From: Quentin Monnet <quentin@isovalent.com>
Date: Wed, 5 Apr 2023 13:21:17 +0000 (+0100)
Subject: bpftool: Return an error on prog dumps if both CFG and JSON are required
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=05a06be722896e51f65dbbb6a3610f85a8353d6b;p=linux.git

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

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>
---

diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 35f26f7c11246..a3cb07172789f 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -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
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index d855118f0d963..736defc6e5d05 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -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 */