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signal.c
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1 /*
2  * linux/arch/alpha/kernel/signal.c
3  *
4  * Copyright (C) 1995 Linus Torvalds
5  *
6  * 1997-11-02 Modified for POSIX.1b signals by Richard Henderson
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/smp.h>
18 #include <linux/stddef.h>
19 #include <linux/tty.h>
20 #include <linux/binfmts.h>
21 #include <linux/bitops.h>
22 #include <linux/syscalls.h>
23 #include <linux/tracehook.h>
24 
25 #include <asm/uaccess.h>
26 #include <asm/sigcontext.h>
27 #include <asm/ucontext.h>
28 
29 #include "proto.h"
30 
31 
32 #define DEBUG_SIG 0
33 
34 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
35 
36 asmlinkage void ret_from_sys_call(void);
37 
38 /*
39  * The OSF/1 sigprocmask calling sequence is different from the
40  * C sigprocmask() sequence..
41  */
42 SYSCALL_DEFINE2(osf_sigprocmask, int, how, unsigned long, newmask)
43 {
44  sigset_t oldmask;
45  sigset_t mask;
46  unsigned long res;
47 
48  siginitset(&mask, newmask & _BLOCKABLE);
49  res = sigprocmask(how, &mask, &oldmask);
50  if (!res) {
52  res = oldmask.sig[0];
53  }
54  return res;
55 }
56 
57 SYSCALL_DEFINE3(osf_sigaction, int, sig,
58  const struct osf_sigaction __user *, act,
59  struct osf_sigaction __user *, oact)
60 {
61  struct k_sigaction new_ka, old_ka;
62  int ret;
63 
64  if (act) {
66  if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
67  __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
68  __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
69  __get_user(mask, &act->sa_mask))
70  return -EFAULT;
71  siginitset(&new_ka.sa.sa_mask, mask);
72  new_ka.ka_restorer = NULL;
73  }
74 
75  ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
76 
77  if (!ret && oact) {
78  if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
79  __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
80  __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
81  __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
82  return -EFAULT;
83  }
84 
85  return ret;
86 }
87 
88 SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
89  struct sigaction __user *, oact,
90  size_t, sigsetsize, void __user *, restorer)
91 {
92  struct k_sigaction new_ka, old_ka;
93  int ret;
94 
95  /* XXX: Don't preclude handling different sized sigset_t's. */
96  if (sigsetsize != sizeof(sigset_t))
97  return -EINVAL;
98 
99  if (act) {
100  new_ka.ka_restorer = restorer;
101  if (copy_from_user(&new_ka.sa, act, sizeof(*act)))
102  return -EFAULT;
103  }
104 
105  ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
106 
107  if (!ret && oact) {
108  if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
109  return -EFAULT;
110  }
111 
112  return ret;
113 }
114 
115 /*
116  * Atomically swap in the new signal mask, and wait for a signal.
117  */
119 {
120  sigset_t blocked;
121  siginitset(&blocked, mask);
122  return sigsuspend(&blocked);
123 }
124 
125 asmlinkage int
126 sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
127 {
128  return do_sigaltstack(uss, uoss, rdusp());
129 }
130 
131 /*
132  * Do a signal return; undo the signal stack.
