Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/nds32/kernel/sys_nds32.c b/arch/nds32/kernel/sys_nds32.c
index 9de93ab..cb2d1e2 100644
--- a/arch/nds32/kernel/sys_nds32.c
+++ b/arch/nds32/kernel/sys_nds32.c
@@ -6,6 +6,8 @@
 
 #include <asm/cachectl.h>
 #include <asm/proc-fns.h>
+#include <asm/fpu.h>
+#include <asm/fp_udfiex_crtl.h>
 
 SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
 	       unsigned long, prot, unsigned long, flags,
@@ -48,3 +50,35 @@
 
 	return 0;
 }
+
+SYSCALL_DEFINE2(fp_udfiex_crtl, unsigned int, cmd, unsigned int, act)
+{
+#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
+	int old_udf_iex;
+
+	if (!used_math()) {
+		load_fpu(&init_fpuregs);
+		current->thread.fpu.UDF_IEX_trap = init_fpuregs.UDF_IEX_trap;
+		set_used_math();
+	}
+
+	old_udf_iex = current->thread.fpu.UDF_IEX_trap;
+	act &= (FPCSR_mskUDFE | FPCSR_mskIEXE);
+
+	switch (cmd) {
+	case DISABLE_UDF_IEX_TRAP:
+		current->thread.fpu.UDF_IEX_trap &= ~act;
+		break;
+	case ENABLE_UDF_IEX_TRAP:
+		current->thread.fpu.UDF_IEX_trap |= act;
+		break;
+	case GET_UDF_IEX_TRAP:
+		break;
+	default:
+		return -EINVAL;
+	}
+	return old_udf_iex;
+#else
+	return -ENOTSUPP;
+#endif
+}