arch/s390/lib/uaccess_pt.c

   1 /*
   2  *  arch/s390/lib/uaccess_pt.c
   3  *
   4  *  User access functions based on page table walks for enhanced
   5  *  system layout without hardware support.
   6  *
   7  *    Copyright IBM Corp. 2006
   8  *    Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
   9  */
  10
  11 #include <linux/errno.h>
  12 #include <linux/hardirq.h>
  13 #include <linux/mm.h>
  14 #include <asm/uaccess.h>
  15 #include <asm/futex.h>
  16 #include "uaccess.h"
  17
  18 static inline pte_t *follow_table(struct mm_struct *mm, unsigned long addr)
  19 {
  20         pgd_t *pgd;
  21         pud_t *pud;
  22         pmd_t *pmd;
  23
  24         pgd = pgd_offset(mm, addr);
  25         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  26                 return (pte_t *) 0x3a;
  27
  28         pud = pud_offset(pgd, addr);
  29         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
  30                 return (pte_t *) 0x3b;
  31
  32         pmd = pmd_offset(pud, addr);
  33         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
  34                 return (pte_t *) 0x10;
  35
  36         return pte_offset_map(pmd, addr);
  37 }
  38
  39 static __always_inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  40                                              size_t n, int write_user)
  41 {
  42         struct mm_struct *mm = current->mm;
  43         unsigned long offset, pfn, done, size;
  44         pte_t *pte;
  45         void *from, *to;
  46
  47         done = 0;
  48 retry:
  49         spin_lock(&mm->page_table_lock);
  50         do {
  51                 pte = follow_table(mm, uaddr);
  52                 if ((unsigned long) pte < 0x1000)
  53                         goto fault;
  54                 if (!pte_present(*pte)) {
  55                         pte = (pte_t *) 0x11;
  56                         goto fault;
  57                 } else if (write_user && !pte_write(*pte)) {
  58                         pte = (pte_t *) 0x04;
  59                         goto fault;
  60                 }
  61
  62                 pfn = pte_pfn(*pte);
  63                 offset = uaddr & (PAGE_SIZE - 1);
  64                 size = min(n - done, PAGE_SIZE - offset);
  65                 if (write_user) {
  66                         to = (void *)((pfn << PAGE_SHIFT) + offset);
  67                         from = kptr + done;
  68                 } else {
  69                         from = (void *)((pfn << PAGE_SHIFT) + offset);
  70                         to = kptr + done;
  71                 }
  72                 memcpy(to, from, size);
  73                 done += size;
  74                 uaddr += size;
  75         } while (done < n);
  76         spin_unlock(&mm->page_table_lock);
  77         return n - done;
  78 fault:
  79         spin_unlock(&mm->page_table_lock);
  80         if (__handle_fault(uaddr, (unsigned long) pte, write_user))
  81                 return n - done;
  82         goto retry;
  83 }
  84
  85 /*
  86  * Do DAT for user address by page table walk, return kernel address.
  87  * This function needs to be called with current->mm->page_table_lock held.
  88  */
  89 static __always_inline unsigned long __dat_user_addr(unsigned long uaddr)
  90 {
  91         struct mm_struct *mm = current->mm;
  92         unsigned long pfn;
  93         pte_t *pte;
  94         int rc;
  95
  96 retry:
  97         pte = follow_table(mm, uaddr);
  98         if ((unsigned long) pte < 0x1000)
  99                 goto fault;
 100         if (!pte_present(*pte)) {
 101                 pte = (pte_t *) 0x11;
 102                 goto fault;
 103         }
 104
 105         pfn = pte_pfn(*pte);
 106         return (pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE - 1));
 107 fault:
 108         spin_unlock(&mm->page_table_lock);
 109         rc = __handle_fault(uaddr, (unsigned long) pte, 0);
 110         spin_lock(&mm->page_table_lock);
 111         if (!rc)
 112                 goto retry;
 113         return 0;
 114 }
 115
 116 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 117 {
 118         size_t rc;
 119
 120         if (segment_eq(get_fs(), KERNEL_DS)) {
 121                 memcpy(to, (void __kernel __force *) from, n);
 122                 return 0;
 123         }
 124         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 125         if (unlikely(rc))
 126                 memset(to + n - rc, 0, rc);
 127         return rc;
 128 }
 129
 130 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 131 {
 132         if (segment_eq(get_fs(), KERNEL_DS)) {
 133                 memcpy((void __kernel __force *) to, from, n);
 134                 return 0;
 135         }
 136         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 137 }
 138
 139 static size_t clear_user_pt(size_t n, void __user *to)
 140 {
 141         long done, size, ret;
 142
 143         if (segment_eq(get_fs(), KERNEL_DS)) {
 144                 memset((void __kernel __force *) to, 0, n);
 145                 return 0;
 146         }
 147         done = 0;
 148         do {
 149                 if (n - done > PAGE_SIZE)
 150                         size = PAGE_SIZE;
 151                 else
