nios2: Memory management
authorLey Foon Tan <lftan@altera.com>
Thu, 6 Nov 2014 07:19:41 +0000 (15:19 +0800)
committerLey Foon Tan <lftan@altera.com>
Mon, 8 Dec 2014 04:55:51 +0000 (12:55 +0800)
This patch contains the initialisation of the memory blocks, MMU
attributes and the memory map.

Signed-off-by: Ley Foon Tan <lftan@altera.com>
arch/nios2/include/asm/mmu.h [new file with mode: 0644]
arch/nios2/include/asm/page.h [new file with mode: 0644]
arch/nios2/include/asm/uaccess.h [new file with mode: 0644]
arch/nios2/mm/init.c [new file with mode: 0644]
arch/nios2/mm/uaccess.c [new file with mode: 0644]

diff --git a/arch/nios2/include/asm/mmu.h b/arch/nios2/include/asm/mmu.h
new file mode 100644 (file)
index 0000000..d9c0b10
--- /dev/null
@@ -0,0 +1,16 @@
+/*
+ * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2004 Microtronix Datacom Ltd.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_MMU_H
+#define _ASM_NIOS2_MMU_H
+
+/* Default "unsigned long" context */
+typedef unsigned long mm_context_t;
+
+#endif /* _ASM_NIOS2_MMU_H */
diff --git a/arch/nios2/include/asm/page.h b/arch/nios2/include/asm/page.h
new file mode 100644 (file)
index 0000000..7a0d9bd
--- /dev/null
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2004 Microtronix Datacom Ltd.
+ *
+ * MMU support based on asm/page.h from mips which is:
+ *
+ * Copyright (C) 1994 - 1999, 2000, 03 Ralf Baechle
+ * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_PAGE_H
+#define _ASM_NIOS2_PAGE_H
+
+#include <linux/pfn.h>
+#include <linux/const.h>
+
+/*
+ * PAGE_SHIFT determines the page size
+ */
+#define PAGE_SHIFT     12
+#define PAGE_SIZE      (_AC(1, UL) << PAGE_SHIFT)
+#define PAGE_MASK      (~(PAGE_SIZE - 1))
+
+/*
+ * PAGE_OFFSET -- the first address of the first page of memory.
+ */
+#define PAGE_OFFSET    \
+       (CONFIG_NIOS2_MEM_BASE + CONFIG_NIOS2_KERNEL_REGION_BASE)
+
+#ifndef __ASSEMBLY__
+
+/*
+ * This gives the physical RAM offset.
+ */
+#define PHYS_OFFSET            CONFIG_NIOS2_MEM_BASE
+
+/*
+ * It's normally defined only for FLATMEM config but it's
+ * used in our early mem init code for all memory models.
+ * So always define it.
+ */
+#define ARCH_PFN_OFFSET                PFN_UP(PHYS_OFFSET)
+
+#define clear_page(page)       memset((page), 0, PAGE_SIZE)
+#define copy_page(to, from)    memcpy((to), (from), PAGE_SIZE)
+
+struct page;
+
+extern void clear_user_page(void *addr, unsigned long vaddr, struct page *page);
+extern void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
+                               struct page *to);
+
+extern unsigned long shm_align_mask;
+
+/*
+ * These are used to make use of C type-checking.
