arch/sparc/kernel/signal_32.c

   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 #include <linux/tracehook.h>
  22
  23 #include <asm/uaccess.h>
  24 #include <asm/ptrace.h>
  25 #include <asm/pgalloc.h>
  26 #include <asm/pgtable.h>
  27 #include <asm/cacheflush.h>     /* flush_sig_insns */
  28
  29 #include "sigutil.h"
  30
  31 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  32
  33 extern void fpsave(unsigned long *fpregs, unsigned long *fsr,
  34                    void *fpqueue, unsigned long *fpqdepth);
  35 extern void fpload(unsigned long *fpregs, unsigned long *fsr);
  36
  37 struct signal_frame {
  38         struct sparc_stackf     ss;
  39         __siginfo32_t           info;
  40         __siginfo_fpu_t __user  *fpu_save;
  41         unsigned long           insns[2] __attribute__ ((aligned (8)));
  42         unsigned int            extramask[_NSIG_WORDS - 1];
  43         unsigned int            extra_size; /* Should be 0 */
  44         __siginfo_rwin_t __user *rwin_save;
  45 } __attribute__((aligned(8)));
  46
  47 struct rt_signal_frame {
  48         struct sparc_stackf     ss;
  49         siginfo_t               info;
  50         struct pt_regs          regs;
  51         sigset_t                mask;
  52         __siginfo_fpu_t __user  *fpu_save;
  53         unsigned int            insns[2];
  54         stack_t                 stack;
  55         unsigned int            extra_size; /* Should be 0 */
  56         __siginfo_rwin_t __user *rwin_save;
  57 } __attribute__((aligned(8)));
  58
  59 /* Align macros */
  60 #define SF_ALIGNEDSZ  (((sizeof(struct signal_frame) + 7) & (~7)))
  61 #define RT_ALIGNEDSZ  (((sizeof(struct rt_signal_frame) + 7) & (~7)))
  62
  63 static int _sigpause_common(old_sigset_t set)
  64 {
  65         set &= _BLOCKABLE;
  66         spin_lock_irq(&current->sighand->siglock);
  67         current->saved_sigmask = current->blocked;
  68         siginitset(&current->blocked, set);
  69         recalc_sigpending();
  70         spin_unlock_irq(&current->sighand->siglock);
  71
  72         current->state = TASK_INTERRUPTIBLE;
  73         schedule();
  74         set_thread_flag(TIF_RESTORE_SIGMASK);
  75
  76         return -ERESTARTNOHAND;
  77 }
  78
  79 asmlinkage int sys_sigsuspend(old_sigset_t set)
  80 {
  81         return _sigpause_common(set);
  82 }
  83
  84 asmlinkage void do_sigreturn(struct pt_regs *regs)
  85 {
  86         struct signal_frame __user *sf;
  87         unsigned long up_psr, pc, npc;
  88         sigset_t set;
  89         __siginfo_fpu_t __user *fpu_save;
  90         __siginfo_rwin_t __user *rwin_save;
  91         int err;
  92
  93         /* Always make any pending restarted system calls return -EINTR */
  94         current_thread_info()->restart_block.fn = do_no_restart_syscall;
  95
  96         synchronize_user_stack();
  97
  98         sf = (struct signal_frame __user *) regs->u_regs[UREG_FP];
  99
 100         /* 1. Make sure we are not getting garbage from the user */
 101         if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
 102                 goto segv_and_exit;
 103
 104         if (((unsigned long) sf) & 3)
 105                 goto segv_and_exit;
 106
 107         err = __get_user(pc,  &sf->info.si_regs.pc);
 108         err |= __get_user(npc, &sf->info.si_regs.npc);
 109
 110         if ((pc | npc) & 3)
 111                 goto segv_and_exit;
 112
 113         /* 2. Restore the state */
 114         up_psr = regs->psr;
 115         err |= __copy_from_user(regs, &sf->info.si_regs, sizeof(struct pt_regs));
 116
 117         /* User can only change condition codes and FPU enabling in %psr. */
 118         regs->psr = (up_psr & ~(PSR_ICC | PSR_EF))
 119                   | (regs->psr & (PSR_ICC | PSR_EF));
 120
 121         /* Prevent syscall restart.  */
 122         pt_regs_clear_syscall(regs);
 123
 124         err |= __get_user(fpu_save, &sf->fpu_save);
 125         if (fpu_save)
 126                 err |= restore_fpu_state(regs, fpu_save);
 127         err |= __get_user(rwin_save, &sf->rwin_save);
 128         if (rwin_save)
 129                 err |= restore_rwin_state(rwin_save);
 130
 131         /* This is pretty much atomic, no amount locking would prevent
 132          * the races which exist anyways.
