--- a/arch/alpha/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/alpha/include/asm/pgtable.h
@@ -46,7 +46,6 @@ struct vm_area_struct;
 #define PTRS_PER_PMD	(1UL << (PAGE_SHIFT-3))
 #define PTRS_PER_PGD	(1UL << (PAGE_SHIFT-3))
 #define USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 
 /* Number of pointers that fit on a page:  this will go away. */
 #define PTRS_PER_PAGE	(1UL << (PAGE_SHIFT-3))
--- a/arch/arc/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/arc/include/asm/pgtable.h
@@ -222,12 +222,6 @@
  */
 #define	USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)
 
-/*
- * No special requirements for lowest virtual address we permit any user space
- * mapping to be mapped at.
- */
-#define FIRST_USER_ADDRESS      0UL
-
 
 /****************************************************************
  * Bucket load of VM Helpers
--- a/arch/arm64/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/arm64/include/asm/pgtable.h
@@ -26,8 +26,6 @@
 
 #define vmemmap			((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
 
-#define FIRST_USER_ADDRESS	0UL
-
 #ifndef __ASSEMBLY__
 
 #include <asm/cmpxchg.h>
--- a/arch/csky/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/csky/include/asm/pgtable.h
@@ -14,7 +14,6 @@
 #define PGDIR_MASK		(~(PGDIR_SIZE-1))
 
 #define USER_PTRS_PER_PGD	(PAGE_OFFSET/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 
 /*
  * C-SKY is two-level paging structure:
--- a/arch/hexagon/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/hexagon/include/asm/pgtable.h
@@ -155,9 +155,6 @@ extern unsigned long _dflt_cache_att;
 
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];  /* located in head.S */
 
-/* Seems to be zero even in architectures where the zero page is firewalled? */
-#define FIRST_USER_ADDRESS 0UL
-
 /*  HUGETLB not working currently  */
 #ifdef CONFIG_HUGETLB_PAGE
 #define pte_mkhuge(pte) __pte((pte_val(pte) & ~0x3) | HVM_HUGEPAGE_SIZE)
--- a/arch/ia64/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/ia64/include/asm/pgtable.h
@@ -128,7 +128,6 @@
 #define PTRS_PER_PGD_SHIFT	PTRS_PER_PTD_SHIFT
 #define PTRS_PER_PGD		(1UL << PTRS_PER_PGD_SHIFT)
 #define USER_PTRS_PER_PGD	(5*PTRS_PER_PGD/8)	/* regions 0-4 are user regions */
-#define FIRST_USER_ADDRESS	0UL
 
 /*
  * All the normal masks have the "page accessed" bits on, as any time
--- a/arch/m68k/include/asm/pgtable_mm.h~mm-define-default-value-for-first_user_address
+++ a/arch/m68k/include/asm/pgtable_mm.h
@@ -72,7 +72,6 @@
 #define PTRS_PER_PGD	128
 #endif
 #define USER_PTRS_PER_PGD	(TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 
 /* Virtual address region for use by kernel_map() */
 #ifdef CONFIG_SUN3
--- a/arch/microblaze/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/microblaze/include/asm/pgtable.h
@@ -25,8 +25,6 @@ extern int mem_init_done;
 #include <asm/mmu.h>
 #include <asm/page.h>
 
-#define FIRST_USER_ADDRESS	0UL
-
 extern unsigned long va_to_phys(unsigned long address);
 extern pte_t *va_to_pte(unsigned long address);
 
--- a/arch/mips/include/asm/pgtable-32.h~mm-define-default-value-for-first_user_address
+++ a/arch/mips/include/asm/pgtable-32.h
@@ -93,7 +93,6 @@ extern int add_temporary_entry(unsigned
 #endif
 
 #define USER_PTRS_PER_PGD	(0x80000000UL/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 
 #define VMALLOC_START	  MAP_BASE
 
--- a/arch/mips/include/asm/pgtable-64.h~mm-define-default-value-for-first_user_address
+++ a/arch/mips/include/asm/pgtable-64.h
@@ -137,7 +137,6 @@
 #define PTRS_PER_PTE	((PAGE_SIZE << PTE_ORDER) / sizeof(pte_t))
 
