arch/x86/kernel/signal_32.c

   1 /*
   2  *  Copyright (C) 1991, 1992  Linus Torvalds
   3  *
   4  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   5  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   6  */
   7
   8 #include <linux/sched.h>
   9 #include <linux/mm.h>
  10 #include <linux/smp.h>
  11 #include <linux/kernel.h>
  12 #include <linux/signal.h>
  13 #include <linux/errno.h>
  14 #include <linux/wait.h>
  15 #include <linux/unistd.h>
  16 #include <linux/stddef.h>
  17 #include <linux/personality.h>
  18 #include <linux/suspend.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/elf.h>
  21 #include <linux/binfmts.h>
  22 #include <asm/processor.h>
  23 #include <asm/ucontext.h>
  24 #include <asm/uaccess.h>
  25 #include <asm/i387.h>
  26 #include <asm/vdso.h>
  27 #include "sigframe_32.h"
  28
  29 #define DEBUG_SIG 0
  30
  31 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  32
  33 /*
  34  * Atomically swap in the new signal mask, and wait for a signal.
  35  */
  36 asmlinkage int
  37 sys_sigsuspend(int history0, int history1, old_sigset_t mask)
  38 {
  39         mask &= _BLOCKABLE;
  40         spin_lock_irq(&current->sighand->siglock);
  41         current->saved_sigmask = current->blocked;
  42         siginitset(&current->blocked, mask);
  43         recalc_sigpending();
  44         spin_unlock_irq(&current->sighand->siglock);
  45
  46         current->state = TASK_INTERRUPTIBLE;
  47         schedule();
  48         set_thread_flag(TIF_RESTORE_SIGMASK);
  49         return -ERESTARTNOHAND;
  50 }
  51
  52 asmlinkage int
  53 sys_sigaction(int sig, const struct old_sigaction __user *act,
  54               struct old_sigaction __user *oact)
  55 {
  56         struct k_sigaction new_ka, old_ka;
  57         int ret;
  58
  59         if (act) {
  60                 old_sigset_t mask;
  61                 if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
  62                     __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
  63                     __get_user(new_ka.sa.sa_restorer, &act->sa_restorer))
  64                         return -EFAULT;
  65                 __get_user(new_ka.sa.sa_flags, &act->sa_flags);
  66                 __get_user(mask, &act->sa_mask);
  67                 siginitset(&new_ka.sa.sa_mask, mask);
  68         }
  69
  70         ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
  71
  72         if (!ret && oact) {
  73                 if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
  74                     __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
  75                     __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer))
  76                         return -EFAULT;
  77                 __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
  78                 __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask);
  79         }
  80
  81         return ret;
  82 }
  83
  84 asmlinkage int
  85 sys_sigaltstack(unsigned long bx)
  86 {
  87         /* This is needed to make gcc realize it doesn't own the "struct pt_regs" */
  88         struct pt_regs *regs = (struct pt_regs *)&bx;
  89         const stack_t __user *uss = (const stack_t __user *)bx;
  90         stack_t __user *uoss = (stack_t __user *)regs->cx;
  91
  92         return do_sigaltstack(uss, uoss, regs->sp);
  93 }
  94
  95
  96 /*
  97  * Do a signal return; undo the signal stack.
