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

Message ID 1556721842-29836-14-git-send-email-jiong.wang@netronome.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series bpf: eliminate zero extensions for sub-register writes | expand

Commit Message

Jiong Wang May 1, 2019, 2:43 p.m. UTC 
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
---
 arch/s390/net/bpf_jit_comp.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)
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Patch

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"
  */