netdev - [PATCH v5 bpf-next 13/17] s390: bpf: eliminate zero extension code-gen

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Date:   Wed,  1 May 2019 15:43:58 +0100
From:   Jiong Wang <jiong.wang@...ronome.com>
To:     alexei.starovoitov@...il.com, daniel@...earbox.net
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        oss-drivers@...ronome.com, Jiong Wang <jiong.wang@...ronome.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>
Subject: [PATCH v5 bpf-next 13/17] s390: bpf: eliminate zero extension code-gen

Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Jiong Wang <jiong.wang@...ronome.com>
---
 arch/s390/net/bpf_jit_comp.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 51dd026..45ee379 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -299,9 +299,11 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
 
 #define EMIT_ZERO(b1)						\
 ({								\
-	/* llgfr %dst,%dst (zero extend to 64 bit) */		\
-	EMIT4(0xb9160000, b1, b1);				\
-	REG_SET_SEEN(b1);					\
+	if (!fp->aux->verifier_zext) {				\
+		/* llgfr %dst,%dst (zero extend to 64 bit) */	\
+		EMIT4(0xb9160000, b1, b1);			\
+		REG_SET_SEEN(b1);				\
+	}							\
 })
 
 /*
@@ -515,6 +517,13 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i
 		jit->seen |= SEEN_REG_AX;
 	switch (insn->code) {
 	/*
+	 * BPF_ZEXT
+	 */
+	case BPF_ALU | BPF_ZEXT: /* dst = (u32) src + always does zext */
+		/* llgfr %dst,%dst (zero extend to 64 bit) */
+		EMIT4(0xb9160000, b1, b1);
+		break;
+	/*
 	 * BPF_MOV
 	 */
 	case BPF_ALU | BPF_MOV | BPF_X: /* dst = (u32) src */
@@ -1282,6 +1291,11 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp)
 	return 0;
 }
 
+bool bpf_jit_hardware_zext(void)
+{
+	return false;
+}
+
 /*
  * Compile eBPF program "fp"
  */
-- 
2.7.4