+ */
+typedef struct page *pgtable_t;
+typedef struct { unsigned long pte; } pte_t;
+typedef struct { unsigned long pgd; } pgd_t;
+typedef struct { unsigned long pgprot; } pgprot_t;
+
+#define pte_val(x)     ((x).pte)
+#define pgd_val(x)     ((x).pgd)
+#define pgprot_val(x)  ((x).pgprot)
+
+#define __pte(x)       ((pte_t) { (x) })
+#define __pgd(x)       ((pgd_t) { (x) })
+#define __pgprot(x)    ((pgprot_t) { (x) })
+
+extern unsigned long memory_start;
+extern unsigned long memory_end;
+extern unsigned long memory_size;
+
+extern struct page *mem_map;
+
+#endif /* !__ASSEMBLY__ */
+
+# define __pa(x)               \
+       ((unsigned long)(x) - PAGE_OFFSET + PHYS_OFFSET)
+# define __va(x)               \
+       ((void *)((unsigned long)(x) + PAGE_OFFSET - PHYS_OFFSET))
+
+#define page_to_virt(page)     \
+       ((((page) - mem_map) << PAGE_SHIFT) + PAGE_OFFSET)
+
+# define pfn_to_kaddr(pfn)     __va((pfn) << PAGE_SHIFT)
+# define pfn_valid(pfn)                ((pfn) >= ARCH_PFN_OFFSET &&    \
+                                       (pfn) < max_mapnr)
+
+# define virt_to_page(vaddr)   pfn_to_page(PFN_DOWN(virt_to_phys(vaddr)))
+# define virt_addr_valid(vaddr)        pfn_valid(PFN_DOWN(virt_to_phys(vaddr)))
+
+# define VM_DATA_DEFAULT_FLAGS (VM_READ | VM_WRITE | \
+                                VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
+
+# define UNCAC_ADDR(addr)      \
+       ((void *)((unsigned)(addr) | CONFIG_NIOS2_IO_REGION_BASE))
+# define CAC_ADDR(addr)                \
+       ((void *)(((unsigned)(addr) & ~CONFIG_NIOS2_IO_REGION_BASE) |   \
+               CONFIG_NIOS2_KERNEL_REGION_BASE))
+
+#include <asm-generic/memory_model.h>
+
+#include <asm-generic/getorder.h>
+
+#endif /* _ASM_NIOS2_PAGE_H */
diff --git a/arch/nios2/include/asm/uaccess.h b/arch/nios2/include/asm/uaccess.h
new file mode 100644 (file)
index 0000000..acedc0a
--- /dev/null
@@ -0,0 +1,231 @@
+/*
+ * User space memory access functions for Nios II
+ *
+ * Copyright (C) 2010-2011, Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009, Wind River Systems Inc
+ *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_UACCESS_H
+#define _ASM_NIOS2_UACCESS_H
+
+#include <linux/errno.h>
+#include <linux/thread_info.h>
+#include <linux/string.h>
+
+#include <asm/page.h>
+
+#define VERIFY_READ    0
+#define VERIFY_WRITE   1
+
+/*
+ * The exception table consists of pairs of addresses: the first is the
+ * address of an instruction that is allowed to fault, and the second is
+ * the address at which the program should continue.  No registers are
+ * modified, so it is entirely up to the continuation code to figure out
+ * what to do.
+ *
+ * All the routines below use bits of fixup code that are out of line
+ * with the main instruction path.  This means when everything is well,
+ * we don't even have to jump over them.  Further, they do not intrude
+ * on our cache or tlb entries.
+ */
+struct exception_table_entry {
+       unsigned long insn;
+       unsigned long fixup;
+};
+
+extern int fixup_exception(struct pt_regs *regs);
+
+/*
+ * Segment stuff
+ */
+#define MAKE_MM_SEG(s)         ((mm_segment_t) { (s) })
+#define USER_DS                        MAKE_MM_SEG(0x80000000UL)
+#define KERNEL_DS              MAKE_MM_SEG(0)
+
+#define get_ds()               (KERNEL_DS)
+
+#define get_fs()               (current_thread_info()->addr_limit)
+#define set_fs(seg)            (current_thread_info()->addr_limit = (seg))
+
+#define segment_eq(a, b)       ((a).seg == (b).seg)
+
+#define __access_ok(addr, len)                 \
+       (((signed long)(((long)get_fs().seg) &  \
+               ((long)(addr) | (((long)(addr)) + (len)) | (len)))) == 0)
+
+#define access_ok(type, addr, len)             \
+       likely(__access_ok((unsigned long)(addr), (unsigned long)(len)))
+
+# define __EX_TABLE_SECTION    ".section __ex_table,\"a\"\n"
+
+/*
+ * Zero Userspace
+ */
+
+static inline unsigned long __must_check __clear_user(void __user *to,
+                                                     unsigned long n)
+{
+       __asm__ __volatile__ (
+               "1:     stb     zero, 0(%1)\n"
+               "       addi    %0, %0, -1\n"
+               "       addi    %1, %1, 1\n"
+               "       bne     %0, zero, 1b\n"
+               "2:\n"
+               __EX_TABLE_SECTION
+               ".word  1b, 2b\n"
+               ".previous\n"
+               : "=r" (n), "=r" (to)
+               : "0" (n), "1" (to)
+       );
+
+       return n;
+}
+
