arch/arm64/kernel/signal32.c

   1 /*
   2  * Based on arch/arm/kernel/signal.c
   3  *
   4  * Copyright (C) 1995-2009 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  * Modified by Will Deacon <will.deacon@arm.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <linux/compat.h>
  22 #include <linux/signal.h>
  23 #include <linux/syscalls.h>
  24 #include <linux/ratelimit.h>
  25
  26 #include <asm/esr.h>
  27 #include <asm/fpsimd.h>
  28 #include <asm/signal32.h>
  29 #include <asm/uaccess.h>
  30 #include <asm/unistd.h>
  31
  32 struct compat_sigcontext {
  33         /* We always set these two fields to 0 */
  34         compat_ulong_t                  trap_no;
  35         compat_ulong_t                  error_code;
  36
  37         compat_ulong_t                  oldmask;
  38         compat_ulong_t                  arm_r0;
  39         compat_ulong_t                  arm_r1;
  40         compat_ulong_t                  arm_r2;
  41         compat_ulong_t                  arm_r3;
  42         compat_ulong_t                  arm_r4;
  43         compat_ulong_t                  arm_r5;
  44         compat_ulong_t                  arm_r6;
  45         compat_ulong_t                  arm_r7;
  46         compat_ulong_t                  arm_r8;
  47         compat_ulong_t                  arm_r9;
  48         compat_ulong_t                  arm_r10;
  49         compat_ulong_t                  arm_fp;
  50         compat_ulong_t                  arm_ip;
  51         compat_ulong_t                  arm_sp;
  52         compat_ulong_t                  arm_lr;
  53         compat_ulong_t                  arm_pc;
  54         compat_ulong_t                  arm_cpsr;
  55         compat_ulong_t                  fault_address;
  56 };
  57
  58 struct compat_ucontext {
  59         compat_ulong_t                  uc_flags;
  60         compat_uptr_t                   uc_link;
  61         compat_stack_t                  uc_stack;
  62         struct compat_sigcontext        uc_mcontext;
  63         compat_sigset_t                 uc_sigmask;
  64         int             __unused[32 - (sizeof (compat_sigset_t) / sizeof (int))];
  65         compat_ulong_t  uc_regspace[128] __attribute__((__aligned__(8)));
  66 };
  67
  68 struct compat_vfp_sigframe {
  69         compat_ulong_t  magic;
  70         compat_ulong_t  size;
  71         struct compat_user_vfp {
  72                 compat_u64      fpregs[32];
  73                 compat_ulong_t  fpscr;
  74         } ufp;
  75         struct compat_user_vfp_exc {
  76                 compat_ulong_t  fpexc;
  77                 compat_ulong_t  fpinst;
  78                 compat_ulong_t  fpinst2;
  79         } ufp_exc;
  80 } __attribute__((__aligned__(8)));
  81
  82 #define VFP_MAGIC               0x56465001
  83 #define VFP_STORAGE_SIZE        sizeof(struct compat_vfp_sigframe)
  84
  85 #define FSR_WRITE_SHIFT         (11)
  86
  87 struct compat_aux_sigframe {
  88         struct compat_vfp_sigframe      vfp;
  89
  90         /* Something that isn't a valid magic number for any coprocessor.  */
  91         unsigned long                   end_magic;
  92 } __attribute__((__aligned__(8)));
  93
  94 struct compat_sigframe {
  95         struct compat_ucontext  uc;
  96         compat_ulong_t          retcode[2];
  97 };
  98
  99 struct compat_rt_sigframe {
 100         struct compat_siginfo info;
 101         struct compat_sigframe sig;
 102 };
 103
 104 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
 105
 106 static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set)
 107 {
 108         compat_sigset_t cset;
 109
 110         cset.sig[0] = set->sig[0] & 0xffffffffull;
 111         cset.sig[1] = set->sig[0] >> 32;
 112
 113         return copy_to_user(uset, &cset, sizeof(*uset));
 114 }
 115
 116 static inline int get_sigset_t(sigset_t *set,
 117                                const compat_sigset_t __user *uset)
 118 {
 119         compat_sigset_t s32;
 120
 121         if (copy_from_user(&s32, uset, sizeof(*uset)))
 122                 return -EFAULT;
 123
 124         set->sig[0] = s32.sig[0] | (((long)s32.sig[1]) << 32);
 125         return 0;
 126 }
 127
 128 int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
 129 {
 130         int err;
 131
 132         if (!access_ok(VERIFY_WRITE, to, sizeof(*to)))
 133                 return -EFAULT;
 134
 135         /* If you change siginfo_t structure, please be sure
 136          * this code is fixed accordingly.
