On 13/05/2024 12:12, Quentin Monnet wrote:
> 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.
>
>
ah good catch, thanks!
>>
>> *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?
>
Sure, will do.
> Other than these, the changes look good to me, thank you
>
> Reviewed-by: Quentin Monnet <qmo@xxxxxxxxxx>
>
Thanks for reviewing!
