[SCSI] bnx2i: Fixed the endian on TTT for NOP out transmission
[linux-2.6.git] / 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 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
30
31 extern void fpsave(unsigned long *fpregs, unsigned long *fsr,
32                    void *fpqueue, unsigned long *fpqdepth);
33 extern void fpload(unsigned long *fpregs, unsigned long *fsr);
34
35 struct signal_frame {
36         struct sparc_stackf     ss;
37         __siginfo32_t           info;
38         __siginfo_fpu_t __user  *fpu_save;
39         unsigned long           insns[2] __attribute__ ((aligned (8)));
40         unsigned int            extramask[_NSIG_WORDS - 1];
41         unsigned int            extra_size; /* Should be 0 */
42         __siginfo_fpu_t         fpu_state;
43 };
44
45 struct rt_signal_frame {
46         struct sparc_stackf     ss;
47         siginfo_t               info;
48         struct pt_regs          regs;
49         sigset_t                mask;
50         __siginfo_fpu_t __user  *fpu_save;
51         unsigned int            insns[2];
52         stack_t                 stack;
53         unsigned int            extra_size; /* Should be 0 */
54         __siginfo_fpu_t         fpu_state;
55 };
56
57 /* Align macros */
58 #define SF_ALIGNEDSZ  (((sizeof(struct signal_frame) + 7) & (~7)))
59 #define RT_ALIGNEDSZ  (((sizeof(struct rt_signal_frame) + 7) & (~7)))
60
61 static int _sigpause_common(old_sigset_t set)
62 {
63         set &= _BLOCKABLE;
64         spin_lock_irq(&current->sighand->siglock);
65         current->saved_sigmask = current->blocked;
66         siginitset(&current->blocked, set);
67         recalc_sigpending();
68         spin_unlock_irq(&current->sighand->siglock);
69
70         current->state = TASK_INTERRUPTIBLE;
71         schedule();
72         set_thread_flag(TIF_RESTORE_SIGMASK);
73
74         return -ERESTARTNOHAND;
75 }
76
77 asmlinkage int sys_sigsuspend(old_sigset_t set)
78 {
79         return _sigpause_common(set);
80 }
81
82 static inline int
83 restore_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
84 {
85         int err;
86 #ifdef CONFIG_SMP
87         if (test_tsk_thread_flag(current, TIF_USEDFPU))
88                 regs->psr &= ~PSR_EF;
89 #else
90         if (current == last_task_used_math) {
91                 last_task_used_math = NULL;
92                 regs->psr &= ~PSR_EF;
93         }
94 #endif
95         set_used_math();
96         clear_tsk_thread_flag(current, TIF_USEDFPU);
97
98         if (!access_ok(VERIFY_READ, fpu, sizeof(*fpu)))
99                 return -EFAULT;
100
101         err = __copy_from_user(&current->thread.float_regs[0], &fpu->si_float_regs[0],
102                                (sizeof(unsigned long) * 32));
103         err |= __get_user(current->thread.fsr, &fpu->si_fsr);
104         err |= __get_user(current->thread.fpqdepth, &fpu->si_fpqdepth);
105         if (current->thread.fpqdepth != 0)
106                 err |= __copy_from_user(&current->thread.fpqueue[0],
107                                         &fpu->si_fpqueue[0],
108                                         ((sizeof(unsigned long) +
109                                         (sizeof(unsigned long *)))*16));
110         return err;
111 }
112
113 asmlinkage void do_sigreturn(struct pt_regs *regs)
114 {
115         struct signal_frame __user *sf;
116         unsigned long up_psr, pc, npc;
117         sigset_t set;
118         __siginfo_fpu_t __user *fpu_save;
119         int err;
120
121         /* Always make any pending restarted system calls return -EINTR */
122         current_thread_info()->restart_block.fn = do_no_restart_syscall;
