Merge branch 'libbpf: Support uniform BTF-defined key/value specification across all BPF maps'

Hengqi Chen says:

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

Currently a bunch of (usually pretty specialized) BPF maps do not support
specifying BTF types for they key and value. For such maps, specifying
their definition like this:

  struct {
      __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
      __type(key, int);
      __type(value, int);
  } my_perf_buf SEC(".maps");

Would actually produce warnings about retrying BPF map creation without BTF.
Users are forced to know such nuances and use __uint(key_size, 4) instead.
This is non-uniform, annoying, and inconvenient.

This patch set teaches libbpf to recognize those specialized maps and removes
BTF type IDs when creating BPF map. Also, update existing BPF selftests to
exericse this change.
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

tools/lib/bpf/libbpf.c

@@ -4669,6 +4669,30 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 			create_attr.inner_map_fd = map->inner_map_fd;
 	}
 
+	switch (def->type) {
+	case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
+	case BPF_MAP_TYPE_CGROUP_ARRAY:
+	case BPF_MAP_TYPE_STACK_TRACE:
+	case BPF_MAP_TYPE_ARRAY_OF_MAPS:
+	case BPF_MAP_TYPE_HASH_OF_MAPS:
+	case BPF_MAP_TYPE_DEVMAP:
+	case BPF_MAP_TYPE_DEVMAP_HASH:
+	case BPF_MAP_TYPE_CPUMAP:
+	case BPF_MAP_TYPE_XSKMAP:
+	case BPF_MAP_TYPE_SOCKMAP:
+	case BPF_MAP_TYPE_SOCKHASH:
+	case BPF_MAP_TYPE_QUEUE:
+	case BPF_MAP_TYPE_STACK:
+	case BPF_MAP_TYPE_RINGBUF:
+		create_attr.btf_fd = 0;
+		create_attr.btf_key_type_id = 0;
+		create_attr.btf_value_type_id = 0;
+		map->btf_key_type_id = 0;
+		map->btf_value_type_id = 0;
+	default:
+		break;
+	}
+
 	if (obj->gen_loader) {
 		bpf_gen__map_create(obj->gen_loader, &create_attr, is_inner ? -1 : map - obj->maps);
 		/* Pretend to have valid FD to pass various fd >= 0 checks.

tools/testing/selftests/bpf/progs/kfree_skb.c

@@ -9,8 +9,8 @@
 char _license[] SEC("license") = "GPL";
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } perf_buf_map SEC(".maps");
 
 #define _(P) (__builtin_preserve_access_index(P))

tools/testing/selftests/bpf/progs/perf_event_stackmap.c

@@ -11,8 +11,8 @@ typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
 struct {
 	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
 	__uint(max_entries, 16384);
-	__uint(key_size, sizeof(__u32));
-	__uint(value_size, sizeof(stack_trace_t));
+	__type(key, __u32);
+	__type(value, stack_trace_t);
 } stackmap SEC(".maps");
 
 struct {

tools/testing/selftests/bpf/progs/sockmap_verdict_prog.c

@@ -7,22 +7,22 @@ int _version SEC("version") = 1;
 struct {
 	__uint(type, BPF_MAP_TYPE_SOCKMAP);
 	__uint(max_entries, 20);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } sock_map_rx SEC(".maps");
 
 struct {
 	__uint(type, BPF_MAP_TYPE_SOCKMAP);
 	__uint(max_entries, 20);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } sock_map_tx SEC(".maps");
 
 struct {
 	__uint(type, BPF_MAP_TYPE_SOCKMAP);
 	__uint(max_entries, 20);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } sock_map_msg SEC(".maps");
 
 struct {

tools/testing/selftests/bpf/progs/test_btf_map_in_map.c

@@ -21,8 +21,8 @@ struct inner_map_sz2 {
 struct outer_arr {
 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
 	__uint(max_entries, 3);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 	/* it's possible to use anonymous struct as inner map definition here */
 	__array(values, struct {
 		__uint(type, BPF_MAP_TYPE_ARRAY);
@@ -61,8 +61,8 @@ struct inner_map_sz4 {
 struct outer_arr_dyn {
 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
 	__uint(max_entries, 3);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 	__array(values, struct {
 		__uint(type, BPF_MAP_TYPE_ARRAY);
 		__uint(map_flags, BPF_F_INNER_MAP);
@@ -81,7 +81,7 @@ struct outer_arr_dyn {
 struct outer_hash {
 	__uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);
 	__uint(max_entries, 5);
-	__uint(key_size, sizeof(int));
+	__type(key, int);
 	/* Here everything works flawlessly due to reuse of struct inner_map
 	 * and compiler will complain at the attempt to use non-inner_map
 	 * references below. This is great experience.
@@ -111,8 +111,8 @@ struct sockarr_sz2 {
 struct outer_sockarr_sz1 {
 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
 	__uint(max_entries, 1);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 	__array(values, struct sockarr_sz1);
 } outer_sockarr SEC(".maps") = {
 	.values = { (void *)&sockarr_sz1 },

