arm64: bpf: add 'store immediate' instruction

aarch64 doesn't have native store immediate instruction, such operation
has to be implemented by the below instruction sequence:

Load immediate to register
Store register
Signed-off-by: Yang Shi <yang.shi@linaro.org>
CC: Zi Shen Lim <zlim.lnx@gmail.com>
CC: Xi Wang <xi.wang@gmail.com>
Reviewed-by: Zi Shen Lim <zlim.lnx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/arm64/net/bpf_jit_comp.c

@@ -590,7 +590,25 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	case BPF_ST | BPF_MEM | BPF_H:
 	case BPF_ST | BPF_MEM | BPF_B:
 	case BPF_ST | BPF_MEM | BPF_DW:
-		goto notyet;
+		/* Load imm to a register then store it */
+		ctx->tmp_used = 1;
+		emit_a64_mov_i(1, tmp2, off, ctx);
+		emit_a64_mov_i(1, tmp, imm, ctx);
+		switch (BPF_SIZE(code)) {
+		case BPF_W:
+			emit(A64_STR32(tmp, dst, tmp2), ctx);
+			break;
+		case BPF_H:
+			emit(A64_STRH(tmp, dst, tmp2), ctx);
+			break;
+		case BPF_B:
+			emit(A64_STRB(tmp, dst, tmp2), ctx);
+			break;
+		case BPF_DW:
+			emit(A64_STR64(tmp, dst, tmp2), ctx);
+			break;
+		}
+		break;
 
 	/* STX: *(size *)(dst + off) = src */
 	case BPF_STX | BPF_MEM | BPF_W: