Commit e3b92422 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

libbpf: add resizable non-thread safe internal hashmap 



There is a need for fast point lookups inside libbpf for multiple use
cases (e.g., name resolution for BTF-to-C conversion, by-name lookups in
BTF for upcoming BPF CO-RE relocation support, etc). This patch
implements simple resizable non-thread safe hashmap using single linked
list chains.

Four different insert strategies are supported:
 - HASHMAP_ADD - only add key/value if key doesn't exist yet;
 - HASHMAP_SET - add key/value pair if key doesn't exist yet; otherwise,
   update value;
 - HASHMAP_UPDATE - update value, if key already exists; otherwise, do
   nothing and return -ENOENT;
 - HASHMAP_APPEND - always add key/value pair, even if key already exists.
   This turns hashmap into a multimap by allowing multiple values to be
   associated with the same key. Most useful read API for such hashmap is
   hashmap__for_each_key_entry() iteration. If hashmap__find() is still
   used, it will return last inserted key/value entry (first in a bucket
   chain).

For HASHMAP_SET and HASHMAP_UPDATE, old key/value pair is returned, so
that calling code can handle proper memory management, if necessary.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 9db32431

tools/lib/bpf/Build

+1 −1
Original line number Diff line number Diff line 
libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o
 
libbpf-y := libbpf.o bpf.o nlattr.o btf.o libbpf_errno.o str_error.o netlink.o bpf_prog_linfo.o libbpf_probes.o xsk.o hashmap.o

tools/lib/bpf/hashmap.c

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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)



/*

 * Generic non-thread safe hash map implementation.

 *

 * Copyright (c) 2019 Facebook

 */

#include <stdint.h>

#include <stdlib.h>

#include <stdio.h>

#include <errno.h>

#include <linux/err.h>

#include "hashmap.h"



/* start with 4 buckets */

#define HASHMAP_MIN_CAP_BITS 2



static void hashmap_add_entry(struct hashmap_entry **pprev,

			      struct hashmap_entry *entry)

{

	entry->next = *pprev;

	*pprev = entry;

}



static void hashmap_del_entry(struct hashmap_entry **pprev,

			      struct hashmap_entry *entry)

{

	*pprev = entry->next;

	entry->next = NULL;

}



void hashmap__init(struct hashmap *map, hashmap_hash_fn hash_fn,

		   hashmap_equal_fn equal_fn, void *ctx)

{

	map->hash_fn = hash_fn;

	map->equal_fn = equal_fn;

	map->ctx = ctx;



	map->buckets = NULL;

	map->cap = 0;

	map->cap_bits = 0;

	map->sz = 0;

}



struct hashmap *hashmap__new(hashmap_hash_fn hash_fn,

			     hashmap_equal_fn equal_fn,

			     void *ctx)

{

	struct hashmap *map = malloc(sizeof(struct hashmap));



	if (!map)

		return ERR_PTR(-ENOMEM);

	hashmap__init(map, hash_fn, equal_fn, ctx);

	return map;

}



void hashmap__clear(struct hashmap *map)

{

	free(map->buckets);

	map->cap = map->cap_bits = map->sz = 0;

}



void hashmap__free(struct hashmap *map)

{

	if (!map)

		return;



	hashmap__clear(map);

	free(map);

}



size_t hashmap__size(const struct hashmap *map)

{

	return map->sz;

}



size_t hashmap__capacity(const struct hashmap *map)

{

	return map->cap;

}



static bool hashmap_needs_to_grow(struct hashmap *map)

{

	/* grow if empty or more than 75% filled */

	return (map->cap == 0) || ((map->sz + 1) * 4 / 3 > map->cap);

}



static int hashmap_grow(struct hashmap *map)

{

	struct hashmap_entry **new_buckets;

	struct hashmap_entry *cur, *tmp;

	size_t new_cap_bits, new_cap;

	size_t h;

	int bkt;



	new_cap_bits = map->cap_bits + 1;

	if (new_cap_bits < HASHMAP_MIN_CAP_BITS)

		new_cap_bits = HASHMAP_MIN_CAP_BITS;



	new_cap = 1UL << new_cap_bits;

	new_buckets = calloc(new_cap, sizeof(new_buckets[0]));

	if (!new_buckets)

		return -ENOMEM;



	hashmap__for_each_entry_safe(map, cur, tmp, bkt) {

		h = hash_bits(map->hash_fn(cur->key, map->ctx), new_cap_bits);

		hashmap_add_entry(&new_buckets[h], cur);