 133          */
 134         err |= __get_user(set.sig[0], &sf->info.si_mask);
 135         err |= __copy_from_user(&set.sig[1], &sf->extramask,
 136                                 (_NSIG_WORDS-1) * sizeof(unsigned int));
 137
 138         if (err)
 139                 goto segv_and_exit;
 140
 141         sigdelsetmask(&set, ~_BLOCKABLE);
 142         spin_lock_irq(&current->sighand->siglock);
 143         current->blocked = set;
 144         recalc_sigpending();
 145         spin_unlock_irq(&current->sighand->siglock);
 146         return;
 147
 148 segv_and_exit:
 149         force_sig(SIGSEGV, current);
 150 }
 151
 152 asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
 153 {
 154         struct rt_signal_frame __user *sf;
 155         unsigned int psr, pc, npc;
 156         __siginfo_fpu_t __user *fpu_save;
 157         __siginfo_rwin_t __user *rwin_save;
 158         mm_segment_t old_fs;
 159         sigset_t set;
 160         stack_t st;
 161         int err;
 162
 163         synchronize_user_stack();
 164         sf = (struct rt_signal_frame __user *) regs->u_regs[UREG_FP];
 165         if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
 166             (((unsigned long) sf) & 0x03))
 167                 goto segv;
 168
 169         err = __get_user(pc, &sf->regs.pc);
 170         err |= __get_user(npc, &sf->regs.npc);
 171         err |= ((pc | npc) & 0x03);
 172
 173         err |= __get_user(regs->y, &sf->regs.y);
 174         err |= __get_user(psr, &sf->regs.psr);
 175
 176         err |= __copy_from_user(&regs->u_regs[UREG_G1],
 177                                 &sf->regs.u_regs[UREG_G1], 15 * sizeof(u32));
 178
 179         regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC);
 180
 181         /* Prevent syscall restart.  */
 182         pt_regs_clear_syscall(regs);
 183
 184         err |= __get_user(fpu_save, &sf->fpu_save);
 185         if (!err && fpu_save)
 186                 err |= restore_fpu_state(regs, fpu_save);
 187         err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
 188
 189         err |= __copy_from_user(&st, &sf->stack, sizeof(stack_t));
 190
 191         if (err)
 192                 goto segv;
 193
 194         regs->pc = pc;
 195         regs->npc = npc;
 196
 197         /* It is more difficult to avoid calling this function than to
 198          * call it and ignore errors.