+static inline unsigned long __must_check clear_user(void __user *to,
+                                                   unsigned long n)
+{
+       if (!access_ok(VERIFY_WRITE, to, n))
+               return n;
+       return __clear_user(to, n);
+}
+
+extern long __copy_from_user(void *to, const void __user *from,
+                               unsigned long n);
+extern long __copy_to_user(void __user *to, const void *from, unsigned long n);
+
+static inline long copy_from_user(void *to, const void __user *from,
+                               unsigned long n)
+{
+       if (!access_ok(VERIFY_READ, from, n))
+               return n;
+       return __copy_from_user(to, from, n);
+}
+
+static inline long copy_to_user(void __user *to, const void *from,
+                               unsigned long n)
+{
+       if (!access_ok(VERIFY_WRITE, to, n))
+               return n;
+       return __copy_to_user(to, from, n);
+}
+
+extern long strncpy_from_user(char *__to, const char __user *__from,
+                               long __len);
+extern long strnlen_user(const char __user *s, long n);
+
+#define __copy_from_user_inatomic      __copy_from_user
+#define __copy_to_user_inatomic                __copy_to_user
+
+/* Optimized macros */
+#define __get_user_asm(val, insn, addr, err)                           \
+{                                                                      \
+       __asm__ __volatile__(                                           \
+       "       movi    %0, %3\n"                                       \
+       "1:   " insn " %1, 0(%2)\n"                                     \
+       "       movi     %0, 0\n"                                       \
+       "2:\n"                                                          \
+       "       .section __ex_table,\"a\"\n"                            \
+       "       .word 1b, 2b\n"                                         \
+       "       .previous"                                              \
+       : "=&r" (err), "=r" (val)                                       \
+       : "r" (addr), "i" (-EFAULT));                                   \
+}
+
+#define __get_user_unknown(val, size, ptr, err) do {                   \
+       err = 0;                                                        \
+       if (copy_from_user(&(val), ptr, size)) {                        \
+               err = -EFAULT;                                          \
+       }                                                               \
+       } while (0)
+
+#define __get_user_common(val, size, ptr, err)                         \
+do {                                                                   \
+       switch (size) {                                                 \
+       case 1:                                                         \
+               __get_user_asm(val, "ldbu", ptr, err);                  \
+               break;                                                  \
+       case 2:                                                         \
+               __get_user_asm(val, "ldhu", ptr, err);                  \
+               break;                                                  \
+       case 4:                                                         \
+               __get_user_asm(val, "ldw", ptr, err);                   \
+               break;                                                  \
+       default:                                                        \
+               __get_user_unknown(val, size, ptr, err);                \
+               break;                                                  \
+       }                                                               \
+} while (0)
+
+#define __get_user(x, ptr)                                             \
+       ({                                                              \
+       long __gu_err = -EFAULT;                                        \
+       const __typeof__(*(ptr)) __user *__gu_ptr = (ptr);              \
+       unsigned long __gu_val;                                         \
+       __get_user_common(__gu_val, sizeof(*(ptr)), __gu_ptr, __gu_err);\
+       (x) = (__typeof__(x))__gu_val;                                  \
+       __gu_err;                                                       \
+       })
+
+#define get_user(x, ptr)                                               \
+({                                                                     \
