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   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 int __handle_fault(struct mm_struct *mm, unsigned long address,
  19                           int write_access)
  20 {
  21         struct vm_area_struct *vma;
  22         int ret = -EFAULT;
  23
  24         if (in_atomic())
  25                 return ret;
  26         down_read(&mm->mmap_sem);
  27         vma = find_vma(mm, address);
  28         if (unlikely(!vma))
  29                 goto out;
  30         if (unlikely(vma->vm_start > address)) {
  31                 if (!(vma->vm_flags & VM_GROWSDOWN))
  32                         goto out;
  33                 if (expand_stack(vma, address))
  34                         goto out;
  35         }
  36
  37         if (!write_access) {
  38                 /* page not present, check vm flags */
  39                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
  40                         goto out;
  41         } else {
  42                 if (!(vma->vm_flags & VM_WRITE))
  43                         goto out;
  44         }
  45
  46 survive:
  47         switch (handle_mm_fault(mm, vma, address, write_access)) {
  48         case VM_FAULT_MINOR:
  49                 current->min_flt++;
  50                 break;
  51         case VM_FAULT_MAJOR:
  52                 current->maj_flt++;
  53                 break;
  54         case VM_FAULT_SIGBUS:
  55                 goto out_sigbus;
  56         case VM_FAULT_OOM:
  57                 goto out_of_memory;
  58         default:
  59                 BUG();
  60         }
  61         ret = 0;
  62 out:
  63         up_read(&mm->mmap_sem);
  64         return ret;
  65
  66 out_of_memory:
  67         up_read(&mm->mmap_sem);
  68         if (is_init(current)) {
  69                 yield();
  70                 down_read(&mm->mmap_sem);
  71                 goto survive;
  72         }
  73         printk("VM: killing process %s\n", current->comm);
  74         return ret;
  75
  76 out_sigbus:
  77         up_read(&mm->mmap_sem);
  78         current->thread.prot_addr = address;
  79         current->thread.trap_no = 0x11;
  80         force_sig(SIGBUS, current);
  81         return ret;
  82 }
  83
  84 static size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  85                              size_t n, int write_user)
  86 {
  87         struct mm_struct *mm = current->mm;
  88         unsigned long offset, pfn, done, size;
  89         pgd_t *pgd;
  90         pmd_t *pmd;
  91         pte_t *pte;
  92         void *from, *to;
  93
  94         done = 0;
  95 retry:
  96         spin_lock(&mm->page_table_lock);
  97         do {
  98                 pgd = pgd_offset(mm, uaddr);
  99                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 100                         goto fault;
 101
 102                 pmd = pmd_offset(pgd, uaddr);
 103                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 104                         goto fault;
 105
 106                 pte = pte_offset_map(pmd, uaddr);
 107                 if (!pte || !pte_present(*pte) ||
 108                     (write_user && !pte_write(*pte)))
 109                         goto fault;
 110
 111                 pfn = pte_pfn(*pte);
 112                 if (!pfn_valid(pfn))
 113                         goto out;
 114
 115                 offset = uaddr & (PAGE_SIZE - 1);
 116                 size = min(n - done, PAGE_SIZE - offset);
 117                 if (write_user) {
 118                         to = (void *)((pfn << PAGE_SHIFT) + offset);
 119                         from = kptr + done;
 120                 } else {
 121                         from = (void *)((pfn << PAGE_SHIFT) + offset);
 122                         to = kptr + done;
 123                 }
 124                 memcpy(to, from, size);
 125                 done += size;
 126                 uaddr += size;
 127         } while (done < n);
 128 out:
 129         spin_unlock(&mm->page_table_lock);
 130         return n - done;
 131 fault:
 132         spin_unlock(&mm->page_table_lock);
 133         if (__handle_fault(mm, uaddr, write_user))
 134                 return n - done;
 135         goto retry;
 136 }
 137
 138 /*
 139  * Do DAT for user address by page table walk, return kernel address.
