Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit bbe5d311 authored by Daniel Borkmann's avatar Daniel Borkmann
Browse files

Merge branch 'bpf-zero-hash-seed' 



Lorenz Bauer says:

====================
Allow forcing the seed of a hash table to zero, for deterministic
execution during benchmarking and testing.

Changes from v2:
* Change ordering of BPF_F_ZERO_SEED in linux/bpf.h

Comments adressed from v1:
* Add comment to discourage production use to linux/bpf.h
* Require CAP_SYS_ADMIN
====================

Acked-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parents 23499442 bf5d68c7

include/uapi/linux/bpf.h

+6 −3
Original line number Diff line number Diff line
@@ -257,9 +257,6 @@ enum bpf_attach_type { 
/* Specify numa node during map creation */

#define BPF_F_NUMA_NODE		(1U << 2)



/* flags for BPF_PROG_QUERY */

#define BPF_F_QUERY_EFFECTIVE	(1U << 0)



#define BPF_OBJ_NAME_LEN 16U



/* Flags for accessing BPF object */
@@ -269,6 +266,12 @@ enum bpf_attach_type { 
/* Flag for stack_map, store build_id+offset instead of pointer */

#define BPF_F_STACK_BUILD_ID	(1U << 5)



/* Zero-initialize hash function seed. This should only be used for testing. */

#define BPF_F_ZERO_SEED		(1U << 6)



/* flags for BPF_PROG_QUERY */

#define BPF_F_QUERY_EFFECTIVE	(1U << 0)



enum bpf_stack_build_id_status {

	/* user space need an empty entry to identify end of a trace */

	BPF_STACK_BUILD_ID_EMPTY = 0,

kernel/bpf/hashtab.c

+11 −2
Original line number Diff line number Diff line
@@ -23,7 +23,7 @@ 


#define HTAB_CREATE_FLAG_MASK						\

	(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU | BPF_F_NUMA_NODE |	\

	 BPF_F_RDONLY | BPF_F_WRONLY)

	 BPF_F_RDONLY | BPF_F_WRONLY | BPF_F_ZERO_SEED)



struct bucket {

	struct hlist_nulls_head head;
@@ -244,6 +244,7 @@ static int htab_map_alloc_check(union bpf_attr *attr) 
	 */

	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);

	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);

	bool zero_seed = (attr->map_flags & BPF_F_ZERO_SEED);

	int numa_node = bpf_map_attr_numa_node(attr);



	BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
@@ -257,6 +258,10 @@ static int htab_map_alloc_check(union bpf_attr *attr) 
		 */

		return -EPERM;



	if (zero_seed && !capable(CAP_SYS_ADMIN))

		/* Guard against local DoS, and discourage production use. */

		return -EPERM;



	if (attr->map_flags & ~HTAB_CREATE_FLAG_MASK)

		/* reserved bits should not be used */

		return -EINVAL;
@@ -373,7 +378,11 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) 
	if (!htab->buckets)

		goto free_htab;



	if (htab->map.map_flags & BPF_F_ZERO_SEED)

		htab->hashrnd = 0;

	else

		htab->hashrnd = get_random_int();



	for (i = 0; i < htab->n_buckets; i++) {

		INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);

		raw_spin_lock_init(&htab->buckets[i].lock);

tools/include/uapi/linux/bpf.h

+10 −3
Original line number Diff line number Diff line
@@ -257,9 +257,6 @@ enum bpf_attach_type { 
/* Specify numa node during map creation */

#define BPF_F_NUMA_NODE		(1U << 2)



/* flags for BPF_PROG_QUERY */

#define BPF_F_QUERY_EFFECTIVE	(1U << 0)



#define BPF_OBJ_NAME_LEN 16U



/* Flags for accessing BPF object */
@@ -269,6 +266,12 @@ enum bpf_attach_type { 
/* Flag for stack_map, store build_id+offset instead of pointer */

#define BPF_F_STACK_BUILD_ID	(1U << 5)



/* Zero-initialize hash function seed. This should only be used for testing. */

#define BPF_F_ZERO_SEED		(1U << 6)



/* flags for BPF_PROG_QUERY */

#define BPF_F_QUERY_EFFECTIVE	(1U << 0)



enum bpf_stack_build_id_status {

	/* user space need an empty entry to identify end of a trace */

	BPF_STACK_BUILD_ID_EMPTY = 0,
@@ -2201,6 +2204,8 @@ union bpf_attr { 
 *		**CONFIG_NET** configuration option.

