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/sched.h>
  10 #include <asm/current.h>
  11 #include <asm/page.h>
  12 #include <asm/pgtable.h>
  13 #include "kern_util.h"
  14 #include "os.h"
  15
  16 pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr)
  17 {
  18         pgd_t *pgd;
  19         pud_t *pud;
  20         pmd_t *pmd;
  21
  22         if (mm == NULL)
  23                 return NULL;
  24
  25         pgd = pgd_offset(mm, addr);
  26         if (!pgd_present(*pgd))
  27                 return NULL;
  28
  29         pud = pud_offset(pgd, addr);
  30         if (!pud_present(*pud))
  31                 return NULL;
  32
  33         pmd = pmd_offset(pud, addr);
  34         if (!pmd_present(*pmd))
  35                 return NULL;
  36
  37         return pte_offset_kernel(pmd, addr);
  38 }
  39
  40 static pte_t *maybe_map(unsigned long virt, int is_write)
  41 {
  42         pte_t *pte = virt_to_pte(current->mm, virt);
  43         int err, dummy_code;
  44
  45         if ((pte == NULL) || !pte_present(*pte) ||
  46             (is_write && !pte_write(*pte))) {
  47                 err = handle_page_fault(virt, 0, is_write, 1, &dummy_code);
  48                 if (err)
  49                         return NULL;
  50                 pte = virt_to_pte(current->mm, virt);
  51         }
  52         if (!pte_present(*pte))
  53                 pte = NULL;
  54
  55         return pte;
  56 }
  57
  58 static int do_op_one_page(unsigned long addr, int len, int is_write,
  59                  int (*op)(unsigned long addr, int len, void *arg), void *arg)
  60 {
  61         jmp_buf buf;
  62         struct page *page;
  63         pte_t *pte;
  64         int n, faulted;
  65
  66         pte = maybe_map(addr, is_write);
  67         if (pte == NULL)
  68                 return -1;
  69
  70         page = pte_page(*pte);
  71         addr = (unsigned long) kmap_atomic(page, KM_UML_USERCOPY) +
  72                 (addr & ~PAGE_MASK);
  73
  74         current->thread.fault_catcher = &buf;
  75
  76         faulted = UML_SETJMP(&buf);
  77         if (faulted == 0)
  78                 n = (*op)(addr, len, arg);
  79         else
  80                 n = -1;
  81
  82         current->thread.fault_catcher = NULL;
  83
  84         kunmap_atomic(page, KM_UML_USERCOPY);
  85
  86         return n;
  87 }
  88
  89 static int buffer_op(unsigned long addr, int len, int is_write,
  90                      int (*op)(unsigned long, int, void *), void *arg)
  91 {
  92         int size, remain, n;
  93
  94         size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
  95         remain = len;
  96
  97         n = do_op_one_page(addr, size, is_write, op, arg);
  98         if (n != 0) {
  99                 remain = (n < 0 ? remain : 0);
 100                 goto out;
 101         }
 102
 103         addr += size;
 104         remain -= size;
 105         if (remain == 0)
 106                 goto out;
 107
 108         while (addr < ((addr + remain) & PAGE_MASK)) {
 109                 n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
 110                 if (n != 0) {
 111                         remain = (n < 0 ? remain : 0);
 112                         goto out;
 113                 }
 114
 115                 addr += PAGE_SIZE;
 116                 remain -= PAGE_SIZE;
 117         }
 118         if (remain == 0)
 119                 goto out;
 120
 121         n = do_op_one_page(addr, remain, is_write, op, arg);
 122         if (n != 0) {
 123                 remain = (n < 0 ? remain : 0);
 124                 goto out;
 125         }
 126
 127         return 0;
 128  out:
 129         return remain;
 130 }
 131
 132 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
 133 {
 134         unsigned long *to_ptr = arg, to = *to_ptr;
 135
 136         memcpy((void *) to, (void *) from, len);
 137         *to_ptr += len;
 138         return 0;
 139 }
 140
 141 int copy_from_user(void *to, const void __user *from, int n)
 142 {
 143         if (segment_eq(get_fs(), KERNEL_DS)) {
 144                 memcpy(to, (__force void*)from, n);
 145                 return 0;
 146         }
 147
 148         return access_ok(VERIFY_READ, from, n) ?
 149                buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
 150                n;
 151 }
 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 int copy_to_user(void __user *to, const void *from, int n)
 163 {
 164         if (segment_eq(get_fs(), KERNEL_DS)) {
 165                 memcpy((__force void *) to, from, n);
 166                 return 0;
 167         }
 168
 169         return access_ok(VERIFY_WRITE, to, n) ?
 170                buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
 171                n;
 172 }
 173
 174 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
 175 {
 176         char **to_ptr = arg, *to = *to_ptr;
 177         int n;
 178
 179         strncpy(to, (void *) from, len);
 180         n = strnlen(to, len);
 181         *to_ptr += n;
 182
 183         if (n < len)
 184                 return 1;
 185         return 0;
 186 }
 187
 188 int strncpy_from_user(char *dst, const char __user *src, int count)
 189 {
 190         int n;
 191         char *ptr = dst;
 192
 193         if (segment_eq(get_fs(), KERNEL_DS)) {
 194                 strncpy(dst, (__force void *) src, count);
 195                 return strnlen(dst, count);
 196         }
 197
 198         if (!access_ok(VERIFY_READ, src, 1))
 199                 return -EFAULT;
 200
 201         n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
 202                       &ptr);
 203         if (n != 0)
 204                 return -EFAULT;
 205         return strnlen(dst, count);
 206 }
 207
 208 static int clear_chunk(unsigned long addr, int len, void *unused)
 209 {
 210         memset((void *) addr, 0, len);
 211         return 0;
 212 }
 213
 214 int __clear_user(void __user *mem, int len)
 215 {
 216         return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
 217 }
 218
 219 int clear_user(void __user *mem, int len)
 220 {
 221         if (segment_eq(get_fs(), KERNEL_DS)) {
 222                 memset((__force void*)mem, 0, len);
 223                 return 0;
 224         }
 225
 226         return access_ok(VERIFY_WRITE, mem, len) ?
 227                buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len;
 228 }
 229
 230 static int strnlen_chunk(unsigned long str, int len, void *arg)
 231 {
 232         int *len_ptr = arg, n;
 233
 234         n = strnlen((void *) str, len);
 235         *len_ptr += n;
 236
 237         if (n < len)
 238                 return 1;
 239         return 0;
 240 }
 241
 242 int strnlen_user(const void __user *str, int len)
 243 {
 244         int count = 0, n;
 245
 246         if (segment_eq(get_fs(), KERNEL_DS))
 247                 return strnlen((__force char*)str, len) + 1;
 248
 249         n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
 250         if (n == 0)
 251                 return count + 1;
 252         return -EFAULT;
 253 }