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         struct page *page;
  62         pte_t *pte;
  63         int n;
  64
  65         pte = maybe_map(addr, is_write);
  66         if (pte == NULL)
  67                 return -1;
  68
  69         page = pte_page(*pte);
  70         addr = (unsigned long) kmap_atomic(page, KM_UML_USERCOPY) +
  71                 (addr & ~PAGE_MASK);
  72
  73         n = (*op)(addr, len, arg);
  74
  75         kunmap_atomic(page, KM_UML_USERCOPY);
  76
  77         return n;
  78 }
  79
  80 static void do_buffer_op(void *jmpbuf, void *arg_ptr)
  81 {
  82         va_list args;
  83         unsigned long addr;
  84         int len, is_write, size, remain, n;
  85         int (*op)(unsigned long, int, void *);
  86         void *arg;
  87         int *res;
  88
  89         va_copy(args, *(va_list *)arg_ptr);
  90         addr = va_arg(args, unsigned long);
  91         len = va_arg(args, int);
  92         is_write = va_arg(args, int);
  93         op = va_arg(args, void *);
  94         arg = va_arg(args, void *);
  95         res = va_arg(args, int *);
  96         va_end(args);
  97         size = min(PAGE_ALIGN(addr) - addr, (unsigned long) len);
  98         remain = len;
  99
 100         current->thread.fault_catcher = jmpbuf;
 101         n = do_op_one_page(addr, size, is_write, op, arg);
 102         if (n != 0) {
 103                 *res = (n < 0 ? remain : 0);
 104                 goto out;
 105         }
 106
 107         addr += size;
 108         remain -= size;
 109         if (remain == 0) {
 110                 *res = 0;
 111                 goto out;
 112         }
 113
 114         while(addr < ((addr + remain) & PAGE_MASK)) {
 115                 n = do_op_one_page(addr, PAGE_SIZE, is_write, op, arg);
 116                 if (n != 0) {
 117                         *res = (n < 0 ? remain : 0);
 118                         goto out;
 119                 }
 120
 121                 addr += PAGE_SIZE;
 122                 remain -= PAGE_SIZE;
 123         }
 124         if (remain == 0) {
 125                 *res = 0;
 126                 goto out;
 127         }
 128
 129         n = do_op_one_page(addr, remain, is_write, op, arg);
 130         if (n != 0)
 131                 *res = (n < 0 ? remain : 0);
 132         else *res = 0;
 133  out:
 134         current->thread.fault_catcher = NULL;
 135 }
 136
 137 static int buffer_op(unsigned long addr, int len, int is_write,
 138                      int (*op)(unsigned long addr, int len, void *arg),
 139                      void *arg)
 140 {
 141         int faulted, res;
 142
 143         faulted = setjmp_wrapper(do_buffer_op, addr, len, is_write, op, arg,
 144                                  &res);
 145         if (!faulted)
 146                 return res;
 147
 148         return addr + len - (unsigned long) current->thread.fault_addr;
 149 }
 150
 151 static int copy_chunk_from_user(unsigned long from, int len, void *arg)
 152 {
 153         unsigned long *to_ptr = arg, to = *to_ptr;
 154
 155         memcpy((void *) to, (void *) from, len);
 156         *to_ptr += len;
 157         return 0;
 158 }
 159
 160 int copy_from_user(void *to, const void __user *from, int n)
 161 {
 162         if (segment_eq(get_fs(), KERNEL_DS)) {
 163                 memcpy(to, (__force void*)from, n);
 164                 return 0;
 165         }
 166
 167         return access_ok(VERIFY_READ, from, n) ?
 168                buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
 169                n;
 170 }
 171
 172 static int copy_chunk_to_user(unsigned long to, int len, void *arg)
 173 {
 174         unsigned long *from_ptr = arg, from = *from_ptr;
 175
 176         memcpy((void *) to, (void *) from, len);
 177         *from_ptr += len;
 178         return 0;
 179 }
 180
 181 int copy_to_user(void __user *to, const void *from, int n)
 182 {
 183         if (segment_eq(get_fs(), KERNEL_DS)) {
 184                 memcpy((__force void *) to, from, n);
 185                 return 0;
 186         }
 187
 188         return access_ok(VERIFY_WRITE, to, n) ?
 189                buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
 190                n;
 191 }
 192
 193 static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
 194 {
 195         char **to_ptr = arg, *to = *to_ptr;
 196         int n;
 197
 198         strncpy(to, (void *) from, len);
 199         n = strnlen(to, len);
 200         *to_ptr += n;
 201
 202         if (n < len)
 203                 return 1;
 204         return 0;
 205 }
 206
 207 int strncpy_from_user(char *dst, const char __user *src, int count)
 208 {
 209         int n;
 210         char *ptr = dst;
 211
 212         if (segment_eq(get_fs(), KERNEL_DS)) {
 213                 strncpy(dst, (__force void *) src, count);
 214                 return strnlen(dst, count);
 215         }
 216
 217         if (!access_ok(VERIFY_READ, src, 1))
 218                 return -EFAULT;
 219
 220         n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
 221                       &ptr);
 222         if (n != 0)
 223                 return -EFAULT;
 224         return strnlen(dst, count);
 225 }
 226
 227 static int clear_chunk(unsigned long addr, int len, void *unused)
 228 {
 229         memset((void *) addr, 0, len);
 230         return 0;
 231 }
 232
 233 int __clear_user(void __user *mem, int len)
 234 {
 235         return buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL);
 236 }
 237
 238 int clear_user(void __user *mem, int len)
 239 {
 240         if (segment_eq(get_fs(), KERNEL_DS)) {
 241                 memset((__force void*)mem, 0, len);
 242                 return 0;
 243         }
 244
 245         return access_ok(VERIFY_WRITE, mem, len) ?
 246                buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len;
 247 }
 248
 249 static int strnlen_chunk(unsigned long str, int len, void *arg)
 250 {
 251         int *len_ptr = arg, n;
 252
 253         n = strnlen((void *) str, len);
 254         *len_ptr += n;
 255
 256         if (n < len)
 257                 return 1;
 258         return 0;
 259 }
 260
 261 int strnlen_user(const void __user *str, int len)
 262 {
 263         int count = 0, n;
 264
 265         if (segment_eq(get_fs(), KERNEL_DS))
 266                 return strnlen((__force char*)str, len) + 1;
 267
 268         n = buffer_op((unsigned long) str, len, 0, strnlen_chunk, &count);
 269         if (n == 0)
 270                 return count + 1;
 271         return -EFAULT;
 272 }