 *	Return

 *		Pointer to *struct bpf_sock*, or NULL in case of failure.

 *		For sockets with reuseport option, *struct bpf_sock*

 *		return is from reuse->socks[] using hash of the packet.

 *

 * struct bpf_sock *bpf_sk_lookup_udp(void *ctx, struct bpf_sock_tuple *tuple, u32 tuple_size, u32 netns, u64 flags)

 *	Description
@@ -2233,6 +2238,8 @@ union bpf_attr { 
 *		**CONFIG_NET** configuration option.

 *	Return

 *		Pointer to *struct bpf_sock*, or NULL in case of failure.

 *		For sockets with reuseport option, *struct bpf_sock*

 *		return is from reuse->socks[] using hash of the packet.

 *

 * int bpf_sk_release(struct bpf_sock *sk)

 *	Description

tools/testing/selftests/bpf/test_maps.c

+55 −9
Original line number Diff line number Diff line
@@ -258,24 +258,36 @@ static void test_hashmap_percpu(int task, void *data) 
	close(fd);

}



static void test_hashmap_walk(int task, void *data)

static int helper_fill_hashmap(int max_entries)

{

	int fd, i, max_entries = 1000;

	long long key, value, next_key;

	bool next_key_valid = true;

	int i, fd, ret;

	long long key, value;



	fd = bpf_create_map(BPF_MAP_TYPE_HASH, sizeof(key), sizeof(value),

			    max_entries, map_flags);

	if (fd < 0) {

		printf("Failed to create hashmap '%s'!\n", strerror(errno));

		exit(1);

	}

	CHECK(fd < 0,

	      "failed to create hashmap",

	      "err: %s, flags: 0x%x\n", strerror(errno), map_flags);



	for (i = 0; i < max_entries; i++) {

		key = i; value = key;

		assert(bpf_map_update_elem(fd, &key, &value, BPF_NOEXIST) == 0);

		ret = bpf_map_update_elem(fd, &key, &value, BPF_NOEXIST);

		CHECK(ret != 0,

		      "can't update hashmap",

		      "err: %s\n", strerror(ret));

	}



	return fd;

}



static void test_hashmap_walk(int task, void *data)

{

	int fd, i, max_entries = 1000;

	long long key, value, next_key;

	bool next_key_valid = true;



	fd = helper_fill_hashmap(max_entries);



	for (i = 0; bpf_map_get_next_key(fd, !i ? NULL : &key,

					 &next_key) == 0; i++) {

		key = next_key;
@@ -306,6 +318,39 @@ static void test_hashmap_walk(int task, void *data) 
	close(fd);

}



static void test_hashmap_zero_seed(void)

{

	int i, first, second, old_flags;

	long long key, next_first, next_second;



	old_flags = map_flags;

	map_flags |= BPF_F_ZERO_SEED;



	first = helper_fill_hashmap(3);

	second = helper_fill_hashmap(3);



	for (i = 0; ; i++) {

		void *key_ptr = !i ? NULL : &key;



		if (bpf_map_get_next_key(first, key_ptr, &next_first) != 0)

			break;



		CHECK(bpf_map_get_next_key(second, key_ptr, &next_second) != 0,

		      "next_key for second map must succeed",

		      "key_ptr: %p", key_ptr);

		CHECK(next_first != next_second,

		      "keys must match",

		      "i: %d first: %lld second: %lld\n", i,

		      next_first, next_second);



		key = next_first;

	}



	map_flags = old_flags;

	close(first);

	close(second);

}



static void test_arraymap(int task, void *data)

{

	int key, next_key, fd;
@@ -1534,6 +1579,7 @@ static void run_all_tests(void) 
	test_hashmap(0, NULL);

	test_hashmap_percpu(0, NULL);

	test_hashmap_walk(0, NULL);

	test_hashmap_zero_seed();



	test_arraymap(0, NULL);

	test_arraymap_percpu(0, NULL);