+       long __gu_err = -EFAULT;                                        \
+       const __typeof__(*(ptr)) __user *__gu_ptr = (ptr);              \
+       unsigned long __gu_val = 0;                                     \
+       if (access_ok(VERIFY_READ,  __gu_ptr, sizeof(*__gu_ptr)))       \
+               __get_user_common(__gu_val, sizeof(*__gu_ptr),          \
+                       __gu_ptr, __gu_err);                            \
+       (x) = (__typeof__(x))__gu_val;                                  \
+       __gu_err;                                                       \
+})
+
+#define __put_user_asm(val, insn, ptr, err)                            \
+{                                                                      \
+       __asm__ __volatile__(                                           \
+       "       movi    %0, %3\n"                                       \
+       "1:   " insn " %1, 0(%2)\n"                                     \
+       "       movi     %0, 0\n"                                       \
+       "2:\n"                                                          \
+       "       .section __ex_table,\"a\"\n"                            \
+       "       .word 1b, 2b\n"                                         \
+       "       .previous\n"                                            \
+       : "=&r" (err)                                                   \
+       : "r" (val), "r" (ptr), "i" (-EFAULT));                         \
+}
+
+#define put_user(x, ptr)                                               \
+({                                                                     \
+       long __pu_err = -EFAULT;                                        \
+       __typeof__(*(ptr)) __user *__pu_ptr = (ptr);                    \
+       __typeof__(*(ptr)) __pu_val = (__typeof(*ptr))(x);              \
+       if (access_ok(VERIFY_WRITE, __pu_ptr, sizeof(*__pu_ptr))) {     \
+               switch (sizeof(*__pu_ptr)) {                            \
+               case 1:                                                 \
+                       __put_user_asm(__pu_val, "stb", __pu_ptr, __pu_err); \
+                       break;                                          \
+               case 2:                                                 \
+                       __put_user_asm(__pu_val, "sth", __pu_ptr, __pu_err); \
+                       break;                                          \
+               case 4:                                                 \
+                       __put_user_asm(__pu_val, "stw", __pu_ptr, __pu_err); \
+                       break;                                          \
+               default:                                                \
+                       /* XXX: This looks wrong... */                  \
+                       __pu_err = 0;                                   \
+                       if (copy_to_user(__pu_ptr, &(__pu_val),         \
+                               sizeof(*__pu_ptr)))                     \
+                               __pu_err = -EFAULT;                     \
+                       break;                                          \
+               }                                                       \
+       }                                                               \
+       __pu_err;                                                       \
+})
+
+#define __put_user(x, ptr) put_user(x, ptr)
+
+#endif /* _ASM_NIOS2_UACCESS_H */
diff --git a/arch/nios2/mm/init.c b/arch/nios2/mm/init.c
new file mode 100644 (file)
index 0000000..e75c75d
--- /dev/null
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2013 Altera Corporation
+ * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2009 Wind River Systems Inc
+ *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ * Copyright (C) 2004 Microtronix Datacom Ltd
+ *
+ * based on arch/m68k/mm/init.c
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/pagemap.h>
+#include <linux/bootmem.h>
+#include <linux/slab.h>
+#include <linux/binfmts.h>
+
+#include <asm/setup.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/sections.h>
+#include <asm/tlb.h>
+#include <asm/mmu_context.h>
+#include <asm/cpuinfo.h>
+#include <asm/processor.h>
+
+pgd_t *pgd_current;
+
+/*
+ * paging_init() continues the virtual memory environment setup which
+ * was begun by the code in arch/head.S.
+ * The parameters are pointers to where to stick the starting and ending
+ * addresses of available kernel virtual memory.
