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   1 /*  linux/arch/sparc/kernel/signal.c
   2  *
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *  Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
   5  *  Copyright (C) 1996 Miguel de Icaza (miguel@nuclecu.unam.mx)
   6  *  Copyright (C) 1997 Eddie C. Dost   (ecd@skynet.be)
   7  */
   8
   9 #include <linux/sched.h>
  10 #include <linux/kernel.h>
  11 #include <linux/signal.h>
  12 #include <linux/errno.h>
  13 #include <linux/wait.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/unistd.h>
  16 #include <linux/mm.h>
  17 #include <linux/tty.h>
  18 #include <linux/smp.h>
  19 #include <linux/binfmts.h>      /* do_coredum */
  20 #include <linux/bitops.h>
  21
  22 #include <asm/uaccess.h>
  23 #include <asm/ptrace.h>
  24 #include <asm/pgalloc.h>
  25 #include <asm/pgtable.h>
  26 #include <asm/cacheflush.h>     /* flush_sig_insns */
  27
  28 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  29
  30 extern void fpsave(unsigned long *fpregs, unsigned long *fsr,
  31                    void *fpqueue, unsigned long *fpqdepth);
  32 extern void fpload(unsigned long *fpregs, unsigned long *fsr);
  33
  34 struct signal_frame {
  35         struct sparc_stackf     ss;
  36         __siginfo_t             info;
  37         __siginfo_fpu_t __user  *fpu_save;
  38         unsigned long           insns[2] __attribute__ ((aligned (8)));
  39         unsigned int            extramask[_NSIG_WORDS - 1];
  40         unsigned int            extra_size; /* Should be 0 */
  41         __siginfo_fpu_t         fpu_state;
  42 };
  43
  44 struct rt_signal_frame {
  45         struct sparc_stackf     ss;
  46         siginfo_t               info;
  47         struct pt_regs          regs;
  48         sigset_t                mask;
  49         __siginfo_fpu_t __user  *fpu_save;
  50         unsigned int            insns[2];
  51         stack_t                 stack;
  52         unsigned int            extra_size; /* Should be 0 */
  53         __siginfo_fpu_t         fpu_state;
  54 };
  55
  56 /* Align macros */
  57 #define SF_ALIGNEDSZ  (((sizeof(struct signal_frame) + 7) & (~7)))
  58 #define RT_ALIGNEDSZ  (((sizeof(struct rt_signal_frame) + 7) & (~7)))
  59
  60 static int _sigpause_common(old_sigset_t set)
  61 {
  62         set &= _BLOCKABLE;
  63         spin_lock_irq(&current->sighand->siglock);
  64         current->saved_sigmask = current->blocked;
  65         siginitset(&current->blocked, set);
  66         recalc_sigpending();
  67         spin_unlock_irq(&current->sighand->siglock);
  68
  69         current->state = TASK_INTERRUPTIBLE;
  70         schedule();
  71         set_thread_flag(TIF_RESTORE_SIGMASK);
  72
  73         return -ERESTARTNOHAND;
  74 }
  75
  76 asmlinkage int sys_sigsuspend(old_sigset_t set)
  77 {
  78         return _sigpause_common(set);
  79 }
  80
  81 static inline int
  82 restore_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
  83 {
  84         int err;
  85 #ifdef CONFIG_SMP
  86         if (test_tsk_thread_flag(current, TIF_USEDFPU))
  87                 regs->psr &= ~PSR_EF;
  88 #else
  89         if (current == last_task_used_math) {
  90                 last_task_used_math = NULL;
  91                 regs->psr &= ~PSR_EF;
  92         }
  93 #endif
  94         set_used_math();
  95         clear_tsk_thread_flag(current, TIF_USEDFPU);
  96
  97         if (!access_ok(VERIFY_READ, fpu, sizeof(*fpu)))
  98                 return -EFAULT;
  99
 100         err = __copy_from_user(&current->thread.float_regs[0], &fpu->si_float_regs[0],
 101                                (sizeof(unsigned long) * 32));
 102         err |= __get_user(current->thread.fsr, &fpu->si_fsr);
 103         err |= __get_user(current->thread.fpqdepth, &fpu->si_fpqdepth);
 104         if (current->thread.fpqdepth != 0)
 105                 err |= __copy_from_user(&current->thread.fpqueue[0],
 106                                         &fpu->si_fpqueue[0],
 107                                         ((sizeof(unsigned long) +
 108                                         (sizeof(unsigned long *)))*16));