 #define USER_PTRS_PER_PGD       ((TASK_SIZE64 / PGDIR_SIZE)?(TASK_SIZE64 / PGDIR_SIZE):1)
-#define FIRST_USER_ADDRESS	0UL
 
 /*
  * TLB refill handlers also map the vmalloc area into xuseg.  Avoid
--- a/arch/nios2/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/nios2/include/asm/pgtable.h
@@ -24,8 +24,6 @@
 #include <asm/pgtable-bits.h>
 #include <asm-generic/pgtable-nopmd.h>
 
-#define FIRST_USER_ADDRESS	0UL
-
 #define VMALLOC_START		CONFIG_NIOS2_KERNEL_MMU_REGION_BASE
 #define VMALLOC_END		(CONFIG_NIOS2_KERNEL_REGION_BASE - 1)
 
--- a/arch/openrisc/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/openrisc/include/asm/pgtable.h
@@ -73,7 +73,6 @@ extern void paging_init(void);
  */
 
 #define USER_PTRS_PER_PGD       (TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS      0UL
 
 /*
  * Kernels own virtual memory area.
--- a/arch/parisc/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/parisc/include/asm/pgtable.h
@@ -171,8 +171,6 @@ static inline void purge_tlb_entries(str
  * pgd entries used up by user/kernel:
  */
 
-#define FIRST_USER_ADDRESS	0UL
-
 /* NB: The tlb miss handlers make certain assumptions about the order */
 /*     of the following bits, so be careful (One example, bits 25-31  */
 /*     are moved together in one instruction).                        */
--- a/arch/powerpc/include/asm/book3s/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/powerpc/include/asm/book3s/pgtable.h
@@ -8,7 +8,6 @@
 #include <asm/book3s/32/pgtable.h>
 #endif
 
-#define FIRST_USER_ADDRESS	0UL
 #ifndef __ASSEMBLY__
 /* Insert a PTE, top-level function is out of line. It uses an inline
  * low level function in the respective pgtable-* files
--- a/arch/powerpc/include/asm/nohash/32/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/powerpc/include/asm/nohash/32/pgtable.h
@@ -54,7 +54,6 @@ extern int icache_44x_need_flush;
 #define PGD_MASKED_BITS		0
 
 #define USER_PTRS_PER_PGD	(TASK_SIZE / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 
 #define pte_ERROR(e) \
 	pr_err("%s:%d: bad pte %llx.\n", __FILE__, __LINE__, \
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -12,8 +12,6 @@
 #include <asm/barrier.h>
 #include <asm/asm-const.h>
 
-#define FIRST_USER_ADDRESS	0UL
-
 /*
  * Size of EA range mapped by our pagetables.
  */
--- a/arch/riscv/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/riscv/include/asm/pgtable.h
@@ -536,8 +536,6 @@ void setup_bootmem(void);
 void paging_init(void);
 void misc_mem_init(void);
 
-#define FIRST_USER_ADDRESS  0
-
 /*
  * ZERO_PAGE is a global shared page that is always zero,
  * used for zero-mapped memory areas, etc.
--- a/arch/s390/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/s390/include/asm/pgtable.h
@@ -65,8 +65,6 @@ extern unsigned long zero_page_mask;
 
 /* TODO: s390 cannot support io_remap_pfn_range... */
 
-#define FIRST_USER_ADDRESS  0UL
-
 #define pte_ERROR(e) \
 	printk("%s:%d: bad pte %p.\n", __FILE__, __LINE__, (void *) pte_val(e))
 #define pmd_ERROR(e) \
--- a/arch/sh/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/sh/include/asm/pgtable.h
@@ -59,8 +59,6 @@ static inline unsigned long long neff_si
 /* Entries per level */
 #define PTRS_PER_PTE	(PAGE_SIZE / (1 << PTE_MAGNITUDE))
 
-#define FIRST_USER_ADDRESS	0UL
-
 #define PHYS_ADDR_MASK29		0x1fffffff
 #define PHYS_ADDR_MASK32		0xffffffff
 
