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bpftool: Return an error on prog dumps if both CFG and JSON are required

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We do not support JSON output for control flow graphs of programs with
bpftool. So far, requiring both the CFG and JSON output would result in
producing a null JSON object. It makes more sense to raise an error
directly when parsing command line arguments and options, so that users
know they won't get any output they might expect.

If JSON is required for the graph, we leave it to Graphviz instead:

    # bpftool prog dump xlated <REF> visual | dot -Tjson

Suggested-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20230405132120.59886-5-quentin@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Quentin Monnet 2023-04-05 14:21:17 +01:00 committed by Alexei Starovoitov
parent 9fd496848b
commit 05a06be722
2 changed files with 11 additions and 6 deletions
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9
tools/bpf/bpftool/bash-completion/bpftool
View file

@ -255,16 +255,19 @@ _bpftool_map_update_get_name()
_bpftool()
{
local cur prev words objword
local cur prev words objword json=0
_init_completion || return
# Deal with options
if [[ ${words[cword]} == -* ]]; then
local c='--version --json --pretty --bpffs --mapcompat --debug \
--use-loader --base-btf'
--use-loader --base-btf'
COMPREPLY=( $( compgen -W "$c" -- "$cur" ) )
return 0
fi
if _bpftool_search_list -j --json -p --pretty; then
json=1
fi
# Deal with simplest keywords
case $prev in
@ -367,7 +370,7 @@ _bpftool()
;;
*)
_bpftool_once_attr 'file'
if _bpftool_search_list 'xlated'; then
if _bpftool_search_list 'xlated' && [[ "$json" == 0 ]]; then
COMPREPLY+=( $( compgen -W 'opcodes visual linum' -- \
"$cur" ) )
else

8
tools/bpf/bpftool/prog.c
View file

@ -849,9 +849,7 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
dd.finfo_rec_size = info->func_info_rec_size;
dd.prog_linfo = prog_linfo;
if (json_output && visual)
jsonw_null(json_wtr);
else if (json_output)
if (json_output)
dump_xlated_json(&dd, buf, member_len, opcodes, linum);
else if (visual)
dump_xlated_cfg(&dd, buf, member_len);
@ -940,6 +938,10 @@ static int do_dump(int argc, char **argv)
usage();
goto exit_close;
}
if (json_output && visual) {
p_err("'visual' is not compatible with JSON output");
goto exit_close;
}
if (json_output && nb_fds > 1)
jsonw_start_array(json_wtr); /* root array */