  98  */
  99
 100 static int
 101 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *peax)
 102 {
 103         unsigned int err = 0;
 104
 105         /* Always make any pending restarted system calls return -EINTR */
 106         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 107
 108 #define COPY(x)         err |= __get_user(regs->x, &sc->x)
 109
 110 #define COPY_SEG(seg)                                                   \
 111         { unsigned short tmp;                                           \
 112           err |= __get_user(tmp, &sc->seg);                             \
 113           regs->seg = tmp; }
 114
 115 #define COPY_SEG_STRICT(seg)                                            \
 116         { unsigned short tmp;                                           \
 117           err |= __get_user(tmp, &sc->seg);                             \
 118           regs->seg = tmp|3; }
 119
 120 #define GET_SEG(seg)                                                    \
 121         { unsigned short tmp;                                           \
 122           err |= __get_user(tmp, &sc->seg);                             \
 123           loadsegment(seg,tmp); }
 124
 125 #define FIX_EFLAGS      (X86_EFLAGS_AC | X86_EFLAGS_RF |                 \
 126                          X86_EFLAGS_OF | X86_EFLAGS_DF |                 \
 127                          X86_EFLAGS_TF | X86_EFLAGS_SF | X86_EFLAGS_ZF | \
 128                          X86_EFLAGS_AF | X86_EFLAGS_PF | X86_EFLAGS_CF)
 129
 130         GET_SEG(gs);
 131         COPY_SEG(fs);
 132         COPY_SEG(es);
 133         COPY_SEG(ds);
 134         COPY(di);
 135         COPY(si);
 136         COPY(bp);
 137         COPY(sp);
 138         COPY(bx);
 139         COPY(dx);
 140         COPY(cx);
 141         COPY(ip);
 142         COPY_SEG_STRICT(cs);
 143         COPY_SEG_STRICT(ss);
 144
 145         {
 146                 unsigned int tmpflags;
 147                 err |= __get_user(tmpflags, &sc->flags);
 148                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 149                 regs->orig_ax = -1;             /* disable syscall checks */
 150         }
 151
 152         {
 153                 struct _fpstate __user * buf;
 154                 err |= __get_user(buf, &sc->fpstate);
 155                 if (buf) {
 156                         if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
 157                                 goto badframe;
 158                         err |= restore_i387(buf);
 159                 } else {
 160                         struct task_struct *me = current;
 161                         if (used_math()) {
 162                                 clear_fpu(me);
 163                                 clear_used_math();
 164                         }
 165                 }
 166         }
 167
 168         err |= __get_user(*peax, &sc->ax);
 169         return err;
 170
 171 badframe:
 172         return 1;
 173 }
 174
 175 asmlinkage int sys_sigreturn(unsigned long __unused)
 176 {
 177         struct pt_regs *regs = (struct pt_regs *) &__unused;
 178         struct sigframe __user *frame = (struct sigframe __user *)(regs->sp - 8);
 179         sigset_t set;
 180         int ax;
 181
 182         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 183                 goto badframe;
 184         if (__get_user(set.sig[0], &frame->sc.oldmask)
 185             || (_NSIG_WORDS > 1
 186                 && __copy_from_user(&set.sig[1], &frame->extramask,
 187                                     sizeof(frame->extramask))))
 188                 goto badframe;
 189
 190         sigdelsetmask(&set, ~_BLOCKABLE);
 191         spin_lock_irq(&current->sighand->siglock);
 192         current->blocked = set;
 193         recalc_sigpending();
 194         spin_unlock_irq(&current->sighand->siglock);
 195
 196         if (restore_sigcontext(regs, &frame->sc, &ax))
 197                 goto badframe;
 198         return ax;
 199
 200 badframe:
 201         if (show_unhandled_signals && printk_ratelimit()) {
 202                 printk("%s%s[%d] bad frame in sigreturn frame:%p ip:%lx"
 203                        " sp:%lx oeax:%lx",
 204                     task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 205                     current->comm, task_pid_nr(current), frame, regs->ip,
 206                     regs->sp, regs->orig_ax);
 207                 print_vma_addr(" in ", regs->ip);
 208                 printk("\n");
 209         }
 210
 211         force_sig(SIGSEGV, current);
 212         return 0;
 213 }
 214
 215 asmlinkage int sys_rt_sigreturn(unsigned long __unused)
 216 {
 217         struct pt_regs *regs = (struct pt_regs *) &__unused;
 218         struct rt_sigframe __user *frame = (struct rt_sigframe __user *)(regs->sp - 4);
 219         sigset_t set;
 220         int ax;
 221
 222         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 223                 goto badframe;
 224         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 225                 goto badframe;
 226
 227         sigdelsetmask(&set, ~_BLOCKABLE);
 228         spin_lock_irq(&current->sighand->siglock);
 229         current->blocked = set;
 230         recalc_sigpending();
 231         spin_unlock_irq(&current->sighand->siglock);
 232
 233         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
 234                 goto badframe;
 235
 236         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->sp) == -EFAULT)
 237                 goto badframe;
 238
 239         return ax;
 240
 241 badframe:
 242         force_sig(SIGSEGV, current);
 243         return 0;
 244 }
 245
 246 /*
 247  * Set up a signal frame.