123
124         synchronize_user_stack();
125
126         sf = (struct signal_frame __user *) regs->u_regs[UREG_FP];
127
128         /* 1. Make sure we are not getting garbage from the user */
129         if (!access_ok(VERIFY_READ, sf, sizeof(*sf)))
130                 goto segv_and_exit;
131
132         if (((unsigned long) sf) & 3)
133                 goto segv_and_exit;
134
135         err = __get_user(pc,  &sf->info.si_regs.pc);
136         err |= __get_user(npc, &sf->info.si_regs.npc);
137
138         if ((pc | npc) & 3)
139                 goto segv_and_exit;
140
141         /* 2. Restore the state */
142         up_psr = regs->psr;
143         err |= __copy_from_user(regs, &sf->info.si_regs, sizeof(struct pt_regs));
144
145         /* User can only change condition codes and FPU enabling in %psr. */
146         regs->psr = (up_psr & ~(PSR_ICC | PSR_EF))
147                   | (regs->psr & (PSR_ICC | PSR_EF));
148
149         /* Prevent syscall restart.  */
150         pt_regs_clear_syscall(regs);
151
152         err |= __get_user(fpu_save, &sf->fpu_save);
153
154         if (fpu_save)
155                 err |= restore_fpu_state(regs, fpu_save);
156
157         /* This is pretty much atomic, no amount locking would prevent
158          * the races which exist anyways.
159          */
160         err |= __get_user(set.sig[0], &sf->info.si_mask);
161         err |= __copy_from_user(&set.sig[1], &sf->extramask,
162                                 (_NSIG_WORDS-1) * sizeof(unsigned int));
163                            
164         if (err)
165                 goto segv_and_exit;
166
167         sigdelsetmask(&set, ~_BLOCKABLE);
168         spin_lock_irq(&current->sighand->siglock);
169         current->blocked = set;
170         recalc_sigpending();
171         spin_unlock_irq(&current->sighand->siglock);
172         return;
173
174 segv_and_exit:
175         force_sig(SIGSEGV, current);
176 }
177
178 asmlinkage void do_rt_sigreturn(struct pt_regs *regs)
179 {
180         struct rt_signal_frame __user *sf;
181         unsigned int psr, pc, npc;
182         __siginfo_fpu_t __user *fpu_save;
183         mm_segment_t old_fs;
184         sigset_t set;
185         stack_t st;
186         int err;
187
188         synchronize_user_stack();
189         sf = (struct rt_signal_frame __user *) regs->u_regs[UREG_FP];
190         if (!access_ok(VERIFY_READ, sf, sizeof(*sf)) ||
191             (((unsigned long) sf) & 0x03))
192                 goto segv;
193
194         err = __get_user(pc, &sf->regs.pc);
195         err |= __get_user(npc, &sf->regs.npc);
196         err |= ((pc | npc) & 0x03);
197
198         err |= __get_user(regs->y, &sf->regs.y);
199         err |= __get_user(psr, &sf->regs.psr);
200
201         err |= __copy_from_user(&regs->u_regs[UREG_G1],
202                                 &sf->regs.u_regs[UREG_G1], 15 * sizeof(u32));
203
204         regs->psr = (regs->psr & ~PSR_ICC) | (psr & PSR_ICC);
205
206         /* Prevent syscall restart.  */
207         pt_regs_clear_syscall(regs);
208
209         err |= __get_user(fpu_save, &sf->fpu_save);
210
211         if (fpu_save)
212                 err |= restore_fpu_state(regs, fpu_save);
213         err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
214         
215         err |= __copy_from_user(&st, &sf->stack, sizeof(stack_t));
216         
217         if (err)
218                 goto segv;
219                 
220         regs->pc = pc;
221         regs->npc = npc;
222         
223         /* It is more difficult to avoid calling this function than to
224          * call it and ignore errors.
