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
  82 static unsigned long follow_table(struct mm_struct *mm,
  83                                   unsigned long address, int write)
  84 {
  85         unsigned long *table = (unsigned long *)__pa(mm->pgd);
  86
  87         if (unlikely(address > mm->context.asce_limit - 1))
  88                 return -0x38UL;
  89         switch (mm->context.asce_bits & _ASCE_TYPE_MASK) {
  90         case _ASCE_TYPE_REGION1:
  91                 table = table + ((address >> 53) & 0x7ff);
  92                 if (unlikely(*table & _REGION_ENTRY_INVALID))
  93                         return -0x39UL;
  94                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  95                 /* fallthrough */
  96         case _ASCE_TYPE_REGION2:
  97                 table = table + ((address >> 42) & 0x7ff);
  98                 if (unlikely(*table & _REGION_ENTRY_INVALID))
  99                         return -0x3aUL;
 100                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
 101                 /* fallthrough */
 102         case _ASCE_TYPE_REGION3:
 103                 table = table + ((address >> 31) & 0x7ff);
 104                 if (unlikely(*table & _REGION_ENTRY_INVALID))
 105                         return -0x3bUL;
 106                 table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
 107                 /* fallthrough */
 108         case _ASCE_TYPE_SEGMENT:
 109                 table = table + ((address >> 20) & 0x7ff);
 110                 if (unlikely(*table & _SEGMENT_ENTRY_INVALID))
 111                         return -0x10UL;
 112                 if (unlikely(*table & _SEGMENT_ENTRY_LARGE)) {
 113                         if (write && (*table & _SEGMENT_ENTRY_PROTECT))
 114                                 return -0x04UL;
 115                         return (*table & _SEGMENT_ENTRY_ORIGIN_LARGE) +
 116                                 (address & ~_SEGMENT_ENTRY_ORIGIN_LARGE);
 117                 }
 118                 table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
 119         }
 120         table = table + ((address >> 12) & 0xff);
 121         if (unlikely(*table & _PAGE_INVALID))
 122                 return -0x11UL;
 123         if (write && (*table & _PAGE_PROTECT))
 124                 return -0x04UL;
 125         return (*table & PAGE_MASK) + (address & ~PAGE_MASK);
 126 }
 127
 128 #else /* CONFIG_64BIT */
 129
 130 static unsigned long follow_table(struct mm_struct *mm,
 131                                   unsigned long address, int write)
 132 {
 133         unsigned long *table = (unsigned long *)__pa(mm->pgd);
 134
 135         table = table + ((address >> 20) & 0x7ff);
 136         if (unlikely(*table & _SEGMENT_ENTRY_INVALID))
 137                 return -0x10UL;
 138         table = (unsigned long *)(*table & _SEGMENT_ENTRY_ORIGIN);
 139         table = table + ((address >> 12) & 0xff);
 140         if (unlikely(*table & _PAGE_INVALID))
 141                 return -0x11UL;
 142         if (write && (*table & _PAGE_PROTECT))
 143                 return -0x04UL;
 144         return (*table & PAGE_MASK) + (address & ~PAGE_MASK);
 145 }
 146
 147 #endif /* CONFIG_64BIT */
 148
 149 static __always_inline size_t __user_copy_pt(unsigned long uaddr, void *kptr,
 150                                              size_t n, int write_user)
 151 {
 152         struct mm_struct *mm = current->mm;
 153         unsigned long offset, done, size, kaddr;
 154         void *from, *to;
 155
 156         done = 0;
 157 retry:
 158         spin_lock(&mm->page_table_lock);
 159         do {
 160                 kaddr = follow_table(mm, uaddr, write_user);
 161                 if (IS_ERR_VALUE(kaddr))
 162                         goto fault;
 163
 164                 offset = uaddr & ~PAGE_MASK;
 165                 size = min(n - done, PAGE_SIZE - offset);
 166                 if (write_user) {
 167                         to = (void *) kaddr;
 168                         from = kptr + done;
 169                 } else {
 170                         from = (void *) kaddr;
 171                         to = kptr + done;
 172                 }
 173                 memcpy(to, from, size);
 174                 done += size;
 175                 uaddr += size;
 176         } while (done < n);
 177         spin_unlock(&mm->page_table_lock);
 178         return n - done;
 179 fault:
 180         spin_unlock(&mm->page_table_lock);
 181         if (__handle_fault(uaddr, -kaddr, write_user))
 182                 return n - done;
 183         goto retry;
 184 }
 185
 186 /*
 187  * Do DAT for user address by page table walk, return kernel address.
 188  * This function needs to be called with current->mm->page_table_lock held.
