND*
> +
> + *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
> +
> + *COMMANDS* :=
> + { **dump** | **help** }
Commands fit on a single line.
> +
> +MAP COMMANDS
> +=============
> +
> +| **bpftool** **btf dump** *BTF_SRC*
Why so much space between "dump" and "BTF_SRC"? Is it to make it easier
to align it if other commands are added in the future? For now it looks
a bit strange in my opinion.
> +| **bpftool** **btf help**
> +|
> +| *BTF_SRC* := { **id** *BTF_ID* | **prog** *PROG* | **map** *MAP* [{**key** | **value** | **kv** | **all**}] | **file** *FILE* }
> +| *MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
> +| *PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
> +
> +DESCRIPTION
> +===========
> + **bpftool map dump** *MAP*
That's a lot of space again. I think you copied it from bpftool-map.rst.
But it looks like you forgot to replace "map dump MAP" with "btf dump
BTF_SRC" :).
A brief description of key/value/kv/all, or of what kind of FILE is
expected, would be welcome here.
> + Dump BTF entries from a given *BTF_SRC*.
> +
> + **bpftool map help**
"bpftool btf help"
> + Print short help message.
> +
> +OPTIONS
> +=======
> + -h, --help
> + Print short generic help message (similar to **bpftool help**).
> +
> + -V, --version
> + Print version number (similar to **bpftool version**).
> +
> + -j, --json
> + Generate JSON output. For commands that cannot produce JSON, this
> + option has no effect.
> +
> + -p, --pretty
> + Generate human-readable JSON output. Implies **-j**.
> +
> +EXAMPLES
> +========
> +**# bpftool btf dump id 1226**
> +::
> +
> + [1] PTR '(anon)' type_id=2
> + [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
> + 'pad' type_id=3 bits_offset=0
> + 'sock' type_id=4 bits_offset=64
> + [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
> + [4] PTR '(anon)' type_id=5
> + [5] FWD 'sock' fwd_kind=union
> +
> +This gives an example of default output for all supported BTF kinds.
> +
> +**$ cat prog.c**
> +::
> +
> + struct fwd_struct;
> +
> + enum my_enum {
> + VAL1 = 3,
> + VAL2 = 7,
> + };
> +
> + typedef struct my_struct my_struct_t;
> +
> + struct my_struct {
> + const unsigned int const_int_field;
> + int bitfield_field: 4;
> + char arr_field[16];
> + const struct fwd_struct *restrict fwd_field;
> + enum my_enum enum_field;
> + volatile my_struct_t *typedef_ptr_field;
> + };
> +
> + union my_union {
> + int a;
> + struct my_struct b;
> + };
> +
> + struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
> + .bitfield_field = 3,
> + .enum_field = VAL1,
> + };
> + int global_var __attribute__((section("data_sec"))) = 7;
> +
> + __attribute__((noinline))
> + int my_func(union my_union *arg1, int arg2)
> + {
> + static int static_var __attribute__((section("data_sec"))) = 123;
> + static_var++;
> + return static_var;
> + }
> +
> +**$ bpftool btf dump file prog.o**
> +::
> +
> + [1] PTR '(anon)' type_id=2
> + [2] UNION 'my_union' size=48 vlen=2
> + 'a' type_id=3 bits_offset=0
> + 'b' type_id=4 bits_offset=0
> + [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
> + [4] STRUCT 'my_struct' size=48 vlen=6
> + 'const_int_field' type_id=5 bits_offset=0
> + 'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
> + 'arr_field' type_id=8 bits_offset=40
> + 'fwd_field' type_id=10 bits_offset=192
> + 'enum_field' type_id=14 bits_offset=256
> + 'typedef_ptr_field' type_id=15 bits_offset=320
> + [5] CONST '(anon)' type_id=6
> + [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)
> + [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
> + [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
> + [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
> + [10] RESTRICT '(anon)' type_id=11
> + [11] PTR '(anon)' type_id=12
> + [12] CONST '(anon)' type_id=13
> + [13] FWD 'fwd_struct' fwd_kind=union
> + [14] ENUM 'my_enum' size=4 vlen=2
> + 'VAL1' val=3
> + 'VAL2' val=7
> + [15] PTR '(anon)' type_id=16
> + [16] VOLATILE '(anon)' type_id=17
> + [17] TYPEDEF 'my_struct_t' type_id=4
> + [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
> + 'arg1' type_id=1
> + 'arg2' type_id=3
> + [19] FUNC 'my_func' type_id=18
> + [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
> + [21] VAR 'global_var' type_id=3, linkage=global-alloc
> + [22] VAR 'my_func.static_var' type_id=3, linkage=static
> + [23] DATASEC 'data_sec' size=0 vlen=3
> + type_id=20 offset=0 size=48
> + type_id=21 offset=0 size=4
> + type_id=22 offset=52 size=4
> +
> +The following commands print BTF types associated with specified map's key,
> +value, both key and value, and all BTF types, respectively. By default, both
> +key and value types will be printed.
This kind of info should go into the command's description (although I
don't mind if we also repeat it here).
> +
> +**# bpftool btf dump map id 123 key**
> +
> +::
> +
> + [39] TYPEDEF 'u32' type_id=37
> +
> +**# bpftool btf dump map id 123 value**
> +
> +::
> +
> + [86] PTR '(anon)' type_id=87
> +
> +**# bpftool btf dump map id 123 kv**
> +
> +::
> +
> + [39] TYPEDEF 'u32' type_id=37
> + [86] PTR '(anon)' type_id=87
> +
> +**# bpftool btf dump map id 123 all**
> +
> +::
> +
> + [1] PTR '(anon)' type_id=0
> + .
> + .
> + .
> + [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4
> +
> +All the standard ways to specify map or program is supported:
s/is/are/
> +
> +**# bpftool btf dump map id 123**
> +
> +**# bpftool btf dump map pinned /sys/fs/bpf/map_name**
> +
> +**# bpftool btf dump prog id 456**
> +
> +**# bpftool btf dump prog tag b88e0a09b1d9759d**
> +
> +**# bpftool btf dump prog pinned /sys/fs/bpf/prog_name**
> +
> +SEE ALSO
> +========
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