225          */
226         old_fs = get_fs();
227         set_fs(KERNEL_DS);
228         do_sigaltstack((const stack_t __user *) &st, NULL, (unsigned long)sf);
229         set_fs(old_fs);
230
231         sigdelsetmask(&set, ~_BLOCKABLE);
232         spin_lock_irq(&current->sighand->siglock);
233         current->blocked = set;
234         recalc_sigpending();
235         spin_unlock_irq(&current->sighand->siglock);
236         return;
237 segv:
238         force_sig(SIGSEGV, current);
239 }
240
241 /* Checks if the fp is valid */
242 static inline int invalid_frame_pointer(void __user *fp, int fplen)
243 {
244         if ((((unsigned long) fp) & 7) ||
245             !__access_ok((unsigned long)fp, fplen) ||
246             ((sparc_cpu_model == sun4 || sparc_cpu_model == sun4c) &&
247              ((unsigned long) fp < 0xe0000000 && (unsigned long) fp >= 0x20000000)))
248                 return 1;
249         
250         return 0;
251 }
252
253 static inline void __user *get_sigframe(struct sigaction *sa, struct pt_regs *regs, unsigned long framesize)
254 {
255         unsigned long sp = regs->u_regs[UREG_FP];
256
257         /*
258          * If we are on the alternate signal stack and would overflow it, don't.
259          * Return an always-bogus address instead so we will die with SIGSEGV.
260          */
261         if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
262                 return (void __user *) -1L;
263
264         /* This is the X/Open sanctioned signal stack switching.  */
265         if (sa->sa_flags & SA_ONSTACK) {
266                 if (sas_ss_flags(sp) == 0)
267                         sp = current->sas_ss_sp + current->sas_ss_size;
268         }
269
270         sp -= framesize;
271
272         /* Always align the stack frame.  This handles two cases.  First,
273          * sigaltstack need not be mindful of platform specific stack
274          * alignment.  Second, if we took this signal because the stack
275          * is not aligned properly, we'd like to take the signal cleanly
276          * and report that.
277          */
278         sp &= ~15UL;
279
280         return (void __user *) sp;
281 }
282
283 static inline int
284 save_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
285 {
286         int err = 0;
287 #ifdef CONFIG_SMP
288         if (test_tsk_thread_flag(current, TIF_USEDFPU)) {
289                 put_psr(get_psr() | PSR_EF);
290                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
291                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
292                 regs->psr &= ~(PSR_EF);
293                 clear_tsk_thread_flag(current, TIF_USEDFPU);
294         }
295 #else
296         if (current == last_task_used_math) {
297                 put_psr(get_psr() | PSR_EF);
298                 fpsave(&current->thread.float_regs[0], &current->thread.fsr,
299                        &current->thread.fpqueue[0], &current->thread.fpqdepth);
300                 last_task_used_math = NULL;
301                 regs->psr &= ~(PSR_EF);
302         }
303 #endif
304         err |= __copy_to_user(&fpu->si_float_regs[0],
305                               &current->thread.float_regs[0],
306                               (sizeof(unsigned long) * 32));
307         err |= __put_user(current->thread.fsr, &fpu->si_fsr);
308         err |= __put_user(current->thread.fpqdepth, &fpu->si_fpqdepth);
309         if (current->thread.fpqdepth != 0)
310                 err |= __copy_to_user(&fpu->si_fpqueue[0],
311                                       &current->thread.fpqueue[0],
312                                       ((sizeof(unsigned long) +
313                                       (sizeof(unsigned long *)))*16));
314         clear_used_math();
315         return err;
316 }
317
318 static int setup_frame(struct k_sigaction *ka, struct pt_regs *regs,
319                        int signo, sigset_t *oldset)
320 {
321         struct signal_frame __user *sf;