 248  */
 249
 250 static int
 251 setup_sigcontext(struct sigcontext __user *sc, struct _fpstate __user *fpstate,
 252                  struct pt_regs *regs, unsigned long mask)
 253 {
 254         int tmp, err = 0;
 255
 256         err |= __put_user(regs->fs, (unsigned int __user *)&sc->fs);
 257         savesegment(gs, tmp);
 258         err |= __put_user(tmp, (unsigned int __user *)&sc->gs);
 259
 260         err |= __put_user(regs->es, (unsigned int __user *)&sc->es);
 261         err |= __put_user(regs->ds, (unsigned int __user *)&sc->ds);
 262         err |= __put_user(regs->di, &sc->di);
 263         err |= __put_user(regs->si, &sc->si);
 264         err |= __put_user(regs->bp, &sc->bp);
 265         err |= __put_user(regs->sp, &sc->sp);
 266         err |= __put_user(regs->bx, &sc->bx);
 267         err |= __put_user(regs->dx, &sc->dx);
 268         err |= __put_user(regs->cx, &sc->cx);
 269         err |= __put_user(regs->ax, &sc->ax);
 270         err |= __put_user(current->thread.trap_no, &sc->trapno);
 271         err |= __put_user(current->thread.error_code, &sc->err);
 272         err |= __put_user(regs->ip, &sc->ip);
 273         err |= __put_user(regs->cs, (unsigned int __user *)&sc->cs);
 274         err |= __put_user(regs->flags, &sc->flags);
 275         err |= __put_user(regs->sp, &sc->sp_at_signal);
 276         err |= __put_user(regs->ss, (unsigned int __user *)&sc->ss);
 277
 278         tmp = save_i387(fpstate);
 279         if (tmp < 0)
 280           err = 1;
 281         else
 282           err |= __put_user(tmp ? fpstate : NULL, &sc->fpstate);
 283
 284         /* non-iBCS2 extensions.. */
 285         err |= __put_user(mask, &sc->oldmask);
 286         err |= __put_user(current->thread.cr2, &sc->cr2);
 287
 288         return err;
 289 }
 290
 291 /*
 292  * Determine which stack to use..
 293  */
 294 static inline void __user *
 295 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
 296 {
 297         unsigned long sp;
 298
 299         /* Default to using normal stack */
 300         sp = regs->sp;
 301
 302         /*
 303          * If we are on the alternate signal stack and would overflow it, don't.
 304          * Return an always-bogus address instead so we will die with SIGSEGV.
 305          */
 306         if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
 307                 return (void __user *) -1L;
 308
 309         /* This is the X/Open sanctioned signal stack switching.  */
 310         if (ka->sa.sa_flags & SA_ONSTACK) {
 311                 if (sas_ss_flags(sp) == 0)
 312                         sp = current->sas_ss_sp + current->sas_ss_size;
 313         }
 314
 315         /* This is the legacy signal stack switching. */
 316         else if ((regs->ss & 0xffff) != __USER_DS &&
 317                  !(ka->sa.sa_flags & SA_RESTORER) &&
 318                  ka->sa.sa_restorer) {
 319                 sp = (unsigned long) ka->sa.sa_restorer;
 320         }
 321
 322         sp -= frame_size;
 323         /* Align the stack pointer according to the i386 ABI,
 324          * i.e. so that on function entry ((sp + 4) & 15) == 0. */
 325         sp = ((sp + 4) & -16ul) - 4;
 326         return (void __user *) sp;
 327 }
 328
 329 /* These symbols are defined with the addresses in the vsyscall page.
