linux/kernel/compat.c
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   1/*
   2 *  linux/kernel/compat.c
   3 *
   4 *  Kernel compatibililty routines for e.g. 32 bit syscall support
   5 *  on 64 bit kernels.
   6 *
   7 *  Copyright (C) 2002-2003 Stephen Rothwell, IBM Corporation
   8 *
   9 *  This program is free software; you can redistribute it and/or modify
  10 *  it under the terms of the GNU General Public License version 2 as
  11 *  published by the Free Software Foundation.
  12 */
  13
  14#include <linux/linkage.h>
  15#include <linux/compat.h>
  16#include <linux/errno.h>
  17#include <linux/time.h>
  18#include <linux/signal.h>
  19#include <linux/sched.h>        /* for MAX_SCHEDULE_TIMEOUT */
  20#include <linux/syscalls.h>
  21#include <linux/unistd.h>
  22#include <linux/security.h>
  23#include <linux/timex.h>
  24#include <linux/export.h>
  25#include <linux/migrate.h>
  26#include <linux/posix-timers.h>
  27#include <linux/times.h>
  28#include <linux/ptrace.h>
  29#include <linux/gfp.h>
  30
  31#include <linux/uaccess.h>
  32
  33int compat_get_timex(struct timex *txc, const struct compat_timex __user *utp)
  34{
  35        struct compat_timex tx32;
  36
  37        if (copy_from_user(&tx32, utp, sizeof(struct compat_timex)))
  38                return -EFAULT;
  39
  40        txc->modes = tx32.modes;
  41        txc->offset = tx32.offset;
  42        txc->freq = tx32.freq;
  43        txc->maxerror = tx32.maxerror;
  44        txc->esterror = tx32.esterror;
  45        txc->status = tx32.status;
  46        txc->constant = tx32.constant;
  47        txc->precision = tx32.precision;
  48        txc->tolerance = tx32.tolerance;
  49        txc->time.tv_sec = tx32.time.tv_sec;
  50        txc->time.tv_usec = tx32.time.tv_usec;
  51        txc->tick = tx32.tick;
  52        txc->ppsfreq = tx32.ppsfreq;
  53        txc->jitter = tx32.jitter;
  54        txc->shift = tx32.shift;
  55        txc->stabil = tx32.stabil;
  56        txc->jitcnt = tx32.jitcnt;
  57        txc->calcnt = tx32.calcnt;
  58        txc->errcnt = tx32.errcnt;
  59        txc->stbcnt = tx32.stbcnt;
  60
  61        return 0;
  62}
  63
  64int compat_put_timex(struct compat_timex __user *utp, const struct timex *txc)
  65{
  66        struct compat_timex tx32;
  67
  68        memset(&tx32, 0, sizeof(struct compat_timex));
  69        tx32.modes = txc->modes;
  70        tx32.offset = txc->offset;
  71        tx32.freq = txc->freq;
  72        tx32.maxerror = txc->maxerror;
  73        tx32.esterror = txc->esterror;
  74        tx32.status = txc->status;
  75        tx32.constant = txc->constant;
  76        tx32.precision = txc->precision;
  77        tx32.tolerance = txc->tolerance;
  78        tx32.time.tv_sec = txc->time.tv_sec;
  79        tx32.time.tv_usec = txc->time.tv_usec;
  80        tx32.tick = txc->tick;
  81        tx32.ppsfreq = txc->ppsfreq;
  82        tx32.jitter = txc->jitter;
  83        tx32.shift = txc->shift;
  84        tx32.stabil = txc->stabil;
  85        tx32.jitcnt = txc->jitcnt;
  86        tx32.calcnt = txc->calcnt;
  87        tx32.errcnt = txc->errcnt;
  88        tx32.stbcnt = txc->stbcnt;
  89        tx32.tai = txc->tai;
  90        if (copy_to_user(utp, &tx32, sizeof(struct compat_timex)))
  91                return -EFAULT;
  92        return 0;
  93}
  94
  95static int __compat_get_timeval(struct timeval *tv, const struct compat_timeval __user *ctv)
  96{
  97        return (!access_ok(VERIFY_READ, ctv, sizeof(*ctv)) ||
  98                        __get_user(tv->tv_sec, &ctv->tv_sec) ||
  99                        __get_user(tv->tv_usec, &ctv->tv_usec)) ? -EFAULT : 0;
 100}
 101
 102static int __compat_put_timeval(const struct timeval *tv, struct compat_timeval __user *ctv)