322         int sigframe_size, err;
323
324         /* 1. Make sure everything is clean */
325         synchronize_user_stack();
326
327         sigframe_size = SF_ALIGNEDSZ;
328         if (!used_math())
329                 sigframe_size -= sizeof(__siginfo_fpu_t);
330
331         sf = (struct signal_frame __user *)
332                 get_sigframe(&ka->sa, regs, sigframe_size);
333
334         if (invalid_frame_pointer(sf, sigframe_size))
335                 goto sigill_and_return;
336
337         if (current_thread_info()->w_saved != 0)
338                 goto sigill_and_return;
339
340         /* 2. Save the current process state */
341         err = __copy_to_user(&sf->info.si_regs, regs, sizeof(struct pt_regs));
342         
343         err |= __put_user(0, &sf->extra_size);
344
345         if (used_math()) {
346                 err |= save_fpu_state(regs, &sf->fpu_state);
347                 err |= __put_user(&sf->fpu_state, &sf->fpu_save);
348         } else {
349                 err |= __put_user(0, &sf->fpu_save);
350         }
351
352         err |= __put_user(oldset->sig[0], &sf->info.si_mask);
353         err |= __copy_to_user(sf->extramask, &oldset->sig[1],
354                               (_NSIG_WORDS - 1) * sizeof(unsigned int));
355         err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
356                               sizeof(struct reg_window32));
357         if (err)
358                 goto sigsegv;
359         
360         /* 3. signal handler back-trampoline and parameters */
361         regs->u_regs[UREG_FP] = (unsigned long) sf;
362         regs->u_regs[UREG_I0] = signo;
363         regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
364         regs->u_regs[UREG_I2] = (unsigned long) &sf->info;
365
366         /* 4. signal handler */
367         regs->pc = (unsigned long) ka->sa.sa_handler;
368         regs->npc = (regs->pc + 4);
369
370         /* 5. return to kernel instructions */
371         if (ka->ka_restorer)
372                 regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
373         else {
374                 regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
375
376                 /* mov __NR_sigreturn, %g1 */
377                 err |= __put_user(0x821020d8, &sf->insns[0]);
378
379                 /* t 0x10 */
380                 err |= __put_user(0x91d02010, &sf->insns[1]);
381                 if (err)
382                         goto sigsegv;
383
384                 /* Flush instruction space. */
385                 flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
386         }
387         return 0;
388
389 sigill_and_return:
390         do_exit(SIGILL);
391         return -EINVAL;
392
393 sigsegv:
394         force_sigsegv(signo, current);
395         return -EFAULT;
396 }
397
398 static int setup_rt_frame(struct k_sigaction *ka, struct pt_regs *regs,
399                           int signo, sigset_t *oldset, siginfo_t *info)
400 {
401         struct rt_signal_frame __user *sf;
402         int sigframe_size;
403         unsigned int psr;
404         int err;
405
406         synchronize_user_stack();
407         sigframe_size = RT_ALIGNEDSZ;
408         if (!used_math())
409                 sigframe_size -= sizeof(__siginfo_fpu_t);
410         sf = (struct rt_signal_frame __user *)
411                 get_sigframe(&ka->sa, regs, sigframe_size);
412         if (invalid_frame_pointer(sf, sigframe_size))
413                 goto sigill;
414         if (current_thread_info()->w_saved != 0)
415                 goto sigill;
416
417         err  = __put_user(regs->pc, &sf->regs.pc);
418         err |= __put_user(regs->npc, &sf->regs.npc);
419         err |= __put_user(regs->y, &sf->regs.y);
420         psr = regs->psr;
421         if (used_math())
422                 psr |= PSR_EF;
423         err |= __put_user(psr, &sf->regs.psr);
424         err |= __copy_to_user(&sf->regs.u_regs, regs->u_regs, sizeof(regs->u_regs));