 109         return err;
 110 }
 111
 112 asmlinkage void do_sigreturn(struct pt_regs *regs)
 113 {
 114         struct signal_frame __user *sf;
 115         unsigned long up_psr, pc, npc;
 116         sigset_t set;
 117         __siginfo_fpu_t __user *fpu_save;
 118         int err;
 119
 120         /* Always make any pending restarted system calls return -EINTR */
 121         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 122
 123         synchronize_user_stack();
 124
 125         sf = (struct signal_frame __user *) regs->u_regs[UREG_FP];
 126
 127         /* 1. Make sure we are not getting garbage from the user */
 128         if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
 129                 goto segv_and_exit;
 130
 131         if (((unsigned long) sf) & 3)
 132                 goto segv_and_exit;
 133
 134         err = __get_user(pc,  &sf->info.si_regs.pc);
 135         err |= __get_user(npc, &sf->info.si_regs.npc);
 136
 137         if ((pc | npc) & 3)
 138                 goto segv_and_exit;
 139
 140         /* 2. Restore the state */
 141         up_psr = regs->psr;
 142         err |= __copy_from_user(regs, &sf->info.si_regs, sizeof(struct pt_regs));
 143
 144         /* User can only change condition codes and FPU enabling in %psr. */
 145         regs->psr = (up_psr & ~(PSR_ICC | PSR_EF))
 146                   | (regs->psr & (PSR_ICC | PSR_EF));
 147
 148         /* Prevent syscall restart.  */
 149         pt_regs_clear_syscall(regs);
 150
 151         err |= __get_user(fpu_save, &sf->fpu_save);
 152
 153         if (fpu_save)
 154                 err |= restore_fpu_state(regs, fpu_save);
 155
 156         /* This is pretty much atomic, no amount locking would prevent
 157          * the races which exist anyways.
 158          */
 159         err |= __get_user(set.sig[0], &sf->info.si_mask);
 160         err |= __copy_from_user(&set.sig[1], &sf->extramask,
 161                                 (_NSIG_WORDS-1) * sizeof(unsigned int));
 162
 163         if (err)
 164                 goto segv_and_exit;
 165
 166         sigdelsetmask(&set, ~_BLOCKABLE);
 167         spin_lock_irq(&current->sighand->siglock);
 168         current->blocked = set;
 169         recalc_sigpending();
 170         spin_unlock_irq(&current->sighand->siglock);
 171         return;
 172
 173 segv_and_exit:
 174         force_sig(SIGSEGV, current);
 175 }
 176
 177 asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
 178 {
 179         struct rt_signal_frame __user *sf;
 180         unsigned int psr, pc, npc;
 181         __siginfo_fpu_t __user *fpu_save;
 182         mm_segment_t old_fs;
 183         sigset_t set;
 184         stack_t st;
 185         int err;
 186
 187         synchronize_user_stack();
 188         sf = (struct rt_signal_frame __user *) regs->u_regs[UREG_FP];
 189         if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
 190             (((unsigned long) sf) & 0x03))
 191                 goto segv;
 192
 193         err = __get_user(pc, &sf->regs.pc);
 194         err |= __get_user(npc, &sf->regs.npc);
 195         err |= ((pc | npc) & 0x03);
 196
 197         err |= __get_user(regs->y, &sf->regs.y);
 198         err |= __get_user(psr, &sf->regs.psr);
 199
 200         err |= __copy_from_user(&regs->u_regs[UREG_G1],
 201                                 &sf->regs.u_regs[UREG_G1], 15 * sizeof(u32));
 202
 203         regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC);
 204
 205         /* Prevent syscall restart.  */
 206         pt_regs_clear_syscall(regs);
 207
 208         err |= __get_user(fpu_save, &sf->fpu_save);
 209
 210         if (fpu_save)
 211                 err |= restore_fpu_state(regs, fpu_save);
 212         err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
 213
 214         err |= __copy_from_user(&st, &sf->stack, sizeof(stack_t));
 215
 216         if (err)
 217                 goto segv;
 218
 219         regs->pc = pc;
 220         regs->npc = npc;
 221
 222         /* It is more difficult to avoid calling this function than to
 223          * call it and ignore errors.