 137          * It should never copy any pad contained in the structure
 138          * to avoid security leaks, but must copy the generic
 139          * 3 ints plus the relevant union member.
 140          * This routine must convert siginfo from 64bit to 32bit as well
 141          * at the same time.
 142          */
 143         err = __put_user(from->si_signo, &to->si_signo);
 144         err |= __put_user(from->si_errno, &to->si_errno);
 145         err |= __put_user((short)from->si_code, &to->si_code);
 146         if (from->si_code < 0)
 147                 err |= __copy_to_user(&to->_sifields._pad, &from->_sifields._pad,
 148                                       SI_PAD_SIZE);
 149         else switch (from->si_code & __SI_MASK) {
 150         case __SI_KILL:
 151                 err |= __put_user(from->si_pid, &to->si_pid);
 152                 err |= __put_user(from->si_uid, &to->si_uid);
 153                 break;
 154         case __SI_TIMER:
 155                  err |= __put_user(from->si_tid, &to->si_tid);
 156                  err |= __put_user(from->si_overrun, &to->si_overrun);
 157                  err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr,
 158                                    &to->si_ptr);
 159                 break;
 160         case __SI_POLL:
 161                 err |= __put_user(from->si_band, &to->si_band);
 162                 err |= __put_user(from->si_fd, &to->si_fd);
 163                 break;
 164         case __SI_FAULT:
 165                 err |= __put_user((compat_uptr_t)(unsigned long)from->si_addr,
 166                                   &to->si_addr);
 167 #ifdef BUS_MCEERR_AO
 168                 /*
 169                  * Other callers might not initialize the si_lsb field,
 170                  * so check explicitely for the right codes here.
 171                  */
 172                 if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
 173                         err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
 174 #endif
 175                 break;
 176         case __SI_CHLD:
 177                 err |= __put_user(from->si_pid, &to->si_pid);
 178                 err |= __put_user(from->si_uid, &to->si_uid);
 179                 err |= __put_user(from->si_status, &to->si_status);
 180                 err |= __put_user(from->si_utime, &to->si_utime);
 181                 err |= __put_user(from->si_stime, &to->si_stime);
 182                 break;
 183         case __SI_RT: /* This is not generated by the kernel as of now. */
 184         case __SI_MESGQ: /* But this is */
 185                 err |= __put_user(from->si_pid, &to->si_pid);
 186                 err |= __put_user(from->si_uid, &to->si_uid);
 187                 err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr, &to->si_ptr);
 188                 break;
 189         default: /* this is just in case for now ... */
 190                 err |= __put_user(from->si_pid, &to->si_pid);
 191                 err |= __put_user(from->si_uid, &to->si_uid);
 192                 break;
 193         }
 194         return err;
 195 }
 196
 197 int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
 198 {
 199         memset(to, 0, sizeof *to);
 200
 201         if (copy_from_user(to, from, __ARCH_SI_PREAMBLE_SIZE) ||
 202             copy_from_user(to->_sifields._pad,
 203                            from->_sifields._pad, SI_PAD_SIZE))
 204                 return -EFAULT;
 205
 206         return 0;
 207 }
 208
 209 /*
 210  * VFP save/restore code.
 211  */
 212 static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame)
 213 {
 214         struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
 215         compat_ulong_t magic = VFP_MAGIC;
 216         compat_ulong_t size = VFP_STORAGE_SIZE;
 217         compat_ulong_t fpscr, fpexc;
 218         int err = 0;
 219
 220         /*
 221          * Save the hardware registers to the fpsimd_state structure.
 222          * Note that this also saves V16-31, which aren't visible
 223          * in AArch32.
 224          */
 225         fpsimd_preserve_current_state();
 226
 227         /* Place structure header on the stack */
 228         __put_user_error(magic, &frame->magic, err);
 229         __put_user_error(size, &frame->size, err);
 230
 231         /*
 232          * Now copy the FP registers. Since the registers are packed,
 233          * we can copy the prefix we want (V0-V15) as it is.
 234          * FIXME: Won't work if big endian.
 235          */
 236         err |= __copy_to_user(&frame->ufp.fpregs, fpsimd->vregs,
 237                               sizeof(frame->ufp.fpregs));
 238
 239         /* Create an AArch32 fpscr from the fpsr and the fpcr. */
 240         fpscr = (fpsimd->fpsr & VFP_FPSCR_STAT_MASK) |
 241                 (fpsimd->fpcr & VFP_FPSCR_CTRL_MASK);
 242         __put_user_error(fpscr, &frame->ufp.fpscr, err);
 243
 244         /*
 245          * The exception register aren't available so we fake up a
 246          * basic FPEXC and zero everything else.
