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, 2 insertions, 12 deletions

diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 467d8472df0c..d4e8a1aef787 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -240,8 +240,8 @@ int do_filter_dump(struct tcmsg *ifinfo, struct nlattr **tb, const char *kind,
 int print_all_levels(__maybe_unused enum libbpf_print_level level,
 		     const char *format, va_list args);
 
-size_t hash_fn_for_key_as_id(const void *key, void *ctx);
-bool equal_fn_for_key_as_id(const void *k1, const void *k2, void *ctx);
+size_t hash_fn_for_key_as_id(long key, void *ctx);
+bool equal_fn_for_key_as_id(long k1, long k2, void *ctx);
 
 /* bpf_attach_type_input_str - convert the provided attach type value into a
  * textual representation that we accept for input purposes.
@@ -257,16 +257,6 @@ bool equal_fn_for_key_as_id(const void *k1, const void *k2, void *ctx);
  */
 const char *bpf_attach_type_input_str(enum bpf_attach_type t);
 
-static inline void *u32_as_hash_field(__u32 x)
-{
-	return (void *)(uintptr_t)x;
-}
-
-static inline __u32 hash_field_as_u32(const void *x)
-{
-	return (__u32)(uintptr_t)x;
-}
-
 static inline bool hashmap__empty(struct hashmap *map)
 {
 	return map ? hashmap__size(map) == 0 : true;