 330    See vsyscall-sigreturn.S.  */
 331 extern void __user __kernel_sigreturn;
 332 extern void __user __kernel_rt_sigreturn;
 333
 334 static int setup_frame(int sig, struct k_sigaction *ka,
 335                        sigset_t *set, struct pt_regs * regs)
 336 {
 337         void __user *restorer;
 338         struct sigframe __user *frame;
 339         int err = 0;
 340         int usig;
 341
 342         frame = get_sigframe(ka, regs, sizeof(*frame));
 343
 344         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 345                 goto give_sigsegv;
 346
 347         usig = current_thread_info()->exec_domain
 348                 && current_thread_info()->exec_domain->signal_invmap
 349                 && sig < 32
 350                 ? current_thread_info()->exec_domain->signal_invmap[sig]
 351                 : sig;
 352
 353         err = __put_user(usig, &frame->sig);
 354         if (err)
 355                 goto give_sigsegv;
 356
 357         err = setup_sigcontext(&frame->sc, &frame->fpstate, regs, set->sig[0]);
 358         if (err)
 359                 goto give_sigsegv;
 360
 361         if (_NSIG_WORDS > 1) {
 362                 err = __copy_to_user(&frame->extramask, &set->sig[1],
 363                                       sizeof(frame->extramask));
 364                 if (err)
 365                         goto give_sigsegv;
 366         }
 367
 368         if (current->binfmt->hasvdso)
 369                 restorer = VDSO32_SYMBOL(current->mm->context.vdso, sigreturn);
 370         else
 371                 restorer = &frame->retcode;
 372         if (ka->sa.sa_flags & SA_RESTORER)
 373                 restorer = ka->sa.sa_restorer;
 374
 375         /* Set up to return from userspace.  */
 376         err |= __put_user(restorer, &frame->pretcode);
 377
 378         /*
 379          * This is popl %eax ; movl $,%eax ; int $0x80
 380          *
 381          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 382          * reasons and because gdb uses it as a signature to notice
 383          * signal handler stack frames.
 384          */
 385         err |= __put_user(0xb858, (short __user *)(frame->retcode+0));
 386         err |= __put_user(__NR_sigreturn, (int __user *)(frame->retcode+2));
 387         err |= __put_user(0x80cd, (short __user *)(frame->retcode+6));
 388
 389         if (err)
 390                 goto give_sigsegv;
 391
 392         /* Set up registers for signal handler */
 393         regs->sp = (unsigned long) frame;
 394         regs->ip = (unsigned long) ka->sa.sa_handler;
 395         regs->ax = (unsigned long) sig;
 396         regs->dx = (unsigned long) 0;
 397         regs->cx = (unsigned long) 0;
 398
 399         regs->ds = __USER_DS;
 400         regs->es = __USER_DS;
 401         regs->ss = __USER_DS;
 402         regs->cs = __USER_CS;
 403
 404         /*
 405          * Clear TF when entering the signal handler, but
 406          * notify any tracer that was single-stepping it.
 407          * The tracer may want to single-step inside the
 408          * handler too.