 152                         size = n - done;
 153                 ret = __user_copy_pt((unsigned long) to + done,
 154                                       &empty_zero_page, size, 1);
 155                 done += size;
 156                 if (ret)
 157                         return ret + n - done;
 158         } while (done < n);
 159         return 0;
 160 }
 161
 162 static size_t strnlen_user_pt(size_t count, const char __user *src)
 163 {
 164         char *addr;
 165         unsigned long uaddr = (unsigned long) src;
 166         struct mm_struct *mm = current->mm;
 167         unsigned long offset, pfn, done, len;
 168         pte_t *pte;
 169         size_t len_str;
 170
 171         if (segment_eq(get_fs(), KERNEL_DS))
 172                 return strnlen((const char __kernel __force *) src, count) + 1;
 173         done = 0;
 174 retry:
 175         spin_lock(&mm->page_table_lock);
 176         do {
 177                 pte = follow_table(mm, uaddr);
 178                 if ((unsigned long) pte < 0x1000)
 179                         goto fault;
 180                 if (!pte_present(*pte)) {
 181                         pte = (pte_t *) 0x11;
 182                         goto fault;
 183                 }
 184
 185                 pfn = pte_pfn(*pte);
 186                 offset = uaddr & (PAGE_SIZE-1);
 187                 addr = (char *)(pfn << PAGE_SHIFT) + offset;
 188                 len = min(count - done, PAGE_SIZE - offset);
 189                 len_str = strnlen(addr, len);
 190                 done += len_str;
 191                 uaddr += len_str;
 192         } while ((len_str == len) && (done < count));
 193         spin_unlock(&mm->page_table_lock);
 194         return done + 1;
 195 fault:
 196         spin_unlock(&mm->page_table_lock);
 197         if (__handle_fault(uaddr, (unsigned long) pte, 0))
 198                 return 0;
 199         goto retry;
 200 }
 201
 202 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 203                                    char *dst)
 204 {
 205         size_t n = strnlen_user_pt(count, src);
 206
 207         if (!n)
 208                 return -EFAULT;
 209         if (n > count)
 210                 n = count;
 211         if (segment_eq(get_fs(), KERNEL_DS)) {
 212                 memcpy(dst, (const char __kernel __force *) src, n);
 213                 if (dst[n-1] == '\0')
 214                         return n-1;
 215                 else
 216                         return n;
 217         }
 218         if (__user_copy_pt((unsigned long) src, dst, n, 0))
 219                 return -EFAULT;
 220         if (dst[n-1] == '\0')
 221                 return n-1;
 222         else
 223                 return n;
 224 }
 225
 226 static size_t copy_in_user_pt(size_t n, void __user *to,
 227                               const void __user *from)
 228 {
 229         struct mm_struct *mm = current->mm;
 230         unsigned long offset_from, offset_to, offset_max, pfn_from, pfn_to,
 231                       uaddr, done, size, error_code;
 232         unsigned long uaddr_from = (unsigned long) from;
 233         unsigned long uaddr_to = (unsigned long) to;
 234         pte_t *pte_from, *pte_to;
 235         int write_user;
 236
 237         if (segment_eq(get_fs(), KERNEL_DS)) {
 238                 memcpy((void __force *) to, (void __force *) from, n);
 239                 return 0;
 240         }
 241         done = 0;
 242 retry:
 243         spin_lock(&mm->page_table_lock);
 244         do {
 245                 write_user = 0;
 246                 uaddr = uaddr_from;
 247                 pte_from = follow_table(mm, uaddr_from);
 248                 error_code = (unsigned long) pte_from;
 249                 if (error_code < 0x1000)
 250                         goto fault;
 251                 if (!pte_present(*pte_from)) {
 252                         error_code = 0x11;
 253                         goto fault;
 254                 }
 255
 256                 write_user = 1;
 257                 uaddr = uaddr_to;
 258                 pte_to = follow_table(mm, uaddr_to);
 259                 error_code = (unsigned long) pte_to;
 260                 if (error_code < 0x1000)
 261                         goto fault;
 262                 if (!pte_present(*pte_to)) {
 263                         error_code = 0x11;
 264                         goto fault;
 265                 } else if (!pte_write(*pte_to)) {
 266                         error_code = 0x04;
 267                         goto fault;
 268                 }
 269
 270                 pfn_from = pte_pfn(*pte_from);
 271                 pfn_to = pte_pfn(*pte_to);
 272                 offset_from = uaddr_from & (PAGE_SIZE-1);
 273                 offset_to = uaddr_from & (PAGE_SIZE-1);
 274                 offset_max = max(offset_from, offset_to);
 275                 size = min(n - done, PAGE_SIZE - offset_max);
 276
 277                 memcpy((void *)(pfn_to << PAGE_SHIFT) + offset_to,
 278                        (void *)(pfn_from << PAGE_SHIFT) + offset_from, size);
 279                 done += size;
 280                 uaddr_from += size;
 281                 uaddr_to += size;
 282         } while (done < n);
 283         spin_unlock(&mm->page_table_lock);
