arch/s390/lib/uaccess_pt.c

   1 /*
   2  *  User access functions based on page table walks for enhanced
   3  *  system layout without hardware support.
   4  *
   5  *    Copyright IBM Corp. 2006, 2012
   6  *    Author(s): Gerald Schaefer (gerald.schaefer@de.ibm.com)
   7  */
   8
   9 #include <linux/errno.h>
  10 #include <linux/hardirq.h>
  11 #include <linux/mm.h>
  12 #include <linux/hugetlb.h>
  13 #include <asm/uaccess.h>
  14 #include <asm/futex.h>
  15 #include "uaccess.h"
  16
  17 #ifndef CONFIG_64BIT
  18 #define AHI     "ahi"
  19 #define SLR     "slr"
  20 #else
  21 #define AHI     "aghi"
  22 #define SLR     "slgr"
  23 #endif
  24
  25 static size_t strnlen_kernel(size_t count, const char __user *src)
  26 {
  27         register unsigned long reg0 asm("0") = 0UL;
  28         unsigned long tmp1, tmp2;
  29
  30         asm volatile(
  31                 "   la    %2,0(%1)\n"
  32                 "   la    %3,0(%0,%1)\n"
  33                 "  "SLR"  %0,%0\n"
  34                 "0: srst  %3,%2\n"
  35                 "   jo    0b\n"
  36                 "   la    %0,1(%3)\n"   /* strnlen_kernel results includes \0 */
  37                 "  "SLR"  %0,%1\n"
  38                 "1:\n"
  39                 EX_TABLE(0b,1b)
  40                 : "+a" (count), "+a" (src), "=a" (tmp1), "=a" (tmp2)
  41                 : "d" (reg0) : "cc", "memory");
  42         return count;
  43 }
  44
  45 static size_t copy_in_kernel(size_t count, void __user *to,
  46                              const void __user *from)
  47 {
  48         unsigned long tmp1;
  49
  50         asm volatile(
  51                 "  "AHI"  %0,-1\n"
  52                 "   jo    5f\n"
  53                 "   bras  %3,3f\n"
  54                 "0:"AHI"  %0,257\n"
  55                 "1: mvc   0(1,%1),0(%2)\n"
  56                 "   la    %1,1(%1)\n"
  57                 "   la    %2,1(%2)\n"
  58                 "  "AHI"  %0,-1\n"
  59                 "   jnz   1b\n"
  60                 "   j     5f\n"
  61                 "2: mvc   0(256,%1),0(%2)\n"
  62                 "   la    %1,256(%1)\n"
  63                 "   la    %2,256(%2)\n"
  64                 "3:"AHI"  %0,-256\n"
  65                 "   jnm   2b\n"
  66                 "4: ex    %0,1b-0b(%3)\n"
  67                 "5:"SLR"  %0,%0\n"
  68                 "6:\n"
  69                 EX_TABLE(1b,6b) EX_TABLE(2b,0b) EX_TABLE(4b,0b)
  70                 : "+a" (count), "+a" (to), "+a" (from), "=a" (tmp1)
  71                 : : "cc", "memory");
  72         return count;
  73 }
  74
  75 /*
  76  * Returns kernel address for user virtual address. If the returned address is
  77  * >= -4095 (IS_ERR_VALUE(x) returns true), a fault has occured and the address
  78  * contains the (negative) exception code.
