arch/um/kernel/skas/uaccess.c

   1 /*
   2  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <linux/err.h>
   7 #include <linux/highmem.h>
   8 #include <linux/mm.h>
   9 #include <linux/module.h>
  10 #include <linux/sched.h>
  11 #include <asm/current.h>
  12 #include <asm/page.h>
  13 #include <asm/pgtable.h>
  14 #include <kern_util.h>
  15 #include <os.h>
  16
  17 pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
  18 {
  19         pgd_t *pgd;
  20         pud_t *pud;
  21         pmd_t *pmd;
  22
  23         if (mm == NULL)
  24                 return NULL;
  25
  26         pgd = pgd_offset(mm, addr);
  27         if (!pgd_present(*pgd))
  28                 return NULL;
  29
  30         pud = pud_offset(pgd, addr);
  31         if (!pud_present(*pud))
  32                 return NULL;
  33
  34         pmd = pmd_offset(pud, addr);
  35         if (!pmd_present(*pmd))
  36                 return NULL;
  37
  38         return pte_offset_kernel(pmd, addr);
  39 }
  40
  41 static pte_t *maybe_map(unsigned long virt, int is_write)
  42 {
  43         pte_t *pte = virt_to_pte(current->mm, virt);
  44         int err, dummy_code;
  45
  46         if ((pte == NULL) || !pte_present(*pte) ||
  47             (is_write && !pte_write(*pte))) {
  48                 err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
  49                 if (err)
  50                         return NULL;
  51                 pte = virt_to_pte(current->mm, virt);
  52         }
  53         if (!pte_present(*pte))
  54                 pte = NULL;
  55
  56         return pte;
  57 }
  58
  59 static int do_op_one_page(unsigned long addr, int len, int is_write,
  60                  int (*op)(unsigned long addr, int len, void *arg), void *arg)
  61 {
  62         jmp_buf buf;
  63         struct page *page;
  64         pte_t *pte;
  65         int n, faulted;
  66
  67         pte = maybe_map(addr, is_write);
  68         if (pte == NULL)
  69                 return -1;
  70
  71         page = pte_page(*pte);
  72         addr = (unsigned long) kmap_atomic(page) +
  73                 (addr & ~PAGE_MASK);
  74
  75         current->thread.fault_catcher = &buf;
  76
  77         faulted = UML_SETJMP(&buf);
  78         if (faulted == 0)
  79                 n = (*op)(addr, len, arg);
  80         else
  81                 n = -1;
  82
  83         current->thread.fault_catcher = NULL;
  84
  85         kunmap_atomic((void *)addr);
  86
  87         return n;
  88 }
  89
  90 static long buffer_op(unsigned long addr, int len, int is_write,
  91                       int (*op)(unsigned long, int, void *), void *arg)
  92 {
  93         long size, remain, n;
  94
  95         size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
  96         remain = len;
  97
  98         n = do_op_one_page(addr, size, is_write, op, arg);
  99         if (n != 0) {
 100                 remain = (n < 0 ? remain : 0);
 101                 goto out;
 102         }
 103
 104         addr += size;
 105         remain -= size;
 106         if (remain == 0)
 107                 goto out;
 108
 109         while (addr < ((addr + remain) & PAGE_MASK)) {
 110                 n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
 111                 if (n != 0) {
 112                         remain = (n < 0 ? remain : 0);
 113                         goto out;
 114                 }
 115
 116                 addr += PAGE_SIZE;
 117                 remain -= PAGE_SIZE;
 118         }
 119         if (remain == 0)
 120                 goto out;
 121
 122         n = do_op_one_page(addr, remain, is_write, op, arg);
 123         if (n != 0) {
 124                 remain = (n < 0 ? remain : 0);
 125                 goto out;
 126         }
 127
 128         return 0;
 129  out:
 130         return remain;
 131 }
 132
 133 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
 134 {
 135         unsigned long *to_ptr = arg, to = *to_ptr;
 136
 137         memcpy((void *) to, (void *) from, len);
 138         *to_ptr += len;
 139         return 0;
 140 }
 141
 142 long __copy_from_user(void *to, const void __user *from, unsigned long n)
 143 {
 144         if (segment_eq(get_fs(), KERNEL_DS)) {
 145                 memcpy(to, (__force void*)from, n);
 146                 return 0;
 147         }
 148
 149         return buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to);
 150 }
 151 EXPORT_SYMBOL(__copy_from_user);
 152
 153 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
 154 {
 155         unsigned long *from_ptr = arg, from = *from_ptr;
 156
 157         memcpy((void *) to, (void *) from, len);
 158         *from_ptr += len;
 159         return 0;
 160 }
 161
 162 long __copy_to_user(void __user *to, const void *from, unsigned long n)
 163 {
 164         if (segment_eq(get_fs(), KERNEL_DS)) {
 165                 memcpy((__force void *) to, from, n);
 166                 return 0;
 167         }
 168
 169         return buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from);
 170 }
 171 EXPORT_SYMBOL(__copy_to_user);
 172
 173 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
 174 {
 175         char **to_ptr = arg, *to = *to_ptr;
 176         int n;
 177
 178         strncpy(to, (void *) from, len);
 179         n = strnlen(to, len);
 180         *to_ptr += n;
 181
 182         if (n < len)
 183                 return 1;
 184         return 0;
 185 }
 186
 187 long __strncpy_from_user(char *dst, const char __user *src, long count)
 188 {
 189         long n;
 190         char *ptr = dst;
 191
 192         if (segment_eq(get_fs(), KERNEL_DS)) {
 193                 strncpy(dst, (__force void *) src, count);
 194                 return strnlen(dst, count);
 195         }
 196
 197         n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
 198                       &ptr);
 199         if (n != 0)
 200                 return -EFAULT;
 201         return strnlen(dst, count);
 202 }
 203 EXPORT_SYMBOL(__strncpy_from_user);
 204
 205 static int clear_chunk(unsigned long addr, int len, void *unused)
 206 {
 207         memset((void *) addr, 0, len);
 208         return 0;
 209 }
 210
 211 unsigned long __clear_user(void __user *mem, unsigned long len)
 212 {
 213         if (segment_eq(get_fs(), KERNEL_DS)) {
 214                 memset((__force void*)mem, 0, len);
 215                 return 0;
 216         }
 217
 218         return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
 219 }
 220 EXPORT_SYMBOL(__clear_user);
 221
 222 static int strnlen_chunk(unsigned long str, int len, void *arg)
 223 {
 224         int *len_ptr = arg, n;
 225
 226         n = strnlen((void *) str, len);
 227         *len_ptr += n;
 228
 229         if (n < len)
 230                 return 1;
 231         return 0;
 232 }
 233
 234 long __strnlen_user(const void __user *str, long len)
 235 {
 236         int count = 0, n;
 237
 238         if (segment_eq(get_fs(), KERNEL_DS))
 239                 return strnlen((__force char*)str, len) + 1;
 240
 241         n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
 242         if (n == 0)
 243                 return count + 1;
 244         return 0;
 245 }
 246 EXPORT_SYMBOL(__strnlen_user);