bpf: Implement map_gen_lookup() callback for XSKMAP

Inline the xsk_map_lookup_elem() via implementing the map_gen_lookup()
callback. This results in emitting the bpf instructions in place of
bpf_map_lookup_elem() helper call and better performance of bpf
programs.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Link: https://lore.kernel.org/bpf/20191101110346.15004-3-bjorn.topel@gmail.com

diff --git a/kernel/bpf/xskmap.c b/kernel/bpf/xskmap.c
index edcbd86..554939f 100644 (file)
--- a/kernel/bpf/xskmap.c
+++ b/kernel/bpf/xskmap.c
@@ -163,6 +163,22 @@ struct xdp_sock *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
        return xs;
 }
 
+static u32 xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
+{
+       const int ret = BPF_REG_0, mp = BPF_REG_1, index = BPF_REG_2;
+       struct bpf_insn *insn = insn_buf;
+
+       *insn++ = BPF_LDX_MEM(BPF_W, ret, index, 0);
+       *insn++ = BPF_JMP_IMM(BPF_JGE, ret, map->max_entries, 5);
+       *insn++ = BPF_ALU64_IMM(BPF_LSH, ret, ilog2(sizeof(struct xsk_sock *)));
+       *insn++ = BPF_ALU64_IMM(BPF_ADD, mp, offsetof(struct xsk_map, xsk_map));
+       *insn++ = BPF_ALU64_REG(BPF_ADD, ret, mp);
+       *insn++ = BPF_LDX_MEM(BPF_SIZEOF(struct xsk_sock *), ret, ret, 0);
+       *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+       *insn++ = BPF_MOV64_IMM(ret, 0);
+       return insn - insn_buf;
+}
+
 int __xsk_map_redirect(struct bpf_map *map, struct xdp_buff *xdp,
                       struct xdp_sock *xs)
 {
@@ -303,6 +319,7 @@ const struct bpf_map_ops xsk_map_ops = {
        .map_free = xsk_map_free,
        .map_get_next_key = xsk_map_get_next_key,
        .map_lookup_elem = xsk_map_lookup_elem,
+       .map_gen_lookup = xsk_map_gen_lookup,
        .map_lookup_elem_sys_only = xsk_map_lookup_elem_sys_only,
        .map_update_elem = xsk_map_update_elem,
        .map_delete_elem = xsk_map_delete_elem,