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: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2019-05-24 11:59:00 -07:00 committed by Alexei Starovoitov
parent 9db324314d
commit e3b9242240
3 changed files with 403 additions and 1 deletions

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@ -1 +1 @@
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

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tools/lib/bpf/hashmap.c Normal file
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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;
}

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tools/lib/bpf/hashmap.h Normal file
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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 */