Merge branch 'libbpf: Textual representation of enums'

Daniel Müller says:

====================

This patch set introduces the means for querying a textual representation of
the following BPF related enum types:
- enum bpf_map_type
- enum bpf_prog_type
- enum bpf_attach_type
- enum bpf_link_type

To make that possible, we introduce a new public function for each of the types:
libbpf_bpf_<type>_type_str.

Having a way to query a textual representation has been asked for in the past
(by systemd, among others). Such representations can generally be useful in
tracing and logging contexts, among others. At this point, at least one client,
bpftool, maintains such a mapping manually, which is prone to get out of date as
new enum variants are introduced. libbpf is arguably best situated to keep this
list complete and up-to-date. This patch series adds BTF based tests to ensure
that exhaustiveness is upheld moving forward.

The libbpf provided textual representation can be inferred from the
corresponding enum variant name by removing the prefix and lowercasing the
remainder. E.g., BPF_PROG_TYPE_SOCKET_FILTER -> socket_filter. Unfortunately,
bpftool does not use such a programmatic approach for some of the
bpf_attach_type variants. We decided in favor of changing its behavior to work
with libbpf representations. However, for user inputs, specifically, we do
maintain support for the traditionally used names around (please see patch
"bpftool: Use libbpf_bpf_attach_type_str").

The patch series is structured as follows:
- for each enumeration type in {bpf_prog_type, bpf_map_type, bpf_attach_type,
  bpf_link_type}:
  - we first introduce the corresponding public libbpf API function
  - we then add BTF based self-tests
  - we lastly adjust bpftool to use the libbpf provided functionality

Signed-off-by: Daniel Müller <deso@posteo.net>
Cc: Quentin Monnet <quentin@isovalent.com>
---
Changelog:
v3 -> v4:
- use full string comparison for newly added attach types
- switched away from erroneously used kdoc-style comments
- removed unused prog_types variable and containing section from
  test_bpftool_synctypes.py
- adjusted wording in documentation of get_types_from_array function
- split various test_bpftool_synctypes.py changes into commits where they are
  required to eliminate temporary failures of this test

v2 -> v3:
- use LIBBPF_1.0.0 section in libbpf.map for newly added exports

v1 -> v2:
- adjusted bpftool to work with algorithmically determined attach types as
  libbpf now uses (just removed prefix from enum name and lowercased the rest)
  - adjusted tests, man page, and completion script to work with the new names
  - renamed bpf_attach_type_str -> bpf_attach_type_input_str
  - for input: added special cases that accept the traditionally used strings as
    well
- changed 'char const *' -> 'const char *'
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 31 insertions, 30 deletions

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 6353a789322b..7a20931c3250 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -13,19 +13,6 @@
 #include "json_writer.h"
 #include "main.h"
 
-static const char * const link_type_name[] = {
-	[BPF_LINK_TYPE_UNSPEC]			= "unspec",
-	[BPF_LINK_TYPE_RAW_TRACEPOINT]		= "raw_tracepoint",
-	[BPF_LINK_TYPE_TRACING]			= "tracing",
-	[BPF_LINK_TYPE_CGROUP]			= "cgroup",
-	[BPF_LINK_TYPE_ITER]			= "iter",
-	[BPF_LINK_TYPE_NETNS]			= "netns",
-	[BPF_LINK_TYPE_XDP]			= "xdp",
-	[BPF_LINK_TYPE_PERF_EVENT]		= "perf_event",
-	[BPF_LINK_TYPE_KPROBE_MULTI]		= "kprobe_multi",
-	[BPF_LINK_TYPE_STRUCT_OPS]               = "struct_ops",
-};
-
 static struct hashmap *link_table;
 
 static int link_parse_fd(int *argc, char ***argv)
@@ -67,9 +54,12 @@ static int link_parse_fd(int *argc, char ***argv)
 static void
 show_link_header_json(struct bpf_link_info *info, json_writer_t *wtr)
 {
+	const char *link_type_str;
+
 	jsonw_uint_field(wtr, "id", info->id);
-	if (info->type < ARRAY_SIZE(link_type_name))
-		jsonw_string_field(wtr, "type", link_type_name[info->type]);
+	link_type_str = libbpf_bpf_link_type_str(info->type);
+	if (link_type_str)
+		jsonw_string_field(wtr, "type", link_type_str);
 	else
 		jsonw_uint_field(wtr, "type", info->type);
 
