libbpf: Hashmap interface update to allow both long and void* keys/values

An update for libbpf's hashmap interface from void* -> void* to a
polymorphic one, allowing both long and void* keys and values.

This simplifies many use cases in libbpf as hashmaps there are mostly
integer to integer.

Perf copies hashmap implementation from libbpf and has to be
updated as well.

Changes to libbpf, selftests/bpf and perf are packed as a single
commit to avoid compilation issues with any future bisect.

Polymorphic interface is acheived by hiding hashmap interface
functions behind auxiliary macros that take care of necessary
type casts, for example:

    #define hashmap_cast_ptr(p)						\
	({								\
		_Static_assert((p) == NULL || sizeof(*(p)) == sizeof(long),\
			       #p " pointee should be a long-sized integer or a pointer"); \
		(long *)(p);						\
	})

    bool hashmap_find(const struct hashmap *map, long key, long *value);

    #define hashmap__find(map, key, value) \
		hashmap_find((map), (long)(key), hashmap_cast_ptr(value))

- hashmap__find macro casts key and value parameters to long
  and long* respectively
- hashmap_cast_ptr ensures that value pointer points to a memory
  of appropriate size.

This hack was suggested by Andrii Nakryiko in [1].
This is a follow up for [2].

[1] https://lore.kernel.org/bpf/CAEf4BzZ8KFneEJxFAaNCCFPGqp20hSpS2aCj76uRk3-qZUH5xg@mail.gmail.com/
[2] https://lore.kernel.org/bpf/af1facf9-7bc8-8a3d-0db4-7b3f333589a2@meta.com/T/#m65b28f1d6d969fcd318b556db6a3ad499a42607d

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20221109142611.879983-2-eddyz87@gmail.com

1 files changed, 20 insertions, 21 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 71d68bf7788c..442d4d0f98b8 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1559,15 +1559,15 @@ struct btf_pipe {
 static int btf_rewrite_str(__u32 *str_off, void *ctx)
 {
 	struct btf_pipe *p = ctx;
-	void *mapped_off;
+	long mapped_off;
 	int off, err;
 
 	if (!*str_off) /* nothing to do for empty strings */
 		return 0;
 
 	if (p->str_off_map &&
-	    hashmap__find(p->str_off_map, (void *)(long)*str_off, &mapped_off)) {
-		*str_off = (__u32)(long)mapped_off;
+	    hashmap__find(p->str_off_map, *str_off, &mapped_off)) {
+		*str_off = mapped_off;
 		return 0;
 	}
 
@@ -1579,7 +1579,7 @@ static int btf_rewrite_str(__u32 *str_off, void *ctx)
 	 * performing expensive string comparisons.
 	 */
 	if (p->str_off_map) {
-		err = hashmap__append(p->str_off_map, (void *)(long)*str_off, (void *)(long)off);
+		err = hashmap__append(p->str_off_map, *str_off, off);
 		if (err)
 			return err;
 	}
@@ -1630,8 +1630,8 @@ static int btf_rewrite_type_ids(__u32 *type_id, void *ctx)
 	return 0;
 }
 
-static size_t btf_dedup_identity_hash_fn(const void *key, void *ctx);
-static bool btf_dedup_equal_fn(const void *k1, const void *k2, void *ctx);
+static size_t btf_dedup_identity_hash_fn(long key, void *ctx);
+static bool btf_dedup_equal_fn(long k1, long k2, void *ctx);
 
 int btf__add_btf(struct btf *btf, const struct btf *src_btf)
 {
@@ -3126,12 +3126,11 @@ static long hash_combine(long h, long value)
 }
 
 #define for_each_dedup_cand(d, node, hash) \
-	hashmap__for_each_key_entry(d->dedup_table, node, (void *)hash)
+	hashmap__for_each_key_entry(d->dedup_table, node, hash)
 
 static int btf_dedup_table_add(struct btf_dedup *d, long hash, __u32 type_id)
 {
-	return hashmap__append(d->dedup_table,
-			       (void *)hash, (void *)(long)type_id);
+	return hashmap__append(d->dedup_table, hash, type_id);
 }
 
 static int btf_dedup_hypot_map_add(struct btf_dedup *d,
@@ -3178,17 +3177,17 @@ static void btf_dedup_free(struct btf_dedup *d)
 	free(d);
 }
 
-static size_t btf_dedup_identity_hash_fn(const void *key, void *ctx)
+static size_t btf_dedup_identity_hash_fn(long key, void *ctx)
 {
-	return (size_t)key;
+	return key;
 }
 
-static size_t btf_dedup_collision_hash_fn(const void *key, void *ctx)
+static size_t btf_dedup_collision_hash_fn(long key, void *ctx)
 {
 	return 0;
 }
 
-static bool btf_dedup_equal_fn(const void *k1, const void *k2, void *ctx)
+static bool btf_dedup_equal_fn(long k1, long k2, void *ctx)
 {
 	return k1 == k2;
 }
@@ -3750,7 +3749,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
 	case BTF_KIND_INT:
 		h = btf_hash_int_decl_tag(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_int_tag(t, cand)) {
 				new_id = cand_id;
@@ -3763,7 +3762,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
 	case BTF_KIND_ENUM64:
 		h = btf_hash_enum(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_enum(t, cand)) {
 				new_id = cand_id;
@@ -3785,7 +3784,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
 	case BTF_KIND_FLOAT:
 		h = btf_hash_common(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_common(t, cand)) {
 				new_id = cand_id;
@@ -4288,7 +4287,7 @@ static int btf_dedup_struct_type(struct btf_dedup *d, __u32 type_id)
 
 	h = btf_hash_struct(t);
 	for_each_dedup_cand(d, hash_entry, h) {
-		__u32 cand_id = (__u32)(long)hash_entry->value;
+		__u32 cand_id = hash_entry->value;
 		int eq;
 
 		/*
@@ -4393,7 +4392,7 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
 
 		h = btf_hash_common(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_common(t, cand)) {
 				new_id = cand_id;
@@ -4410,7 +4409,7 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
 
 		h = btf_hash_int_decl_tag(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_int_tag(t, cand)) {
 				new_id = cand_id;
@@ -4434,7 +4433,7 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
 
 		h = btf_hash_array(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_array(t, cand)) {
 				new_id = cand_id;
@@ -4466,7 +4465,7 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
 
 		h = btf_hash_fnproto(t);
 		for_each_dedup_cand(d, hash_entry, h) {
-			cand_id = (__u32)(long)hash_entry->value;
+			cand_id = hash_entry->value;
 			cand = btf_type_by_id(d->btf, cand_id);
 			if (btf_equal_fnproto(t, cand)) {
 				new_id = cand_id;