arm64: insn: Add N immediate encoding

We're missing the a way to generate the encoding of the N immediate,
which is only a single bit used in a number of instruction that take
an immediate.

Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/include/asm/insn.h

@@ -70,6 +70,7 @@ enum aarch64_insn_imm_type {
 	AARCH64_INSN_IMM_6,
 	AARCH64_INSN_IMM_S,
 	AARCH64_INSN_IMM_R,
+	AARCH64_INSN_IMM_N,
 	AARCH64_INSN_IMM_MAX
 };
 

arch/arm64/kernel/insn.c

@@ -343,6 +343,10 @@ static int __kprobes aarch64_get_imm_shift_mask(enum aarch64_insn_imm_type type,
 		mask = BIT(6) - 1;
 		shift = 16;
 		break;
+	case AARCH64_INSN_IMM_N:
+		mask = 1;
+		shift = 22;
+		break;
 	default:
 		return -EINVAL;
 	}