 199          */
 200         old_fs = get_fs();
 201         set_fs(KERNEL_DS);
 202         do_sigaltstack((const stack_t __user *) &st, NULL, (unsigned long)sf);
 203         set_fs(old_fs);
 204
 205         err |= __get_user(rwin_save, &sf->rwin_save);
 206         if (!err && rwin_save) {
 207                 if (restore_rwin_state(rwin_save))
 208                         goto segv;
 209         }
 210
 211         sigdelsetmask(&set, ~_BLOCKABLE);
 212         spin_lock_irq(&current->sighand->siglock);
 213         current->blocked = set;
 214         recalc_sigpending();
 215         spin_unlock_irq(&current->sighand->siglock);
 216         return;
 217 segv:
 218         force_sig(SIGSEGV, current);
 219 }
 220
 221 /* Checks if the fp is valid */
 222 static inline int invalid_frame_pointer(void __user *fp, int fplen)
 223 {
 224         if ((((unsigned long) fp) & 7) ||
 225             !__access_ok((unsigned long)fp, fplen) ||
 226             ((sparc_cpu_model == sun4 || sparc_cpu_model == sun4c) &&
 227              ((unsigned long) fp < 0xe0000000 && (unsigned long) fp >= 0x20000000)))
 228                 return 1;
 229
 230         return 0;
 231 }
 232
 233 static inline void __user *get_sigframe(struct sigaction *sa, struct pt_regs *regs, unsigned long framesize)
 234 {
 235         unsigned long sp = regs->u_regs[UREG_FP];
 236
 237         /*
 238          * If we are on the alternate signal stack and would overflow it, don't.
 239          * Return an always-bogus address instead so we will die with SIGSEGV.
 240          */
 241         if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
 242                 return (void __user *) -1L;
 243
 244         /* This is the X/Open sanctioned signal stack switching.  */
 245         if (sa->sa_flags & SA_ONSTACK) {
 246                 if (sas_ss_flags(sp) == 0)
 247                         sp = current->sas_ss_sp + current->sas_ss_size;
 248         }
 249
 250         sp -= framesize;
 251
 252         /* Always align the stack frame.  This handles two cases.  First,
 253          * sigaltstack need not be mindful of platform specific stack
 254          * alignment.  Second, if we took this signal because the stack
 255          * is not aligned properly, we'd like to take the signal cleanly
 256          * and report that.
 257          */
 258         sp &= ~15UL;
 259
 260         return (void __user *) sp;
 261 }
 262
 263 static int setup_frame(struct k_sigaction *ka, struct pt_regs *regs,
 264                        int signo, sigset_t *oldset)
 265 {
 266         struct signal_frame __user *sf;
 267         int sigframe_size, err, wsaved;
 268         void __user *tail;
 269
 270         /* 1. Make sure everything is clean */
 271         synchronize_user_stack();
 272
 273         wsaved = current_thread_info()->w_saved;
 274
 275         sigframe_size = sizeof(*sf);
 276         if (used_math())
 277                 sigframe_size += sizeof(__siginfo_fpu_t);
 278         if (wsaved)
 279                 sigframe_size += sizeof(__siginfo_rwin_t);
 280
 281         sf = (struct signal_frame __user *)
 282                 get_sigframe(&ka->sa, regs, sigframe_size);
 283
 284         if (invalid_frame_pointer(sf, sigframe_size))
 285                 goto sigill_and_return;
 286
 287         tail = sf + 1;
 288
 289         /* 2. Save the current process state */
 290         err = __copy_to_user(&sf->info.si_regs, regs, sizeof(struct pt_regs));
 291
 292         err |= __put_user(0, &sf->extra_size);
 293
 294         if (used_math()) {
 295                 __siginfo_fpu_t __user *fp = tail;
 296                 tail += sizeof(*fp);
 297                 err |= save_fpu_state(regs, fp);
 298                 err |= __put_user(fp, &sf->fpu_save);
 299         } else {
 300                 err |= __put_user(0, &sf->fpu_save);
 301         }
 302         if (wsaved) {
 303                 __siginfo_rwin_t __user *rwp = tail;
 304                 tail += sizeof(*rwp);
