Merge branch 'bpf-annotate-kv-pair'

Martin KaFai Lau says:

====================
The series allows the BPF loader to figure out the btf_key_id
and btf_value_id from a map's name by using BPF_ANNOTATE_KV_PAIR()
similarly as in iproute2 commit f823f36012fb ("bpf: implement
btf handling and map annotation").

It also removes the old 'typedef' way which requires two separate
typedefs (one for the key and one for the value).

By doing this, iproute2 and libbpf have one consistent way to
figure out the btf_key_type_id and btf_value_type_id for a map.

The first two patches are some prep/cleanup works. The last patch
introduces BPF_ANNOTATE_KV_PAIR.

v3:
- Replace some more *int*_t and u* usages with the
  equivalent __[su]* in btf.c

v2:
- Fix the incorrect '&&' check on container_type
  in bpf_map_find_btf_info().
- Expose the existing static btf_type_by_id() instead of
  creating a new one.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/include/uapi/linux/btf.h

@@ -76,7 +76,7 @@ struct btf_type {
  */
 #define BTF_INT_ENCODING(VAL)	(((VAL) & 0x0f000000) >> 24)
 #define BTF_INT_OFFSET(VAL)	(((VAL  & 0x00ff0000)) >> 16)
-#define BTF_INT_BITS(VAL)	((VAL)  & 0x0000ffff)
+#define BTF_INT_BITS(VAL)	((VAL)  & 0x000000ff)
 
 /* Attributes stored in the BTF_INT_ENCODING */
 #define BTF_INT_SIGNED	(1 << 0)

tools/lib/bpf/btf.c

@@ -2,7 +2,6 @@
 /* Copyright (c) 2018 Facebook */
 
 #include <stdlib.h>
-#include <stdint.h>
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
@@ -27,13 +26,13 @@ struct btf {
 	struct btf_type **types;
 	const char *strings;
 	void *nohdr_data;
-	uint32_t nr_types;
-	uint32_t types_size;
-	uint32_t data_size;
+	__u32 nr_types;
+	__u32 types_size;
+	__u32 data_size;
 	int fd;
 };
 
-static const char *btf_name_by_offset(const struct btf *btf, uint32_t offset)
+static const char *btf_name_by_offset(const struct btf *btf, __u32 offset)
 {
 	if (offset < btf->hdr->str_len)
 		return &btf->strings[offset];
@@ -45,7 +44,7 @@ static int btf_add_type(struct btf *btf, struct btf_type *t)
 {
 	if (btf->types_size - btf->nr_types < 2) {
 		struct btf_type **new_types;
-		u32 expand_by, new_size;
+		__u32 expand_by, new_size;
 
 		if (btf->types_size == BTF_MAX_NR_TYPES)
 			return -E2BIG;
@@ -72,7 +71,7 @@ static int btf_add_type(struct btf *btf, struct btf_type *t)
 static int btf_parse_hdr(struct btf *btf, btf_print_fn_t err_log)
 {
 	const struct btf_header *hdr = btf->hdr;
-	u32 meta_left;
+	__u32 meta_left;
 
 	if (btf->data_size < sizeof(struct btf_header)) {
 		elog("BTF header not found\n");
@@ -151,7 +150,7 @@ static int btf_parse_type_sec(struct btf *btf, btf_print_fn_t err_log)
 
 	while (next_type < end_type) {
 		struct btf_type *t = next_type;
-		uint16_t vlen = BTF_INFO_VLEN(t->info);
+		__u16 vlen = BTF_INFO_VLEN(t->info);
 		int err;
 
 		next_type += sizeof(*t);
@@ -190,8 +189,7 @@ static int btf_parse_type_sec(struct btf *btf, btf_print_fn_t err_log)
 	return 0;
 }
 
-static const struct btf_type *btf_type_by_id(const struct btf *btf,
-					     uint32_t type_id)
+const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
 {
 	if (type_id > btf->nr_types)
 		return NULL;
@@ -209,7 +207,7 @@ static bool btf_type_is_void_or_null(const struct btf_type *t)
 	return !t || btf_type_is_void(t);
 }
 
-static int64_t btf_type_size(const struct btf_type *t)
+static __s64 btf_type_size(const struct btf_type *t)
 {
 	switch (BTF_INFO_KIND(t->info)) {
 	case BTF_KIND_INT:
@@ -226,15 +224,15 @@ static int64_t btf_type_size(const struct btf_type *t)
 
 #define MAX_RESOLVE_DEPTH 32
 
-int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id)
+__s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
 {
 	const struct btf_array *array;
 	const struct btf_type *t;
-	uint32_t nelems = 1;
-	int64_t size = -1;
+	__u32 nelems = 1;
+	__s64 size = -1;
 	int i;
 
-	t = btf_type_by_id(btf, type_id);
+	t = btf__type_by_id(btf, type_id);
 	for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
 	     i++) {
 		size = btf_type_size(t);
@@ -259,7 +257,7 @@ int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id)
 			return -EINVAL;
 		}
 
