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