  79  */
  80 #ifdef CONFIG_64BIT
  81 static unsigned long follow_table(struct mm_struct *mm,
  82                                   unsigned long address, int write)
  83 {
  84         unsigned long *table = (unsigned long *)__pa(mm->pgd);
  85
  86         switch (mm->context.asce_bits & _ASCE_TYPE_MASK) {
  87         case _ASCE_TYPE_REGION1:
  88                 table = table + ((address >> 53) & 0x7ff);
  89                 if (unlikely(*table & _REGION_ENTRY_INV))
  90                         return -0x39UL;
  91                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  92         case _ASCE_TYPE_REGION2:
  93                 table = table + ((address >> 42) & 0x7ff);
  94                 if (unlikely(*table & _REGION_ENTRY_INV))
  95                         return -0x3aUL;
  96                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  97         case _ASCE_TYPE_REGION3:
  98                 table = table + ((address >> 31) & 0x7ff);
  99                 if (unlikely(*table & _REGION_ENTRY_INV))
 100                         return -0x3bUL;
 101                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
 102         case _ASCE_TYPE_SEGMENT:
 103                 table = table + ((address >> 20) & 0x7ff);
 104                 if (unlikely(*table & _SEGMENT_ENTRY_INV))
 105                         return -0x10UL;
 106                 if (unlikely(*table & _SEGMENT_ENTRY_LARGE)) {
 107                         if (write && (*table & _SEGMENT_ENTRY_RO))
 108                                 return -0x04UL;
 109                         return (*table & _SEGMENT_ENTRY_ORIGIN_LARGE) +
 110                                 (address & ~_SEGMENT_ENTRY_ORIGIN_LARGE);
 111                 }
 112                 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
 113         }
 114         table = table + ((address >> 12) & 0xff);
 115         if (unlikely(*table & _PAGE_INVALID))
 116                 return -0x11UL;
 117         if (write && (*table & _PAGE_RO))
 118                 return -0x04UL;
 119         return (*table & PAGE_MASK) + (address & ~PAGE_MASK);
 120 }
 121
 122 #else /* CONFIG_64BIT */
 123
 124 static unsigned long follow_table(struct mm_struct *mm,
 125                                   unsigned long address, int write)
 126 {
 127         unsigned long *table = (unsigned long *)__pa(mm->pgd);
 128
 129         table = table + ((address >> 20) & 0x7ff);
 130         if (unlikely(*table & _SEGMENT_ENTRY_INV))
 131                 return -0x10UL;
 132         table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
 133         table = table + ((address >> 12) & 0xff);
 134         if (unlikely(*table & _PAGE_INVALID))
 135                 return -0x11UL;
 136         if (write && (*table & _PAGE_RO))
 137                 return -0x04UL;
 138         return (*table & PAGE_MASK) + (address & ~PAGE_MASK);
 139 }
 140
 141 #endif /* CONFIG_64BIT */
 142
 143 static __always_inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
 144                                              size_t n, int write_user)
 145 {
 146         struct mm_struct *mm = current->mm;
 147         unsigned long offset, done, size, kaddr;
 148         void *from, *to;
 149
 150         done = 0;
 151 retry:
 152         spin_lock(&mm->page_table_lock);
 153         do {
 154                 kaddr = follow_table(mm, uaddr, write_user);
 155                 if (IS_ERR_VALUE(kaddr))
 156                         goto fault;
 157
 158                 offset = uaddr & ~PAGE_MASK;
 159                 size = min(n - done, PAGE_SIZE - offset);
 160                 if (write_user) {
 161                         to = (void *) kaddr;
 162                         from = kptr + done;
 163                 } else {
 164                         from = (void *) kaddr;
 165                         to = kptr + done;
 166                 }
 167                 memcpy(to, from, size);
 168                 done += size;
 169                 uaddr += size;
 170         } while (done < n);
 171         spin_unlock(&mm->page_table_lock);
 172         return n - done;
 173 fault:
 174         spin_unlock(&mm->page_table_lock);
 175         if (__handle_fault(uaddr, -kaddr, write_user))
 176                 return n - done;
 177         goto retry;
 178 }
 179
 180 /*
 181  * Do DAT for user address by page table walk, return kernel address.
 182  * This function needs to be called with current->mm->page_table_lock held.
 183  */
 184 static __always_inline unsigned long __dat_user_addr(unsigned long uaddr,
 185                                                      int write)
 186 {
 187         struct mm_struct *mm = current->mm;
 188         unsigned long kaddr;
 189         int rc;
 190
 191 retry:
 192         kaddr = follow_table(mm, uaddr, write);
 193         if (IS_ERR_VALUE(kaddr))
 194                 goto fault;
 195
 196         return kaddr;
 197 fault:
 198         spin_unlock(&mm->page_table_lock);
 199         rc = __handle_fault(uaddr, -kaddr, write);
 200         spin_lock(&mm->page_table_lock);
 201         if (!rc)
 202                 goto retry;
 203         return 0;
 204 }
 205
 206 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 207 {
 208         size_t rc;
 209
 210         if (segment_eq(get_fs(), KERNEL_DS))
