s390/bpf: fix lcgr instruction encoding

[ Upstream commit bb2d267c448f4bc3a3389d97c56391cb779178ae ]

"masking, test in bounds 3" fails on s390, because
BPF_ALU64_IMM(BPF_NEG, BPF_REG_2, 0) ignores the top 32 bits of
BPF_REG_2. The reason is that JIT emits lcgfr instead of lcgr.
The associated comment indicates that the code was intended to
emit lcgr in the first place, it's just that the wrong opcode
was used.

Fix by using the correct opcode.

Fixes: 05462310 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Signed-off-by: NIlya Leoshkevich <iii@linux.ibm.com>
Acked-by: NVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>

arch/s390/net/bpf_jit_comp.c

@@ -841,7 +841,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i
 		break;
 	case BPF_ALU64 | BPF_NEG: /* dst = -dst */
 		/* lcgr %dst,%dst */
-		EMIT4(0xb9130000, dst_reg, dst_reg);
+		EMIT4(0xb9030000, dst_reg, dst_reg);
 		break;
 	/*
 	 * BPF_FROM_BE/LE