133  */
134 
135 #if _NSIG_WORDS > 1
136 # error "Non SA_SIGINFO frame needs rearranging"
137 #endif
138 
139 struct sigframe
140 {
141  struct sigcontext sc;
142  unsigned int retcode[3];
143 };
144 
146 {
147  struct siginfo info;
148  struct ucontext uc;
149  unsigned int retcode[3];
150 };
151 
152 /* If this changes, userland unwinders that Know Things about our signal
153  frame will break. Do not undertake lightly. It also implies an ABI
154  change wrt the size of siginfo_t, which may cause some pain. */
155 extern char compile_time_assert
156  [offsetof(struct rt_sigframe, uc.uc_mcontext) == 176 ? 1 : -1];
157 
158 #define INSN_MOV_R30_R16 0x47fe0410
159 #define INSN_LDI_R0 0x201f0000
160 #define INSN_CALLSYS 0x00000083
161 
162 static long
163 restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
164  struct switch_stack *sw)
165 {
166  unsigned long usp;
167  long i, err = __get_user(regs->pc, &sc->sc_pc);
168 
169  current_thread_info()->restart_block.fn = do_no_restart_syscall;
170 
171  sw->r26 = (unsigned long) ret_from_sys_call;
172 
173  err |= __get_user(regs->r0, sc->sc_regs+0);
174  err |= __get_user(regs->r1, sc->sc_regs+1);
175  err |= __get_user(regs->r2, sc->sc_regs+2);
176  err |= __get_user(regs->r3, sc->sc_regs+3);
177  err |= __get_user(regs->r4, sc->sc_regs+4);
178  err |= __get_user(regs->r5, sc->sc_regs+5);
179  err |= __get_user(regs->r6, sc->sc_regs+6);
180  err |= __get_user(regs->r7, sc->sc_regs+7);
181  err |= __get_user(regs->r8, sc->sc_regs+8);
182  err |= __get_user(sw->r9, sc->sc_regs+9);
183  err |= __get_user(sw->r10, sc->sc_regs+10);
184  err |= __get_user(sw->r11, sc->sc_regs+11);
185  err |= __get_user(sw->r12, sc->sc_regs+12);
186  err |= __get_user(sw->r13, sc->sc_regs+13);
187  err |= __get_user(sw->r14, sc->sc_regs+14);
188  err |= __get_user(sw->r15, sc->sc_regs+15);
189  err |= __get_user(regs->r16, sc->sc_regs+16);
190  err |= __get_user(regs->r17, sc->sc_regs+17);
191  err |= __get_user(regs->r18, sc->sc_regs+18);
192  err |= __get_user(regs->r19, sc->sc_regs+19);
193  err |= __get_user(regs->r20, sc->sc_regs+20);
194  err |= __get_user(regs->r21, sc->sc_regs+21);
195  err |= __get_user(regs->r22, sc->sc_regs+22);
196  err |= __get_user(regs->r23, sc->sc_regs+23);
197  err |= __get_user(regs->r24, sc->sc_regs+24);
198  err |= __get_user(regs->r25, sc->sc_regs+25);
199  err |= __get_user(regs->r26, sc->sc_regs+26);
200  err |= __get_user(regs->r27, sc->sc_regs+27);
201  err |= __get_user(regs->r28, sc->sc_regs+28);
202  err |= __get_user(regs->gp, sc->sc_regs+29);
203  err |= __get_user(usp, sc->sc_regs+30);
204  wrusp(usp);
205 
206  for (i = 0; i < 31; i++)
207  err |= __get_user(sw->fp[i], sc->sc_fpregs+i);
208  err |= __get_user(sw->fp[31], &sc->sc_fpcr);
209 
210  return err;
211 }
212 
213 /* Note that this syscall is also used by setcontext(3) to install
214  a given sigcontext. This because it's impossible to set *all*
215  registers and transfer control from userland. */
216 
217 asmlinkage void
218 do_sigreturn(struct sigcontext __user *sc, struct pt_regs *regs,
219  struct switch_stack *sw)
220 {
221  sigset_t set;
222 
223  /* Verify that it's a good sigcontext before using it */
224  if (!access_ok(VERIFY_READ, sc, sizeof(*sc)))
225  goto give_sigsegv;
226  if (__get_user(set.sig[0], &sc->sc_mask))
227  goto give_sigsegv;
228 
229  set_current_blocked(&set);
230 
231  if (restore_sigcontext(sc, regs, sw))
232  goto give_sigsegv;
233 
234  /* Send SIGTRAP if we're single-stepping: */
235  if (ptrace_cancel_bpt (current)) {
236  siginfo_t info;
237 
238  info.si_signo = SIGTRAP;
239  info.si_errno = 0;
240  info.si_code = TRAP_BRKPT;
241  info.si_addr = (void __user *) regs->pc;
242  info.si_trapno = 0;
243  send_sig_info(SIGTRAP, &info, current);
244  }
245  return;
246 
247 give_sigsegv:
249 }
250 
251 asmlinkage void
252 do_rt_sigreturn(struct rt_sigframe __user *frame, struct pt_regs *regs,
253  struct switch_stack *sw)
254 {
255  sigset_t set;
256 
257  /* Verify that it's a good ucontext_t before using it */
258  if (!access_ok(VERIFY_READ, &frame->uc, sizeof(frame->uc)))
259  goto give_sigsegv;
260  if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
261  goto give_sigsegv;
262 
263  set_current_blocked(&set);
264 
265  if (restore_sigcontext(&frame->uc.uc_mcontext, regs, sw))
266  goto give_sigsegv;
267 
268  /* Send SIGTRAP if we're single-stepping: */
269  if (ptrace_cancel_bpt (current)) {
270  siginfo_t info;
271 
272  info.si_signo = SIGTRAP;
273  info.si_errno = 0;
274  info.si_code = TRAP_BRKPT;
275  info.si_addr = (void __user *) regs->pc;
276  info.si_trapno = 0;
277  send_sig_info(SIGTRAP, &info, current);
278  }
279  return;
280 
281 give_sigsegv:
283 }
284 
285 
286 /*
287  * Set up a signal frame.