 224          */
 225         old_fs = get_fs();
 226         set_fs(KERNEL_DS);
 227         do_sigaltstack((const stack_t __user *) &st, NULL, (unsigned long)sf);
 228         set_fs(old_fs);
 229
 230         sigdelsetmask(&set, ~_BLOCKABLE);
 231         spin_lock_irq(&current->sighand->siglock);
 232         current->blocked = set;
 233         recalc_sigpending();
 234         spin_unlock_irq(&current->sighand->siglock);
 235         return;
 236 segv:
 237         force_sig(SIGSEGV, current);
 238 }
 239
 240 /* Checks if the fp is valid */
 241 static inline int invalid_frame_pointer(void __user *fp, int fplen)
 242 {
 243         if ((((unsigned long) fp) & 7) ||
 244             !__access_ok((unsigned long)fp, fplen) ||
 245             ((sparc_cpu_model == sun4 || sparc_cpu_model == sun4c) &&
 246              ((unsigned long) fp < 0xe0000000 && (unsigned long) fp >= 0x20000000)))
 247                 return 1;
 248
 249         return 0;
 250 }
 251
 252 static inline void __user *get_sigframe(struct sigaction *sa, struct pt_regs *regs, unsigned long framesize)
 253 {
 254         unsigned long sp = regs->u_regs[UREG_FP];
 255
 256         /*
 257          * If we are on the alternate signal stack and would overflow it, don't.
 258          * Return an always-bogus address instead so we will die with SIGSEGV.
 259          */
 260         if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
 261                 return (void __user *) -1L;
 262
 263         /* This is the X/Open sanctioned signal stack switching.  */
 264         if (sa->sa_flags & SA_ONSTACK) {
 265                 if (sas_ss_flags(sp) == 0)
 266                         sp = current->sas_ss_sp + current->sas_ss_size;
 267         }
 268
 269         /* Always align the stack frame.  This handles two cases.  First,
 270          * sigaltstack need not be mindful of platform specific stack
 271          * alignment.  Second, if we took this signal because the stack
 272          * is not aligned properly, we'd like to take the signal cleanly
 273          * and report that.