 103{
 104        return (!access_ok(VERIFY_WRITE, ctv, sizeof(*ctv)) ||
 105                        __put_user(tv->tv_sec, &ctv->tv_sec) ||
 106                        __put_user(tv->tv_usec, &ctv->tv_usec)) ? -EFAULT : 0;
 107}
 108
 109static int __compat_get_timespec(struct timespec *ts, const struct compat_timespec __user *cts)
 110{
 111        return (!access_ok(VERIFY_READ, cts, sizeof(*cts)) ||
 112                        __get_user(ts->tv_sec, &cts->tv_sec) ||
 113                        __get_user(ts->tv_nsec, &cts->tv_nsec)) ? -EFAULT : 0;
 114}
 115
 116static int __compat_put_timespec(const struct timespec *ts, struct compat_timespec __user *cts)
 117{
 118        return (!access_ok(VERIFY_WRITE, cts, sizeof(*cts)) ||
 119                        __put_user(ts->tv_sec, &cts->tv_sec) ||
 120                        __put_user(ts->tv_nsec, &cts->tv_nsec)) ? -EFAULT : 0;
 121}
 122
 123static int __compat_get_timespec64(struct timespec64 *ts64,
 124                                   const struct compat_timespec __user *cts)
 125{
 126        struct compat_timespec ts;
 127        int ret;
 128
 129        ret = copy_from_user(&ts, cts, sizeof(ts));
 130        if (ret)
 131                return -EFAULT;
 132
 133        ts64->tv_sec = ts.tv_sec;
 134        ts64->tv_nsec = ts.tv_nsec;
 135
 136        return 0;
 137}
 138
 139static int __compat_put_timespec64(const struct timespec64 *ts64,
 140                                   struct compat_timespec __user *cts)
 141{
 142        struct compat_timespec ts = {
 143                .tv_sec = ts64->tv_sec,
 144                .tv_nsec = ts64->tv_nsec
 145        };
 146        return copy_to_user(cts, &ts, sizeof(ts)) ? -EFAULT : 0;
 147}
 148
 149int compat_get_timespec64(struct timespec64 *ts, const void __user *uts)
 150{
 151        if (COMPAT_USE_64BIT_TIME)
 152                return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
 153        else
 154                return __compat_get_timespec64(ts, uts);
 155}
 156EXPORT_SYMBOL_GPL(compat_get_timespec64);
 157
 158int compat_put_timespec64(const struct timespec64 *ts, void __user *uts)
 159{
 160        if (COMPAT_USE_64BIT_TIME)
 161                return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
 162        else
 163                return __compat_put_timespec64(ts, uts);
 164}
 165EXPORT_SYMBOL_GPL(compat_put_timespec64);
 166
 167int compat_get_timeval(struct timeval *tv, const void __user *utv)
 168{
 169        if (COMPAT_USE_64BIT_TIME)
 170                return copy_from_user(tv, utv, sizeof(*tv)) ? -EFAULT : 0;
 171        else
 172                return __compat_get_timeval(tv, utv);
 173}
 174EXPORT_SYMBOL_GPL(compat_get_timeval);
 175
 176int compat_put_timeval(const struct timeval *tv, void __user *utv)
 177{
 178        if (COMPAT_USE_64BIT_TIME)
 179                return copy_to_user(utv, tv, sizeof(*tv)) ? -EFAULT : 0;
 180        else
 181                return __compat_put_timeval(tv, utv);
 182}
 183EXPORT_SYMBOL_GPL(compat_put_timeval);
 184
 185int compat_get_timespec(struct timespec *ts, const void __user *uts)
 186{
 187        if (COMPAT_USE_64BIT_TIME)
 188                return copy_from_user(ts, uts, sizeof(*ts)) ? -EFAULT : 0;
 189        else
 190                return __compat_get_timespec(ts, uts);
 191}
 192EXPORT_SYMBOL_GPL(compat_get_timespec);
 193
 194int compat_put_timespec(const struct timespec *ts, void __user *uts)
 195{
 196        if (COMPAT_USE_64BIT_TIME)
 197                return copy_to_user(uts, ts, sizeof(*ts)) ? -EFAULT : 0;
 198        else
 199                return __compat_put_timespec(ts, uts);
 200}
 201EXPORT_SYMBOL_GPL(compat_put_timespec);
 202
 203int get_compat_itimerval(struct itimerval *o, const struct compat_itimerval __user *i)