 247          */
 248         fpexc = (1 << 30);
 249         __put_user_error(fpexc, &frame->ufp_exc.fpexc, err);
 250         __put_user_error(0, &frame->ufp_exc.fpinst, err);
 251         __put_user_error(0, &frame->ufp_exc.fpinst2, err);
 252
 253         return err ? -EFAULT : 0;
 254 }
 255
 256 static int compat_restore_vfp_context(struct compat_vfp_sigframe __user *frame)
 257 {
 258         struct fpsimd_state fpsimd;
 259         compat_ulong_t magic = VFP_MAGIC;
 260         compat_ulong_t size = VFP_STORAGE_SIZE;
 261         compat_ulong_t fpscr;
 262         int err = 0;
 263
 264         __get_user_error(magic, &frame->magic, err);
 265         __get_user_error(size, &frame->size, err);
 266
 267         if (err)
 268                 return -EFAULT;
 269         if (magic != VFP_MAGIC || size != VFP_STORAGE_SIZE)
 270                 return -EINVAL;
 271
 272         /*
 273          * Copy the FP registers into the start of the fpsimd_state.
 274          * FIXME: Won't work if big endian.
 275          */
 276         err |= __copy_from_user(fpsimd.vregs, frame->ufp.fpregs,
 277                                 sizeof(frame->ufp.fpregs));
 278
 279         /* Extract the fpsr and the fpcr from the fpscr */
 280         __get_user_error(fpscr, &frame->ufp.fpscr, err);
 281         fpsimd.fpsr = fpscr & VFP_FPSCR_STAT_MASK;
 282         fpsimd.fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
 283
 284         /*
 285          * We don't need to touch the exception register, so
 286          * reload the hardware state.
 287          */
 288         if (!err)
 289                 fpsimd_update_current_state(&fpsimd);
 290
 291         return err ? -EFAULT : 0;
 292 }
 293
 294 static int compat_restore_sigframe(struct pt_regs *regs,
 295                                    struct compat_sigframe __user *sf)
 296 {
 297         int err;
 298         sigset_t set;
 299         struct compat_aux_sigframe __user *aux;
 300
 301         err = get_sigset_t(&set, &sf->uc.uc_sigmask);
 302         if (err == 0) {
 303                 sigdelsetmask(&set, ~_BLOCKABLE);
 304                 set_current_blocked(&set);
 305         }
 306
 307         __get_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
 308         __get_user_error(regs->regs[1], &sf->uc.uc_mcontext.arm_r1, err);
 309         __get_user_error(regs->regs[2], &sf->uc.uc_mcontext.arm_r2, err);
 310         __get_user_error(regs->regs[3], &sf->uc.uc_mcontext.arm_r3, err);
 311         __get_user_error(regs->regs[4], &sf->uc.uc_mcontext.arm_r4, err);
 312         __get_user_error(regs->regs[5], &sf->uc.uc_mcontext.arm_r5, err);
 313         __get_user_error(regs->regs[6], &sf->uc.uc_mcontext.arm_r6, err);
 314         __get_user_error(regs->regs[7], &sf->uc.uc_mcontext.arm_r7, err);
 315         __get_user_error(regs->regs[8], &sf->uc.uc_mcontext.arm_r8, err);
 316         __get_user_error(regs->regs[9], &sf->uc.uc_mcontext.arm_r9, err);
 317         __get_user_error(regs->regs[10], &sf->uc.uc_mcontext.arm_r10, err);
 318         __get_user_error(regs->regs[11], &sf->uc.uc_mcontext.arm_fp, err);
 319         __get_user_error(regs->regs[12], &sf->uc.uc_mcontext.arm_ip, err);
 320         __get_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
 321         __get_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
 322         __get_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
 323         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.arm_cpsr, err);
 324
 325         /*
 326          * Avoid compat_sys_sigreturn() restarting.
 327          */
 328         regs->syscallno = ~0UL;
 329
 330         err |= !valid_user_regs(&regs->user_regs);
 331
 332         aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace;
 333         if (err == 0)
 334                 err |= compat_restore_vfp_context(&aux->vfp);
 335
 336         return err;
 337 }
 338
 339 asmlinkage int compat_sys_sigreturn(struct pt_regs *regs)
 340 {
 341         struct compat_sigframe __user *frame;
 342
 343         /* Always make any pending restarted system calls return -EINTR */
 344         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 345
 346         /*
 347          * Since we stacked the signal on a 64-bit boundary,
 348          * then 'sp' should be word aligned here.  If it's
 349          * not, then the user is trying to mess with us.