 274          */
 275         sp &= ~7UL;
 276
 277         return (void __user *)(sp - framesize);
 278 }
 279
 280 static inline int
 281 save_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
 282 {
 283         int err = 0;
 284 #ifdef CONFIG_SMP
 285         if (test_tsk_thread_flag(current, TIF_USEDFPU)) {
 286                 put_psr(get_psr() | PSR_EF);
 287                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
 288                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
 289                 regs->psr &= ~(PSR_EF);
 290                 clear_tsk_thread_flag(current, TIF_USEDFPU);
 291         }
 292 #else
 293         if (current == last_task_used_math) {
 294                 put_psr(get_psr() | PSR_EF);
 295                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
 296                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
 297                 last_task_used_math = NULL;
 298                 regs->psr &= ~(PSR_EF);
 299         }
 300 #endif
 301         err |= __copy_to_user(&fpu->si_float_regs[0],
 302                               &current->thread.float_regs[0],
 303                               (sizeof(unsigned long) * 32));
 304         err |= __put_user(current->thread.fsr, &fpu->si_fsr);
 305         err |= __put_user(current->thread.fpqdepth, &fpu->si_fpqdepth);
 306         if (current->thread.fpqdepth != 0)
 307                 err |= __copy_to_user(&fpu->si_fpqueue[0],
 308                                       &current->thread.fpqueue[0],
 309                                       ((sizeof(unsigned long) +
 310                                       (sizeof(unsigned long *)))*16));
 311         clear_used_math();
 312         return err;
 313 }
 314
 315 static void setup_frame(struct k_sigaction *ka, struct pt_regs *regs,
 316                         int signo, sigset_t *oldset)
 317 {
 318         struct signal_frame __user *sf;
 319         int sigframe_size, err;
 320
 321         /* 1. Make sure everything is clean */
 322         synchronize_user_stack();
 323
 324         sigframe_size = SF_ALIGNEDSZ;
 325         if (!used_math())
 326                 sigframe_size -= sizeof(__siginfo_fpu_t);
 327
 328         sf = (struct signal_frame __user *)
 329                 get_sigframe(&ka->sa, regs, sigframe_size);
 330
 331         if (invalid_frame_pointer(sf, sigframe_size))
 332                 goto sigill_and_return;
 333
 334         if (current_thread_info()->w_saved != 0)
 335                 goto sigill_and_return;
 336
 337         /* 2. Save the current process state */
 338         err = __copy_to_user(&sf->info.si_regs, regs, sizeof(struct pt_regs));
 339
 340         err |= __put_user(0, &sf->extra_size);
 341
 342         if (used_math()) {
 343                 err |= save_fpu_state(regs, &sf->fpu_state);
 344                 err |= __put_user(&sf->fpu_state, &sf->fpu_save);
 345         } else {
 346                 err |= __put_user(0, &sf->fpu_save);
 347         }
 348
 349         err |= __put_user(oldset->sig[0], &sf->info.si_mask);
 350         err |= __copy_to_user(sf->extramask, &oldset->sig[1],
 351                               (_NSIG_WORDS - 1) * sizeof(unsigned int));
 352         err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
 353                               sizeof(struct reg_window));
 354         if (err)
 355                 goto sigsegv;
 356
 357         /* 3. signal handler back-trampoline and parameters */
 358         regs->u_regs[UREG_FP] = (unsigned long) sf;
 359         regs->u_regs[UREG_I0] = signo;
 360         regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
 361         regs->u_regs[UREG_I2] = (unsigned long) &sf->info;
 362
 363         /* 4. signal handler */
 364         regs->pc = (unsigned long) ka->sa.sa_handler;
 365         regs->npc = (regs->pc + 4);
 366
 367         /* 5. return to kernel instructions */
 368         if (ka->ka_restorer)
 369                 regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
 370         else {
 371                 regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
 372
 373                 /* mov __NR_sigreturn, %g1 */
 374                 err |= __put_user(0x821020d8, &sf->insns[0]);
 375
 376                 /* t 0x10 */
 377                 err |= __put_user(0x91d02010, &sf->insns[1]);
 378                 if (err)
 379                         goto sigsegv;
 380
 381                 /* Flush instruction space. */
 382                 flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
 383         }
 384         return;
 385
 386 sigill_and_return:
 387         do_exit(SIGILL);
 388 sigsegv:
 389         force_sigsegv(signo, current);
 390 }
 391
 392 static void setup_rt_frame(struct k_sigaction *ka, struct pt_regs *regs,