@@ -78,9 +68,11 @@ show_link_header_json(struct bpf_link_info *info, json_writer_t *wtr)
 
 static void show_link_attach_type_json(__u32 attach_type, json_writer_t *wtr)
 {
-	if (attach_type < ARRAY_SIZE(attach_type_name))
-		jsonw_string_field(wtr, "attach_type",
-				   attach_type_name[attach_type]);
+	const char *attach_type_str;
+
+	attach_type_str = libbpf_bpf_attach_type_str(attach_type);
+	if (attach_type_str)
+		jsonw_string_field(wtr, "attach_type", attach_type_str);
 	else
 		jsonw_uint_field(wtr, "attach_type", attach_type);
 }
@@ -121,6 +113,7 @@ static int get_prog_info(int prog_id, struct bpf_prog_info *info)
 static int show_link_close_json(int fd, struct bpf_link_info *info)
 {
 	struct bpf_prog_info prog_info;
+	const char *prog_type_str;
 	int err;
 
 	jsonw_start_object(json_wtr);
@@ -137,12 +130,12 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
 		if (err)
 			return err;
 
-		if (prog_info.type < prog_type_name_size)
-			jsonw_string_field(json_wtr, "prog_type",
-					   prog_type_name[prog_info.type]);
+		prog_type_str = libbpf_bpf_prog_type_str(prog_info.type);
+		/* libbpf will return NULL for variants unknown to it. */
+		if (prog_type_str)
+			jsonw_string_field(json_wtr, "prog_type", prog_type_str);
 		else
-			jsonw_uint_field(json_wtr, "prog_type",
-					 prog_info.type);
+			jsonw_uint_field(json_wtr, "prog_type", prog_info.type);
 
 		show_link_attach_type_json(info->tracing.attach_type,
 					   json_wtr);
@@ -184,9 +177,12 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
 
 static void show_link_header_plain(struct bpf_link_info *info)
 {
+	const char *link_type_str;
+
 	printf("%u: ", info->id);
-	if (info->type < ARRAY_SIZE(link_type_name))
-		printf("%s  ", link_type_name[info->type]);
+	link_type_str = libbpf_bpf_link_type_str(info->type);
+	if (link_type_str)
+		printf("%s  ", link_type_str);
 	else
 		printf("type %u  ", info->type);
 
@@ -195,8 +191,11 @@ static void show_link_header_plain(struct bpf_link_info *info)
 
 static void show_link_attach_type_plain(__u32 attach_type)
 {
-	if (attach_type < ARRAY_SIZE(attach_type_name))
-		printf("attach_type %s  ", attach_type_name[attach_type]);
+	const char *attach_type_str;
+
+	attach_type_str = libbpf_bpf_attach_type_str(attach_type);
+	if (attach_type_str)
+		printf("attach_type %s  ", attach_type_str);
 	else
 		printf("attach_type %u  ", attach_type);
 }
@@ -214,6 +213,7 @@ static void show_iter_plain(struct bpf_link_info *info)
 static int show_link_close_plain(int fd, struct bpf_link_info *info)
 {
 	struct bpf_prog_info prog_info;
+	const char *prog_type_str;
 	int err;
 
 	show_link_header_plain(info);
@@ -228,9 +228,10 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
 		if (err)
 			return err;
 
-		if (prog_info.type < prog_type_name_size)
-			printf("\n\tprog_type %s  ",
-			       prog_type_name[prog_info.type]);
+		prog_type_str = libbpf_bpf_prog_type_str(prog_info.type);
+		/* libbpf will return NULL for variants unknown to it. */
+		if (prog_type_str)
+			printf("\n\tprog_type %s  ", prog_type_str);
 		else
 			printf("\n\tprog_type %u  ", prog_info.type);