 305                 err |= save_rwin_state(wsaved, rwp);
 306                 err |= __put_user(rwp, &sf->rwin_save);
 307         } else {
 308                 err |= __put_user(0, &sf->rwin_save);
 309         }
 310
 311         err |= __put_user(oldset->sig[0], &sf->info.si_mask);
 312         err |= __copy_to_user(sf->extramask, &oldset->sig[1],
 313                               (_NSIG_WORDS - 1) * sizeof(unsigned int));
 314         if (!wsaved) {
 315                 err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
 316                                       sizeof(struct reg_window32));
 317         } else {
 318                 struct reg_window32 *rp;
 319
 320                 rp = &current_thread_info()->reg_window[wsaved - 1];
 321                 err |= __copy_to_user(sf, rp, sizeof(struct reg_window32));
 322         }
 323         if (err)
 324                 goto sigsegv;
 325
 326         /* 3. signal handler back-trampoline and parameters */
 327         regs->u_regs[UREG_FP] = (unsigned long) sf;
 328         regs->u_regs[UREG_I0] = signo;
 329         regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
 330         regs->u_regs[UREG_I2] = (unsigned long) &sf->info;
 331
 332         /* 4. signal handler */
 333         regs->pc = (unsigned long) ka->sa.sa_handler;
 334         regs->npc = (regs->pc + 4);
 335
 336         /* 5. return to kernel instructions */
 337         if (ka->ka_restorer)
 338                 regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
 339         else {
 340                 regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
 341
 342                 /* mov __NR_sigreturn, %g1 */
 343                 err |= __put_user(0x821020d8, &sf->insns[0]);
 344
 345                 /* t 0x10 */
 346                 err |= __put_user(0x91d02010, &sf->insns[1]);
 347                 if (err)
 348                         goto sigsegv;
 349
 350                 /* Flush instruction space. */
 351                 flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
 352         }
 353         return 0;
 354
 355 sigill_and_return:
 356         do_exit(SIGILL);
 357         return -EINVAL;
 358
 359 sigsegv:
 360         force_sigsegv(signo, current);
 361         return -EFAULT;
 362 }
 363
 364 static int setup_rt_frame(struct k_sigaction *ka, struct pt_regs *regs,
 365                           int signo, sigset_t *oldset, siginfo_t *info)
 366 {
 367         struct rt_signal_frame __user *sf;
 368         int sigframe_size, wsaved;
 369         void __user *tail;
 370         unsigned int psr;
 371         int err;
 372
 373         synchronize_user_stack();
 374         wsaved = current_thread_info()->w_saved;
 375         sigframe_size = sizeof(*sf);
 376         if (used_math())
 377                 sigframe_size += sizeof(__siginfo_fpu_t);
 378         if (wsaved)
 379                 sigframe_size += sizeof(__siginfo_rwin_t);
 380         sf = (struct rt_signal_frame __user *)
 381                 get_sigframe(&ka->sa, regs, sigframe_size);
 382         if (invalid_frame_pointer(sf, sigframe_size))
 383                 goto sigill;
 384
 385         tail = sf + 1;
 386         err  = __put_user(regs->pc, &sf->regs.pc);
 387         err |= __put_user(regs->npc, &sf->regs.npc);
 388         err |= __put_user(regs->y, &sf->regs.y);
 389         psr = regs->psr;
 390         if (used_math())
 391                 psr |= PSR_EF;
 392         err |= __put_user(psr, &sf->regs.psr);
 393         err |= __copy_to_user(&sf->regs.u_regs, regs->u_regs, sizeof(regs->u_regs));
 394         err |= __put_user(0, &sf->extra_size);
 395
 396         if (psr & PSR_EF) {
 397                 __siginfo_fpu_t *fp = tail;
 398                 tail += sizeof(*fp);
 399                 err |= save_fpu_state(regs, fp);
 400                 err |= __put_user(fp, &sf->fpu_save);
 401         } else {
 402                 err |= __put_user(0, &sf->fpu_save);
 403         }
