tools: bpftool: add probes for eBPF map types

Add new probes for eBPF map types, to detect what are the ones available
on the system. Try creating one map of each type, and see if the kernel
complains.

Sample output:

    # bpftool feature probe kernel
    ...
    Scanning eBPF map types...
    eBPF map_type hash is available
    eBPF map_type array is available
    eBPF map_type prog_array is available
    ...

    # bpftool --json --pretty feature probe kernel
    {
        ...
        "map_types": {
            "have_hash_map_type": true,
            "have_array_map_type": true,
            "have_prog_array_map_type": true,
            ...
        }
    }

v5:
- In libbpf.map, move global symbol to the new LIBBPF_0.0.2 section.

v3:
- Use a switch with all enum values for setting specific map parameters,
  so that gcc complains at compile time (-Wswitch-enum) if new map types
  were added to the kernel but libbpf was not updated.

v2:
- Move probes from bpftool to libbpf.
- Remove C-style macros output from this patch.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 32 insertions, 1 deletions

diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
index d6508dde4808..cc731475c74b 100644
--- a/tools/bpf/bpftool/feature.c
+++ b/tools/bpf/bpftool/feature.c
@@ -438,6 +438,26 @@ static void probe_prog_type(enum bpf_prog_type prog_type, bool *supported_types)
 	print_bool_feature(feat_name, plain_desc, res);
 }
 
+static void probe_map_type(enum bpf_map_type map_type)
+{
+	const char *plain_comment = "eBPF map_type ";
+	char feat_name[128], plain_desc[128];
+	size_t maxlen;
+	bool res;
+
+	res = bpf_probe_map_type(map_type, 0);
+
+	maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
+	if (strlen(map_type_name[map_type]) > maxlen) {
+		p_info("map type name too long");
+		return;
+	}
+
+	sprintf(feat_name, "have_%s_map_type", map_type_name[map_type]);
+	sprintf(plain_desc, "%s%s", plain_comment, map_type_name[map_type]);
+	print_bool_feature(feat_name, plain_desc, res);
+}
+
 static int do_probe(int argc, char **argv)
 {
 	enum probe_component target = COMPONENT_UNSPEC;
@@ -507,6 +527,12 @@ static int do_probe(int argc, char **argv)
 	for (i = BPF_PROG_TYPE_UNSPEC + 1; i < ARRAY_SIZE(prog_type_name); i++)
 		probe_prog_type(i, supported_types);
 
+	print_end_then_start_section("map_types",
+				     "Scanning eBPF map types...");
+
+	for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++)
+		probe_map_type(i);
+
 exit_close_json:
 	if (json_output) {
 		/* End current "section" of probes */
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 5cfc6601de9b..d7dd84d3c660 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -75,6 +75,9 @@ static const char * const prog_type_name[] = {
 	[BPF_PROG_TYPE_FLOW_DISSECTOR]		= "flow_dissector",
 };
 
+extern const char * const map_type_name[];
+extern const size_t map_type_name_size;
+
 enum bpf_obj_type {
 	BPF_OBJ_UNKNOWN,
 	BPF_OBJ_PROG,
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 850c99ac980f..f15c520195b7 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -21,7 +21,7 @@
 #include "json_writer.h"
 #include "main.h"
 
-static const char * const map_type_name[] = {
+const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_UNSPEC]			= "unspec",
 	[BPF_MAP_TYPE_HASH]			= "hash",
 	[BPF_MAP_TYPE_ARRAY]			= "array",
@@ -48,6 +48,8 @@ static const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_STACK]			= "stack",
 };
 
+const size_t map_type_name_size = ARRAY_SIZE(map_type_name);
+
 static bool map_is_per_cpu(__u32 type)
 {
 	return type == BPF_MAP_TYPE_PERCPU_HASH ||