425         err |= __put_user(0, &sf->extra_size);
426
427         if (psr & PSR_EF) {
428                 err |= save_fpu_state(regs, &sf->fpu_state);
429                 err |= __put_user(&sf->fpu_state, &sf->fpu_save);
430         } else {
431                 err |= __put_user(0, &sf->fpu_save);
432         }
433         err |= __copy_to_user(&sf->mask, &oldset->sig[0], sizeof(sigset_t));
434         
435         /* Setup sigaltstack */
436         err |= __put_user(current->sas_ss_sp, &sf->stack.ss_sp);
437         err |= __put_user(sas_ss_flags(regs->u_regs[UREG_FP]), &sf->stack.ss_flags);
438         err |= __put_user(current->sas_ss_size, &sf->stack.ss_size);
439         
440         err |= __copy_to_user(sf, (char *) regs->u_regs[UREG_FP],
441                               sizeof(struct reg_window32));
442
443         err |= copy_siginfo_to_user(&sf->info, info);
444
445         if (err)
446                 goto sigsegv;
447
448         regs->u_regs[UREG_FP] = (unsigned long) sf;
449         regs->u_regs[UREG_I0] = signo;
450         regs->u_regs[UREG_I1] = (unsigned long) &sf->info;
451         regs->u_regs[UREG_I2] = (unsigned long) &sf->regs;
452
453         regs->pc = (unsigned long) ka->sa.sa_handler;
454         regs->npc = (regs->pc + 4);
455
456         if (ka->ka_restorer)
457                 regs->u_regs[UREG_I7] = (unsigned long)ka->ka_restorer;
458         else {
459                 regs->u_regs[UREG_I7] = (unsigned long)(&(sf->insns[0]) - 2);
460
461                 /* mov __NR_sigreturn, %g1 */
462                 err |= __put_user(0x821020d8, &sf->insns[0]);
463
464                 /* t 0x10 */
465                 err |= __put_user(0x91d02010, &sf->insns[1]);
466                 if (err)
467                         goto sigsegv;
468
469                 /* Flush instruction space. */
470                 flush_sig_insns(current->mm, (unsigned long) &(sf->insns[0]));
471         }
472         return 0;
473
474 sigill:
475         do_exit(SIGILL);
476         return -EINVAL;
477
478 sigsegv:
479         force_sigsegv(signo, current);
480         return -EFAULT;
481 }
482
483 static inline int
484 handle_signal(unsigned long signr, struct k_sigaction *ka,
485               siginfo_t *info, sigset_t *oldset, struct pt_regs *regs)
486 {
487         int err;
488
489         if (ka->sa.sa_flags & SA_SIGINFO)
490                 err = setup_rt_frame(ka, regs, signr, oldset, info);
491         else
492                 err = setup_frame(ka, regs, signr, oldset);
493
494         if (err)
495                 return err;
496
497         spin_lock_irq(&current->sighand->siglock);
498         sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
499         if (!(ka->sa.sa_flags & SA_NOMASK))
500                 sigaddset(&current->blocked, signr);
501         recalc_sigpending();
502         spin_unlock_irq(&current->sighand->siglock);
503
504         tracehook_signal_handler(signr, info, ka, regs, 0);
505
506         return 0;
507 }
508
509 static inline void syscall_restart(unsigned long orig_i0, struct pt_regs *regs,
510                                    struct sigaction *sa)
511 {
512         switch(regs->u_regs[UREG_I0]) {
513         case ERESTART_RESTARTBLOCK:
514         case ERESTARTNOHAND:
515         no_system_call_restart:
516                 regs->u_regs[UREG_I0] = EINTR;
517                 regs->psr |= PSR_C;
518                 break;
519         case ERESTARTSYS:
520                 if (!(sa->sa_flags & SA_RESTART))
521                         goto no_system_call_restart;
522                 /* fallthrough */
523         case ERESTARTNOINTR:
524                 regs->u_regs[UREG_I0] = orig_i0;
525                 regs->pc -= 4;
526                 regs->npc -= 4;
527         }
528 }
529
530 /* Note that 'init' is a special process: it doesn't get signals it doesn't
531  * want to handle. Thus you cannot kill init even with a SIGKILL even by
532  * mistake.
