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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         int fault;
  24
  25         if (in_atomic())
  26                 return ret;
  27         down_read(&mm->mmap_sem);
  28         vma = find_vma(mm, address);
  29         if (unlikely(!vma))
  30                 goto out;
  31         if (unlikely(vma->vm_start > address)) {
  32                 if (!(vma->vm_flags & VM_GROWSDOWN))
  33                         goto out;
  34                 if (expand_stack(vma, address))
  35                         goto out;
  36         }
  37
  38         if (!write_access) {
  39                 /* page not present, check vm flags */
  40                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
  41                         goto out;
  42         } else {
  43                 if (!(vma->vm_flags & VM_WRITE))
  44                         goto out;
  45         }
  46
  47 survive:
  48         fault = handle_mm_fault(mm, vma, address, write_access);
  49         if (unlikely(fault & VM_FAULT_ERROR)) {
  50                 if (fault & VM_FAULT_OOM)
  51                         goto out_of_memory;
  52                 else if (fault & VM_FAULT_SIGBUS)
  53                         goto out_sigbus;
  54                 BUG();
  55         }
  56         if (fault & VM_FAULT_MAJOR)
  57                 current->maj_flt++;
  58         else
  59                 current->min_flt++;
  60         ret = 0;
  61 out:
  62         up_read(&mm->mmap_sem);
  63         return ret;
  64
  65 out_of_memory:
  66         up_read(&mm->mmap_sem);
  67         if (is_global_init(current)) {
  68                 yield();
  69                 down_read(&mm->mmap_sem);
  70                 goto survive;
  71         }
  72         printk("VM: killing process %s\n", current->comm);
  73         return ret;
  74
  75 out_sigbus:
  76         up_read(&mm->mmap_sem);
  77         current->thread.prot_addr = address;
  78         current->thread.trap_no = 0x11;
  79         force_sig(SIGBUS, current);
  80         return ret;
  81 }
  82
  83 static size_t __user_copy_pt(unsigned long uaddr, void *kptr,
  84                              size_t n, int write_user)
  85 {
  86         struct mm_struct *mm = current->mm;
  87         unsigned long offset, pfn, done, size;
  88         pgd_t *pgd;
  89         pmd_t *pmd;
  90         pte_t *pte;
  91         void *from, *to;
  92
  93         done = 0;
  94 retry:
  95         spin_lock(&mm->page_table_lock);
  96         do {
  97                 pgd = pgd_offset(mm, uaddr);
  98                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  99                         goto fault;
 100
 101                 pmd = pmd_offset(pgd, uaddr);
 102                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 103                         goto fault;
 104
 105                 pte = pte_offset_map(pmd, uaddr);
 106                 if (!pte || !pte_present(*pte) ||
 107                     (write_user && !pte_write(*pte)))
 108                         goto fault;
 109
 110                 pfn = pte_pfn(*pte);
 111                 if (!pfn_valid(pfn))
 112                         goto out;
 113
 114                 offset = uaddr & (PAGE_SIZE - 1);
 115                 size = min(n - done, PAGE_SIZE - offset);
 116                 if (write_user) {
 117                         to = (void *)((pfn << PAGE_SHIFT) + offset);
 118                         from = kptr + done;
 119                 } else {
 120                         from = (void *)((pfn << PAGE_SHIFT) + offset);
 121                         to = kptr + done;
 122                 }
 123                 memcpy(to, from, size);
 124                 done += size;
 125                 uaddr += size;
 126         } while (done < n);
 127 out:
 128         spin_unlock(&mm->page_table_lock);
 129         return n - done;
 130 fault:
 131         spin_unlock(&mm->page_table_lock);
 132         if (__handle_fault(mm, uaddr, write_user))
 133                 return n - done;
 134         goto retry;
 135 }
 136
 137 /*
 138  * Do DAT for user address by page table walk, return kernel address.
 139  * This function needs to be called with current->mm->page_table_lock held.