 204{
 205        struct compat_itimerval v32;
 206
 207        if (copy_from_user(&v32, i, sizeof(struct compat_itimerval)))
 208                return -EFAULT;
 209        o->it_interval.tv_sec = v32.it_interval.tv_sec;
 210        o->it_interval.tv_usec = v32.it_interval.tv_usec;
 211        o->it_value.tv_sec = v32.it_value.tv_sec;
 212        o->it_value.tv_usec = v32.it_value.tv_usec;
 213        return 0;
 214}
 215
 216int put_compat_itimerval(struct compat_itimerval __user *o, const struct itimerval *i)
 217{
 218        struct compat_itimerval v32;
 219
 220        v32.it_interval.tv_sec = i->it_interval.tv_sec;
 221        v32.it_interval.tv_usec = i->it_interval.tv_usec;
 222        v32.it_value.tv_sec = i->it_value.tv_sec;
 223        v32.it_value.tv_usec = i->it_value.tv_usec;
 224        return copy_to_user(o, &v32, sizeof(struct compat_itimerval)) ? -EFAULT : 0;
 225}
 226
 227#ifdef __ARCH_WANT_SYS_SIGPROCMASK
 228
 229/*
 230 * sys_sigprocmask SIG_SETMASK sets the first (compat) word of the
 231 * blocked set of signals to the supplied signal set
 232 */
 233static inline void compat_sig_setmask(sigset_t *blocked, compat_sigset_word set)
 234{
 235        memcpy(blocked->sig, &set, sizeof(set));
 236}
 237
 238COMPAT_SYSCALL_DEFINE3(sigprocmask, int, how,
 239                       compat_old_sigset_t __user *, nset,
 240                       compat_old_sigset_t __user *, oset)
 241{
 242        old_sigset_t old_set, new_set;
 243        sigset_t new_blocked;
 244
 245        old_set = current->blocked.sig[0];
 246
 247        if (nset) {
 248                if (get_user(new_set, nset))
 249                        return -EFAULT;
 250                new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP));
 251
 252                new_blocked = current->blocked;
 253
 254                switch (how) {
 255                case SIG_BLOCK:
 256                        sigaddsetmask(&new_blocked, new_set);
 257                        break;
 258                case SIG_UNBLOCK:
 259                        sigdelsetmask(&new_blocked, new_set);
 260                        break;
 261                case SIG_SETMASK:
 262                        compat_sig_setmask(&new_blocked, new_set);
 263                        break;
 264                default:
 265                        return -EINVAL;
 266                }
 267
 268                set_current_blocked(&new_blocked);
 269        }
 270
 271        if (oset) {
 272                if (put_user(old_set, oset))
 273                        return -EFAULT;
 274        }
 275
 276        return 0;
 277}
 278
 279#endif
 280
 281int put_compat_rusage(const struct rusage *r, struct compat_rusage __user *ru)
 282{
 283        struct compat_rusage r32;
 284        memset(&r32, 0, sizeof(r32));
 285        r32.ru_utime.tv_sec = r->ru_utime.tv_sec;
 286        r32.ru_utime.tv_usec = r->ru_utime.tv_usec;
 287        r32.ru_stime.tv_sec = r->ru_stime.tv_sec;
 288        r32.ru_stime.tv_usec = r->ru_stime.tv_usec;
 289        r32.ru_maxrss = r->ru_maxrss;
 290        r32.ru_ixrss = r->ru_ixrss;
 291        r32.ru_idrss = r->ru_idrss;
 292        r32.ru_isrss = r->ru_isrss;
 293        r32.ru_minflt = r->ru_minflt;
 294        r32.ru_majflt = r->ru_majflt;
 295        r32.ru_nswap = r->ru_nswap;
 296        r32.ru_inblock = r->ru_inblock;
 297        r32.ru_oublock = r->ru_oublock;
 298        r32.ru_msgsnd = r->ru_msgsnd;
 299        r32.ru_msgrcv = r->ru_msgrcv;
 300        r32.ru_nsignals = r->ru_nsignals;
 301        r32.ru_nvcsw = r->ru_nvcsw;
 302        r32.ru_nivcsw = r->ru_nivcsw;
 303        if (copy_to_user(ru, &r32, sizeof(r32)))
 304                return -EFAULT;
 305        return 0;
 306}
 307
 308static int compat_get_user_cpu_mask(compat_ulong_t __user *user_mask_ptr,
