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add new map type BPF_MAP_TYPE_ARRAY and its implementation - optimized for fastest possible lookup() . in the future verifier/JIT may recognize lookup() with constant key and optimize it into constant pointer. Can optimize non-constant key into direct pointer arithmetic as well, since pointers and value_size are constant for the life of the eBPF program. In other words array_map_lookup_elem() may be 'inlined' by verifier/JIT while preserving concurrent access to this map from user space - two main use cases for array type: . 'global' eBPF variables: array of 1 element with key=0 and value is a collection of 'global' variables which programs can use to keep the state between events . aggregation of tracing events into fixed set of buckets - all array elements pre-allocated and zero initialized at init time - key as an index in array and can only be 4 byte - map_delete_elem() returns EINVAL, since elements cannot be deleted - map_update_elem() replaces elements in an non-atomic way (for atomic updates hashtable type should be used instead) Signed-off-by: Alexei Starovoitov <[email protected]> Signed-off-by: David S. Miller <[email protected]>
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obj-y := core.o | ||
obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o | ||
obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o arraymap.o | ||
ifdef CONFIG_TEST_BPF | ||
obj-$(CONFIG_BPF_SYSCALL) += test_stub.o | ||
endif |
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/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com | ||
* | ||
* This program is free software; you can redistribute it and/or | ||
* modify it under the terms of version 2 of the GNU General Public | ||
* License as published by the Free Software Foundation. | ||
* | ||
* This program is distributed in the hope that it will be useful, but | ||
* WITHOUT ANY WARRANTY; without even the implied warranty of | ||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
* General Public License for more details. | ||
*/ | ||
#include <linux/bpf.h> | ||
#include <linux/err.h> | ||
#include <linux/vmalloc.h> | ||
#include <linux/slab.h> | ||
#include <linux/mm.h> | ||
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struct bpf_array { | ||
struct bpf_map map; | ||
u32 elem_size; | ||
char value[0] __aligned(8); | ||
}; | ||
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/* Called from syscall */ | ||
static struct bpf_map *array_map_alloc(union bpf_attr *attr) | ||
{ | ||
struct bpf_array *array; | ||
u32 elem_size; | ||
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/* check sanity of attributes */ | ||
if (attr->max_entries == 0 || attr->key_size != 4 || | ||
attr->value_size == 0) | ||
return ERR_PTR(-EINVAL); | ||
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elem_size = round_up(attr->value_size, 8); | ||
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/* allocate all map elements and zero-initialize them */ | ||
array = kzalloc(sizeof(*array) + attr->max_entries * elem_size, | ||
GFP_USER | __GFP_NOWARN); | ||
if (!array) { | ||
array = vzalloc(array->map.max_entries * array->elem_size); | ||
if (!array) | ||
return ERR_PTR(-ENOMEM); | ||
} | ||
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/* copy mandatory map attributes */ | ||
array->map.key_size = attr->key_size; | ||
array->map.value_size = attr->value_size; | ||
array->map.max_entries = attr->max_entries; | ||
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array->elem_size = elem_size; | ||
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return &array->map; | ||
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} | ||
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/* Called from syscall or from eBPF program */ | ||
static void *array_map_lookup_elem(struct bpf_map *map, void *key) | ||
{ | ||
struct bpf_array *array = container_of(map, struct bpf_array, map); | ||
u32 index = *(u32 *)key; | ||
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if (index >= array->map.max_entries) | ||
return NULL; | ||
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return array->value + array->elem_size * index; | ||
} | ||
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/* Called from syscall */ | ||
static int array_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | ||
{ | ||
struct bpf_array *array = container_of(map, struct bpf_array, map); | ||
u32 index = *(u32 *)key; | ||
u32 *next = (u32 *)next_key; | ||
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if (index >= array->map.max_entries) { | ||
*next = 0; | ||
return 0; | ||
} | ||
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if (index == array->map.max_entries - 1) | ||
return -ENOENT; | ||
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*next = index + 1; | ||
return 0; | ||
} | ||
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/* Called from syscall or from eBPF program */ | ||
static int array_map_update_elem(struct bpf_map *map, void *key, void *value, | ||
u64 map_flags) | ||
{ | ||
struct bpf_array *array = container_of(map, struct bpf_array, map); | ||
u32 index = *(u32 *)key; | ||
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if (map_flags > BPF_EXIST) | ||
/* unknown flags */ | ||
return -EINVAL; | ||
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if (index >= array->map.max_entries) | ||
/* all elements were pre-allocated, cannot insert a new one */ | ||
return -E2BIG; | ||
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if (map_flags == BPF_NOEXIST) | ||
/* all elemenets already exist */ | ||
return -EEXIST; | ||
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memcpy(array->value + array->elem_size * index, value, array->elem_size); | ||
return 0; | ||
} | ||
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/* Called from syscall or from eBPF program */ | ||
static int array_map_delete_elem(struct bpf_map *map, void *key) | ||
{ | ||
return -EINVAL; | ||
} | ||
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/* Called when map->refcnt goes to zero, either from workqueue or from syscall */ | ||
static void array_map_free(struct bpf_map *map) | ||
{ | ||
struct bpf_array *array = container_of(map, struct bpf_array, map); | ||
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/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0, | ||
* so the programs (can be more than one that used this map) were | ||
* disconnected from events. Wait for outstanding programs to complete | ||
* and free the array | ||
*/ | ||
synchronize_rcu(); | ||
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kvfree(array); | ||
} | ||
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static struct bpf_map_ops array_ops = { | ||
.map_alloc = array_map_alloc, | ||
.map_free = array_map_free, | ||
.map_get_next_key = array_map_get_next_key, | ||
.map_lookup_elem = array_map_lookup_elem, | ||
.map_update_elem = array_map_update_elem, | ||
.map_delete_elem = array_map_delete_elem, | ||
}; | ||
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static struct bpf_map_type_list tl = { | ||
.ops = &array_ops, | ||
.type = BPF_MAP_TYPE_ARRAY, | ||
}; | ||
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static int __init register_array_map(void) | ||
{ | ||
bpf_register_map_type(&tl); | ||
return 0; | ||
} | ||
late_initcall(register_array_map); |