	}



	map->cap = new_cap;

	map->cap_bits = new_cap_bits;

	free(map->buckets);

	map->buckets = new_buckets;



	return 0;

}



static bool hashmap_find_entry(const struct hashmap *map,

			       const void *key, size_t hash,

			       struct hashmap_entry ***pprev,

			       struct hashmap_entry **entry)

{

	struct hashmap_entry *cur, **prev_ptr;



	if (!map->buckets)

		return false;



	for (prev_ptr = &map->buckets[hash], cur = *prev_ptr;

	     cur;

	     prev_ptr = &cur->next, cur = cur->next) {

		if (map->equal_fn(cur->key, key, map->ctx)) {

			if (pprev)

				*pprev = prev_ptr;

			*entry = cur;

			return true;

		}

	}



	return false;

}



int hashmap__insert(struct hashmap *map, const void *key, void *value,

		    enum hashmap_insert_strategy strategy,

		    const void **old_key, void **old_value)

{

	struct hashmap_entry *entry;

	size_t h;

	int err;



	if (old_key)

		*old_key = NULL;

	if (old_value)

		*old_value = NULL;



	h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);

	if (strategy != HASHMAP_APPEND &&

	    hashmap_find_entry(map, key, h, NULL, &entry)) {

		if (old_key)

			*old_key = entry->key;

		if (old_value)

			*old_value = entry->value;



		if (strategy == HASHMAP_SET || strategy == HASHMAP_UPDATE) {

			entry->key = key;

			entry->value = value;

			return 0;

		} else if (strategy == HASHMAP_ADD) {

			return -EEXIST;

		}

	}



	if (strategy == HASHMAP_UPDATE)

		return -ENOENT;



	if (hashmap_needs_to_grow(map)) {

		err = hashmap_grow(map);

		if (err)

			return err;

		h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);

	}



	entry = malloc(sizeof(struct hashmap_entry));

	if (!entry)

		return -ENOMEM;



	entry->key = key;

	entry->value = value;

	hashmap_add_entry(&map->buckets[h], entry);

	map->sz++;



	return 0;

}



bool hashmap__find(const struct hashmap *map, const void *key, void **value)

{

	struct hashmap_entry *entry;

	size_t h;



	h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);

	if (!hashmap_find_entry(map, key, h, NULL, &entry))

		return false;



	if (value)

		*value = entry->value;

	return true;

}



bool hashmap__delete(struct hashmap *map, const void *key,

		     const void **old_key, void **old_value)

{

	struct hashmap_entry **pprev, *entry;

	size_t h;



	h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits);

	if (!hashmap_find_entry(map, key, h, &pprev, &entry))

		return false;



	if (old_key)

		*old_key = entry->key;

	if (old_value)

		*old_value = entry->value;



	hashmap_del_entry(pprev, entry);

	free(entry);

	map->sz--;



	return true;

}

tools/lib/bpf/hashmap.h

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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */



/*

 * Generic non-thread safe hash map implementation.

 *

 * Copyright (c) 2019 Facebook

 */

#ifndef __LIBBPF_HASHMAP_H

#define __LIBBPF_HASHMAP_H



#include <stdbool.h>

#include <stddef.h>

#include "libbpf_internal.h"



static inline size_t hash_bits(size_t h, int bits)

{

	/* shuffle bits and return requested number of upper bits */

	return (h * 11400714819323198485llu) >> (__WORDSIZE - bits);

}



typedef size_t (*hashmap_hash_fn)(const void *key, void *ctx);

typedef bool (*hashmap_equal_fn)(const void *key1, const void *key2, void *ctx);



struct hashmap_entry {

	const void *key;

	void *value;

	struct hashmap_entry *next;

};



struct hashmap {

	hashmap_hash_fn hash_fn;

	hashmap_equal_fn equal_fn;

	void *ctx;



	struct hashmap_entry **buckets;

	size_t cap;

	size_t cap_bits;

	size_t sz;

};



#define HASHMAP_INIT(hash_fn, equal_fn, ctx) {	\

	.hash_fn = (hash_fn),			\

	.equal_fn = (equal_fn),			\

	.ctx = (ctx),				\

	.buckets = NULL,			\

	.cap = 0,				\

	.cap_bits = 0,				\

	.sz = 0,				\

}



void hashmap__init(struct hashmap *map, hashmap_hash_fn hash_fn,

		   hashmap_equal_fn equal_fn, void *ctx);

struct hashmap *hashmap__new(hashmap_hash_fn hash_fn,

			     hashmap_equal_fn equal_fn,

			     void *ctx);

void hashmap__clear(struct hashmap *map);

void hashmap__free(struct hashmap *map);



size_t hashmap__size(const struct hashmap *map);

size_t hashmap__capacity(const struct hashmap *map);



/*

 * Hashmap insertion strategy:

 * - HASHMAP_ADD - only add key/value if key doesn't exist yet;

 * - HASHMAP_SET - add key/value pair if key doesn't exist yet; otherwise,

 *   update value;

 * - HASHMAP_UPDATE - update value, if key already exists; otherwise, do

 *   nothing and return -ENOENT;

 * - HASHMAP_APPEND - always add key/value pair, even if key already exists.