 309                                    unsigned len, struct cpumask *new_mask)
 310{
 311        unsigned long *k;
 312
 313        if (len < cpumask_size())
 314                memset(new_mask, 0, cpumask_size());
 315        else if (len > cpumask_size())
 316                len = cpumask_size();
 317
 318        k = cpumask_bits(new_mask);
 319        return compat_get_bitmap(k, user_mask_ptr, len * 8);
 320}
 321
 322COMPAT_SYSCALL_DEFINE3(sched_setaffinity, compat_pid_t, pid,
 323                       unsigned int, len,
 324                       compat_ulong_t __user *, user_mask_ptr)
 325{
 326        cpumask_var_t new_mask;
 327        int retval;
 328
 329        if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
 330                return -ENOMEM;
 331
 332        retval = compat_get_user_cpu_mask(user_mask_ptr, len, new_mask);
 333        if (retval)
 334                goto out;
 335
 336        retval = sched_setaffinity(pid, new_mask);
 337out:
 338        free_cpumask_var(new_mask);
 339        return retval;
 340}
 341
 342COMPAT_SYSCALL_DEFINE3(sched_getaffinity, compat_pid_t,  pid, unsigned int, len,
 343                       compat_ulong_t __user *, user_mask_ptr)
 344{
 345        int ret;
 346        cpumask_var_t mask;
 347
 348        if ((len * BITS_PER_BYTE) < nr_cpu_ids)
 349                return -EINVAL;
 350        if (len & (sizeof(compat_ulong_t)-1))
 351                return -EINVAL;
 352
 353        if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 354                return -ENOMEM;
 355
 356        ret = sched_getaffinity(pid, mask);
 357        if (ret == 0) {
 358                size_t retlen = min_t(size_t, len, cpumask_size());
 359
 360                if (compat_put_bitmap(user_mask_ptr, cpumask_bits(mask), retlen * 8))
 361                        ret = -EFAULT;
 362                else
 363                        ret = retlen;
 364        }
 365        free_cpumask_var(mask);
 366
 367        return ret;
 368}
 369
 370int get_compat_itimerspec(struct itimerspec *dst,
 371                          const struct compat_itimerspec __user *src)
 372{
 373        if (__compat_get_timespec(&dst->it_interval, &src->it_interval) ||
 374            __compat_get_timespec(&dst->it_value, &src->it_value))
 375                return -EFAULT;
 376        return 0;
 377}
 378
 379int put_compat_itimerspec(struct compat_itimerspec __user *dst,
 380                          const struct itimerspec *src)
 381{
 382        if (__compat_put_timespec(&src->it_interval, &dst->it_interval) ||
 383            __compat_put_timespec(&src->it_value, &dst->it_value))
 384                return -EFAULT;
 385        return 0;
 386}
 387
 388int get_compat_itimerspec64(struct itimerspec64 *its,
 389                        const struct compat_itimerspec __user *uits)
 390{
 391
 392        if (__compat_get_timespec64(&its->it_interval, &uits->it_interval) ||
 393            __compat_get_timespec64(&its->it_value, &uits->it_value))
 394                return -EFAULT;
 395        return 0;
 396}
 397EXPORT_SYMBOL_GPL(get_compat_itimerspec64);
 398
 399int put_compat_itimerspec64(const struct itimerspec64 *its,
 400                        struct compat_itimerspec __user *uits)
 401{
 402        if (__compat_put_timespec64(&its->it_interval, &uits->it_interval) ||
 403            __compat_put_timespec64(&its->it_value, &uits->it_value))
 404                return -EFAULT;
 405        return 0;
 406}
 407EXPORT_SYMBOL_GPL(put_compat_itimerspec64);
 408
 409/*
 410 * We currently only need the following fields from the sigevent
 411 * structure: sigev_value, sigev_signo, sig_notify and (sometimes
 412 * sigev_notify_thread_id).  The others are handled in user mode.
