2024-05-10 11:32 UTC+0100 ~ Alan Maguire <alan.maguire@xxxxxxxxxx>
> If the -R <base_btf> option is used, we can display BTF that has been
> generated with distilled base BTF in its relocated form. For example
> for bpf_testmod.ko (which is built as an out-of-tree module, so has
> a distilled .BTF.base section:
>
> bpftool btf dump file bpf_testmod.ko
>
> Alternatively, we can display content relocated with
> (a possibly changed) base BTF via
>
> bpftool btf dump -R /sys/kernel/btf/vmlinux bpf_testmod.ko
>
> The latter mirrors how the kernel will handle such split
> BTF; it relocates its representation with the running
> kernel, and if successful, renumbers BTF ids to reference
> the current vmlinux BTF.
>
> Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
> ---
> tools/bpf/bpftool/Documentation/bpftool-btf.rst | 15 ++++++++++++++-
> tools/bpf/bpftool/bash-completion/bpftool | 7 ++++---
> tools/bpf/bpftool/btf.c | 11 ++++++++++-
> tools/bpf/bpftool/main.c | 14 +++++++++++++-
> tools/bpf/bpftool/main.h | 2 ++
> 5 files changed, 43 insertions(+), 6 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> index eaba24320fb2..fd6bb1280e7b 100644
> --- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> +++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
> @@ -16,7 +16,7 @@ SYNOPSIS
>
> **bpftool** [*OPTIONS*] **btf** *COMMAND*
>
> -*OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } }
> +*OPTIONS* := { |COMMON_OPTIONS| | { **-B** | **--base-btf** } { **-R** | **relocate-base-btf** } }
The double-dash is missing at the beginning of --relocate-base-btf.
>
> *COMMANDS* := { **dump** | **help** }
>
> @@ -85,6 +85,19 @@ OPTIONS
> BTF object is passed through other handles, this option becomes
> necessary.
>
> +-R, --relocate-base-btf *FILE*
> + When split BTF is generated with distilled base BTF for relocation,
> + the latter is stored in a .BTF.base section and allows us to later
> + relocate split BTF and a potentially-changed base BTF by using
> + information in the .BTF.base section about the base types referenced
> + from split BTF. Relocation is carried out against the split BTF
> + supplied via this parameter and the split BTF will then refer to
> + the base types supplied in *FILE*.
> +
> + If this option is not used, split BTF is shown relative to the
> + .BTF.base, which contains just enough information to support later
> + relocation.
> +
> EXAMPLES
> ========
> **# bpftool btf dump id 1226**
> diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
> index 04afe2ac2228..878cf3d49a76 100644
> --- a/tools/bpf/bpftool/bash-completion/bpftool
> +++ b/tools/bpf/bpftool/bash-completion/bpftool
> @@ -262,7 +262,7 @@ _bpftool()
> # Deal with options
> if [[ ${words[cword]} == -* ]]; then
> local c='--version --json --pretty --bpffs --mapcompat --debug \
> - --use-loader --base-btf'
> + --use-loader --base-btf --relocate-base-btf'
> COMPREPLY=( $( compgen -W "$c" -- "$cur" ) )
> return 0
> fi
> @@ -283,7 +283,7 @@ _bpftool()
> _sysfs_get_netdevs
> return 0
> ;;
> - file|pinned|-B|--base-btf)
> + file|pinned|-B|-R|--base-btf|--relocate-base-btf)
> _filedir
> return 0
> ;;
> @@ -297,7 +297,8 @@ _bpftool()
> local i pprev
> for (( i=1; i < ${#words[@]}; )); do
> if [[ ${words[i]::1} == - ]] &&
> - [[ ${words[i]} != "-B" ]] && [[ ${words[i]} != "--base-btf" ]]; then
> + [[ ${words[i]} != "-B" ]] && [[ ${words[i]} != "--base-btf" ]] &&
> + [[ ${words[i]} != "-R" ]] && [[ ${words[i]} != "--relocate-base-btf" ]]; then
> words=( "${words[@]:0:i}" "${words[@]:i+1}" )
> [[ $i -le $cword ]] && cword=$(( cword - 1 ))
> else
> diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
> index 0ca1f2417801..34f60d9e433d 100644
> --- a/tools/bpf/bpftool/btf.c
> +++ b/tools/bpf/bpftool/btf.c
> @@ -638,6 +638,14 @@ static int do_dump(int argc, char **argv)
> base_btf = btf__parse_opts(*argv, &optp);
> if (base_btf)
> btf = btf__parse_split(*argv, base_btf);
> + if (btf && relocate_base_btf) {
> + err = btf__relocate(btf, relocate_base_btf);
> + if (err) {
> + p_err("could not relocate BTF from '%s' with base BTF '%s': %s\n",
> + *argv, relocate_base_btf_path, strerror(-err));
> + goto done;
> + }
> + }
> }
> if (!btf) {
> err = -errno;
> @@ -1075,7 +1083,8 @@ static int do_help(int argc, char **argv)
> " " HELP_SPEC_MAP "\n"
> " " HELP_SPEC_PROGRAM "\n"
> " " HELP_SPEC_OPTIONS " |\n"
> - " {-B|--base-btf} }\n"
> + " {-B|--base-btf} |\n"
> + " {-R|--relocate-base-btf} }\n"
> "",
> bin_name, "btf");
>
> diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> index 08d0ac543c67..69d4906bec5c 100644
> --- a/tools/bpf/bpftool/main.c
> +++ b/tools/bpf/bpftool/main.c
> @@ -32,6 +32,8 @@ bool verifier_logs;
> bool relaxed_maps;
> bool use_loader;
> struct btf *base_btf;
> +struct btf *relocate_base_btf;
> +const char *relocate_base_btf_path;
> struct hashmap *refs_table;
>
> static void __noreturn clean_and_exit(int i)
> @@ -448,6 +450,7 @@ int main(int argc, char **argv)
> { "debug", no_argument, NULL, 'd' },
> { "use-loader", no_argument, NULL, 'L' },
> { "base-btf", required_argument, NULL, 'B' },
> + { "relocate-base-btf", required_argument, NULL, 'R' },
Nit: The lines above yours use tabs to visually align the different
fields, would you mind (optionally) re-aligning them, or at least using
tabs in your own line, please?
Other than these, the changes look good to me, thank you
Reviewed-by: Quentin Monnet <qmo@xxxxxxxxxx>