 409          */
 410         regs->flags &= ~TF_MASK;
 411         if (test_thread_flag(TIF_SINGLESTEP))
 412                 ptrace_notify(SIGTRAP);
 413
 414 #if DEBUG_SIG
 415         printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
 416                 current->comm, current->pid, frame, regs->ip, frame->pretcode);
 417 #endif
 418
 419         return 0;
 420
 421 give_sigsegv:
 422         force_sigsegv(sig, current);
 423         return -EFAULT;
 424 }
 425
 426 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 427                            sigset_t *set, struct pt_regs * regs)
 428 {
 429         void __user *restorer;
 430         struct rt_sigframe __user *frame;
 431         int err = 0;
 432         int usig;
 433
 434         frame = get_sigframe(ka, regs, sizeof(*frame));
 435
 436         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 437                 goto give_sigsegv;
 438
 439         usig = current_thread_info()->exec_domain
 440                 && current_thread_info()->exec_domain->signal_invmap
 441                 && sig < 32
 442                 ? current_thread_info()->exec_domain->signal_invmap[sig]
 443                 : sig;
 444
 445         err |= __put_user(usig, &frame->sig);
 446         err |= __put_user(&frame->info, &frame->pinfo);
 447         err |= __put_user(&frame->uc, &frame->puc);
 448         err |= copy_siginfo_to_user(&frame->info, info);
 449         if (err)
 450                 goto give_sigsegv;
 451
 452         /* Create the ucontext.  */
 453         err |= __put_user(0, &frame->uc.uc_flags);
 454         err |= __put_user(0, &frame->uc.uc_link);
 455         err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
 456         err |= __put_user(sas_ss_flags(regs->sp),
 457                           &frame->uc.uc_stack.ss_flags);
 458         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
 459         err |= setup_sigcontext(&frame->uc.uc_mcontext, &frame->fpstate,
 460                                 regs, set->sig[0]);
 461         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 462         if (err)
 463                 goto give_sigsegv;
 464
 465         /* Set up to return from userspace.  */
 466         restorer = VDSO32_SYMBOL(current->mm->context.vdso, rt_sigreturn);
 467         if (ka->sa.sa_flags & SA_RESTORER)
 468                 restorer = ka->sa.sa_restorer;
 469         err |= __put_user(restorer, &frame->pretcode);
 470
 471         /*
 472          * This is movl $,%ax ; int $0x80
 473          *
 474          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 475          * reasons and because gdb uses it as a signature to notice
 476          * signal handler stack frames.
 477          */
 478         err |= __put_user(0xb8, (char __user *)(frame->retcode+0));
 479         err |= __put_user(__NR_rt_sigreturn, (int __user *)(frame->retcode+1));
 480         err |= __put_user(0x80cd, (short __user *)(frame->retcode+5));
 481
 482         if (err)
 483                 goto give_sigsegv;
 484
 485         /* Set up registers for signal handler */
 486         regs->sp = (unsigned long) frame;
 487         regs->ip = (unsigned long) ka->sa.sa_handler;
 488         regs->ax = (unsigned long) usig;
 489         regs->dx = (unsigned long) &frame->info;
 490         regs->cx = (unsigned long) &frame->uc;
 491
 492         regs->ds = __USER_DS;
 493         regs->es = __USER_DS;
 494         regs->ss = __USER_DS;
 495         regs->cs = __USER_CS;
 496
 497         /*
 498          * Clear TF when entering the signal handler, but
 499          * notify any tracer that was single-stepping it.
 500          * The tracer may want to single-step inside the
 501          * handler too.
 502          */
 503         regs->flags &= ~TF_MASK;
 504         if (test_thread_flag(TIF_SINGLESTEP))
 505                 ptrace_notify(SIGTRAP);
 506
 507 #if DEBUG_SIG
 508         printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
 509                 current->comm, current->pid, frame, regs->ip, frame->pretcode);
 510 #endif
 511
 512         return 0;
 513
 514 give_sigsegv:
 515         force_sigsegv(sig, current);
 516         return -EFAULT;
 517 }
 518
 519 /*
 520  * OK, we're invoking a handler
 521  */
 522
 523 static int
 524 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 525               sigset_t *oldset, struct pt_regs * regs)
 526 {
 527         int ret;
 528
 529         /* Are we from a system call? */
 530         if (regs->orig_ax >= 0) {
 531                 /* If so, check system call restarting.. */
 532                 switch (regs->ax) {
 533                         case -ERESTART_RESTARTBLOCK:
 534                         case -ERESTARTNOHAND:
 535                                 regs->ax = -EINTR;
 536                                 break;
 537
 538                         case -ERESTARTSYS:
 539                                 if (!(ka->sa.sa_flags & SA_RESTART)) {
 540                                         regs->ax = -EINTR;
 541                                         break;
 542                                 }
 543                         /* fallthrough */
 544                         case -ERESTARTNOINTR:
 545                                 regs->ax = regs->orig_ax;
 546                                 regs->ip -= 2;
 547                 }
 548         }
 549
 550         /*
 551          * If TF is set due to a debugger (TIF_FORCED_TF), clear the TF
 552          * flag so that register information in the sigcontext is correct.