 211                 return copy_in_kernel(n, (void __user *) to, from);
 212         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 213         if (unlikely(rc))
 214                 memset(to + n - rc, 0, rc);
 215         return rc;
 216 }
 217
 218 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 219 {
 220         if (segment_eq(get_fs(), KERNEL_DS))
 221                 return copy_in_kernel(n, to, (void __user *) from);
 222         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 223 }
 224
 225 static size_t clear_user_pt(size_t n, void __user *to)
 226 {
 227         void *zpage = (void *) empty_zero_page;
 228         long done, size, ret;
 229
 230         done = 0;
 231         do {
 232                 if (n - done > PAGE_SIZE)
 233                         size = PAGE_SIZE;
 234                 else
 235                         size = n - done;
 236                 if (segment_eq(get_fs(), KERNEL_DS))
 237                         ret = copy_in_kernel(n, to, (void __user *) zpage);
 238                 else
 239                         ret = __user_copy_pt((unsigned long) to, zpage, size, 1);
 240                 done += size;
 241                 to += size;
 242                 if (ret)
 243                         return ret + n - done;
 244         } while (done < n);
 245         return 0;
 246 }
 247
 248 static size_t strnlen_user_pt(size_t count, const char __user *src)
 249 {
 250         unsigned long uaddr = (unsigned long) src;
 251         struct mm_struct *mm = current->mm;
 252         unsigned long offset, done, len, kaddr;
 253         size_t len_str;
 254
 255         if (unlikely(!count))
 256                 return 0;
 257         if (segment_eq(get_fs(), KERNEL_DS))
 258                 return strnlen_kernel(count, src);
 259         done = 0;
 260 retry:
 261         spin_lock(&mm->page_table_lock);
 262         do {
 263                 kaddr = follow_table(mm, uaddr, 0);
 264                 if (IS_ERR_VALUE(kaddr))
 265                         goto fault;
 266
 267                 offset = uaddr & ~PAGE_MASK;
 268                 len = min(count - done, PAGE_SIZE - offset);
 269                 len_str = strnlen((char *) kaddr, len);
 270                 done += len_str;
 271                 uaddr += len_str;
 272         } while ((len_str == len) && (done < count));
 273         spin_unlock(&mm->page_table_lock);
 274         return done + 1;
 275 fault:
 276         spin_unlock(&mm->page_table_lock);
 277         if (__handle_fault(uaddr, -kaddr, 0))
 278                 return 0;
 279         goto retry;
 280 }
 281
 282 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 283                                    char *dst)
 284 {
 285         size_t done, len, offset, len_str;
 286
 287         if (unlikely(!count))
 288                 return 0;
 289         done = 0;
 290         do {
 291                 offset = (size_t)src & ~PAGE_MASK;
 292                 len = min(count - done, PAGE_SIZE - offset);
 293                 if (segment_eq(get_fs(), KERNEL_DS)) {
 294                         if (copy_in_kernel(len, (void __user *) dst, src))
 295                                 return -EFAULT;
 296                 } else {
 297                         if (__user_copy_pt((unsigned long) src, dst, len, 0))
 298                                 return -EFAULT;
 299                 }
 300                 len_str = strnlen(dst, len);
 301                 done += len_str;
 302                 src += len_str;
 303                 dst += len_str;
 304         } while ((len_str == len) && (done < count));
 305         return done;
 306 }
 307
 308 static size_t copy_in_user_pt(size_t n, void __user *to,
 309                               const void __user *from)
 310 {
 311         struct mm_struct *mm = current->mm;
 312         unsigned long offset_max, uaddr, done, size, error_code;
 313         unsigned long uaddr_from = (unsigned long) from;
 314         unsigned long uaddr_to = (unsigned long) to;
 315         unsigned long kaddr_to, kaddr_from;
 316         int write_user;
 317
 318         if (segment_eq(get_fs(), KERNEL_DS))
 319                 return copy_in_kernel(n, to, from);
 320         done = 0;
 321 retry:
 322         spin_lock(&mm->page_table_lock);
 323         do {
 324                 write_user = 0;
 325                 uaddr = uaddr_from;
 326                 kaddr_from = follow_table(mm, uaddr_from, 0);
 327                 error_code = kaddr_from;
 328                 if (IS_ERR_VALUE(error_code))
 329                         goto fault;
 330
 331                 write_user = 1;
 332                 uaddr = uaddr_to;
 333                 kaddr_to = follow_table(mm, uaddr_to, 1);
 334                 error_code = (unsigned long) kaddr_to;
 335                 if (IS_ERR_VALUE(error_code))
 336                         goto fault;
 337
 338                 offset_max = max(uaddr_from & ~PAGE_MASK,
 339                                  uaddr_to & ~PAGE_MASK);
 340                 size = min(n - done, PAGE_SIZE - offset_max);
 341
 342                 memcpy((void *) kaddr_to, (void *) kaddr_from, size);
 343                 done += size;
 344                 uaddr_from += size;
 345                 uaddr_to += size;
 346         } while (done < n);
 347         spin_unlock(&mm->page_table_lock);
