2021-03-13 11:35 UTC-0800 ~ Andrii Nakryiko <andrii@xxxxxxxxxx>
> Add `bpftool gen object <output-file> <input_file>...` command to statically
> link multiple BPF ELF object files into a single output BPF ELF object file.
>
> Similarly to existing '*.o' convention, bpftool is establishing a '*.bpfo'
> convention for statically-linked BPF object files. Both .o and .bpfo suffixes
> will be stripped out during BPF skeleton generation to infer BPF object name.
>
> This patch also updates bash completions and man page. Man page gets a short
> section on `gen object` command, but also updates the skeleton example to show
> off workflow for BPF application with two .bpf.c files, compiled individually
> with Clang, then resulting object files are linked together with `gen object`,
> and then final object file is used to generate usable BPF skeleton. This
> should help new users understand realistic workflow w.r.t. compiling
> mutli-file BPF application.
>
> Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> ---
> .../bpf/bpftool/Documentation/bpftool-gen.rst | 65 +++++++++++++++----
> tools/bpf/bpftool/bash-completion/bpftool | 2 +-
> tools/bpf/bpftool/gen.c | 49 +++++++++++++-
> 3 files changed, 99 insertions(+), 17 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Documentation/bpftool-gen.rst b/tools/bpf/bpftool/Documentation/bpftool-gen.rst
> index 84cf0639696f..4cdce187c393 100644
> --- a/tools/bpf/bpftool/Documentation/bpftool-gen.rst
> +++ b/tools/bpf/bpftool/Documentation/bpftool-gen.rst
> @@ -14,16 +14,37 @@ SYNOPSIS
>
> *OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
>
> - *COMMAND* := { **skeleton** | **help** }
> + *COMMAND* := { **object** | **skeleton** | **help** }
>
> GEN COMMANDS
> =============
>
> +| **bpftool** **gen object** *OUTPUT_FILE* *INPUT_FILE* [*INPUT_FILE*...]
> | **bpftool** **gen skeleton** *FILE*
> | **bpftool** **gen help**
>
> DESCRIPTION
> ===========
> + **bpftool gen object** *OUTPUT_FILE* *INPUT_FILE* [*INPUT_FILE*...]
> + Statically link (combine) together one or more *INPUT_FILE*'s
> + into a single resulting *OUTPUT_FILE*. All the files involed
Typo: "involed"
> + are BPF ELF object files.
> +
> + The rules of BPF static linking are mostly the same as for
> + user-space object files, but in addition to combining data
> + and instruction sections, .BTF and .BTF.ext (if present in
> + any of the input files) data are combined together. .BTF
> + data is deduplicated, so all the common types across
> + *INPUT_FILE*'s will only be represented once in the resulting
> + BTF information.
> +
> + BPF static linking allows to partition BPF source code into
> + individually compiled files that are then linked into
> + a single resulting BPF object file, which can be used to
> + generated BPF skeleton (with **gen skeleton** command) or
> + passed directly into **libbpf** (using **bpf_object__open()**
> + family of APIs).
> +
> **bpftool gen skeleton** *FILE*
> Generate BPF skeleton C header file for a given *FILE*.
>
> diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
> index fdffbc64c65c..7ca23c58f2c0 100644
> --- a/tools/bpf/bpftool/bash-completion/bpftool
> +++ b/tools/bpf/bpftool/bash-completion/bpftool
> @@ -981,7 +981,7 @@ _bpftool()
> ;;
> gen)
> case $command in
> - skeleton)
> + object|skeleton)
> _filedir
> ;;
> *)
Suggesting the "object" keyword for completing "bpftool gen [tab]"
is missing. It is just a few lines below:
------
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index fdffbc64c65c..223438e86932 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -981,12 +981,12 @@ _bpftool()
;;
gen)
case $command in
- skeleton)
+ object|skeleton)
_filedir
;;
*)
[[ $prev == $object ]] && \
- COMPREPLY=( $( compgen -W 'skeleton help' -- "$cur" ) )
+ COMPREPLY=( $( compgen -W 'object skeleton help' -- "$cur" ) )
;;
esac
;;
------
Looks good otherwise. Thanks for the documentation, it's great to
have the example in the man page.
Pending the two nits above are fixed:
Reviewed-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Quentin
