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, KM_UML_USERCOPY) +
  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, KM_UML_USERCOPY);
  86
  87         return n;
  88 }
  89
  90 static int buffer_op(unsigned long addr, int len, int is_write,
  91                      int (*op)(unsigned long, int, void *), void *arg)
  92 {
  93         int 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 int copy_from_user(void *to, const void __user *from, int n)
 143 {
 144         if (segment_eq(get_fs(), KERNEL_DS)) {
 145                 memcpy(to, (__force void*)from, n);
 146                 return 0;
 147         }
 148
 149         return access_ok(VERIFY_READ, from, n) ?
 150                buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
 151                n;
 152 }
 153 EXPORT_SYMBOL(copy_from_user);
 154
 155 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
 156 {
 157         unsigned long *from_ptr = arg, from = *from_ptr;
 158
 159         memcpy((void *) to, (void *) from, len);
 160         *from_ptr += len;
 161         return 0;
 162 }
 163
 164 int copy_to_user(void __user *to, const void *from, int n)
 165 {
 166         if (segment_eq(get_fs(), KERNEL_DS)) {
 167                 memcpy((__force void *) to, from, n);
 168                 return 0;
 169         }
 170
 171         return access_ok(VERIFY_WRITE, to, n) ?
 172                buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
 173                n;
 174 }
 175 EXPORT_SYMBOL(copy_to_user);
 176
 177 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
 178 {
 179         char **to_ptr = arg, *to = *to_ptr;
 180         int n;
 181
 182         strncpy(to, (void *) from, len);
 183         n = strnlen(to, len);
 184         *to_ptr += n;
 185
 186         if (n < len)
 187                 return 1;
 188         return 0;
 189 }
 190
 191 int strncpy_from_user(char *dst, const char __user *src, int count)
 192 {
 193         int n;
 194         char *ptr = dst;
 195
 196         if (segment_eq(get_fs(), KERNEL_DS)) {
 197                 strncpy(dst, (__force void *) src, count);
 198                 return strnlen(dst, count);
 199         }
 200
 201         if (!access_ok(VERIFY_READ, src, 1))
 202                 return -EFAULT;
 203
 204         n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
 205                       &ptr);
 206         if (n != 0)
 207                 return -EFAULT;
 208         return strnlen(dst, count);
 209 }
 210 EXPORT_SYMBOL(strncpy_from_user);
 211
 212 static int clear_chunk(unsigned long addr, int len, void *unused)
 213 {
 214         memset((void *) addr, 0, len);
 215         return 0;
 216 }
 217
 218 int __clear_user(void __user *mem, int len)
 219 {
 220         return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
 221 }
 222
 223 int clear_user(void __user *mem, int len)
 224 {
 225         if (segment_eq(get_fs(), KERNEL_DS)) {
 226                 memset((__force void*)mem, 0, len);
 227                 return 0;
 228         }
 229
 230         return access_ok(VERIFY_WRITE, mem, len) ?
 231                buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len;
 232 }
 233 EXPORT_SYMBOL(clear_user);
 234
 235 static int strnlen_chunk(unsigned long str, int len, void *arg)
 236 {
 237         int *len_ptr = arg, n;
 238
 239         n = strnlen((void *) str, len);
 240         *len_ptr += n;
 241
 242         if (n < len)
 243                 return 1;
 244         return 0;
 245 }
 246
 247 int strnlen_user(const void __user *str, int len)
 248 {
 249         int count = 0, n;
 250
 251         if (segment_eq(get_fs(), KERNEL_DS))
 252                 return strnlen((__force char*)str, len) + 1;
 253
 254         n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
 255         if (n == 0)
 256                 return count + 1;
 257         return -EFAULT;
 258 }
 259 EXPORT_SYMBOL(strnlen_user);