533  */
534 static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
535 {
536         struct k_sigaction ka;
537         int restart_syscall;
538         sigset_t *oldset;
539         siginfo_t info;
540         int signr;
541
542         if (pt_regs_is_syscall(regs) && (regs->psr & PSR_C))
543                 restart_syscall = 1;
544         else
545                 restart_syscall = 0;
546
547         if (test_thread_flag(TIF_RESTORE_SIGMASK))
548                 oldset = &current->saved_sigmask;
549         else
550                 oldset = &current->blocked;
551
552         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
553
554         /* If the debugger messes with the program counter, it clears
555          * the software "in syscall" bit, directing us to not perform
556          * a syscall restart.
557          */
558         if (restart_syscall && !pt_regs_is_syscall(regs))
559                 restart_syscall = 0;
560
561         if (signr > 0) {
562                 if (restart_syscall)
563                         syscall_restart(orig_i0, regs, &ka.sa);
564                 if (handle_signal(signr, &ka, &info, oldset, regs) == 0) {
565                         /* a signal was successfully delivered; the saved
566                          * sigmask will have been stored in the signal frame,
567                          * and will be restored by sigreturn, so we can simply
568                          * clear the TIF_RESTORE_SIGMASK flag.
569                          */
570                         if (test_thread_flag(TIF_RESTORE_SIGMASK))
571                                 clear_thread_flag(TIF_RESTORE_SIGMASK);
572                 }
573                 return;
574         }
575         if (restart_syscall &&
576             (regs->u_regs[UREG_I0] == ERESTARTNOHAND ||
577              regs->u_regs[UREG_I0] == ERESTARTSYS ||
578              regs->u_regs[UREG_I0] == ERESTARTNOINTR)) {
579                 /* replay the system call when we are done */
580                 regs->u_regs[UREG_I0] = orig_i0;
581                 regs->pc -= 4;
582                 regs->npc -= 4;
583                 pt_regs_clear_syscall(regs);
584         }
585         if (restart_syscall &&
586             regs->u_regs[UREG_I0] == ERESTART_RESTARTBLOCK) {
587                 regs->u_regs[UREG_G1] = __NR_restart_syscall;
588                 regs->pc -= 4;
589                 regs->npc -= 4;
590                 pt_regs_clear_syscall(regs);
591         }
592
593         /* if there's no signal to deliver, we just put the saved sigmask
594          * back
595          */
596         if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
597                 clear_thread_flag(TIF_RESTORE_SIGMASK);
598                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
599         }
600 }
601
602 void do_notify_resume(struct pt_regs *regs, unsigned long orig_i0,
603                       unsigned long thread_info_flags)
604 {
605         if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
606                 do_signal(regs, orig_i0);
607         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
608                 clear_thread_flag(TIF_NOTIFY_RESUME);
609                 tracehook_notify_resume(regs);
610                 if (current->replacement_session_keyring)
611                         key_replace_session_keyring();
612         }
613 }
614
615 asmlinkage int
616 do_sys_sigstack(struct sigstack __user *ssptr, struct sigstack __user *ossptr,
617                 unsigned long sp)
618 {
619         int ret = -EFAULT;
620
621         /* First see if old state is wanted. */
622         if (ossptr) {
623                 if (put_user(current->sas_ss_sp + current->sas_ss_size,
624                              &ossptr->the_stack) ||
625                     __put_user(on_sig_stack(sp), &ossptr->cur_status))
626                         goto out;
627         }
628
629         /* Now see if we want to update the new state. */
630         if (ssptr) {
631                 char *ss_sp;
632
633                 if (get_user(ss_sp, &ssptr->the_stack))
634                         goto out;
635                 /* If the current stack was set with sigaltstack, don't
636                    swap stacks while we are on it.  */
637                 ret = -EPERM;
638                 if (current->sas_ss_sp && on_sig_stack(sp))
639                         goto out;
640
641                 /* Since we don't know the extent of the stack, and we don't
642                    track onstack-ness, but rather calculate it, we must
643                    presume a size.  Ho hum this interface is lossy.  */
644                 current->sas_ss_sp = (unsigned long)ss_sp - SIGSTKSZ;
645                 current->sas_ss_size = SIGSTKSZ;
646         }
647         ret = 0;
648 out:
649         return ret;
650 }