[PATCH 1/3] bpf: allow zero-initializing hash map seed
From: Lorenz Bauer <hidden>
Date: 2018-10-01 17:24:20
Also in:
linux-api
Subsystem:
bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
Add a new flag BPF_F_ZERO_SEED, which forces a hash map to initialize the seed to zero. --- include/uapi/linux/bpf.h | 2 ++ kernel/bpf/hashtab.c | 8 ++++++-- 2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index aa5ccd2385ed..9d15c8f179ac 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h@@ -252,6 +252,8 @@ enum bpf_attach_type { #define BPF_F_NO_COMMON_LRU (1U << 1) /* Specify numa node during map creation */ #define BPF_F_NUMA_NODE (1U << 2) +/* Zero-initialize hash function seed */ +#define BPF_F_ZERO_SEED (1U << 6) /* flags for BPF_PROG_QUERY */ #define BPF_F_QUERY_EFFECTIVE (1U << 0)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 2c1790288138..a79e123dae62 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c@@ -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;
@@ -373,7 +373,11 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) if (!htab->buckets) goto free_htab; - htab->hashrnd = get_random_int(); + 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);
--
2.17.1