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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 inline pte_t *follow_table(struct mm_struct *mm, unsigned long addr)
  19 {
  20         pgd_t *pgd;
  21         pud_t *pud;
  22         pmd_t *pmd;
  23
  24         pgd = pgd_offset(mm, addr);
  25         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
  26                 return NULL;
  27
  28         pud = pud_offset(pgd, addr);
  29         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
  30                 return NULL;
  31
  32         pmd = pmd_offset(pud, addr);
  33         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
  34                 return NULL;
  35
  36         return pte_offset_map(pmd, addr);
  37 }
  38
  39 static int __handle_fault(struct mm_struct *mm, unsigned long address,
  40                           int write_access)
  41 {
  42         struct vm_area_struct *vma;
  43         int ret = -EFAULT;
  44         int fault;
  45
  46         if (in_atomic())
  47                 return ret;
  48         down_read(&mm->mmap_sem);
  49         vma = find_vma(mm, address);
  50         if (unlikely(!vma))
  51                 goto out;
  52         if (unlikely(vma->vm_start > address)) {
  53                 if (!(vma->vm_flags & VM_GROWSDOWN))
  54                         goto out;
  55                 if (expand_stack(vma, address))
  56                         goto out;
  57         }
  58
  59         if (!write_access) {
  60                 /* page not present, check vm flags */
  61                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
  62                         goto out;
  63         } else {
  64                 if (!(vma->vm_flags & VM_WRITE))
  65                         goto out;
  66         }
  67
  68 survive:
  69         fault = handle_mm_fault(mm, vma, address, write_access);
  70         if (unlikely(fault & VM_FAULT_ERROR)) {
  71                 if (fault & VM_FAULT_OOM)
  72                         goto out_of_memory;
  73                 else if (fault & VM_FAULT_SIGBUS)
  74                         goto out_sigbus;
  75                 BUG();
  76         }
  77         if (fault & VM_FAULT_MAJOR)
  78                 current->maj_flt++;
  79         else
  80                 current->min_flt++;
  81         ret = 0;
  82 out:
  83         up_read(&mm->mmap_sem);
  84         return ret;
  85
  86 out_of_memory:
  87         up_read(&mm->mmap_sem);
  88         if (is_global_init(current)) {
  89                 yield();
  90                 down_read(&mm->mmap_sem);
  91                 goto survive;
  92         }
  93         printk("VM: killing process %s\n", current->comm);
  94         return ret;
  95
  96 out_sigbus:
  97         up_read(&mm->mmap_sem);
  98         current->thread.prot_addr = address;
  99         current->thread.trap_no = 0x11;
 100         force_sig(SIGBUS, current);
 101         return ret;
 102 }
 103
 104 static size_t __user_copy_pt(unsigned long uaddr, void *kptr,
 105                              size_t n, int write_user)
 106 {
 107         struct mm_struct *mm = current->mm;
 108         unsigned long offset, pfn, done, size;
 109         pte_t *pte;
 110         void *from, *to;
 111
 112         done = 0;
 113 retry:
 114         spin_lock(&mm->page_table_lock);
 115         do {
 116                 pte = follow_table(mm, uaddr);
 117                 if (!pte || !pte_present(*pte) ||
 118                     (write_user && !pte_write(*pte)))
 119                         goto fault;
 120
 121                 pfn = pte_pfn(*pte);
 122                 if (!pfn_valid(pfn))
 123                         goto out;
 124
 125                 offset = uaddr & (PAGE_SIZE - 1);
 126                 size = min(n - done, PAGE_SIZE - offset);
 127                 if (write_user) {
 128                         to = (void *)((pfn << PAGE_SHIFT) + offset);
 129                         from = kptr + done;
 130                 } else {
 131                         from = (void *)((pfn << PAGE_SHIFT) + offset);
 132                         to = kptr + done;
 133                 }
 134                 memcpy(to, from, size);
 135                 done += size;
 136                 uaddr += size;
 137         } while (done < n);
 138 out:
 139         spin_unlock(&mm->page_table_lock);
 140         return n - done;
 141 fault:
 142         spin_unlock(&mm->page_table_lock);
 143         if (__handle_fault(mm, uaddr, write_user))
 144                 return n - done;
 145         goto retry;
 146 }
 147
 148 /*
 149  * Do DAT for user address by page table walk, return kernel address.
