[PATCH bpf-next v2 1/3] tools: bpftool: add -d option to get debug output from libbpf

[Quentin Monnet <quentin.monnet@netronome.com>]

libbpf has three levels of priority for output messages: warn, info,
debug. By default, debug output is not printed to the console.

Add a new "--debug" (short name: "-d") option to bpftool to print libbpf
logs for all three levels.

Internally, we simply use the function provided by libbpf to replace the
default printing function by one that prints logs regardless of their
level.

v2:
- Remove the possibility to select the log-levels to use (v1 offered a
  combination of "warn", "info" and "debug").
- Rename option and offer a short name: -d|--debug.
- Add option description to all bpftool manual pages (instead of
  bpftool-prog.rst only), as all commands use libbpf.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
---
 tools/bpf/bpftool/Documentation/bpftool-btf.rst    |  4 ++++
 tools/bpf/bpftool/Documentation/bpftool-cgroup.rst |  4 ++++
 .../bpf/bpftool/Documentation/bpftool-feature.rst  |  4 ++++
 tools/bpf/bpftool/Documentation/bpftool-map.rst    |  4 ++++
 tools/bpf/bpftool/Documentation/bpftool-net.rst    |  4 ++++
 tools/bpf/bpftool/Documentation/bpftool-perf.rst   |  4 ++++
 tools/bpf/bpftool/Documentation/bpftool-prog.rst   |  4 ++++
 tools/bpf/bpftool/Documentation/bpftool.rst        |  3 +++
 tools/bpf/bpftool/bash-completion/bpftool          |  2 +-
 tools/bpf/bpftool/main.c                           | 14 +++++++++++++-
 10 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/bpftool-btf.rst b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
index 2dbc1413fabd..00668df1bf7a 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-btf.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-btf.rst
@@ -67,6 +67,10 @@ OPTIONS
 	-p, --pretty
 		  Generate human-readable JSON output. Implies **-j**.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 EXAMPLES
 ========
 **# bpftool btf dump id 1226**
diff --git a/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst b/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst
index ac26876389c2..36807735e2a5 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst
@@ -113,6 +113,10 @@ OPTIONS
 	-f, --bpffs
 		  Show file names of pinned programs.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 EXAMPLES
 ========
 |
diff --git a/tools/bpf/bpftool/Documentation/bpftool-feature.rst b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
index 14180e887082..4d08f35034a2 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-feature.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
@@ -73,6 +73,10 @@ OPTIONS
 	-p, --pretty
 		  Generate human-readable JSON output. Implies **-j**.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 SEE ALSO
 ========
 	**bpf**\ (2),
diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 13ef27b39f20..490b4501cb6e 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -152,6 +152,10 @@ OPTIONS
 		  Do not automatically attempt to mount any virtual file system
 		  (such as tracefs or BPF virtual file system) when necessary.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 EXAMPLES
 ========
 **# bpftool map show**
diff --git a/tools/bpf/bpftool/Documentation/bpftool-net.rst b/tools/bpf/bpftool/Documentation/bpftool-net.rst
index 934580850f42..d8e5237a2085 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-net.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-net.rst
@@ -65,6 +65,10 @@ OPTIONS
 	-p, --pretty
 		  Generate human-readable JSON output. Implies **-j**.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 EXAMPLES
 ========
 
diff --git a/tools/bpf/bpftool/Documentation/bpftool-perf.rst b/tools/bpf/bpftool/Documentation/bpftool-perf.rst
index 0c7576523a21..e252bd0bc434 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-perf.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-perf.rst
@@ -53,6 +53,10 @@ OPTIONS
 	-p, --pretty
 		  Generate human-readable JSON output. Implies **-j**.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 EXAMPLES
 ========
 
diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
index e8118544d118..9a92614569e6 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
@@ -174,6 +174,10 @@ OPTIONS
 		  Do not automatically attempt to mount any virtual file system
 		  (such as tracefs or BPF virtual file system) when necessary.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
+
 EXAMPLES
 ========
 **# bpftool prog show**
diff --git a/tools/bpf/bpftool/Documentation/bpftool.rst b/tools/bpf/bpftool/Documentation/bpftool.rst
index 3e562d7fd56f..43dba0717953 100644
--- a/tools/bpf/bpftool/Documentation/bpftool.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool.rst
@@ -66,6 +66,9 @@ OPTIONS
 		  Do not automatically attempt to mount any virtual file system
 		  (such as tracefs or BPF virtual file system) when necessary.
 
+	-d, --debug
+		  Print all logs available from libbpf, including debug-level
+		  information.
 
 SEE ALSO
 ========
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 50e402a5a9c8..3a476e25d046 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -181,7 +181,7 @@ _bpftool()
 
     # Deal with options
     if [[ ${words[cword]} == -* ]]; then
-        local c='--version --json --pretty --bpffs --mapcompat'
+        local c='--version --json --pretty --bpffs --mapcompat --debug'
         COMPREPLY=( $( compgen -W "$c" -- "$cur" ) )
         return 0
     fi
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 1ac1fc520e6a..d74293938a05 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -10,6 +10,7 @@
 #include <string.h>
 
 #include <bpf.h>
+#include <libbpf.h>
 
 #include "main.h"
 
@@ -77,6 +78,13 @@ static int do_version(int argc, char **argv)
 	return 0;
 }
 
+static int __printf(2, 0)
+print_all_levels(__maybe_unused enum libbpf_print_level level,
+		 const char *format, va_list args)
+{
+	return vfprintf(stderr, format, args);
+}
+
 int cmd_select(const struct cmd *cmds, int argc, char **argv,
 	       int (*help)(int argc, char **argv))
 {
@@ -317,6 +325,7 @@ int main(int argc, char **argv)
 		{ "bpffs",	no_argument,	NULL,	'f' },
 		{ "mapcompat",	no_argument,	NULL,	'm' },
 		{ "nomount",	no_argument,	NULL,	'n' },
+		{ "debug",	no_argument,	NULL,	'd' },
 		{ 0 }
 	};
 	int opt, ret;
@@ -332,7 +341,7 @@ int main(int argc, char **argv)
 	hash_init(map_table.table);
 
 	opterr = 0;
-	while ((opt = getopt_long(argc, argv, "Vhpjfmn",
+	while ((opt = getopt_long(argc, argv, "Vhpjfmnd",
 				  options, NULL)) >= 0) {
 		switch (opt) {
 		case 'V':
@@ -362,6 +371,9 @@ int main(int argc, char **argv)
 		case 'n':
 			block_mount = true;
 			break;
+		case 'd':
+			libbpf_set_print(print_all_levels);
+			break;
 		default:
 			p_err("unrecognized option '%s'", argv[optind - 1]);
 			if (json_output)
-- 
2.17.1