netdev - [PATCH bpf-next 19/19] nfp: bpf: support removing dead code

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Message-Id: <20181219182930.8825-20-jakub.kicinski@netronome.com>
Date:   Wed, 19 Dec 2018 10:29:30 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     alexei.starovoitov@...il.com, daniel@...earbox.net
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH bpf-next 19/19] nfp: bpf: support removing dead code

Add a verifier callback to the nfp JIT to remove the instructions
the verifier deemed to be dead.

Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>
---
 drivers/net/ethernet/netronome/nfp/bpf/main.h |  6 ++++-
 .../net/ethernet/netronome/nfp/bpf/offload.c  |  1 +
 .../net/ethernet/netronome/nfp/bpf/verifier.c | 23 +++++++++++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/netronome/nfp/bpf/main.h b/drivers/net/ethernet/netronome/nfp/bpf/main.h
index a33aa7df1979..5813c3e13ebe 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/main.h
+++ b/drivers/net/ethernet/netronome/nfp/bpf/main.h
@@ -247,9 +247,12 @@ struct nfp_bpf_reg_state {
 #define FLAG_INSN_SKIP_NOOP			BIT(3)
 /* Instruction is optimized out based on preceding instructions */
 #define FLAG_INSN_SKIP_PREC_DEPENDENT		BIT(4)
+/* Instruction is optimized by the verifier */
+#define FLAG_INSN_SKIP_VERIFIER_OPT		BIT(5)
 
 #define FLAG_INSN_SKIP_MASK		(FLAG_INSN_SKIP_NOOP | \
-					 FLAG_INSN_SKIP_PREC_DEPENDENT)
+					 FLAG_INSN_SKIP_PREC_DEPENDENT | \
+					 FLAG_INSN_SKIP_VERIFIER_OPT)
 
 /**
  * struct nfp_insn_meta - BPF instruction wrapper
@@ -533,6 +536,7 @@ int nfp_bpf_finalize(struct bpf_verifier_env *env);
 
 int nfp_bpf_opt_replace_insn(struct bpf_verifier_env *env, u32 off,
 			     struct bpf_insn *insn);
+int nfp_bpf_opt_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 
 extern const struct bpf_prog_offload_ops nfp_bpf_dev_ops;
 
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/offload.c b/drivers/net/ethernet/netronome/nfp/bpf/offload.c
index 877c1b8f95e2..1bf37b2c7eef 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/offload.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/offload.c
@@ -593,6 +593,7 @@ const struct bpf_prog_offload_ops nfp_bpf_dev_ops = {
 	.insn_hook	= nfp_verify_insn,
 	.finalize	= nfp_bpf_finalize,
 	.replace_insn	= nfp_bpf_opt_replace_insn,
+	.remove_insns	= nfp_bpf_opt_remove_insns,
 	.prepare	= nfp_bpf_verifier_prep,
 	.translate	= nfp_bpf_translate,
 	.destroy	= nfp_bpf_destroy,
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
index 02a4d1050a89..df584e035f9e 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -810,3 +810,26 @@ int nfp_bpf_opt_replace_insn(struct bpf_verifier_env *env, u32 off,
 		meta->insn.code, insn->code);
 	return -EINVAL;
 }
+
+int nfp_bpf_opt_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
+{
+	struct nfp_prog *nfp_prog = env->prog->aux->offload->dev_priv;
+	struct nfp_insn_meta *meta;
+	unsigned int i;
+
+	meta = nfp_bpf_goto_meta(nfp_prog, nfp_prog->verifier_meta, off);
+
+	for (i = 0; i < cnt; i++) {
+		if (WARN_ON_ONCE(&meta->l == &nfp_prog->insns))
+			return -EINVAL;
+
+		/* doesn't count if it already has the flag */
+		if (meta->flags & FLAG_INSN_SKIP_VERIFIER_OPT)
+			i--;
+
+		meta->flags |= FLAG_INSN_SKIP_VERIFIER_OPT;
+		meta = list_next_entry(meta, l);
+	}
+
+	return 0;
+}
-- 
2.19.2