 393                            int signo, sigset_t *oldset, siginfo_t *info)
 394 {
 395         struct rt_signal_frame __user *sf;
 396         int sigframe_size;
 397         unsigned int psr;
 398         int err;
 399
 400         synchronize_user_stack();
 401         sigframe_size = RT_ALIGNEDSZ;
 402         if (!used_math())
 403                 sigframe_size -= sizeof(__siginfo_fpu_t);
 404         sf = (struct rt_signal_frame __user *)
 405                 get_sigframe(&ka->sa, regs, sigframe_size);
 406         if (invalid_frame_pointer(sf, sigframe_size))
 407                 goto sigill;
 408         if (current_thread_info()->w_saved != 0)
 409                 goto sigill;
 410
 411         err  = __put_user(regs->pc, &sf->regs.pc);
 412         err |= __put_user(regs->npc, &sf->regs.npc);
 413         err |= __put_user(regs->y, &sf->regs.y);
 414         psr = regs->psr;
 415         if (used_math())
 416                 psr |= PSR_EF;
 417         err |= __put_user(psr, &sf->regs.psr);
 418         err |= __copy_to_user(&sf->regs.u_regs, regs->u_regs, sizeof(regs->u_regs));
 419         err |= __put_user(0, &sf->extra_size);
 420
 421         if (psr & PSR_EF) {
 422                 err |= save_fpu_state(regs, &sf->fpu_state);
 423                 err |= __put_user(&sf->fpu_state, &sf->fpu_save);
 424         } else {
 425                 err |= __put_user(0, &sf->fpu_save);
 426         }
 427         err |= __copy_to_user(&sf->mask, &oldset->sig[0], sizeof(sigset_t));
 428
 429         /* Setup sigaltstack */
 430         err |= __put_user(current->sas_ss_sp, &sf->stack.ss_sp);
 431         err |= __put_user(sas_ss_flags(regs->u_regs[UREG_FP]), &sf->stack.ss_flags);
 432         err |= __put_user(current->sas_ss_size, &sf->stack.ss_size);
 433
 434         err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
 435                               sizeof(struct reg_window));
 436
 437         err |= copy_siginfo_to_user(&sf->info, info);
 438
 439         if (err)
 440                 goto sigsegv;
 441
 442         regs->u_regs[UREG_FP] = (unsigned long) sf;
 443         regs->u_regs[UREG_I0] = signo;
 444         regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
 445         regs->u_regs[UREG_I2] = (unsigned long) &sf->regs;
 446
 447         regs->pc = (unsigned long) ka->sa.sa_handler;
 448         regs->npc = (regs->pc + 4);
 449
 450         if (ka->ka_restorer)
 451                 regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
 452         else {
 453                 regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
 454
 455                 /* mov __NR_sigreturn, %g1 */
 456                 err |= __put_user(0x821020d8, &sf->insns[0]);
 457
 458                 /* t 0x10 */
 459                 err |= __put_user(0x91d02010, &sf->insns[1]);
 460                 if (err)
 461                         goto sigsegv;
 462
 463                 /* Flush instruction space. */
 464                 flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
 465         }
 466         return;
 467
 468 sigill:
 469         do_exit(SIGILL);
 470 sigsegv:
 471         force_sigsegv(signo, current);
 472 }
 473
 474 static inline void
 475 handle_signal(unsigned long signr, struct k_sigaction *ka,
 476               siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
 477 {
 478         if (ka->sa.sa_flags & SA_SIGINFO)
 479                 setup_rt_frame(ka, regs, signr, oldset, info);
 480         else
 481                 setup_frame(ka, regs, signr, oldset);
 482
 483         spin_lock_irq(&current->sighand->siglock);
 484         sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
 485         if (!(ka->sa.sa_flags & SA_NOMASK))
 486                 sigaddset(&current->blocked, signr);
 487         recalc_sigpending();
 488         spin_unlock_irq(&current->sighand->siglock);
 489 }
 490
 491 static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
 492                                    struct sigaction *sa)
 493 {
 494         switch(regs->u_regs[UREG_I0]) {
 495         case ERESTART_RESTARTBLOCK:
 496         case ERESTARTNOHAND:
 497         no_system_call_restart:
 498                 regs->u_regs[UREG_I0] = EINTR;
 499                 regs->psr |= PSR_C;
 500                 break;
 501         case ERESTARTSYS:
 502                 if (!(sa->sa_flags & SA_RESTART))
 503                         goto no_system_call_restart;
 504                 /* fallthrough */
 505         case ERESTARTNOINTR:
 506                 regs->u_regs[UREG_I0] = orig_i0;
 507                 regs->pc -= 4;
 508                 regs->npc -= 4;
 509         }
 510 }
 511
 512 /* Note that 'init' is a special process: it doesn't get signals it doesn't
 513  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 514  * mistake.