-		t = btf_type_by_id(btf, type_id);
+		t = btf__type_by_id(btf, type_id);
 	}
 
 	if (size < 0)
@@ -271,9 +269,9 @@ int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id)
 	return nelems * size;
 }
 
-int32_t btf__find_by_name(const struct btf *btf, const char *type_name)
+__s32 btf__find_by_name(const struct btf *btf, const char *type_name)
 {
-	uint32_t i;
+	__u32 i;
 
 	if (!strcmp(type_name, "void"))
 		return 0;
@@ -302,10 +300,9 @@ void btf__free(struct btf *btf)
 	free(btf);
 }
 
-struct btf *btf__new(uint8_t *data, uint32_t size,
-		     btf_print_fn_t err_log)
+struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log)
 {
-	uint32_t log_buf_size = 0;
+	__u32 log_buf_size = 0;
 	char *log_buf = NULL;
 	struct btf *btf;
 	int err;

tools/lib/bpf/btf.h

@@ -4,19 +4,21 @@
 #ifndef __BPF_BTF_H
 #define __BPF_BTF_H
 
-#include <stdint.h>
+#include <linux/types.h>
 
 #define BTF_ELF_SEC ".BTF"
 
 struct btf;
+struct btf_type;
 
 typedef int (*btf_print_fn_t)(const char *, ...)
 	__attribute__((format(printf, 1, 2)));
 
 void btf__free(struct btf *btf);
-struct btf *btf__new(uint8_t *data, uint32_t size, btf_print_fn_t err_log);
-int32_t btf__find_by_name(const struct btf *btf, const char *type_name);
-int64_t btf__resolve_size(const struct btf *btf, uint32_t type_id);
+struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log);
+__s32 btf__find_by_name(const struct btf *btf, const char *type_name);
+const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 id);
+__s64 btf__resolve_size(const struct btf *btf, __u32 type_id);
 int btf__fd(const struct btf *btf);
 
 #endif

tools/lib/bpf/libbpf.c

@@ -36,6 +36,7 @@
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/bpf.h>
+#include <linux/btf.h>
 #include <linux/list.h>
 #include <linux/limits.h>
 #include <sys/stat.h>
@@ -216,8 +217,8 @@ struct bpf_map {
 	size_t offset;
 	int map_ifindex;
 	struct bpf_map_def def;
-	uint32_t btf_key_type_id;
-	uint32_t btf_value_type_id;
+	__u32 btf_key_type_id;
+	__u32 btf_value_type_id;
 	void *priv;
 	bpf_map_clear_priv_t clear_priv;
 };
@@ -1014,68 +1015,72 @@ bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
 
 static int bpf_map_find_btf_info(struct bpf_map *map, const struct btf *btf)
 {
+	const struct btf_type *container_type;
+	const struct btf_member *key, *value;
 	struct bpf_map_def *def = &map->def;
 	const size_t max_name = 256;
-	int64_t key_size, value_size;
-	int32_t key_id, value_id;
-	char name[max_name];
+	char container_name[max_name];
+	__s64 key_size, value_size;
+	__s32 container_id;
 
-	/* Find key type by name from BTF */
-	if (snprintf(name, max_name, "%s_key", map->name) == max_name) {
-		pr_warning("map:%s length of BTF key_type:%s_key is too long\n",
+	if (snprintf(container_name, max_name, "____btf_map_%s", map->name) ==
+	    max_name) {
+		pr_warning("map:%s length of '____btf_map_%s' is too long\n",
 			   map->name, map->name);
 		return -EINVAL;
 	}
 
-	key_id = btf__find_by_name(btf, name);
-	if (key_id < 0) {
-		pr_debug("map:%s key_type:%s cannot be found in BTF\n",
-			 map->name, name);
-		return key_id;
+	container_id = btf__find_by_name(btf, container_name);
+	if (container_id < 0) {
+		pr_debug("map:%s container_name:%s cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?\n",
+			 map->name, container_name);
+		return container_id;
 	}
 
-	key_size = btf__resolve_size(btf, key_id);
-	if (key_size < 0) {
-		pr_warning("map:%s key_type:%s cannot get the BTF type_size\n",
-			   map->name, name);
-		return key_size;
+	container_type = btf__type_by_id(btf, container_id);
+	if (!container_type) {
+		pr_warning("map:%s cannot find BTF type for container_id:%u\n",
+			   map->name, container_id);
+		return -EINVAL;
 	}
 
-	if (def->key_size != key_size) {
-		pr_warning("map:%s key_type:%s has BTF type_size:%u != key_size:%u\n",
-			   map->name, name, (unsigned int)key_size, def->key_size);
+	if (BTF_INFO_KIND(container_type->info) != BTF_KIND_STRUCT ||
+	    BTF_INFO_VLEN(container_type->info) < 2) {
+		pr_warning("map:%s container_name:%s is an invalid container struct\n",
+			   map->name, container_name);
 		return -EINVAL;
 	}
 