 404         if (wsaved) {
 405                 __siginfo_rwin_t *rwp = tail;
 406                 tail += sizeof(*rwp);
 407                 err |= save_rwin_state(wsaved, rwp);
 408                 err |= __put_user(rwp, &sf->rwin_save);
 409         } else {
 410                 err |= __put_user(0, &sf->rwin_save);
 411         }
 412         err |= __copy_to_user(&sf->mask, &oldset->sig[0], sizeof(sigset_t));
 413
 414         /* Setup sigaltstack */
 415         err |= __put_user(current->sas_ss_sp, &sf->stack.ss_sp);
 416         err |= __put_user(sas_ss_flags(regs->u_regs[UREG_FP]), &sf->stack.ss_flags);
 417         err |= __put_user(current->sas_ss_size, &sf->stack.ss_size);
 418
 419         if (!wsaved) {
 420                 err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
 421                                       sizeof(struct reg_window32));
 422         } else {
 423                 struct reg_window32 *rp;
 424
 425                 rp = &current_thread_info()->reg_window[wsaved - 1];
 426                 err |= __copy_to_user(sf, rp, sizeof(struct reg_window32));
 427         }
 428
 429         err |= copy_siginfo_to_user(&sf->info, info);
 430
 431         if (err)
 432                 goto sigsegv;
 433
 434         regs->u_regs[UREG_FP] = (unsigned long) sf;
 435         regs->u_regs[UREG_I0] = signo;
 436         regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
 437         regs->u_regs[UREG_I2] = (unsigned long) &sf->regs;
 438
 439         regs->pc = (unsigned long) ka->sa.sa_handler;
 440         regs->npc = (regs->pc + 4);
 441
 442         if (ka->ka_restorer)
 443                 regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
 444         else {
 445                 regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
 446
 447                 /* mov __NR_sigreturn, %g1 */
 448                 err |= __put_user(0x821020d8, &sf->insns[0]);
 449
 450                 /* t 0x10 */
 451                 err |= __put_user(0x91d02010, &sf->insns[1]);
 452                 if (err)
 453                         goto sigsegv;
 454
 455                 /* Flush instruction space. */
 456                 flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
 457         }
 458         return 0;
 459
 460 sigill:
 461         do_exit(SIGILL);
 462         return -EINVAL;
 463
 464 sigsegv:
 465         force_sigsegv(signo, current);
 466         return -EFAULT;
 467 }
 468
 469 static inline int
 470 handle_signal(unsigned long signr, struct k_sigaction *ka,
 471               siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
 472 {
 473         int err;
 474
 475         if (ka->sa.sa_flags & SA_SIGINFO)
 476                 err = setup_rt_frame(ka, regs, signr, oldset, info);
 477         else
 478                 err = setup_frame(ka, regs, signr, oldset);
 479
 480         if (err)
 481                 return err;
 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         tracehook_signal_handler(signr, info, ka, regs, 0);
 491
 492         return 0;
 493 }
 494
 495 static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
 496                                    struct sigaction *sa)
 497 {
 498         switch(regs->u_regs[UREG_I0]) {
 499         case ERESTART_RESTARTBLOCK:
 500         case ERESTARTNOHAND:
 501         no_system_call_restart:
 502                 regs->u_regs[UREG_I0] = EINTR;
 503                 regs->psr |= PSR_C;
 504                 break;
 505         case ERESTARTSYS:
 506                 if (!(sa->sa_flags & SA_RESTART))
 507                         goto no_system_call_restart;
 508                 /* fallthrough */
 509         case ERESTARTNOINTR:
 510                 regs->u_regs[UREG_I0] = orig_i0;
 511                 regs->pc -= 4;
 512                 regs->npc -= 4;
 513         }
 514 }
 515
 516 /* Note that 'init' is a special process: it doesn't get signals it doesn't
 517  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 518  * mistake.
