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, 8 insertions, 8 deletions

diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c
index bb6c969a114a..00c77edb6331 100644
--- a/tools/bpf/bpftool/pids.c
+++ b/tools/bpf/bpftool/pids.c
@@ -36,8 +36,8 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
 	int err, i;
 	void *tmp;
 
-	hashmap__for_each_key_entry(map, entry, u32_as_hash_field(e->id)) {
-		refs = entry->value;
+	hashmap__for_each_key_entry(map, entry, e->id) {
+		refs = entry->pvalue;
 
 		for (i = 0; i < refs->ref_cnt; i++) {
 			if (refs->refs[i].pid == e->pid)
@@ -81,7 +81,7 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
 	refs->has_bpf_cookie = e->has_bpf_cookie;
 	refs->bpf_cookie = e->bpf_cookie;
 
-	err = hashmap__append(map, u32_as_hash_field(e->id), refs);
+	err = hashmap__append(map, e->id, refs);
 	if (err)
 		p_err("failed to append entry to hashmap for ID %u: %s",
 		      e->id, strerror(errno));
@@ -183,7 +183,7 @@ void delete_obj_refs_table(struct hashmap *map)
 		return;
 
 	hashmap__for_each_entry(map, entry, bkt) {
-		struct obj_refs *refs = entry->value;
+		struct obj_refs *refs = entry->pvalue;
 
 		free(refs->refs);
 		free(refs);
@@ -200,8 +200,8 @@ void emit_obj_refs_json(struct hashmap *map, __u32 id,
 	if (hashmap__empty(map))
 		return;
 
-	hashmap__for_each_key_entry(map, entry, u32_as_hash_field(id)) {
-		struct obj_refs *refs = entry->value;
+	hashmap__for_each_key_entry(map, entry, id) {
+		struct obj_refs *refs = entry->pvalue;
 		int i;
 
 		if (refs->ref_cnt == 0)
@@ -232,8 +232,8 @@ void emit_obj_refs_plain(struct hashmap *map, __u32 id, const char *prefix)
 	if (hashmap__empty(map))
 		return;
 
-	hashmap__for_each_key_entry(map, entry, u32_as_hash_field(id)) {
-		struct obj_refs *refs = entry->value;
+	hashmap__for_each_key_entry(map, entry, id) {
+		struct obj_refs *refs = entry->pvalue;
 		int i;
 
 		if (refs->ref_cnt == 0)