 515  */
 516 asmlinkage void do_signal(struct pt_regs * regs, unsigned long orig_i0)
 517 {
 518         struct k_sigaction ka;
 519         int restart_syscall;
 520         sigset_t *oldset;
 521         siginfo_t info;
 522         int signr;
 523
 524         if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C))
 525                 restart_syscall = 1;
 526         else
 527                 restart_syscall = 0;
 528
 529         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 530                 oldset = &current->saved_sigmask;
 531         else
 532                 oldset = &current->blocked;
 533
 534         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 535
 536         /* If the debugger messes with the program counter, it clears
 537          * the software "in syscall" bit, directing us to not perform
 538          * a syscall restart.
 539          */
 540         if (restart_syscall && !pt_regs_is_syscall(regs))
 541                 restart_syscall = 0;
 542
 543         if (signr > 0) {
 544                 if (restart_syscall)
 545                         syscall_restart(orig_i0, regs, &ka.sa);
 546                 handle_signal(signr, &ka, &info, oldset, regs);
 547
 548                 /* a signal was successfully delivered; the saved
 549                  * sigmask will have been stored in the signal frame,
 550                  * and will be restored by sigreturn, so we can simply
 551                  * clear the TIF_RESTORE_SIGMASK flag.
 552                  */
 553                 if (test_thread_flag(TIF_RESTORE_SIGMASK))
 554                         clear_thread_flag(TIF_RESTORE_SIGMASK);
 555                 return;
 556         }
 557         if (restart_syscall &&
 558             (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
 559              regs->u_regs[UREG_I0] == ERESTARTSYS ||
 560              regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
 561                 /* replay the system call when we are done */
 562                 regs->u_regs[UREG_I0] = orig_i0;
 563                 regs->pc -= 4;
 564                 regs->npc -= 4;
 565         }
 566         if (restart_syscall &&
 567             regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
 568                 regs->u_regs[UREG_G1] = __NR_restart_syscall;
 569                 regs->pc -= 4;
 570                 regs->npc -= 4;
 571         }
 572
 573         /* if there's no signal to deliver, we just put the saved sigmask
 574          * back
 575          */
 576         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 577                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 578                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 579         }
 580 }
 581
 582 asmlinkage int
 583 do_sys_sigstack(struct sigstack __user *ssptr, struct sigstack __user *ossptr,
 584                 unsigned long sp)
 585 {
 586         int ret = -EFAULT;
 587
 588         /* First see if old state is wanted. */
 589         if (ossptr) {
 590                 if (put_user(current->sas_ss_sp + current->sas_ss_size,
 591                              &ossptr->the_stack) ||
 592                     __put_user(on_sig_stack(sp), &ossptr->cur_status))
 593                         goto out;
 594         }
 595
 596         /* Now see if we want to update the new state. */
 597         if (ssptr) {
 598                 char *ss_sp;
 599
 600                 if (get_user(ss_sp, &ssptr->the_stack))
 601                         goto out;
 602                 /* If the current stack was set with sigaltstack, don't
 603                    swap stacks while we are on it.  */
 604                 ret = -EPERM;
 605                 if (current->sas_ss_sp && on_sig_stack(sp))
 606                         goto out;
 607
 608                 /* Since we don't know the extent of the stack, and we don't
 609                    track onstack-ness, but rather calculate it, we must
 610                    presume a size.  Ho hum this interface is lossy.  */
 611                 current->sas_ss_sp = (unsigned long)ss_sp - SIGSTKSZ;
 612                 current->sas_ss_size = SIGSTKSZ;
 613         }
 614         ret = 0;
 615 out:
 616         return ret;
 617 }