+ */
+void __init paging_init(void)
+{
+       unsigned long zones_size[MAX_NR_ZONES];
+
+       memset(zones_size, 0, sizeof(zones_size));
+
+       pagetable_init();
+       pgd_current = swapper_pg_dir;
+
+       zones_size[ZONE_NORMAL] = max_mapnr;
+
+       /* pass the memory from the bootmem allocator to the main allocator */
+       free_area_init(zones_size);
+
+       flush_dcache_range((unsigned long)empty_zero_page,
+                       (unsigned long)empty_zero_page + PAGE_SIZE);
+}
+
+void __init mem_init(void)
+{
+       unsigned long end_mem   = memory_end; /* this must not include
+                                               kernel stack at top */
+
+       pr_debug("mem_init: start=%lx, end=%lx\n", memory_start, memory_end);
+
+       end_mem &= PAGE_MASK;
+       high_memory = __va(end_mem);
+
+       /* this will put all memory onto the freelists */
+       free_all_bootmem();
+       mem_init_print_info(NULL);
+}
+
+void __init mmu_init(void)
+{
+       flush_tlb_all();
+}
+
+#ifdef CONFIG_BLK_DEV_INITRD
+void __init free_initrd_mem(unsigned long start, unsigned long end)
+{
+       free_reserved_area((void *)start, (void *)end, -1, "initrd");
+}
+#endif
+
+void __init_refok free_initmem(void)
+{
+       free_initmem_default(-1);
+}
+
+#define __page_aligned(order) __aligned(PAGE_SIZE << (order))
+pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned(PGD_ORDER);
+pte_t invalid_pte_table[PTRS_PER_PTE] __page_aligned(PTE_ORDER);
+static struct page *kuser_page[1];
+
+static int alloc_kuser_page(void)
+{
+       extern char __kuser_helper_start[], __kuser_helper_end[];
+       int kuser_sz = __kuser_helper_end - __kuser_helper_start;
+       unsigned long vpage;
+
+       vpage = get_zeroed_page(GFP_ATOMIC);
+       if (!vpage)
+               return -ENOMEM;
+
+       /* Copy kuser helpers */
+       memcpy((void *)vpage, __kuser_helper_start, kuser_sz);
+
+       flush_icache_range(vpage, vpage + KUSER_SIZE);
+       kuser_page[0] = virt_to_page(vpage);
+
+       return 0;
+}
+arch_initcall(alloc_kuser_page);
+
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+       struct mm_struct *mm = current->mm;
+       int ret;
+
+       down_write(&mm->mmap_sem);
+
+       /* Map kuser helpers to user space address */
+       ret = install_special_mapping(mm, KUSER_BASE, KUSER_SIZE,
+                                     VM_READ | VM_EXEC | VM_MAYREAD |
+                                     VM_MAYEXEC, kuser_page);
+
+       up_write(&mm->mmap_sem);
+
+       return ret;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+       return (vma->vm_start == KUSER_BASE) ? "[kuser]" : NULL;
+}
diff --git a/arch/nios2/mm/uaccess.c b/arch/nios2/mm/uaccess.c
new file mode 100644 (file)
index 0000000..7663e15
--- /dev/null
@@ -0,0 +1,163 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2009, Wind River Systems Inc
+ * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ */
+
+#include <linux/export.h>
+#include <linux/uaccess.h>
+
+asm(".global   __copy_from_user\n"
+       "   .type __copy_from_user, @function\n"
+       "__copy_from_user:\n"
+       "   movi  r2,7\n"
+       "   mov   r3,r4\n"
+       "   bge   r2,r6,1f\n"
+       "   xor   r2,r4,r5\n"
+       "   andi  r2,r2,3\n"
+       "   movi  r7,3\n"
+       "   beq   r2,zero,4f\n"
+       "1: addi  r6,r6,-1\n"
+       "   movi  r2,-1\n"
+       "   beq   r6,r2,3f\n"
+       "   mov   r7,r2\n"
+       "2: ldbu  r2,0(r5)\n"
+       "   addi  r6,r6,-1\n"
+       "   addi  r5,r5,1\n"
+       "   stb   r2,0(r3)\n"
+       "   addi  r3,r3,1\n"