--- a/arch/sparc/include/asm/pgtable_32.h~mm-define-default-value-for-first_user_address
+++ a/arch/sparc/include/asm/pgtable_32.h
@@ -48,7 +48,6 @@ unsigned long __init bootmem_init(unsign
 #define PTRS_PER_PMD    	64
 #define PTRS_PER_PGD    	256
 #define USER_PTRS_PER_PGD	PAGE_OFFSET / PGDIR_SIZE
-#define FIRST_USER_ADDRESS	0UL
 #define PTE_SIZE		(PTRS_PER_PTE*4)
 
 #define PAGE_NONE	SRMMU_PAGE_NONE
--- a/arch/sparc/include/asm/pgtable_64.h~mm-define-default-value-for-first_user_address
+++ a/arch/sparc/include/asm/pgtable_64.h
@@ -95,9 +95,6 @@ bool kern_addr_valid(unsigned long addr)
 #define PTRS_PER_PUD	(1UL << PUD_BITS)
 #define PTRS_PER_PGD	(1UL << PGDIR_BITS)
 
-/* Kernel has a separate 44bit address space. */
-#define FIRST_USER_ADDRESS	0UL
-
 #define pmd_ERROR(e)							\
 	pr_err("%s:%d: bad pmd %p(%016lx) seen at (%pS)\n",		\
 	       __FILE__, __LINE__, &(e), pmd_val(e), __builtin_return_address(0))
--- a/arch/um/include/asm/pgtable-2level.h~mm-define-default-value-for-first_user_address
+++ a/arch/um/include/asm/pgtable-2level.h
@@ -23,7 +23,6 @@
 #define PTRS_PER_PTE	1024
 #define USER_PTRS_PER_PGD ((TASK_SIZE + (PGDIR_SIZE - 1)) / PGDIR_SIZE)
 #define PTRS_PER_PGD	1024
-#define FIRST_USER_ADDRESS	0UL
 
 #define pte_ERROR(e) \
         printk("%s:%d: bad pte %p(%08lx).\n", __FILE__, __LINE__, &(e), \
--- a/arch/um/include/asm/pgtable-3level.h~mm-define-default-value-for-first_user_address
+++ a/arch/um/include/asm/pgtable-3level.h
@@ -41,7 +41,6 @@
 #endif
 
 #define USER_PTRS_PER_PGD ((TASK_SIZE + (PGDIR_SIZE - 1)) / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 
 #define pte_ERROR(e) \
         printk("%s:%d: bad pte %p(%016lx).\n", __FILE__, __LINE__, &(e), \
--- a/arch/x86/include/asm/pgtable_types.h~mm-define-default-value-for-first_user_address
+++ a/arch/x86/include/asm/pgtable_types.h
@@ -7,8 +7,6 @@
 
 #include <asm/page_types.h>
 
-#define FIRST_USER_ADDRESS	0UL
-
 #define _PAGE_BIT_PRESENT	0	/* is present */
 #define _PAGE_BIT_RW		1	/* writeable */
 #define _PAGE_BIT_USER		2	/* userspace addressable */
--- a/arch/xtensa/include/asm/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/arch/xtensa/include/asm/pgtable.h
@@ -59,7 +59,6 @@
 #define PTRS_PER_PGD		1024
 #define PGD_ORDER		0
 #define USER_PTRS_PER_PGD	(TASK_SIZE/PGDIR_SIZE)
-#define FIRST_USER_ADDRESS	0UL
 #define FIRST_USER_PGD_NR	(FIRST_USER_ADDRESS >> PGDIR_SHIFT)
 
 #ifdef CONFIG_MMU
--- a/include/linux/pgtable.h~mm-define-default-value-for-first_user_address
+++ a/include/linux/pgtable.h
@@ -29,6 +29,15 @@
 #endif
 
 /*
+ * This defines the first usable user address. Platforms
+ * can override its value with custom FIRST_USER_ADDRESS
+ * defined in their respective <asm/pgtable.h>.
+ */
+#ifndef FIRST_USER_ADDRESS
+#define FIRST_USER_ADDRESS	0UL
+#endif
+
+/*
  * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
  *
  * The pXx_index() functions return the index of the entry in the page
