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

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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
This commit is contained in:
Eduard Zingerman
2022-11-09 16:26:09 +02:00
committed by Andrii Nakryiko
parent e5659e4e19
commit c302378bc1
27 changed files with 410 additions and 340 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
tools/bpf/bpftool/map.c
View File

@@ -518,9 +518,8 @@ static int show_map_close_json(int fd, struct bpf_map_info *info)
jsonw_name(json_wtr, "pinned");
jsonw_start_array(json_wtr);
hashmap__for_each_key_entry(map_table, entry,
u32_as_hash_field(info->id))
jsonw_string(json_wtr, entry->value);
hashmap__for_each_key_entry(map_table, entry, info->id)
jsonw_string(json_wtr, entry->pvalue);
jsonw_end_array(json_wtr);
}
@@ -595,9 +594,8 @@ static int show_map_close_plain(int fd, struct bpf_map_info *info)
if (!hashmap__empty(map_table)) {
struct hashmap_entry *entry;
hashmap__for_each_key_entry(map_table, entry,
u32_as_hash_field(info->id))
printf("\n\tpinned %s", (char *)entry->value);
hashmap__for_each_key_entry(map_table, entry, info->id)
printf("\n\tpinned %s", (char *)entry->pvalue);
}
if (frozen_str) {