 140  */
 141 static unsigned long __dat_user_addr(unsigned long uaddr)
 142 {
 143         struct mm_struct *mm = current->mm;
 144         unsigned long pfn, ret;
 145         pgd_t *pgd;
 146         pmd_t *pmd;
 147         pte_t *pte;
 148         int rc;
 149
 150         ret = 0;
 151 retry:
 152         pgd = pgd_offset(mm, uaddr);
 153         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 154                 goto fault;
 155
 156         pmd = pmd_offset(pgd, uaddr);
 157         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 158                 goto fault;
 159
 160         pte = pte_offset_map(pmd, uaddr);
 161         if (!pte || !pte_present(*pte))
 162                 goto fault;
 163
 164         pfn = pte_pfn(*pte);
 165         if (!pfn_valid(pfn))
 166                 goto out;
 167
 168         ret = (pfn << PAGE_SHIFT) + (uaddr & (PAGE_SIZE - 1));
 169 out:
 170         return ret;
 171 fault:
 172         spin_unlock(&mm->page_table_lock);
 173         rc = __handle_fault(mm, uaddr, 0);
 174         spin_lock(&mm->page_table_lock);
 175         if (rc)
 176                 goto out;
 177         goto retry;
 178 }
 179
 180 size_t copy_from_user_pt(size_t n, const void __user *from, void *to)
 181 {
 182         size_t rc;
 183
 184         if (segment_eq(get_fs(), KERNEL_DS)) {
 185                 memcpy(to, (void __kernel __force *) from, n);
 186                 return 0;
 187         }
 188         rc = __user_copy_pt((unsigned long) from, to, n, 0);
 189         if (unlikely(rc))
 190                 memset(to + n - rc, 0, rc);
 191         return rc;
 192 }
 193
 194 size_t copy_to_user_pt(size_t n, void __user *to, const void *from)
 195 {
 196         if (segment_eq(get_fs(), KERNEL_DS)) {
 197                 memcpy((void __kernel __force *) to, from, n);
 198                 return 0;
 199         }
 200         return __user_copy_pt((unsigned long) to, (void *) from, n, 1);
 201 }
 202
 203 static size_t clear_user_pt(size_t n, void __user *to)
 204 {
 205         long done, size, ret;
 206
 207         if (segment_eq(get_fs(), KERNEL_DS)) {
 208                 memset((void __kernel __force *) to, 0, n);
 209                 return 0;
 210         }
 211         done = 0;
 212         do {
 213                 if (n - done > PAGE_SIZE)
 214                         size = PAGE_SIZE;
 215                 else
 216                         size = n - done;
 217                 ret = __user_copy_pt((unsigned long) to + done,
 218                                       &empty_zero_page, size, 1);
 219                 done += size;
 220                 if (ret)
 221                         return ret + n - done;
 222         } while (done < n);
 223         return 0;
 224 }
 225
 226 static size_t strnlen_user_pt(size_t count, const char __user *src)
 227 {
 228         char *addr;
 229         unsigned long uaddr = (unsigned long) src;
 230         struct mm_struct *mm = current->mm;
 231         unsigned long offset, pfn, done, len;
 232         pgd_t *pgd;
 233         pmd_t *pmd;
 234         pte_t *pte;
 235         size_t len_str;
 236
 237         if (segment_eq(get_fs(), KERNEL_DS))
 238                 return strnlen((const char __kernel __force *) src, count) + 1;
 239         done = 0;
 240 retry:
 241         spin_lock(&mm->page_table_lock);
 242         do {
 243                 pgd = pgd_offset(mm, uaddr);
 244                 if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
 245                         goto fault;
 246
 247                 pmd = pmd_offset(pgd, uaddr);
 248                 if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
 249                         goto fault;
 250
 251                 pte = pte_offset_map(pmd, uaddr);
 252                 if (!pte || !pte_present(*pte))
 253                         goto fault;
 254
 255                 pfn = pte_pfn(*pte);
 256                 if (!pfn_valid(pfn)) {
 257                         done = -1;
 258                         goto out;
 259                 }
 260
 261                 offset = uaddr & (PAGE_SIZE-1);
 262                 addr = (char *)(pfn << PAGE_SHIFT) + offset;
 263                 len = min(count - done, PAGE_SIZE - offset);
 264                 len_str = strnlen(addr, len);
 265                 done += len_str;
 266                 uaddr += len_str;
