2 files changed, 142 insertions, 0 deletions

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 866f84a586ff..030ba7219f48 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -29,6 +29,9 @@ else
 endif
 endif
 
+# using lib_ here won't override already available weak symbols
+obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o
+
 lib-$(CONFIG_MMU) += $(mmu-y)
 
 ifeq ($(CONFIG_CPU_32v3),y)
diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
new file mode 100644
index 000000000000..bf987b4a2571
--- /dev/null
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -0,0 +1,139 @@
+/*
+ *  linux/arch/arm/lib/uaccess_with_memcpy.c
+ *
+ *  Written by: Lennert Buytenhek and Nicolas Pitre
+ *  Copyright (C) 2009 Marvell Semiconductor
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/uaccess.h>
+#include <linux/rwsem.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/hardirq.h> /* for in_atomic() */
+#include <asm/current.h>
+#include <asm/page.h>
+
+static int
+pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
+{
+        unsigned long addr = (unsigned long)_addr;
+        pgd_t *pgd;
+        pmd_t *pmd;
+        pte_t *pte;
+        spinlock_t *ptl;
+
+        pgd = pgd_offset(current->mm, addr);
+        if (unlikely(pgd_none(*pgd) || pgd_bad(*pgd)))
+                return 0;
+
+        pmd = pmd_offset(pgd, addr);
+        if (unlikely(pmd_none(*pmd) || pmd_bad(*pmd)))
+                return 0;
+
+        pte = pte_offset_map_lock(current->mm, pmd, addr, &ptl);
+        if (unlikely(!pte_present(*pte) || !pte_young(*pte) ||
+            !pte_write(*pte) || !pte_dirty(*pte))) {
+                pte_unmap_unlock(pte, ptl);
+                return 0;
+        }
+
+        *ptep = pte;
+        *ptlp = ptl;
+
+        return 1;
+}
+
+unsigned long
+__copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+        int atomic;
+
+        if (n < 1024)
+                return __copy_to_user_std(to, from, n);
+
+        if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
+                memcpy((void *)to, from, n);
+                return 0;
+        }
+
+        /* the mmap semaphore is taken only if not in an atomic context */
+        atomic = in_atomic();
+
+        if (!atomic)
+                down_read(&current->mm->mmap_sem);
+        while (n) {
+                pte_t *pte;
+                spinlock_t *ptl;
+                int tocopy;
+
+                while (!pin_page_for_write(to, &pte, &ptl)) {
+                        if (!atomic)
+                                up_read(&current->mm->mmap_sem);
+                        if (__put_user(0, (char __user *)to))
+                                goto out;
+                        if (!atomic)
+                                down_read(&current->mm->mmap_sem);
+                }
+
+                tocopy = (~(unsigned long)to & ~PAGE_MASK) + 1;
+                if (tocopy > n)
+                        tocopy = n;
+
+                memcpy((void *)to, from, tocopy);
+                to += tocopy;
+                from += tocopy;
+                n -= tocopy;
+
+                pte_unmap_unlock(pte, ptl);
+        }
+        if (!atomic)
+                up_read(&current->mm->mmap_sem);
+
+out:
+        return n;
+}
+
+unsigned long __clear_user(void __user *addr, unsigned long n)
+{
+        if (n < 256)
+                return __clear_user_std(addr, n);
+
+        if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
+                memset((void *)addr, 0, n);
+                return 0;
+        }
+
+        down_read(&current->mm->mmap_sem);
+        while (n) {
+                pte_t *pte;
+                spinlock_t *ptl;
+                int tocopy;
+
+                while (!pin_page_for_write(addr, &pte, &ptl)) {
+                        up_read(&current->mm->mmap_sem);
+                        if (__put_user(0, (char __user *)addr))
+                                goto out;
+                        down_read(&current->mm->mmap_sem);
+                }
+
+                tocopy = (~(unsigned long)addr & ~PAGE_MASK) + 1;
+                if (tocopy > n)
+                        tocopy = n;
+
+                memset((void *)addr, 0, tocopy);
+                addr += tocopy;
+                n -= tocopy;
+
+                pte_unmap_unlock(pte, ptl);
+        }
+        up_read(&current->mm->mmap_sem);
+
+out:
+        return n;
+}