test: bpf: extend "load 64-bit immediate" testcase

Extend the testcase to catch a signedness bug in the arm64 JIT:

test_bpf: #58 load 64-bit immediate jited:1 ret -1 != 1 FAIL (1 times)

This is useful to ensure other JITs won't have a similar bug.

Link: https://lkml.org/lkml/2015/5/8/458
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NXi Wang <xi.wang@gmail.com>
Acked-by: NAlexei Starovoitov <ast@plumgrid.com>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

lib/test_bpf.c

@@ -1755,7 +1755,8 @@ static struct bpf_test tests[] = {
 			BPF_EXIT_INSN(),
 			BPF_JMP_IMM(BPF_JEQ, R3, 0x1234, 1),
 			BPF_EXIT_INSN(),
-			BPF_ALU64_IMM(BPF_MOV, R0, 1),
+			BPF_LD_IMM64(R0, 0x1ffffffffLL),
+			BPF_ALU64_IMM(BPF_RSH, R0, 32), /* R0 = 1 */
 			BPF_EXIT_INSN(),
 		},
 		INTERNAL,