diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 6b99389..127310c 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -185,6 +185,11 @@
 
 	  If unsure, say Y.
 
+config PLATFORM_MOCK
+	bool "Enable a mock architecture used for unit testing."
+	depends on TEST && OF
+	default n
+
 endmenu
 
 source "arch/um/drivers/Kconfig"
diff --git a/arch/um/include/asm/Kbuild b/arch/um/include/asm/Kbuild
index b10dde6..9fd2827 100644
--- a/arch/um/include/asm/Kbuild
+++ b/arch/um/include/asm/Kbuild
@@ -12,7 +12,6 @@
 generic-y += futex.h
 generic-y += hardirq.h
 generic-y += hw_irq.h
-generic-y += io.h
 generic-y += irq_regs.h
 generic-y += irq_work.h
 generic-y += kdebug.h
diff --git a/arch/um/include/asm/io-mock-shared.h b/arch/um/include/asm/io-mock-shared.h
new file mode 100644
index 0000000..6baf59cb
--- /dev/null
+++ b/arch/um/include/asm/io-mock-shared.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_UM_IO_MOCK_SHARED_H
+#define _ASM_UM_IO_MOCK_SHARED_H
+
+#define readb readb
+u8 readb(const volatile void __iomem *);
+
+#define readw readw
+u16 readw(const volatile void __iomem *);
+
+#define readl readl
+u32 readl(const volatile void __iomem *);
+
+#ifdef CONFIG_64BIT
+#define readq readq
+u64 readq(const volatile void __iomem *);
+#endif /* CONFIG_64BIT */
+
+#define writeb writeb
+void writeb(u8, const volatile void __iomem *);
+
+#define writew writew
+void writew(u16, const volatile void __iomem *);
+
+#define writel writel
+void writel(u32, const volatile void __iomem *);
+
+#ifdef CONFIG_64BIT
+#define writeq writeq
+void writeq(u64, const volatile void __iomem *);
+#endif /* CONFIG_64BIT */
+
+#endif /* _ASM_UM_IO_MOCK_SHARED_H */
diff --git a/arch/um/include/asm/io-mock.h b/arch/um/include/asm/io-mock.h
new file mode 100644
index 0000000..bd2538a
--- /dev/null
+++ b/arch/um/include/asm/io-mock.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_UM_IO_MOCK_H
+#define _ASM_UM_IO_MOCK_H
+
+#include <asm/io-mock-shared.h>
+#include <test/mock.h>
+
+DECLARE_FUNCTION_MOCK(readb,
+		      RETURNS(u8), PARAMS(const volatile void __iomem *));
+
+DECLARE_FUNCTION_MOCK(readw,
+		      RETURNS(u16), PARAMS(const volatile void __iomem *));
+
+DECLARE_FUNCTION_MOCK(readl,
+		      RETURNS(u32), PARAMS(const volatile void __iomem *));
+
+#ifdef CONFIG_64BIT
+DECLARE_FUNCTION_MOCK(readq,
+		      RETURNS(u64), PARAMS(const volatile void __iomem *));
+#endif /* CONFIG_64BIT */
+
+DECLARE_FUNCTION_MOCK_VOID_RETURN(writeb,
+				  PARAMS(u8, const volatile void __iomem *));
+
+DECLARE_FUNCTION_MOCK_VOID_RETURN(writew,
+				  PARAMS(u16, const volatile void __iomem *));
+
+DECLARE_FUNCTION_MOCK_VOID_RETURN(writel,
+				  PARAMS(u32, const volatile void __iomem *));
+
+#ifdef CONFIG_64BIT
+DECLARE_FUNCTION_MOCK_VOID_RETURN(writeq,
+				  PARAMS(u64, const volatile void __iomem *));
+#endif /* CONFIG_64BIT */
+
+#endif /* _ASM_UM_IO_MOCK_H */
diff --git a/arch/um/include/asm/io.h b/arch/um/include/asm/io.h
index 96f77b5..a7f61cf 100644
--- a/arch/um/include/asm/io.h
+++ b/arch/um/include/asm/io.h
@@ -2,11 +2,19 @@
 #ifndef _ASM_UM_IO_H
 #define _ASM_UM_IO_H
 
+#include <linux/types.h>
+#include <asm/byteorder.h>
+
+#if IS_ENABLED(CONFIG_PLATFORM_MOCK)
+#include <asm/io-mock-shared.h>
+#endif
+
 #define ioremap ioremap
 static inline void __iomem *ioremap(phys_addr_t offset, size_t size)
 {
 	return (void __iomem *)(unsigned long)offset;
 }
+#define ioremap_nocache ioremap
 
 #define iounmap iounmap
 static inline void iounmap(void __iomem *addr)
diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
index 2f36d51..770c480 100644
--- a/arch/um/kernel/Makefile
+++ b/arch/um/kernel/Makefile
@@ -25,6 +25,7 @@
 obj-$(CONFIG_GCOV)	+= gmon_syms.o
 obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
+obj-$(CONFIG_PLATFORM_MOCK)	+= io-mock.o
 
 USER_OBJS := config.o
 
diff --git a/arch/um/kernel/io-mock.c b/arch/um/kernel/io-mock.c
new file mode 100644
index 0000000..4b1eee8
--- /dev/null
+++ b/arch/um/kernel/io-mock.c
@@ -0,0 +1,32 @@
+#include <linux/mm.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <test/mock.h>
+
+DEFINE_FUNCTION_MOCK(readb,
+		     RETURNS(u8), PARAMS(const volatile void __iomem *));
+
+DEFINE_FUNCTION_MOCK(readw,
+		     RETURNS(u16), PARAMS(const volatile void __iomem *));
+
+DEFINE_FUNCTION_MOCK(readl,
+		     RETURNS(u32), PARAMS(const volatile void __iomem *));
+
+#ifdef CONFIG_64BIT
+DEFINE_FUNCTION_MOCK(readq,
+		     RETURNS(u64), PARAMS(const volatile void __iomem *));
+#endif /* CONFIG_64BIT */
+
+DEFINE_FUNCTION_MOCK_VOID_RETURN(writeb,
+				 PARAMS(u8, const volatile void __iomem *));
+
+DEFINE_FUNCTION_MOCK_VOID_RETURN(writew,
+				 PARAMS(u16, const volatile void __iomem *));
+
+DEFINE_FUNCTION_MOCK_VOID_RETURN(writel,
+				 PARAMS(u32, const volatile void __iomem *));
+
+#ifdef CONFIG_64BIT
+DEFINE_FUNCTION_MOCK_VOID_RETURN(writeq,
+				 PARAMS(u64, const volatile void __iomem *));
+#endif /* CONFIG_64BIT */