 553          */
 554         if (unlikely(regs->flags & X86_EFLAGS_TF) &&
 555             likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 556                 regs->flags &= ~X86_EFLAGS_TF;
 557
 558         /* Set up the stack frame */
 559         if (ka->sa.sa_flags & SA_SIGINFO)
 560                 ret = setup_rt_frame(sig, ka, info, oldset, regs);
 561         else
 562                 ret = setup_frame(sig, ka, oldset, regs);
 563
 564         if (ret == 0) {
 565                 spin_lock_irq(&current->sighand->siglock);
 566                 sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 567                 if (!(ka->sa.sa_flags & SA_NODEFER))
 568                         sigaddset(&current->blocked,sig);
 569                 recalc_sigpending();
 570                 spin_unlock_irq(&current->sighand->siglock);
 571         }
 572
 573         return ret;
 574 }
 575
 576 /*
 577  * Note that 'init' is a special process: it doesn't get signals it doesn't
 578  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 579  * mistake.
 580  */
 581 static void do_signal(struct pt_regs *regs)
 582 {
 583         siginfo_t info;
 584         int signr;
 585         struct k_sigaction ka;
 586         sigset_t *oldset;
 587
 588         /*
 589          * We want the common case to go fast, which
 590          * is why we may in certain cases get here from
 591          * kernel mode. Just return without doing anything
 592          * if so.  vm86 regs switched out by assembly code
 593          * before reaching here, so testing against kernel
 594          * CS suffices.
 595          */
 596         if (!user_mode(regs))
 597                 return;
 598
 599         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 600                 oldset = &current->saved_sigmask;
 601         else
 602                 oldset = &current->blocked;
 603
 604         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 605         if (signr > 0) {
 606                 /* Re-enable any watchpoints before delivering the
 607                  * signal to user space. The processor register will
 608                  * have been cleared if the watchpoint triggered
 609                  * inside the kernel.
 610                  */
 611                 if (unlikely(current->thread.debugreg7))
 612                         set_debugreg(current->thread.debugreg7, 7);
 613
 614                 /* Whee!  Actually deliver the signal.  */
 615                 if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 616                         /* a signal was successfully delivered; the saved
 617                          * sigmask will have been stored in the signal frame,
 618                          * and will be restored by sigreturn, so we can simply
 619                          * clear the TIF_RESTORE_SIGMASK flag */
 620                         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 621                                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 622                 }
 623
 624                 return;
 625         }
 626
 627         /* Did we come from a system call? */
 628         if (regs->orig_ax >= 0) {
 629                 /* Restart the system call - no handlers present */
 630                 switch (regs->ax) {
 631                 case -ERESTARTNOHAND:
 632                 case -ERESTARTSYS:
 633                 case -ERESTARTNOINTR:
 634                         regs->ax = regs->orig_ax;
 635                         regs->ip -= 2;
 636                         break;
 637
 638                 case -ERESTART_RESTARTBLOCK:
 639                         regs->ax = __NR_restart_syscall;
 640                         regs->ip -= 2;
 641                         break;
 642                 }
 643         }
 644
 645         /* if there's no signal to deliver, we just put the saved sigmask
 646          * back */
 647         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 648                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 649                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 650         }
 651 }
 652
 653 /*
 654  * notification of userspace execution resumption
 655  * - triggered by the TIF_WORK_MASK flags
 656  */
 657 __attribute__((regparm(3)))
 658 void do_notify_resume(struct pt_regs *regs, void *_unused,
 659                       __u32 thread_info_flags)
 660 {
 661         /* Pending single-step? */
 662         if (thread_info_flags & _TIF_SINGLESTEP) {
 663                 regs->flags |= TF_MASK;
 664                 clear_thread_flag(TIF_SINGLESTEP);
 665         }
 666
 667         /* deal with pending signal delivery */
 668         if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
 669                 do_signal(regs);
 670
 671         if (thread_info_flags & _TIF_HRTICK_RESCHED)
 672                 hrtick_resched();
 673
 674         clear_thread_flag(TIF_IRET);
 675 }