 267         } while ((len_str == len) && (done < count));
 268 out:
 269         spin_unlock(&mm->page_table_lock);
 270         return done + 1;
 271 fault:
 272         spin_unlock(&mm->page_table_lock);
 273         if (__handle_fault(mm, uaddr, 0)) {
 274                 return 0;
 275         }
 276         goto retry;
 277 }
 278
 279 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 280                                    char *dst)
 281 {
 282         size_t n = strnlen_user_pt(count, src);
 283
 284         if (!n)
 285                 return -EFAULT;
 286         if (n > count)
 287                 n = count;
 288         if (segment_eq(get_fs(), KERNEL_DS)) {
 289                 memcpy(dst, (const char __kernel __force *) src, n);
 290                 if (dst[n-1] == '\0')
 291                         return n-1;
 292                 else
 293                         return n;
 294         }
 295         if (__user_copy_pt((unsigned long) src, dst, n, 0))
 296                 return -EFAULT;
 297         if (dst[n-1] == '\0')
 298                 return n-1;
 299         else
 300                 return n;
 301 }
 302
 303 static size_t copy_in_user_pt(size_t n, void __user *to,
 304                               const void __user *from)
 305 {
 306         struct mm_struct *mm = current->mm;
 307         unsigned long offset_from, offset_to, offset_max, pfn_from, pfn_to,
 308                       uaddr, done, size;
 309         unsigned long uaddr_from = (unsigned long) from;
 310         unsigned long uaddr_to = (unsigned long) to;
 311         pgd_t *pgd_from, *pgd_to;
 312         pmd_t *pmd_from, *pmd_to;
 313         pte_t *pte_from, *pte_to;
 314         int write_user;
 315
 316         done = 0;
 317 retry:
 318         spin_lock(&mm->page_table_lock);
 319         do {
 320                 pgd_from = pgd_offset(mm, uaddr_from);
 321                 if (pgd_none(*pgd_from) || unlikely(pgd_bad(*pgd_from))) {
 322                         uaddr = uaddr_from;
 323                         write_user = 0;
 324                         goto fault;
 325                 }
 326                 pgd_to = pgd_offset(mm, uaddr_to);
 327                 if (pgd_none(*pgd_to) || unlikely(pgd_bad(*pgd_to))) {
 328                         uaddr = uaddr_to;
 329                         write_user = 1;
 330                         goto fault;
 331                 }
 332
 333                 pmd_from = pmd_offset(pgd_from, uaddr_from);
 334                 if (pmd_none(*pmd_from) || unlikely(pmd_bad(*pmd_from))) {
 335                         uaddr = uaddr_from;
 336                         write_user = 0;
 337                         goto fault;
 338                 }
 339                 pmd_to = pmd_offset(pgd_to, uaddr_to);
 340                 if (pmd_none(*pmd_to) || unlikely(pmd_bad(*pmd_to))) {
 341                         uaddr = uaddr_to;
 342                         write_user = 1;
 343                         goto fault;
 344                 }
 345
 346                 pte_from = pte_offset_map(pmd_from, uaddr_from);
 347                 if (!pte_from || !pte_present(*pte_from)) {
 348                         uaddr = uaddr_from;
 349                         write_user = 0;
 350                         goto fault;
 351                 }
 352                 pte_to = pte_offset_map(pmd_to, uaddr_to);
 353                 if (!pte_to || !pte_present(*pte_to) || !pte_write(*pte_to)) {
 354                         uaddr = uaddr_to;
 355                         write_user = 1;
 356                         goto fault;
 357                 }
 358
 359                 pfn_from = pte_pfn(*pte_from);
 360                 if (!pfn_valid(pfn_from))
 361                         goto out;
 362                 pfn_to = pte_pfn(*pte_to);
 363                 if (!pfn_valid(pfn_to))
 364                         goto out;
 365
 366                 offset_from = uaddr_from & (PAGE_SIZE-1);
 367                 offset_to = uaddr_from & (PAGE_SIZE-1);
 368                 offset_max = max(offset_from, offset_to);
 369                 size = min(n - done, PAGE_SIZE - offset_max);
 370
 371                 memcpy((void *)(pfn_to << PAGE_SHIFT) + offset_to,
 372                        (void *)(pfn_from << PAGE_SHIFT) + offset_from, size);
 373                 done += size;
 374                 uaddr_from += size;
 375                 uaddr_to += size;