+       "   bne   r6,r7,2b\n"
+       "3:\n"
+       "   addi  r2,r6,1\n"
+       "   ret\n"
+       "13:mov   r2,r6\n"
+       "   ret\n"
+       "4: andi  r2,r4,1\n"
+       "   cmpeq r2,r2,zero\n"
+       "   beq   r2,zero,7f\n"
+       "5: andi  r2,r3,2\n"
+       "   beq   r2,zero,6f\n"
+       "9: ldhu  r2,0(r5)\n"
+       "   addi  r6,r6,-2\n"
+       "   addi  r5,r5,2\n"
+       "   sth   r2,0(r3)\n"
+       "   addi  r3,r3,2\n"
+       "6: bge   r7,r6,1b\n"
+       "10:ldw   r2,0(r5)\n"
+       "   addi  r6,r6,-4\n"
+       "   addi  r5,r5,4\n"
+       "   stw   r2,0(r3)\n"
+       "   addi  r3,r3,4\n"
+       "   br    6b\n"
+       "7: ldbu  r2,0(r5)\n"
+       "   addi  r6,r6,-1\n"
+       "   addi  r5,r5,1\n"
+       "   addi  r3,r4,1\n"
+       "   stb   r2,0(r4)\n"
+       "   br    5b\n"
+       ".section __ex_table,\"a\"\n"
+       ".word 2b,3b\n"
+       ".word 9b,13b\n"
+       ".word 10b,13b\n"
+       ".word 7b,13b\n"
+       ".previous\n"
+       );
+EXPORT_SYMBOL(__copy_from_user);
+
+asm(
+       "   .global __copy_to_user\n"
+       "   .type __copy_to_user, @function\n"
+       "__copy_to_user:\n"
+       "   movi  r2,7\n"
+       "   mov   r3,r4\n"
+       "   bge   r2,r6,1f\n"
+       "   xor   r2,r4,r5\n"
+       "   andi  r2,r2,3\n"
+       "   movi  r7,3\n"
+       "   beq   r2,zero,4f\n"
+       /* Bail if we try to copy zero bytes  */
+       "1: addi  r6,r6,-1\n"
+       "   movi  r2,-1\n"
+       "   beq   r6,r2,3f\n"
+       /* Copy byte by byte for small copies and if src^dst != 0 */
+       "   mov   r7,r2\n"
+       "2: ldbu  r2,0(r5)\n"
+       "   addi  r5,r5,1\n"
+       "9: stb   r2,0(r3)\n"
+       "   addi  r6,r6,-1\n"
+       "   addi  r3,r3,1\n"
+       "   bne   r6,r7,2b\n"
+       "3: addi  r2,r6,1\n"
+       "   ret\n"
+       "13:mov   r2,r6\n"
+       "   ret\n"
+       /*  If 'to' is an odd address byte copy */
+       "4: andi  r2,r4,1\n"
+       "   cmpeq r2,r2,zero\n"
+       "   beq   r2,zero,7f\n"
+       /* If 'to' is not divideable by four copy halfwords */
+       "5: andi  r2,r3,2\n"
+       "   beq   r2,zero,6f\n"
+       "   ldhu  r2,0(r5)\n"
+       "   addi  r5,r5,2\n"
+       "10:sth   r2,0(r3)\n"
+       "   addi  r6,r6,-2\n"
+       "   addi  r3,r3,2\n"
+       /* Copy words */
+       "6: bge   r7,r6,1b\n"
+       "   ldw   r2,0(r5)\n"
+       "   addi  r5,r5,4\n"
+       "11:stw   r2,0(r3)\n"
+       "   addi  r6,r6,-4\n"
+       "   addi  r3,r3,4\n"
+       "   br    6b\n"
+       /* Copy remaining bytes */
+       "7: ldbu  r2,0(r5)\n"
+       "   addi  r5,r5,1\n"
+       "   addi  r3,r4,1\n"
+       "12: stb  r2,0(r4)\n"
+       "   addi  r6,r6,-1\n"
+       "   br    5b\n"
+       ".section __ex_table,\"a\"\n"
+       ".word 9b,3b\n"
+       ".word 10b,13b\n"
+       ".word 11b,13b\n"
+       ".word 12b,13b\n"
+       ".previous\n");
+EXPORT_SYMBOL(__copy_to_user);
+
+long strncpy_from_user(char *__to, const char __user *__from, long __len)
+{
+       int l = strnlen_user(__from, __len);
+       int is_zt = 1;
+
+       if (l > __len) {
+               is_zt = 0;
+               l = __len;
+       }
+
+       if (l == 0 || copy_from_user(__to, __from, l))
+               return -EFAULT;
+
+       if (is_zt)
+               l--;
+       return l;
+}
+
+long strnlen_user(const char __user *s, long n)
+{
+       long i;
+
+       for (i = 0; i < n; i++) {
+               char c;
+
+               if (get_user(c, s + i) == -EFAULT)
+                       return 0;
+               if (c == 0)
+                       return i + 1;
+       }
+       return n + 1;
+}