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: 054623105728 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 727693e283da2398a7c11fccdd879f9ef1b6fcb8..e53d410e88703bd962685439e0cd500b42dabb4b 100644 (file)
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -886,7 +886,7 @@ 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