 350          */
 351         if (regs->compat_sp & 7)
 352                 goto badframe;
 353
 354         frame = (struct compat_sigframe __user *)regs->compat_sp;
 355
 356         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 357                 goto badframe;
 358
 359         if (compat_restore_sigframe(regs, frame))
 360                 goto badframe;
 361
 362         return regs->regs[0];
 363
 364 badframe:
 365         if (show_unhandled_signals)
 366                 pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 367                                     current->comm, task_pid_nr(current), __func__,
 368                                     regs->pc, regs->sp);
 369         force_sig(SIGSEGV, current);
 370         return 0;
 371 }
 372
 373 asmlinkage int compat_sys_rt_sigreturn(struct pt_regs *regs)
 374 {
 375         struct compat_rt_sigframe __user *frame;
 376
 377         /* Always make any pending restarted system calls return -EINTR */
 378         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 379
 380         /*
 381          * Since we stacked the signal on a 64-bit boundary,
 382          * then 'sp' should be word aligned here.  If it's
 383          * not, then the user is trying to mess with us.
 384          */
 385         if (regs->compat_sp & 7)
 386                 goto badframe;
 387
 388         frame = (struct compat_rt_sigframe __user *)regs->compat_sp;
 389
 390         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 391                 goto badframe;
 392
 393         if (compat_restore_sigframe(regs, &frame->sig))
 394                 goto badframe;
 395
 396         if (compat_restore_altstack(&frame->sig.uc.uc_stack))
 397                 goto badframe;
 398
 399         return regs->regs[0];
 400
 401 badframe:
 402         if (show_unhandled_signals)
 403                 pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 404                                     current->comm, task_pid_nr(current), __func__,
 405                                     regs->pc, regs->sp);
 406         force_sig(SIGSEGV, current);
 407         return 0;
 408 }
 409
 410 static void __user *compat_get_sigframe(struct ksignal *ksig,
 411                                         struct pt_regs *regs,
 412                                         int framesize)
 413 {
 414         compat_ulong_t sp = sigsp(regs->compat_sp, ksig);
 415         void __user *frame;
 416
 417         /*
 418          * ATPCS B01 mandates 8-byte alignment
 419          */
 420         frame = compat_ptr((compat_uptr_t)((sp - framesize) & ~7));
 421
 422         /*
 423          * Check that we can actually write to the signal frame.
 424          */
 425         if (!access_ok(VERIFY_WRITE, frame, framesize))
 426                 frame = NULL;
 427
 428         return frame;
 429 }
 430
 431 static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 432                                 compat_ulong_t __user *rc, void __user *frame,
 433                                 int usig)
 434 {
 435         compat_ulong_t handler = ptr_to_compat(ka->sa.sa_handler);
 436         compat_ulong_t retcode;
 437         compat_ulong_t spsr = regs->pstate & ~PSR_f;
 438         int thumb;
 439
 440         /* Check if the handler is written for ARM or Thumb */
 441         thumb = handler & 1;
 442
 443         if (thumb)
 444                 spsr |= COMPAT_PSR_T_BIT;
 445         else
 446                 spsr &= ~COMPAT_PSR_T_BIT;
 447
 448         /* The IT state must be cleared for both ARM and Thumb-2 */
 449         spsr &= ~COMPAT_PSR_IT_MASK;
 450
 451         if (ka->sa.sa_flags & SA_RESTORER) {
 452                 retcode = ptr_to_compat(ka->sa.sa_restorer);
 453         } else {
 454                 /* Set up sigreturn pointer */
 455                 unsigned int idx = thumb << 1;
 456
 457                 if (ka->sa.sa_flags & SA_SIGINFO)
 458                         idx += 3;
 459
 460                 retcode = AARCH32_VECTORS_BASE +
 461                           AARCH32_KERN_SIGRET_CODE_OFFSET +
 462                           (idx << 2) + thumb;
 463         }
 464
 465         regs->regs[0]   = usig;
 466         regs->compat_sp = ptr_to_compat(frame);
 467         regs->compat_lr = retcode;
 468         regs->pc        = handler;