 *   This turns hashmap into a multimap by allowing multiple values to be

 *   associated with the same key. Most useful read API for such hashmap is

 *   hashmap__for_each_key_entry() iteration. If hashmap__find() is still

 *   used, it will return last inserted key/value entry (first in a bucket

 *   chain).

 */

enum hashmap_insert_strategy {

	HASHMAP_ADD,

	HASHMAP_SET,

	HASHMAP_UPDATE,

	HASHMAP_APPEND,

};



/*

 * hashmap__insert() adds key/value entry w/ various semantics, depending on

 * provided strategy value. If a given key/value pair replaced already

 * existing key/value pair, both old key and old value will be returned

 * through old_key and old_value to allow calling code do proper memory

 * management.

 */

int hashmap__insert(struct hashmap *map, const void *key, void *value,

		    enum hashmap_insert_strategy strategy,

		    const void **old_key, void **old_value);



static inline int hashmap__add(struct hashmap *map,

			       const void *key, void *value)

{

	return hashmap__insert(map, key, value, HASHMAP_ADD, NULL, NULL);

}



static inline int hashmap__set(struct hashmap *map,

			       const void *key, void *value,

			       const void **old_key, void **old_value)

{

	return hashmap__insert(map, key, value, HASHMAP_SET,

			       old_key, old_value);

}



static inline int hashmap__update(struct hashmap *map,

				  const void *key, void *value,

				  const void **old_key, void **old_value)

{

	return hashmap__insert(map, key, value, HASHMAP_UPDATE,

			       old_key, old_value);

}



static inline int hashmap__append(struct hashmap *map,

				  const void *key, void *value)

{

	return hashmap__insert(map, key, value, HASHMAP_APPEND, NULL, NULL);

}



bool hashmap__delete(struct hashmap *map, const void *key,

		     const void **old_key, void **old_value);



bool hashmap__find(const struct hashmap *map, const void *key, void **value);



/*

 * hashmap__for_each_entry - iterate over all entries in hashmap

 * @map: hashmap to iterate

 * @cur: struct hashmap_entry * used as a loop cursor

 * @bkt: integer used as a bucket loop cursor

 */

#define hashmap__for_each_entry(map, cur, bkt)				    \

	for (bkt = 0; bkt < map->cap; bkt++)				    \

		for (cur = map->buckets[bkt]; cur; cur = cur->next)



/*

 * hashmap__for_each_entry_safe - iterate over all entries in hashmap, safe

 * against removals

 * @map: hashmap to iterate

 * @cur: struct hashmap_entry * used as a loop cursor

 * @tmp: struct hashmap_entry * used as a temporary next cursor storage

 * @bkt: integer used as a bucket loop cursor

 */

#define hashmap__for_each_entry_safe(map, cur, tmp, bkt)		    \

	for (bkt = 0; bkt < map->cap; bkt++)				    \

		for (cur = map->buckets[bkt];				    \

		     cur && ({tmp = cur->next; true; });		    \

		     cur = tmp)



/*

 * hashmap__for_each_key_entry - iterate over entries associated with given key

 * @map: hashmap to iterate

 * @cur: struct hashmap_entry * used as a loop cursor

 * @key: key to iterate entries for

 */

#define hashmap__for_each_key_entry(map, cur, _key)			    \

	for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\

					     map->cap_bits);		    \

		     map->buckets ? map->buckets[bkt] : NULL; });	    \

	     cur;							    \

	     cur = cur->next)						    \

		if (map->equal_fn(cur->key, (_key), map->ctx))



#define hashmap__for_each_key_entry_safe(map, cur, tmp, _key)		    \

	for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\

					     map->cap_bits);		    \

		     cur = map->buckets ? map->buckets[bkt] : NULL; });	    \

	     cur && ({ tmp = cur->next; true; });			    \

	     cur = tmp)							    \

		if (map->equal_fn(cur->key, (_key), map->ctx))



#endif /* __LIBBPF_HASHMAP_H */

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