 348         return n - done;
 349 fault:
 350         spin_unlock(&mm->page_table_lock);
 351         if (__handle_fault(uaddr, -error_code, write_user))
 352                 return n - done;
 353         goto retry;
 354 }
 355
 356 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 357         asm volatile("0: l   %1,0(%6)\n"                                \
 358                      "1: " insn                                         \
 359                      "2: cs  %1,%2,0(%6)\n"                             \
 360                      "3: jl  1b\n"                                      \
 361                      "   lhi %0,0\n"                                    \
 362                      "4:\n"                                             \
 363                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 364                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 365                        "=m" (*uaddr)                                    \
 366                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 367                        "m" (*uaddr) : "cc" );
 368
 369 static int __futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 370 {
 371         int oldval = 0, newval, ret;
 372
 373         switch (op) {
 374         case FUTEX_OP_SET:
 375                 __futex_atomic_op("lr %2,%5\n",
 376                                   ret, oldval, newval, uaddr, oparg);
 377                 break;
 378         case FUTEX_OP_ADD:
 379                 __futex_atomic_op("lr %2,%1\nar %2,%5\n",
 380                                   ret, oldval, newval, uaddr, oparg);
 381                 break;
 382         case FUTEX_OP_OR:
 383                 __futex_atomic_op("lr %2,%1\nor %2,%5\n",
 384                                   ret, oldval, newval, uaddr, oparg);
 385                 break;
 386         case FUTEX_OP_ANDN:
 387                 __futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 388                                   ret, oldval, newval, uaddr, oparg);
 389                 break;
 390         case FUTEX_OP_XOR:
 391                 __futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 392                                   ret, oldval, newval, uaddr, oparg);
 393                 break;
 394         default:
 395                 ret = -ENOSYS;
 396         }
 397         if (ret == 0)
 398                 *old = oldval;
 399         return ret;
 400 }
 401
 402 int futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 403 {
 404         int ret;
 405
 406         if (segment_eq(get_fs(), KERNEL_DS))
 407                 return __futex_atomic_op_pt(op, uaddr, oparg, old);
 408         spin_lock(&current->mm->page_table_lock);
 409         uaddr = (u32 __force __user *)
 410                 __dat_user_addr((__force unsigned long) uaddr, 1);
 411         if (!uaddr) {
 412                 spin_unlock(&current->mm->page_table_lock);
 413                 return -EFAULT;
 414         }
 415         get_page(virt_to_page(uaddr));
 416         spin_unlock(&current->mm->page_table_lock);
 417         ret = __futex_atomic_op_pt(op, uaddr, oparg, old);
 418         put_page(virt_to_page(uaddr));
 419         return ret;
 420 }
 421
 422 static int __futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 423                                      u32 oldval, u32 newval)
 424 {
 425         int ret;
 426
 427         asm volatile("0: cs   %1,%4,0(%5)\n"
 428                      "1: la   %0,0\n"
 429                      "2:\n"
 430                      EX_TABLE(0b,2b) EX_TABLE(1b,2b)
 431                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 432                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 433                      : "cc", "memory" );
 434         *uval = oldval;
 435         return ret;
 436 }
 437
 438 int futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 439                             u32 oldval, u32 newval)
 440 {
 441         int ret;
 442
 443         if (segment_eq(get_fs(), KERNEL_DS))
 444                 return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 445         spin_lock(&current->mm->page_table_lock);
 446         uaddr = (u32 __force __user *)
 447                 __dat_user_addr((__force unsigned long) uaddr, 1);
 448         if (!uaddr) {
 449                 spin_unlock(&current->mm->page_table_lock);
 450                 return -EFAULT;
 451         }
 452         get_page(virt_to_page(uaddr));
 453         spin_unlock(&current->mm->page_table_lock);
 454         ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 455         put_page(virt_to_page(uaddr));
 456         return ret;
 457 }
 458
 459 struct uaccess_ops uaccess_pt = {
 460         .copy_from_user         = copy_from_user_pt,
 461         .copy_from_user_small   = copy_from_user_pt,
 462         .copy_to_user           = copy_to_user_pt,
 463         .copy_to_user_small     = copy_to_user_pt,
 464         .copy_in_user           = copy_in_user_pt,
 465         .clear_user             = clear_user_pt,
 466         .strnlen_user           = strnlen_user_pt,
 467         .strncpy_from_user      = strncpy_from_user_pt,
 468         .futex_atomic_op        = futex_atomic_op_pt,
 469         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 470 };