 469         regs->pstate    = spsr;
 470 }
 471
 472 static int compat_setup_sigframe(struct compat_sigframe __user *sf,
 473                                  struct pt_regs *regs, sigset_t *set)
 474 {
 475         struct compat_aux_sigframe __user *aux;
 476         int err = 0;
 477
 478         __put_user_error(regs->regs[0], &sf->uc.uc_mcontext.arm_r0, err);
 479         __put_user_error(regs->regs[1], &sf->uc.uc_mcontext.arm_r1, err);
 480         __put_user_error(regs->regs[2], &sf->uc.uc_mcontext.arm_r2, err);
 481         __put_user_error(regs->regs[3], &sf->uc.uc_mcontext.arm_r3, err);
 482         __put_user_error(regs->regs[4], &sf->uc.uc_mcontext.arm_r4, err);
 483         __put_user_error(regs->regs[5], &sf->uc.uc_mcontext.arm_r5, err);
 484         __put_user_error(regs->regs[6], &sf->uc.uc_mcontext.arm_r6, err);
 485         __put_user_error(regs->regs[7], &sf->uc.uc_mcontext.arm_r7, err);
 486         __put_user_error(regs->regs[8], &sf->uc.uc_mcontext.arm_r8, err);
 487         __put_user_error(regs->regs[9], &sf->uc.uc_mcontext.arm_r9, err);
 488         __put_user_error(regs->regs[10], &sf->uc.uc_mcontext.arm_r10, err);
 489         __put_user_error(regs->regs[11], &sf->uc.uc_mcontext.arm_fp, err);
 490         __put_user_error(regs->regs[12], &sf->uc.uc_mcontext.arm_ip, err);
 491         __put_user_error(regs->compat_sp, &sf->uc.uc_mcontext.arm_sp, err);
 492         __put_user_error(regs->compat_lr, &sf->uc.uc_mcontext.arm_lr, err);
 493         __put_user_error(regs->pc, &sf->uc.uc_mcontext.arm_pc, err);
 494         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.arm_cpsr, err);
 495
 496         __put_user_error((compat_ulong_t)0, &sf->uc.uc_mcontext.trap_no, err);
 497         /* set the compat FSR WnR */
 498         __put_user_error(!!(current->thread.fault_code & ESR_EL1_WRITE) <<
 499                          FSR_WRITE_SHIFT, &sf->uc.uc_mcontext.error_code, err);
 500         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 501         __put_user_error(set->sig[0], &sf->uc.uc_mcontext.oldmask, err);
 502
 503         err |= put_sigset_t(&sf->uc.uc_sigmask, set);
 504
 505         aux = (struct compat_aux_sigframe __user *) sf->uc.uc_regspace;
 506
 507         if (err == 0)
 508                 err |= compat_preserve_vfp_context(&aux->vfp);
 509         __put_user_error(0, &aux->end_magic, err);
 510
 511         return err;
 512 }
 513
 514 /*
 515  * 32-bit signal handling routines called from signal.c
 516  */
 517 int compat_setup_rt_frame(int usig, struct ksignal *ksig,
 518                           sigset_t *set, struct pt_regs *regs)
 519 {
 520         struct compat_rt_sigframe __user *frame;
 521         int err = 0;
 522
 523         frame = compat_get_sigframe(ksig, regs, sizeof(*frame));
 524
 525         if (!frame)
 526                 return 1;
 527
 528         err |= copy_siginfo_to_user32(&frame->info, &ksig->info);
 529
 530         __put_user_error(0, &frame->sig.uc.uc_flags, err);
 531         __put_user_error(0, &frame->sig.uc.uc_link, err);
 532
 533         err |= __compat_save_altstack(&frame->sig.uc.uc_stack, regs->compat_sp);
 534
 535         err |= compat_setup_sigframe(&frame->sig, regs, set);
 536
 537         if (err == 0) {
 538                 compat_setup_return(regs, &ksig->ka, frame->sig.retcode, frame, usig);
 539                 regs->regs[1] = (compat_ulong_t)(unsigned long)&frame->info;
 540                 regs->regs[2] = (compat_ulong_t)(unsigned long)&frame->sig.uc;
 541         }
 542
 543         return err;
 544 }
 545
 546 int compat_setup_frame(int usig, struct ksignal *ksig, sigset_t *set,
 547                        struct pt_regs *regs)
 548 {
 549         struct compat_sigframe __user *frame;
 550         int err = 0;
 551
 552         frame = compat_get_sigframe(ksig, regs, sizeof(*frame));
 553
 554         if (!frame)
 555                 return 1;
 556
 557         __put_user_error(0x5ac3c35a, &frame->uc.uc_flags, err);
 558
 559         err |= compat_setup_sigframe(frame, regs, set);
 560         if (err == 0)
 561                 compat_setup_return(regs, &ksig->ka, frame->retcode, frame, usig);
 562
 563         return err;
 564 }
 565
 566 void compat_setup_restart_syscall(struct pt_regs *regs)
 567 {
 568        regs->regs[7] = __NR_compat_restart_syscall;
 569 }