-	/* Find value type from BTF */
-	if (snprintf(name, max_name, "%s_value", map->name) == max_name) {
-		pr_warning("map:%s length of BTF value_type:%s_value is too long\n",
-			  map->name, map->name);
-		return -EINVAL;
+	key = (struct btf_member *)(container_type + 1);
+	value = key + 1;
+
+	key_size = btf__resolve_size(btf, key->type);
+	if (key_size < 0) {
+		pr_warning("map:%s invalid BTF key_type_size\n",
+			   map->name);
+		return key_size;
 	}
 
-	value_id = btf__find_by_name(btf, name);
-	if (value_id < 0) {
-		pr_debug("map:%s value_type:%s cannot be found in BTF\n",
-			 map->name, name);
-		return value_id;
+	if (def->key_size != key_size) {
+		pr_warning("map:%s btf_key_type_size:%u != map_def_key_size:%u\n",
+			   map->name, (__u32)key_size, def->key_size);
+		return -EINVAL;
 	}
 
-	value_size = btf__resolve_size(btf, value_id);
+	value_size = btf__resolve_size(btf, value->type);
 	if (value_size < 0) {
-		pr_warning("map:%s value_type:%s cannot get the BTF type_size\n",
-			   map->name, name);
+		pr_warning("map:%s invalid BTF value_type_size\n", map->name);
 		return value_size;
 	}
 
 	if (def->value_size != value_size) {
-		pr_warning("map:%s value_type:%s has BTF type_size:%u != value_size:%u\n",
-			   map->name, name, (unsigned int)value_size, def->value_size);
+		pr_warning("map:%s btf_value_type_size:%u != map_def_value_size:%u\n",
+			   map->name, (__u32)value_size, def->value_size);
 		return -EINVAL;
 	}
 
-	map->btf_key_type_id = key_id;
-	map->btf_value_type_id = value_id;
+	map->btf_key_type_id = key->type;
+	map->btf_value_type_id = value->type;
 
 	return 0;
 }
@@ -2089,12 +2094,12 @@ const char *bpf_map__name(struct bpf_map *map)
 	return map ? map->name : NULL;
 }
 
-uint32_t bpf_map__btf_key_type_id(const struct bpf_map *map)
+__u32 bpf_map__btf_key_type_id(const struct bpf_map *map)
 {
 	return map ? map->btf_key_type_id : 0;
 }
 
-uint32_t bpf_map__btf_value_type_id(const struct bpf_map *map)
+__u32 bpf_map__btf_value_type_id(const struct bpf_map *map)
 {
 	return map ? map->btf_value_type_id : 0;
 }

tools/lib/bpf/libbpf.h

@@ -244,8 +244,8 @@ bpf_map__next(struct bpf_map *map, struct bpf_object *obj);
 int bpf_map__fd(struct bpf_map *map);
 const struct bpf_map_def *bpf_map__def(struct bpf_map *map);
 const char *bpf_map__name(struct bpf_map *map);
-uint32_t bpf_map__btf_key_type_id(const struct bpf_map *map);
-uint32_t bpf_map__btf_value_type_id(const struct bpf_map *map);
+__u32 bpf_map__btf_key_type_id(const struct bpf_map *map);
+__u32 bpf_map__btf_value_type_id(const struct bpf_map *map);
 
 typedef void (*bpf_map_clear_priv_t)(struct bpf_map *, void *);
 int bpf_map__set_priv(struct bpf_map *map, void *priv,

tools/testing/selftests/bpf/bpf_helpers.h

@@ -158,6 +158,15 @@ struct bpf_map_def {
 	unsigned int numa_node;
 };
 
+#define BPF_ANNOTATE_KV_PAIR(name, type_key, type_val)		\
+	struct ____btf_map_##name {				\
+		type_key key;					\
+		type_val value;					\
+	};							\
+	struct ____btf_map_##name				\
+	__attribute__ ((section(".maps." #name), used))		\
+		____btf_map_##name = { }
+
 static int (*bpf_skb_load_bytes)(void *ctx, int off, void *to, int len) =
 	(void *) BPF_FUNC_skb_load_bytes;
 static int (*bpf_skb_store_bytes)(void *ctx, int off, void *from, int len, int flags) =

tools/testing/selftests/bpf/test_btf_haskv.c

@@ -10,11 +10,6 @@ struct ipv_counts {
 	unsigned int v6;
 };
 
-typedef int btf_map_key;
-typedef struct ipv_counts btf_map_value;
-btf_map_key dumm_key;
-btf_map_value dummy_value;
-
 struct bpf_map_def SEC("maps") btf_map = {
 	.type = BPF_MAP_TYPE_ARRAY,
 	.key_size = sizeof(int),
@@ -22,6 +17,8 @@ struct bpf_map_def SEC("maps") btf_map = {
 	.max_entries = 4,
 };
 
+BPF_ANNOTATE_KV_PAIR(btf_map, int, struct ipv_counts);
+
 struct dummy_tracepoint_args {
 	unsigned long long pad;
 	struct sock *sock;