 519  */
 520 static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
 521 {
 522         struct k_sigaction ka;
 523         int restart_syscall;
 524         sigset_t *oldset;
 525         siginfo_t info;
 526         int signr;
 527
 528         if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C))
 529                 restart_syscall = 1;
 530         else
 531                 restart_syscall = 0;
 532
 533         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 534                 oldset = &current->saved_sigmask;
 535         else
 536                 oldset = &current->blocked;
 537
 538         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 539
 540         /* If the debugger messes with the program counter, it clears
 541          * the software "in syscall" bit, directing us to not perform
 542          * a syscall restart.
 543          */
 544         if (restart_syscall && !pt_regs_is_syscall(regs))
 545                 restart_syscall = 0;
 546
 547         if (signr > 0) {
 548                 if (restart_syscall)
 549                         syscall_restart(orig_i0, regs, &ka.sa);
 550                 if (handle_signal(signr, &ka, &info, oldset, regs) == 0) {
 551                         /* a signal was successfully delivered; the saved
 552                          * sigmask will have been stored in the signal frame,
 553                          * and will be restored by sigreturn, so we can simply
 554                          * clear the TIF_RESTORE_SIGMASK flag.
 555                          */
 556                         if (test_thread_flag(TIF_RESTORE_SIGMASK))
 557                                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 558                 }
 559                 return;
 560         }
 561         if (restart_syscall &&
 562             (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
 563              regs->u_regs[UREG_I0] == ERESTARTSYS ||
 564              regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
 565                 /* replay the system call when we are done */
 566                 regs->u_regs[UREG_I0] = orig_i0;
 567                 regs->pc -= 4;
 568                 regs->npc -= 4;
 569                 pt_regs_clear_syscall(regs);
 570         }
 571         if (restart_syscall &&
 572             regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
 573                 regs->u_regs[UREG_G1] = __NR_restart_syscall;
 574                 regs->pc -= 4;
 575                 regs->npc -= 4;
 576                 pt_regs_clear_syscall(regs);
 577         }
 578
 579         /* if there's no signal to deliver, we just put the saved sigmask
 580          * back
 581          */
 582         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 583                 clear_thread_flag(TIF_RESTORE_SIGMASK);
 584                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 585         }
 586 }
 587
 588 void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0,
 589                       unsigned long thread_info_flags)
 590 {
 591         if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
 592                 do_signal(regs, orig_i0);
 593         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 594                 clear_thread_flag(TIF_NOTIFY_RESUME);
 595                 tracehook_notify_resume(regs);
 596                 if (current->replacement_session_keyring)
 597                         key_replace_session_keyring();
 598         }
 599 }
 600
 601 asmlinkage int
 602 do_sys_sigstack(struct sigstack __user *ssptr, struct sigstack __user *ossptr,
 603                 unsigned long sp)
 604 {
 605         int ret = -EFAULT;
 606
 607         /* First see if old state is wanted. */
 608         if (ossptr) {
 609                 if (put_user(current->sas_ss_sp + current->sas_ss_size,
 610                              &ossptr->the_stack) ||
 611                     __put_user(on_sig_stack(sp), &ossptr->cur_status))
 612                         goto out;
 613         }
 614
 615         /* Now see if we want to update the new state. */
 616         if (ssptr) {
 617                 char *ss_sp;
 618
 619                 if (get_user(ss_sp, &ssptr->the_stack))
 620                         goto out;
 621                 /* If the current stack was set with sigaltstack, don't
 622                    swap stacks while we are on it.  */
 623                 ret = -EPERM;
 624                 if (current->sas_ss_sp && on_sig_stack(sp))
 625                         goto out;
 626
 627                 /* Since we don't know the extent of the stack, and we don't
 628                    track onstack-ness, but rather calculate it, we must
 629                    presume a size.  Ho hum this interface is lossy.  */
 630                 current->sas_ss_sp = (unsigned long)ss_sp - SIGSTKSZ;
 631                 current->sas_ss_size = SIGSTKSZ;
 632         }
 633         ret = 0;
 634 out:
 635         return ret;
 636 }