 140  * This function needs to be called with current->mm->page_table_lock held.
 141  */
 142 static unsigned long __dat_user_addr(unsigned long uaddr)
 143 {
 144         struct mm_struct *mm = current->mm;
 145         unsigned long pfn, ret;
 146         pgd_t *pgd;
 147         pmd_t *pmd;
 148         pte_t *pte;
 149         int rc;
 150
 151         ret = 0;
 152 retry:
 153         pgd = pgd_offset(mm, uaddr);
 154         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 155                 goto fault;
 156
 157         pmd = pmd_offset(pgd, uaddr);
 158         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 159                 goto fault;
 160
 161         pte = pte_offset_map(pmd, uaddr);
 162         if (!pte || !pte_present(*pte))
 163                 goto fault;
 164
 165         pfn = pte_pfn(*pte);
 166         if (!pfn_valid(pfn))
 167                 goto out;
 168
 169         ret = (pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE - 1));
 170 out:
 171         return ret;
 172 fault:
 173         spin_unlock(&mm->page_table_lock);
 174         rc = __handle_fault(mm, uaddr, 0);
 175         spin_lock(&mm->page_table_lock);
 176         if (rc)
 177                 goto out;
 178         goto retry;
 179 }
 180
 181 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 182 {
 183         size_t rc;
 184
 185         if (segment_eq(get_fs(), KERNEL_DS)) {
 186                 memcpy(to, (void __kernel __force *) from, n);
 187                 return 0;
 188         }
 189         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 190         if (unlikely(rc))
 191                 memset(to + n - rc, 0, rc);
 192         return rc;
 193 }
 194
 195 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 196 {
 197         if (segment_eq(get_fs(), KERNEL_DS)) {
 198                 memcpy((void __kernel __force *) to, from, n);
 199                 return 0;
 200         }
 201         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 202 }
 203
 204 static size_t clear_user_pt(size_t n, void __user *to)
 205 {
 206         long done, size, ret;
 207
 208         if (segment_eq(get_fs(), KERNEL_DS)) {
 209                 memset((void __kernel __force *) to, 0, n);
 210                 return 0;
 211         }
 212         done = 0;
 213         do {
 214                 if (n - done > PAGE_SIZE)
 215                         size = PAGE_SIZE;
 216                 else
 217                         size = n - done;
 218                 ret = __user_copy_pt((unsigned long) to + done,
 219                                       &empty_zero_page, size, 1);
 220                 done += size;
 221                 if (ret)
 222                         return ret + n - done;
 223         } while (done < n);
 224         return 0;
 225 }
 226
 227 static size_t strnlen_user_pt(size_t count, const char __user *src)
 228 {
 229         char *addr;
 230         unsigned long uaddr = (unsigned long) src;
 231         struct mm_struct *mm = current->mm;
 232         unsigned long offset, pfn, done, len;
 233         pgd_t *pgd;
 234         pmd_t *pmd;
 235         pte_t *pte;
 236         size_t len_str;
 237
 238         if (segment_eq(get_fs(), KERNEL_DS))
 239                 return strnlen((const char __kernel __force *) src, count) + 1;
 240         done = 0;
 241 retry:
 242         spin_lock(&mm->page_table_lock);
 243         do {
 244                 pgd = pgd_offset(mm, uaddr);
 245                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 246                         goto fault;
 247
 248                 pmd = pmd_offset(pgd, uaddr);
 249                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 250                         goto fault;
 251
 252                 pte = pte_offset_map(pmd, uaddr);
 253                 if (!pte || !pte_present(*pte))
 254                         goto fault;
 255
 256                 pfn = pte_pfn(*pte);
 257                 if (!pfn_valid(pfn)) {
 258                         done = -1;
 259                         goto out;
 260                 }
 261
 262                 offset = uaddr & (PAGE_SIZE-1);
 263                 addr = (char *)(pfn << PAGE_SHIFT) + offset;
 264                 len = min(count - done, PAGE_SIZE - offset);