 189  */
 190 static __always_inline unsigned long __dat_user_addr(unsigned long uaddr,
 191                                                      int write)
 192 {
 193         struct mm_struct *mm = current->mm;
 194         unsigned long kaddr;
 195         int rc;
 196
 197 retry:
 198         kaddr = follow_table(mm, uaddr, write);
 199         if (IS_ERR_VALUE(kaddr))
 200                 goto fault;
 201
 202         return kaddr;
 203 fault:
 204         spin_unlock(&mm->page_table_lock);
 205         rc = __handle_fault(uaddr, -kaddr, write);
 206         spin_lock(&mm->page_table_lock);
 207         if (!rc)
 208                 goto retry;
 209         return 0;
 210 }
 211
 212 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 213 {
 214         size_t rc;
 215
 216         if (segment_eq(get_fs(), KERNEL_DS))
 217                 return copy_in_kernel(n, (void __user *) to, from);
 218         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 219         if (unlikely(rc))
 220                 memset(to + n - rc, 0, rc);
 221         return rc;
 222 }
 223
 224 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 225 {
 226         if (segment_eq(get_fs(), KERNEL_DS))
 227                 return copy_in_kernel(n, to, (void __user *) from);
 228         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 229 }
 230
 231 static size_t clear_user_pt(size_t n, void __user *to)
 232 {
 233         void *zpage = (void *) empty_zero_page;
 234         long done, size, ret;
 235
 236         done = 0;
 237         do {
 238                 if (n - done > PAGE_SIZE)
 239                         size = PAGE_SIZE;
 240                 else
 241                         size = n - done;
 242                 if (segment_eq(get_fs(), KERNEL_DS))
 243                         ret = copy_in_kernel(n, to, (void __user *) zpage);
 244                 else
 245                         ret = __user_copy_pt((unsigned long) to, zpage, size, 1);
 246                 done += size;
 247                 to += size;
 248                 if (ret)
 249                         return ret + n - done;
 250         } while (done < n);
 251         return 0;
 252 }
 253
 254 static size_t strnlen_user_pt(size_t count, const char __user *src)
 255 {
 256         unsigned long uaddr = (unsigned long) src;
 257         struct mm_struct *mm = current->mm;
 258         unsigned long offset, done, len, kaddr;
 259         size_t len_str;
 260
 261         if (unlikely(!count))
 262                 return 0;
 263         if (segment_eq(get_fs(), KERNEL_DS))
 264                 return strnlen_kernel(count, src);
 265         done = 0;
 266 retry:
 267         spin_lock(&mm->page_table_lock);
 268         do {
 269                 kaddr = follow_table(mm, uaddr, 0);
 270                 if (IS_ERR_VALUE(kaddr))
 271                         goto fault;
 272
 273                 offset = uaddr & ~PAGE_MASK;
 274                 len = min(count - done, PAGE_SIZE - offset);
 275                 len_str = strnlen((char *) kaddr, len);
 276                 done += len_str;
 277                 uaddr += len_str;
 278         } while ((len_str == len) && (done < count));
 279         spin_unlock(&mm->page_table_lock);
 280         return done + 1;
 281 fault:
 282         spin_unlock(&mm->page_table_lock);
 283         if (__handle_fault(uaddr, -kaddr, 0))
 284                 return 0;
 285         goto retry;
 286 }
 287
 288 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 289                                    char *dst)
 290 {
 291         size_t done, len, offset, len_str;
 292
 293         if (unlikely(!count))
 294                 return 0;
 295         done = 0;
 296         do {
 297                 offset = (size_t)src & ~PAGE_MASK;
 298                 len = min(count - done, PAGE_SIZE - offset);
 299                 if (segment_eq(get_fs(), KERNEL_DS)) {
 300                         if (copy_in_kernel(len, (void __user *) dst, src))
 301                                 return -EFAULT;
 302                 } else {
 303                         if (__user_copy_pt((unsigned long) src, dst, len, 0))
 304                                 return -EFAULT;
 305                 }
 306                 len_str = strnlen(dst, len);
 307                 done += len_str;
 308                 src += len_str;
 309                 dst += len_str;
 310         } while ((len_str == len) && (done < count));
 311         return done;
 312 }
 313
 314 static size_t copy_in_user_pt(size_t n, void __user *to,
 315                               const void __user *from)
 316 {
 317         struct mm_struct *mm = current->mm;
 318         unsigned long offset_max, uaddr, done, size, error_code;
 319         unsigned long uaddr_from = (unsigned long) from;
 320         unsigned long uaddr_to = (unsigned long) to;
 321         unsigned long kaddr_to, kaddr_from;
 322         int write_user;
 323
 324         if (segment_eq(get_fs(), KERNEL_DS))
 325                 return copy_in_kernel(n, to, from);
 326         done = 0;
 327 retry:
 328         spin_lock(&mm->page_table_lock);
 329         do {
 330                 write_user = 0;
 331                 uaddr = uaddr_from;
 332                 kaddr_from = follow_table(mm, uaddr_from, 0);
 333                 error_code = kaddr_from;
 334                 if (IS_ERR_VALUE(error_code))
 335                         goto fault;
 336
 337                 write_user = 1;
 338                 uaddr = uaddr_to;
 339                 kaddr_to = follow_table(mm, uaddr_to, 1);
 340                 error_code = (unsigned long) kaddr_to;
 341                 if (IS_ERR_VALUE(error_code))
 342                         goto fault;