 413 * We also assume that copying sigev_value.sival_int is sufficient
 414 * to keep all the bits of sigev_value.sival_ptr intact.
 415 */
 416int get_compat_sigevent(struct sigevent *event,
 417                const struct compat_sigevent __user *u_event)
 418{
 419        memset(event, 0, sizeof(*event));
 420        return (!access_ok(VERIFY_READ, u_event, sizeof(*u_event)) ||
 421                __get_user(event->sigev_value.sival_int,
 422                        &u_event->sigev_value.sival_int) ||
 423                __get_user(event->sigev_signo, &u_event->sigev_signo) ||
 424                __get_user(event->sigev_notify, &u_event->sigev_notify) ||
 425                __get_user(event->sigev_notify_thread_id,
 426                        &u_event->sigev_notify_thread_id))
 427                ? -EFAULT : 0;
 428}
 429
 430long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask,
 431                       unsigned long bitmap_size)
 432{
 433        unsigned long nr_compat_longs;
 434
 435        /* align bitmap up to nearest compat_long_t boundary */
 436        bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
 437        nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
 438
 439        if (!access_ok(VERIFY_READ, umask, bitmap_size / 8))
 440                return -EFAULT;
 441
 442        user_access_begin();
 443        while (nr_compat_longs > 1) {
 444                compat_ulong_t l1, l2;
 445                unsafe_get_user(l1, umask++, Efault);
 446                unsafe_get_user(l2, umask++, Efault);
 447                *mask++ = ((unsigned long)l2 << BITS_PER_COMPAT_LONG) | l1;
 448                nr_compat_longs -= 2;
 449        }
 450        if (nr_compat_longs)
 451                unsafe_get_user(*mask, umask++, Efault);
 452        user_access_end();
 453        return 0;
 454
 455Efault:
 456        user_access_end();
 457        return -EFAULT;
 458}
 459
 460long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask,
 461                       unsigned long bitmap_size)
 462{
 463        unsigned long nr_compat_longs;
 464
 465        /* align bitmap up to nearest compat_long_t boundary */
 466        bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
 467        nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
 468
 469        if (!access_ok(VERIFY_WRITE, umask, bitmap_size / 8))
 470                return -EFAULT;
 471
 472        user_access_begin();
 473        while (nr_compat_longs > 1) {
 474                unsigned long m = *mask++;
 475                unsafe_put_user((compat_ulong_t)m, umask++, Efault);
 476                unsafe_put_user(m >> BITS_PER_COMPAT_LONG, umask++, Efault);
 477                nr_compat_longs -= 2;
 478        }
 479        if (nr_compat_longs)
 480                unsafe_put_user((compat_ulong_t)*mask, umask++, Efault);
 481        user_access_end();
 482        return 0;
 483Efault:
 484        user_access_end();
 485        return -EFAULT;
 486}
 487
 488void
 489sigset_from_compat(sigset_t *set, const compat_sigset_t *compat)
 490{
 491        switch (_NSIG_WORDS) {
 492        case 4: set->sig[3] = compat->sig[6] | (((long)compat->sig[7]) << 32 );
 493        case 3: set->sig[2] = compat->sig[4] | (((long)compat->sig[5]) << 32 );
 494        case 2: set->sig[1] = compat->sig[2] | (((long)compat->sig[3]) << 32 );
 495        case 1: set->sig[0] = compat->sig[0] | (((long)compat->sig[1]) << 32 );
 496        }
 497}
 498EXPORT_SYMBOL_GPL(sigset_from_compat);
 499
 500void
 501sigset_to_compat(compat_sigset_t *compat, const sigset_t *set)
 502{
 503        switch (_NSIG_WORDS) {
 504        case 4: compat->sig[7] = (set->sig[3] >> 32); compat->sig[6] = set->sig[3];
 505        case 3: compat->sig[5] = (set->sig[2] >> 32); compat->sig[4] = set->sig[2];