 265                 len_str = strnlen(addr, len);
 266                 done += len_str;
 267                 uaddr += len_str;
 268         } while ((len_str == len) && (done < count));
 269 out:
 270         spin_unlock(&mm->page_table_lock);
 271         return done + 1;
 272 fault:
 273         spin_unlock(&mm->page_table_lock);
 274         if (__handle_fault(mm, uaddr, 0)) {
 275                 return 0;
 276         }
 277         goto retry;
 278 }
 279
 280 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 281                                    char *dst)
 282 {
 283         size_t n = strnlen_user_pt(count, src);
 284
 285         if (!n)
 286                 return -EFAULT;
 287         if (n > count)
 288                 n = count;
 289         if (segment_eq(get_fs(), KERNEL_DS)) {
 290                 memcpy(dst, (const char __kernel __force *) src, n);
 291                 if (dst[n-1] == '\0')
 292                         return n-1;
 293                 else
 294                         return n;
 295         }
 296         if (__user_copy_pt((unsigned long) src, dst, n, 0))
 297                 return -EFAULT;
 298         if (dst[n-1] == '\0')
 299                 return n-1;
 300         else
 301                 return n;
 302 }
 303
 304 static size_t copy_in_user_pt(size_t n, void __user *to,
 305                               const void __user *from)
 306 {
 307         struct mm_struct *mm = current->mm;
 308         unsigned long offset_from, offset_to, offset_max, pfn_from, pfn_to,
 309                       uaddr, done, size;
 310         unsigned long uaddr_from = (unsigned long) from;
 311         unsigned long uaddr_to = (unsigned long) to;
 312         pgd_t *pgd_from, *pgd_to;
 313         pmd_t *pmd_from, *pmd_to;
 314         pte_t *pte_from, *pte_to;
 315         int write_user;
 316
 317         done = 0;
 318 retry:
 319         spin_lock(&mm->page_table_lock);
 320         do {
 321                 pgd_from = pgd_offset(mm, uaddr_from);
 322                 if (pgd_none(*pgd_from) || unlikely(pgd_bad(*pgd_from))) {
 323                         uaddr = uaddr_from;
 324                         write_user = 0;
 325                         goto fault;
 326                 }
 327                 pgd_to = pgd_offset(mm, uaddr_to);
 328                 if (pgd_none(*pgd_to) || unlikely(pgd_bad(*pgd_to))) {
 329                         uaddr = uaddr_to;
 330                         write_user = 1;
 331                         goto fault;
 332                 }
 333
 334                 pmd_from = pmd_offset(pgd_from, uaddr_from);
 335                 if (pmd_none(*pmd_from) || unlikely(pmd_bad(*pmd_from))) {
 336                         uaddr = uaddr_from;
 337                         write_user = 0;
 338                         goto fault;
 339                 }
 340                 pmd_to = pmd_offset(pgd_to, uaddr_to);
 341                 if (pmd_none(*pmd_to) || unlikely(pmd_bad(*pmd_to))) {
 342                         uaddr = uaddr_to;
 343                         write_user = 1;
 344                         goto fault;
 345                 }
 346
 347                 pte_from = pte_offset_map(pmd_from, uaddr_from);
 348                 if (!pte_from || !pte_present(*pte_from)) {
 349                         uaddr = uaddr_from;
 350                         write_user = 0;
 351                         goto fault;
 352                 }
 353                 pte_to = pte_offset_map(pmd_to, uaddr_to);
 354                 if (!pte_to || !pte_present(*pte_to) || !pte_write(*pte_to)) {
 355                         uaddr = uaddr_to;
 356                         write_user = 1;
 357                         goto fault;
 358                 }
 359
 360                 pfn_from = pte_pfn(*pte_from);
 361                 if (!pfn_valid(pfn_from))
 362                         goto out;
 363                 pfn_to = pte_pfn(*pte_to);
 364                 if (!pfn_valid(pfn_to))
 365                         goto out;
 366
 367                 offset_from = uaddr_from & (PAGE_SIZE-1);
 368                 offset_to = uaddr_from & (PAGE_SIZE-1);
 369                 offset_max = max(offset_from, offset_to);
 370                 size = min(n - done, PAGE_SIZE - offset_max);
 371
 372                 memcpy((void *)(pfn_to << PAGE_SHIFT) + offset_to,