 284         return n - done;
 285 fault:
 286         spin_unlock(&mm->page_table_lock);
 287         if (__handle_fault(uaddr, error_code, write_user))
 288                 return n - done;
 289         goto retry;
 290 }
 291
 292 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 293         asm volatile("0: l   %1,0(%6)\n"                                \
 294                      "1: " insn                                         \
 295                      "2: cs  %1,%2,0(%6)\n"                             \
 296                      "3: jl  1b\n"                                      \
 297                      "   lhi %0,0\n"                                    \
 298                      "4:\n"                                             \
 299                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 300                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 301                        "=m" (*uaddr)                                    \
 302                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 303                        "m" (*uaddr) : "cc" );
 304
 305 static int __futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old)
 306 {
 307         int oldval = 0, newval, ret;
 308
 309         switch (op) {
 310         case FUTEX_OP_SET:
 311                 __futex_atomic_op("lr %2,%5\n",
 312                                   ret, oldval, newval, uaddr, oparg);
 313                 break;
 314         case FUTEX_OP_ADD:
 315                 __futex_atomic_op("lr %2,%1\nar %2,%5\n",
 316                                   ret, oldval, newval, uaddr, oparg);
 317                 break;
 318         case FUTEX_OP_OR:
 319                 __futex_atomic_op("lr %2,%1\nor %2,%5\n",
 320                                   ret, oldval, newval, uaddr, oparg);
 321                 break;
 322         case FUTEX_OP_ANDN:
 323                 __futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 324                                   ret, oldval, newval, uaddr, oparg);
 325                 break;
 326         case FUTEX_OP_XOR:
 327                 __futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 328                                   ret, oldval, newval, uaddr, oparg);
 329                 break;
 330         default:
 331                 ret = -ENOSYS;
 332         }
 333         if (ret == 0)
 334                 *old = oldval;
 335         return ret;
 336 }
 337
 338 int futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old)
 339 {
 340         int ret;
 341
 342         if (segment_eq(get_fs(), KERNEL_DS))
 343                 return __futex_atomic_op_pt(op, uaddr, oparg, old);
 344         spin_lock(&current->mm->page_table_lock);
 345         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 346         if (!uaddr) {
 347                 spin_unlock(&current->mm->page_table_lock);
 348                 return -EFAULT;
 349         }
 350         get_page(virt_to_page(uaddr));
 351         spin_unlock(&current->mm->page_table_lock);
 352         ret = __futex_atomic_op_pt(op, uaddr, oparg, old);
 353         put_page(virt_to_page(uaddr));
 354         return ret;
 355 }
 356
 357 static int __futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr,
 358                                      int oldval, int newval)
 359 {
 360         int ret;
 361
 362         asm volatile("0: cs   %1,%4,0(%5)\n"
 363                      "1: la   %0,0\n"
 364                      "2:\n"
 365                      EX_TABLE(0b,2b) EX_TABLE(1b,2b)
 366                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 367                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 368                      : "cc", "memory" );
 369         *uval = oldval;
 370         return ret;
 371 }
 372
 373 int futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr,
 374                             int oldval, int newval)
 375 {
 376         int ret;
 377
 378         if (segment_eq(get_fs(), KERNEL_DS))
 379                 return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 380         spin_lock(&current->mm->page_table_lock);
 381         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 382         if (!uaddr) {
 383                 spin_unlock(&current->mm->page_table_lock);
 384                 return -EFAULT;
 385         }
 386         get_page(virt_to_page(uaddr));
 387         spin_unlock(&current->mm->page_table_lock);
 388         ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 389         put_page(virt_to_page(uaddr));
 390         return ret;
 391 }
 392
 393 struct uaccess_ops uaccess_pt = {
 394         .copy_from_user         = copy_from_user_pt,
 395         .copy_from_user_small   = copy_from_user_pt,
 396         .copy_to_user           = copy_to_user_pt,
 397         .copy_to_user_small     = copy_to_user_pt,
 398         .copy_in_user           = copy_in_user_pt,
 399         .clear_user             = clear_user_pt,
 400         .strnlen_user           = strnlen_user_pt,
 401         .strncpy_from_user      = strncpy_from_user_pt,
 402         .futex_atomic_op        = futex_atomic_op_pt,
 403         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 404 };