 506        case 2: compat->sig[3] = (set->sig[1] >> 32); compat->sig[2] = set->sig[1];
 507        case 1: compat->sig[1] = (set->sig[0] >> 32); compat->sig[0] = set->sig[0];
 508        }
 509}
 510
 511#ifdef CONFIG_NUMA
 512COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
 513                       compat_uptr_t __user *, pages32,
 514                       const int __user *, nodes,
 515                       int __user *, status,
 516                       int, flags)
 517{
 518        const void __user * __user *pages;
 519        int i;
 520
 521        pages = compat_alloc_user_space(nr_pages * sizeof(void *));
 522        for (i = 0; i < nr_pages; i++) {
 523                compat_uptr_t p;
 524
 525                if (get_user(p, pages32 + i) ||
 526                        put_user(compat_ptr(p), pages + i))
 527                        return -EFAULT;
 528        }
 529        return sys_move_pages(pid, nr_pages, pages, nodes, status, flags);
 530}
 531
 532COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,
 533                       compat_ulong_t, maxnode,
 534                       const compat_ulong_t __user *, old_nodes,
 535                       const compat_ulong_t __user *, new_nodes)
 536{
 537        unsigned long __user *old = NULL;
 538        unsigned long __user *new = NULL;
 539        nodemask_t tmp_mask;
 540        unsigned long nr_bits;
 541        unsigned long size;
 542
 543        nr_bits = min_t(unsigned long, maxnode - 1, MAX_NUMNODES);
 544        size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
 545        if (old_nodes) {
 546                if (compat_get_bitmap(nodes_addr(tmp_mask), old_nodes, nr_bits))
 547                        return -EFAULT;
 548                old = compat_alloc_user_space(new_nodes ? size * 2 : size);
 549                if (new_nodes)
 550                        new = old + size / sizeof(unsigned long);
 551                if (copy_to_user(old, nodes_addr(tmp_mask), size))
 552                        return -EFAULT;
 553        }
 554        if (new_nodes) {
 555                if (compat_get_bitmap(nodes_addr(tmp_mask), new_nodes, nr_bits))
 556                        return -EFAULT;
 557                if (new == NULL)
 558                        new = compat_alloc_user_space(size);
 559                if (copy_to_user(new, nodes_addr(tmp_mask), size))
 560                        return -EFAULT;
 561        }
 562        return sys_migrate_pages(pid, nr_bits + 1, old, new);
 563}
 564#endif
 565
 566COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval,
 567                       compat_pid_t, pid,
 568                       struct compat_timespec __user *, interval)
 569{
 570        struct timespec t;
 571        int ret;
 572        mm_segment_t old_fs = get_fs();
 573
 574        set_fs(KERNEL_DS);
 575        ret = sys_sched_rr_get_interval(pid, (struct timespec __user *)&t);
 576        set_fs(old_fs);
 577        if (compat_put_timespec(&t, interval))
 578                return -EFAULT;
 579        return ret;
 580}
 581
 582/*
 583 * Allocate user-space memory for the duration of a single system call,
 584 * in order to marshall parameters inside a compat thunk.
 585 */
 586void __user *compat_alloc_user_space(unsigned long len)
 587{
 588        void __user *ptr;
 589
 590        /* If len would occupy more than half of the entire compat space... */
 591        if (unlikely(len > (((compat_uptr_t)~0) >> 1)))
 592                return NULL;
 593
 594        ptr = arch_compat_alloc_user_space(len);
 595
 596        if (unlikely(!access_ok(VERIFY_WRITE, ptr, len)))
 597                return NULL;
 598
 599        return ptr;
 600}
 601EXPORT_SYMBOL_GPL(compat_alloc_user_space);
 602