 150  * This function needs to be called with current->mm->page_table_lock held.
 151  */
 152 static unsigned long __dat_user_addr(unsigned long uaddr)
 153 {
 154         struct mm_struct *mm = current->mm;
 155         unsigned long pfn, ret;
 156         pte_t *pte;
 157         int rc;
 158
 159         ret = 0;
 160 retry:
 161         pte = follow_table(mm, 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         pte_t *pte;
 234         size_t len_str;
 235
 236         if (segment_eq(get_fs(), KERNEL_DS))
 237                 return strnlen((const char __kernel __force *) src, count) + 1;
 238         done = 0;
 239 retry:
 240         spin_lock(&mm->page_table_lock);
 241         do {
 242                 pte = follow_table(mm, uaddr);
 243                 if (!pte || !pte_present(*pte))
 244                         goto fault;
 245
 246                 pfn = pte_pfn(*pte);
 247                 if (!pfn_valid(pfn)) {
 248                         done = -1;
 249                         goto out;
 250                 }
 251
 252                 offset = uaddr & (PAGE_SIZE-1);
 253                 addr = (char *)(pfn << PAGE_SHIFT) + offset;
 254                 len = min(count - done, PAGE_SIZE - offset);
 255                 len_str = strnlen(addr, len);
 256                 done += len_str;
 257                 uaddr += len_str;
 258         } while ((len_str == len) && (done < count));
 259 out:
 260         spin_unlock(&mm->page_table_lock);
 261         return done + 1;
 262 fault:
 263         spin_unlock(&mm->page_table_lock);
 264         if (__handle_fault(mm, uaddr, 0)) {
 265                 return 0;
 266         }
 267         goto retry;
 268 }
 269
 270 static size_t strncpy_from_user_pt(size_t count, const char __user *src,
 271                                    char *dst)
 272 {
 273         size_t n = strnlen_user_pt(count, src);
 274
 275         if (!n)
 276                 return -EFAULT;
 277         if (n > count)
 278                 n = count;
 279         if (segment_eq(get_fs(), KERNEL_DS)) {
 280                 memcpy(dst, (const char __kernel __force *) src, n);
 281                 if (dst[n-1] == '\0')
 282                         return n-1;
 283                 else
 284                         return n;
 285         }
 286         if (__user_copy_pt((unsigned long) src, dst, n, 0))
 287                 return -EFAULT;
 288         if (dst[n-1] == '\0')
 289                 return n-1;
 290         else
 291                 return n;
 292 }
 293
 294 static size_t copy_in_user_pt(size_t n, void __user *to,
 295                               const void __user *from)
 296 {
 297         struct mm_struct *mm = current->mm;
 298         unsigned long offset_from, offset_to, offset_max, pfn_from, pfn_to,
 299                       uaddr, done, size;
 300         unsigned long uaddr_from = (unsigned long) from;
 301         unsigned long uaddr_to = (unsigned long) to;
 302         pte_t *pte_from, *pte_to;
 303         int write_user;
 304
 305         done = 0;
 306 retry:
 307         spin_lock(&mm->page_table_lock);
 308         do {
 309                 pte_from = follow_table(mm, uaddr_from);
 310                 if (!pte_from || !pte_present(*pte_from)) {
 311                         uaddr = uaddr_from;
 312                         write_user = 0;
 313                         goto fault;
 314                 }
 315
 316                 pte_to = follow_table(mm, uaddr_to);
 317                 if (!pte_to || !pte_present(*pte_to) || !pte_write(*pte_to)) {
 318                         uaddr = uaddr_to;
 319                         write_user = 1;
 320                         goto fault;
 321                 }
 322
 323                 pfn_from = pte_pfn(*pte_from);
 324                 if (!pfn_valid(pfn_from))
 325                         goto out;
 326                 pfn_to = pte_pfn(*pte_to);
 327                 if (!pfn_valid(pfn_to))
 328                         goto out;