 373                        (void *)(pfn_from << PAGE_SHIFT) + offset_from, size);
 374                 done += size;
 375                 uaddr_from += size;
 376                 uaddr_to += size;
 377         } while (done < n);
 378 out:
 379         spin_unlock(&mm->page_table_lock);
 380         return n - done;
 381 fault:
 382         spin_unlock(&mm->page_table_lock);
 383         if (__handle_fault(mm, uaddr, write_user))
 384                 return n - done;
 385         goto retry;
 386 }
 387
 388 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 389         asm volatile("0: l   %1,0(%6)\n"                                \
 390                      "1: " insn                                         \
 391                      "2: cs  %1,%2,0(%6)\n"                             \
 392                      "3: jl  1b\n"                                      \
 393                      "   lhi %0,0\n"                                    \
 394                      "4:\n"                                             \
 395                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 396                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 397                        "=m" (*uaddr)                                    \
 398                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 399                        "m" (*uaddr) : "cc" );
 400
 401 int futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old)
 402 {
 403         int oldval = 0, newval, ret;
 404
 405         spin_lock(&current->mm->page_table_lock);
 406         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 407         if (!uaddr) {
 408                 spin_unlock(&current->mm->page_table_lock);
 409                 return -EFAULT;
 410         }
 411         get_page(virt_to_page(uaddr));
 412         spin_unlock(&current->mm->page_table_lock);
 413         switch (op) {
 414         case FUTEX_OP_SET:
 415                 __futex_atomic_op("lr %2,%5\n",
 416                                   ret, oldval, newval, uaddr, oparg);
 417                 break;
 418         case FUTEX_OP_ADD:
 419                 __futex_atomic_op("lr %2,%1\nar %2,%5\n",
 420                                   ret, oldval, newval, uaddr, oparg);
 421                 break;
 422         case FUTEX_OP_OR:
 423                 __futex_atomic_op("lr %2,%1\nor %2,%5\n",
 424                                   ret, oldval, newval, uaddr, oparg);
 425                 break;
 426         case FUTEX_OP_ANDN:
 427                 __futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 428                                   ret, oldval, newval, uaddr, oparg);
 429                 break;
 430         case FUTEX_OP_XOR:
 431                 __futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 432                                   ret, oldval, newval, uaddr, oparg);
 433                 break;
 434         default:
 435                 ret = -ENOSYS;
 436         }
 437         put_page(virt_to_page(uaddr));
 438         *old = oldval;
 439         return ret;
 440 }
 441
 442 int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
 443 {
 444         int ret;
 445
 446         spin_lock(&current->mm->page_table_lock);
 447         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 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         asm volatile("   cs   %1,%4,0(%5)\n"
 455                      "0: lr   %0,%1\n"
 456                      "1:\n"
 457                      EX_TABLE(0b,1b)
 458                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 459                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 460                      : "cc", "memory" );
 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_from_user_small   = copy_from_user_pt,
 468         .copy_to_user           = copy_to_user_pt,
 469         .copy_to_user_small     = copy_to_user_pt,
 470         .copy_in_user           = copy_in_user_pt,
 471         .clear_user             = clear_user_pt,
 472         .strnlen_user           = strnlen_user_pt,
 473         .strncpy_from_user      = strncpy_from_user_pt,
 474         .futex_atomic_op        = futex_atomic_op_pt,
 475         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 476 };