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