[PATCH bpf 2/2] bpftool: support queues and stacks in lookup command

[Stanislav Fomichev <sdf@google.com>]

Bpftool expects key for 'lookup' operations. For some map types, key should
not be specified. Support looking up those map types.

Before:
bpftool map create /sys/fs/bpf/q type queue value 4 entries 10 name q
bpftool map update pinned /sys/fs/bpf/q value 0 1 2 3
bpftool map lookup pinned /sys/fs/bpf/q
Error: did not find key

After:
bpftool map create /sys/fs/bpf/q type queue value 4 entries 10 name q
bpftool map update pinned /sys/fs/bpf/q value 0 1 2 3
bpftool map lookup pinned /sys/fs/bpf/q
key:   value: 00 01 02 03

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 tools/bpf/bpftool/Documentation/bpftool-map.rst |  4 ++--
 tools/bpf/bpftool/map.c                         | 15 +++++++++++----
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 81842fdf483d..ea2353330c94 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -26,7 +26,7 @@ MAP COMMANDS
 |		**entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**dev** *NAME*]
 |	**bpftool** **map dump**       *MAP*
 |	**bpftool** **map update**     *MAP* [**key** *DATA*]  **value** *VALUE* [*UPDATE_FLAGS*]
-|	**bpftool** **map lookup**     *MAP*  **key** *DATA*
+|	**bpftool** **map lookup**     *MAP* [**key** *DATA*]
 |	**bpftool** **map getnext**    *MAP* [**key** *DATA*]
 |	**bpftool** **map delete**     *MAP*  **key** *DATA*
 |	**bpftool** **map pin**        *MAP*  *FILE*
@@ -75,7 +75,7 @@ DESCRIPTION
 		  the bytes are parsed as decimal values, unless a "0x" prefix
 		  (for hexadecimal) or a "0" prefix (for octal) is provided.
 
-	**bpftool map lookup**  *MAP*  **key** *DATA*
+	**bpftool map lookup**  *MAP* [**key** *DATA*]
 		  Lookup **key** in the map.
 
 	**bpftool map getnext** *MAP* [**key** *DATA*]
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 30b92715248d..3c7adc31b567 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -835,11 +835,11 @@ static int do_update(int argc, char **argv)
 
 static int do_lookup(int argc, char **argv)
 {
+	void *key = NULL, *value = NULL;
 	struct bpf_map_info info = {};
 	__u32 len = sizeof(info);
 	json_writer_t *btf_wtr;
 	struct btf *btf = NULL;
-	void *key, *value;
 	int err;
 	int fd;
 
@@ -850,9 +850,16 @@ static int do_lookup(int argc, char **argv)
 	if (fd < 0)
 		return -1;
 
-	key = malloc(info.key_size);
+	if (info.key_size) {
+		key = malloc(info.key_size);
+		if (!key) {
+			p_err("mem alloc failed");
+			err = -1;
+			goto exit_free;
+		}
+	}
 	value = alloc_value(&info);
-	if (!key || !value) {
+	if (!value) {
 		p_err("mem alloc failed");
 		err = -1;
 		goto exit_free;
@@ -1143,7 +1150,7 @@ static int do_help(int argc, char **argv)
 		"                              [dev NAME]\n"
 		"       %s %s dump       MAP\n"
 		"       %s %s update     MAP [key DATA] value VALUE [UPDATE_FLAGS]\n"
-		"       %s %s lookup     MAP  key DATA\n"
+		"       %s %s lookup     MAP [key DATA]\n"
 		"       %s %s getnext    MAP [key DATA]\n"
 		"       %s %s delete     MAP  key DATA\n"
 		"       %s %s pin        MAP  FILE\n"
-- 
2.20.1.415.g653613c723-goog