 343
 344                 offset_max = max(uaddr_from & ~PAGE_MASK,
 345                                  uaddr_to & ~PAGE_MASK);
 346                 size = min(n - done, PAGE_SIZE - offset_max);
 347
 348                 memcpy((void *) kaddr_to, (void *) kaddr_from, size);
 349                 done += size;
 350                 uaddr_from += size;
 351                 uaddr_to += size;
 352         } while (done < n);
 353         spin_unlock(&mm->page_table_lock);
 354         return n - done;
 355 fault:
 356         spin_unlock(&mm->page_table_lock);
 357         if (__handle_fault(uaddr, -error_code, write_user))
 358                 return n - done;
 359         goto retry;
 360 }
 361
 362 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 363         asm volatile("0: l   %1,0(%6)\n"                                \
 364                      "1: " insn                                         \
 365                      "2: cs  %1,%2,0(%6)\n"                             \
 366                      "3: jl  1b\n"                                      \
 367                      "   lhi %0,0\n"                                    \
 368                      "4:\n"                                             \
 369                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 370                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 371                        "=m" (*uaddr)                                    \
 372                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 373                        "m" (*uaddr) : "cc" );
 374
 375 static int __futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 376 {
 377         int oldval = 0, newval, ret;
 378
 379         switch (op) {
 380         case FUTEX_OP_SET:
 381                 __futex_atomic_op("lr %2,%5\n",
 382                                   ret, oldval, newval, uaddr, oparg);
 383                 break;
 384         case FUTEX_OP_ADD:
 385                 __futex_atomic_op("lr %2,%1\nar %2,%5\n",
 386                                   ret, oldval, newval, uaddr, oparg);
 387                 break;
 388         case FUTEX_OP_OR:
 389                 __futex_atomic_op("lr %2,%1\nor %2,%5\n",
 390                                   ret, oldval, newval, uaddr, oparg);
 391                 break;
 392         case FUTEX_OP_ANDN:
 393                 __futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 394                                   ret, oldval, newval, uaddr, oparg);
 395                 break;
 396         case FUTEX_OP_XOR:
 397                 __futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 398                                   ret, oldval, newval, uaddr, oparg);
 399                 break;
 400         default:
 401                 ret = -ENOSYS;
 402         }
 403         if (ret == 0)
 404                 *old = oldval;
 405         return ret;
 406 }
 407
 408 int futex_atomic_op_pt(int op, u32 __user *uaddr, int oparg, int *old)
 409 {
 410         int ret;
 411
 412         if (segment_eq(get_fs(), KERNEL_DS))
 413                 return __futex_atomic_op_pt(op, uaddr, oparg, old);
 414         spin_lock(&current->mm->page_table_lock);
 415         uaddr = (u32 __force __user *)
 416                 __dat_user_addr((__force unsigned long) uaddr, 1);
 417         if (!uaddr) {
 418                 spin_unlock(&current->mm->page_table_lock);
 419                 return -EFAULT;
 420         }
 421         get_page(virt_to_page(uaddr));
 422         spin_unlock(&current->mm->page_table_lock);
 423         ret = __futex_atomic_op_pt(op, uaddr, oparg, old);
 424         put_page(virt_to_page(uaddr));
 425         return ret;
 426 }
 427
 428 static int __futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 429                                      u32 oldval, u32 newval)
 430 {
 431         int ret;
 432
 433         asm volatile("0: cs   %1,%4,0(%5)\n"
 434                      "1: la   %0,0\n"
 435                      "2:\n"
 436                      EX_TABLE(0b,2b) EX_TABLE(1b,2b)
 437                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 438                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 439                      : "cc", "memory" );
 440         *uval = oldval;
 441         return ret;
 442 }
 443
 444 int futex_atomic_cmpxchg_pt(u32 *uval, u32 __user *uaddr,
 445                             u32 oldval, u32 newval)
 446 {
 447         int ret;
 448
 449         if (segment_eq(get_fs(), KERNEL_DS))
 450                 return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 451         spin_lock(&current->mm->page_table_lock);
 452         uaddr = (u32 __force __user *)
 453                 __dat_user_addr((__force unsigned long) uaddr, 1);
 454         if (!uaddr) {
 455                 spin_unlock(&current->mm->page_table_lock);
 456                 return -EFAULT;
 457         }
 458         get_page(virt_to_page(uaddr));
 459         spin_unlock(&current->mm->page_table_lock);
 460         ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval);
 461         put_page(virt_to_page(uaddr));
 462         return ret;
 463 }
 464
 465 struct uaccess_ops uaccess_pt = {
 466         .copy_from_user         = copy_from_user_pt,
 467         .copy_to_user           = copy_to_user_pt,
 468         .copy_in_user           = copy_in_user_pt,
 469         .clear_user             = clear_user_pt,
 470         .strnlen_user           = strnlen_user_pt,
 471         .strncpy_from_user      = strncpy_from_user_pt,
 472         .futex_atomic_op        = futex_atomic_op_pt,
 473         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 474 };