 329
 330                 offset_from = uaddr_from & (PAGE_SIZE-1);
 331                 offset_to = uaddr_from & (PAGE_SIZE-1);
 332                 offset_max = max(offset_from, offset_to);
 333                 size = min(n - done, PAGE_SIZE - offset_max);
 334
 335                 memcpy((void *)(pfn_to << PAGE_SHIFT) + offset_to,
 336                        (void *)(pfn_from << PAGE_SHIFT) + offset_from, size);
 337                 done += size;
 338                 uaddr_from += size;
 339                 uaddr_to += size;
 340         } while (done < n);
 341 out:
 342         spin_unlock(&mm->page_table_lock);
 343         return n - done;
 344 fault:
 345         spin_unlock(&mm->page_table_lock);
 346         if (__handle_fault(mm, uaddr, write_user))
 347                 return n - done;
 348         goto retry;
 349 }
 350
 351 #define __futex_atomic_op(insn, ret, oldval, newval, uaddr, oparg)      \
 352         asm volatile("0: l   %1,0(%6)\n"                                \
 353                      "1: " insn                                         \
 354                      "2: cs  %1,%2,0(%6)\n"                             \
 355                      "3: jl  1b\n"                                      \
 356                      "   lhi %0,0\n"                                    \
 357                      "4:\n"                                             \
 358                      EX_TABLE(0b,4b) EX_TABLE(2b,4b) EX_TABLE(3b,4b)    \
 359                      : "=d" (ret), "=&d" (oldval), "=&d" (newval),      \
 360                        "=m" (*uaddr)                                    \
 361                      : "0" (-EFAULT), "d" (oparg), "a" (uaddr),         \
 362                        "m" (*uaddr) : "cc" );
 363
 364 int futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old)
 365 {
 366         int oldval = 0, newval, ret;
 367
 368         spin_lock(&current->mm->page_table_lock);
 369         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 370         if (!uaddr) {
 371                 spin_unlock(&current->mm->page_table_lock);
 372                 return -EFAULT;
 373         }
 374         get_page(virt_to_page(uaddr));
 375         spin_unlock(&current->mm->page_table_lock);
 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         put_page(virt_to_page(uaddr));
 401         *old = oldval;
 402         return ret;
 403 }
 404
 405 int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval)
 406 {
 407         int ret;
 408
 409         spin_lock(&current->mm->page_table_lock);
 410         uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr);
 411         if (!uaddr) {
 412                 spin_unlock(&current->mm->page_table_lock);
 413                 return -EFAULT;
 414         }
 415         get_page(virt_to_page(uaddr));
 416         spin_unlock(&current->mm->page_table_lock);
 417         asm volatile("   cs   %1,%4,0(%5)\n"
 418                      "0: lr   %0,%1\n"
 419                      "1:\n"
 420                      EX_TABLE(0b,1b)
 421                      : "=d" (ret), "+d" (oldval), "=m" (*uaddr)
 422                      : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr)
 423                      : "cc", "memory" );
 424         put_page(virt_to_page(uaddr));
 425         return ret;
 426 }
 427
 428 struct uaccess_ops uaccess_pt = {
 429         .copy_from_user         = copy_from_user_pt,
 430         .copy_from_user_small   = copy_from_user_pt,
 431         .copy_to_user           = copy_to_user_pt,
 432         .copy_to_user_small     = copy_to_user_pt,
 433         .copy_in_user           = copy_in_user_pt,
 434         .clear_user             = clear_user_pt,
 435         .strnlen_user           = strnlen_user_pt,
 436         .strncpy_from_user      = strncpy_from_user_pt,
 437         .futex_atomic_op        = futex_atomic_op_pt,
 438         .futex_atomic_cmpxchg   = futex_atomic_cmpxchg_pt,
 439 };