nfp: bpf: record jump destination to simplify jump fixup

eBPF insns are internally organized as dual-list inside NFP offload JIT.
Random access to an insn needs to be done by either forward or backward
traversal along the list.

One place we need to do such traversal is at nfp_fixup_branches where one
traversal is needed for each jump insn to find the destination. Such
traversals could be avoided if jump destinations are collected through a
single travesal in a pre-scan pass, and such information could also be
useful in other places where jump destination info are needed.

This patch adds such jump destination collection in nfp_prog_prepare.

Suggested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 19 insertions, 3 deletions

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/offload.c b/drivers/net/ethernet/netronome/nfp/bpf/offload.c
index bc879aeb62d4..240db663d83f 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/offload.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/offload.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2016 Netronome Systems, Inc.
+ * Copyright (C) 2016-2017 Netronome Systems, Inc.
  *
  * This software is dual licensed under the GNU General License Version 2,
  * June 1991 as shown in the file COPYING in the top-level directory of this
@@ -55,11 +55,10 @@ static int
 nfp_prog_prepare(struct nfp_prog *nfp_prog, const struct bpf_insn *prog,
 		 unsigned int cnt)
 {
+	struct nfp_insn_meta *meta;
 	unsigned int i;
 
 	for (i = 0; i < cnt; i++) {
-		struct nfp_insn_meta *meta;
-
 		meta = kzalloc(sizeof(*meta), GFP_KERNEL);
 		if (!meta)
 			return -ENOMEM;
@@ -70,6 +69,23 @@ nfp_prog_prepare(struct nfp_prog *nfp_prog, const struct bpf_insn *prog,
 		list_add_tail(&meta->l, &nfp_prog->insns);
 	}
 
+	/* Another pass to record jump information. */
+	list_for_each_entry(meta, &nfp_prog->insns, l) {
+		u64 code = meta->insn.code;
+
+		if (BPF_CLASS(code) == BPF_JMP && BPF_OP(code) != BPF_EXIT &&
+		    BPF_OP(code) != BPF_CALL) {
+			struct nfp_insn_meta *dst_meta;
+			unsigned short dst_indx;
+
+			dst_indx = meta->n + 1 + meta->insn.off;
+			dst_meta = nfp_bpf_goto_meta(nfp_prog, meta, dst_indx,
+						     cnt);
+
+			meta->jmp_dst = dst_meta;
+		}
+	}
+
 	return 0;
 }