 376         } while (done < n);
 377 out:
 378         spin_unlock(&mm->page_table_lock);
 379         return n - done;
 380 fault:
 381         spin_unlock(&mm->page_table_lock);
 382         if (__handle_fault(mm, uaddr, write_user))
 383                 return n - done;
 384         goto retry;
 385 }
 386
 387 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 388         asm volatile("0: l   %1,0(%6)\n"                                \
 389                      "1: " insn                                         \
 390                      "2: cs  %1,%2,0(%6)\n"                             \
 391                      "3: jl  1b\n"                                      \
 392                      "   lhi %0,0\n"                                    \
 393                      "4:\n"                                             \
 394                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 395                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 396                        "=m" (*uaddr)                                    \
 397                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 398                        "m" (*uaddr) : "cc" );
 399
 400 int futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old)
 401 {
 402         int oldval = 0, newval, ret;
 403
 404         spin_lock(&current->mm->page_table_lock);
 405         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 406         if (!uaddr) {
 407                 spin_unlock(&current->mm->page_table_lock);
 408                 return -EFAULT;
 409         }
 410         get_page(virt_to_page(uaddr));
 411         spin_unlock(&current->mm->page_table_lock);
 412         switch (op) {
 413         case FUTEX_OP_SET:
 414                 __futex_atomic_op("lr %2,%5\n",
 415                                   ret, oldval, newval, uaddr, oparg);
 416                 break;
 417         case FUTEX_OP_ADD:
 418                 __futex_atomic_op("lr %2,%1\nar %2,%5\n",
 419                                   ret, oldval, newval, uaddr, oparg);
 420                 break;
 421         case FUTEX_OP_OR:
 422                 __futex_atomic_op("lr %2,%1\nor %2,%5\n",
 423                                   ret, oldval, newval, uaddr, oparg);
 424                 break;
 425         case FUTEX_OP_ANDN:
 426                 __futex_atomic_op("lr %2,%1\nnr %2,%5\n",
 427                                   ret, oldval, newval, uaddr, oparg);
 428                 break;
 429         case FUTEX_OP_XOR:
 430                 __futex_atomic_op("lr %2,%1\nxr %2,%5\n",
 431                                   ret, oldval, newval, uaddr, oparg);
 432                 break;
 433         default:
 434                 ret = -ENOSYS;
 435         }
 436         put_page(virt_to_page(uaddr));
 437         *old = oldval;
 438         return ret;
 439 }
 440
 441 int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
 442 {
 443         int ret;
 444
 445         spin_lock(&current->mm->page_table_lock);
 446         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 447         if (!uaddr) {
 448                 spin_unlock(&current->mm->page_table_lock);
 449                 return -EFAULT;
 450         }
 451         get_page(virt_to_page(uaddr));
 452         spin_unlock(&current->mm->page_table_lock);
 453         asm volatile("   cs   %1,%4,0(%5)\n"
 454                      "0: lr   %0,%1\n"
 455                      "1:\n"
 456                      EX_TABLE(0b,1b)
 457                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 458                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 459                      : "cc", "memory" );
 460         put_page(virt_to_page(uaddr));
 461         return ret;
 462 }
 463
 464 struct uaccess_ops uaccess_pt = {
 465         .copy_from_user         = copy_from_user_pt,
 466         .copy_from_user_small   = copy_from_user_pt,
 467         .copy_to_user           = copy_to_user_pt,
 468         .copy_to_user_small     = copy_to_user_pt,
 469         .copy_in_user           = copy_in_user_pt,
 470         .clear_user             = clear_user_pt,
 471         .strnlen_user           = strnlen_user_pt,
 472         .strncpy_from_user      = strncpy_from_user_pt,
 473         .futex_atomic_op        = futex_atomic_op_pt,
 474         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 475 };