tools/testing/selftests/bpf/progs/test_map_in_map.c

@@ -9,18 +9,16 @@ struct {
 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
 	__uint(max_entries, 1);
 	__uint(map_flags, 0);
-	__uint(key_size, sizeof(__u32));
-	/* must be sizeof(__u32) for map in map */
-	__uint(value_size, sizeof(__u32));
+	__type(key, __u32);
+	__type(value, __u32);
 } mim_array SEC(".maps");
 
 struct {
 	__uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);
 	__uint(max_entries, 1);
 	__uint(map_flags, 0);
-	__uint(key_size, sizeof(int));
-	/* must be sizeof(__u32) for map in map */
-	__uint(value_size, sizeof(__u32));
+	__type(key, int);
+	__type(value, __u32);
 } mim_hash SEC(".maps");
 
 SEC("xdp")

tools/testing/selftests/bpf/progs/test_map_in_map_invalid.c

@@ -13,7 +13,7 @@ struct inner {
 struct {
 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
 	__uint(max_entries, 0); /* This will make map creation to fail */
-	__uint(key_size, sizeof(__u32));
+	__type(key, __u32);
 	__array(values, struct inner);
 } mim SEC(".maps");
 

tools/testing/selftests/bpf/progs/test_pe_preserve_elems.c

@@ -7,15 +7,15 @@
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
 	__uint(max_entries, 1);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } array_1 SEC(".maps");
 
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
 	__uint(max_entries, 1);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 	__uint(map_flags, BPF_F_PRESERVE_ELEMS);
 } array_2 SEC(".maps");
 

tools/testing/selftests/bpf/progs/test_perf_buffer.c

@@ -8,8 +8,8 @@
 
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } perf_buf_map SEC(".maps");
 
 SEC("tp/raw_syscalls/sys_enter")

tools/testing/selftests/bpf/progs/test_select_reuseport_kern.c

@@ -24,8 +24,8 @@ int _version SEC("version") = 1;
 struct {
 	__uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
 	__uint(max_entries, 1);
-	__uint(key_size, sizeof(__u32));
-	__uint(value_size, sizeof(__u32));
+	__type(key, __u32);
+	__type(value, __u32);
 } outer_map SEC(".maps");
 
 struct {

tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c

@@ -28,8 +28,8 @@ struct {
 	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
 	__uint(max_entries, 128);
 	__uint(map_flags, BPF_F_STACK_BUILD_ID);
-	__uint(key_size, sizeof(__u32));
-	__uint(value_size, sizeof(stack_trace_t));
+	__type(key, __u32);
+	__type(value, stack_trace_t);
 } stackmap SEC(".maps");
 
 struct {

tools/testing/selftests/bpf/progs/test_stacktrace_map.c

@@ -27,8 +27,8 @@ typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
 struct {
 	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
 	__uint(max_entries, 16384);
-	__uint(key_size, sizeof(__u32));
-	__uint(value_size, sizeof(stack_trace_t));
+	__type(key, __u32);
+	__type(value, stack_trace_t);
 } stackmap SEC(".maps");
 
 struct {

tools/testing/selftests/bpf/progs/test_tcpnotify_kern.c

@@ -24,8 +24,8 @@ struct {
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
 	__uint(max_entries, 2);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(__u32));
+	__type(key, int);
+	__type(value, __u32);
 } perf_event_map SEC(".maps");
 
 int _version SEC("version") = 1;

tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c

@@ -36,8 +36,8 @@ struct meta {
 
 struct {
 	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
-	__uint(key_size, sizeof(int));
-	__uint(value_size, sizeof(int));
+	__type(key, int);
+	__type(value, int);
 } perf_buf_map SEC(".maps");
 
 __u64 test_result_fentry = 0;