LoongArch: BPF: Support signed mod instructions

Add support for signed mod instructions.
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/net/bpf_jit.c

@@ -588,20 +588,36 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
 	/* dst = dst % src */
 	case BPF_ALU | BPF_MOD | BPF_X:
 	case BPF_ALU64 | BPF_MOD | BPF_X:
-		emit_zext_32(ctx, dst, is32);
-		move_reg(ctx, t1, src);
-		emit_zext_32(ctx, t1, is32);
-		emit_insn(ctx, moddu, dst, dst, t1);
-		emit_zext_32(ctx, dst, is32);
+		if (!off) {
+			emit_zext_32(ctx, dst, is32);
+			move_reg(ctx, t1, src);
+			emit_zext_32(ctx, t1, is32);
+			emit_insn(ctx, moddu, dst, dst, t1);
+			emit_zext_32(ctx, dst, is32);
+		} else {
+			emit_sext_32(ctx, dst, is32);
+			move_reg(ctx, t1, src);
+			emit_sext_32(ctx, t1, is32);
+			emit_insn(ctx, modd, dst, dst, t1);
+			emit_sext_32(ctx, dst, is32);
+		}
 		break;
 
 	/* dst = dst % imm */
 	case BPF_ALU | BPF_MOD | BPF_K:
 	case BPF_ALU64 | BPF_MOD | BPF_K:
-		move_imm(ctx, t1, imm, is32);
-		emit_zext_32(ctx, dst, is32);
-		emit_insn(ctx, moddu, dst, dst, t1);
-		emit_zext_32(ctx, dst, is32);
+		if (!off) {
+			move_imm(ctx, t1, imm, is32);
+			emit_zext_32(ctx, dst, is32);
+			emit_insn(ctx, moddu, dst, dst, t1);
+			emit_zext_32(ctx, dst, is32);
+		} else {
+			move_imm(ctx, t1, imm, false);
+			emit_sext_32(ctx, t1, is32);
+			emit_sext_32(ctx, dst, is32);
+			emit_insn(ctx, modd, dst, dst, t1);
+			emit_sext_32(ctx, dst, is32);
+		}
 		break;
 
 	/* dst = -dst */