288  */
289 
290 static inline void __user *
291 get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
292 {
293  if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! sas_ss_flags(sp))
294  sp = current->sas_ss_sp + current->sas_ss_size;
295 
296  return (void __user *)((sp - frame_size) & -32ul);
297 }
298 
299 static long
300 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
301  unsigned long mask, unsigned long sp)
302 {
303  struct switch_stack *sw = (struct switch_stack *)regs - 1;
304  long i, err = 0;
305 
306  err |= __put_user(on_sig_stack((unsigned long)sc), &sc->sc_onstack);
307  err |= __put_user(mask, &sc->sc_mask);
308  err |= __put_user(regs->pc, &sc->sc_pc);
309  err |= __put_user(8, &sc->sc_ps);
310 
311  err |= __put_user(regs->r0 , sc->sc_regs+0);
312  err |= __put_user(regs->r1 , sc->sc_regs+1);
313  err |= __put_user(regs->r2 , sc->sc_regs+2);
314  err |= __put_user(regs->r3 , sc->sc_regs+3);
315  err |= __put_user(regs->r4 , sc->sc_regs+4);
316  err |= __put_user(regs->r5 , sc->sc_regs+5);
317  err |= __put_user(regs->r6 , sc->sc_regs+6);
318  err |= __put_user(regs->r7 , sc->sc_regs+7);
319  err |= __put_user(regs->r8 , sc->sc_regs+8);
320  err |= __put_user(sw->r9 , sc->sc_regs+9);
321  err |= __put_user(sw->r10 , sc->sc_regs+10);
322  err |= __put_user(sw->r11 , sc->sc_regs+11);
323  err |= __put_user(sw->r12 , sc->sc_regs+12);
324  err |= __put_user(sw->r13 , sc->sc_regs+13);
325  err |= __put_user(sw->r14 , sc->sc_regs+14);
326  err |= __put_user(sw->r15 , sc->sc_regs+15);
327  err |= __put_user(regs->r16, sc->sc_regs+16);
328  err |= __put_user(regs->r17, sc->sc_regs+17);
329  err |= __put_user(regs->r18, sc->sc_regs+18);
330  err |= __put_user(regs->r19, sc->sc_regs+19);
331  err |= __put_user(regs->r20, sc->sc_regs+20);
332  err |= __put_user(regs->r21, sc->sc_regs+21);
333  err |= __put_user(regs->r22, sc->sc_regs+22);
334  err |= __put_user(regs->r23, sc->sc_regs+23);
335  err |= __put_user(regs->r24, sc->sc_regs+24);
336  err |= __put_user(regs->r25, sc->sc_regs+25);
337  err |= __put_user(regs->r26, sc->sc_regs+26);
338  err |= __put_user(regs->r27, sc->sc_regs+27);
339  err |= __put_user(regs->r28, sc->sc_regs+28);
340  err |= __put_user(regs->gp , sc->sc_regs+29);
341  err |= __put_user(sp, sc->sc_regs+30);
342  err |= __put_user(0, sc->sc_regs+31);
343 
344  for (i = 0; i < 31; i++)
345  err |= __put_user(sw->fp[i], sc->sc_fpregs+i);
346  err |= __put_user(0, sc->sc_fpregs+31);
347  err |= __put_user(sw->fp[31], &sc->sc_fpcr);
348 
349  err |= __put_user(regs->trap_a0, &sc->sc_traparg_a0);
350  err |= __put_user(regs->trap_a1, &sc->sc_traparg_a1);
351  err |= __put_user(regs->trap_a2, &sc->sc_traparg_a2);
352 
353  return err;
354 }
355 
356 static int
357 setup_frame(int sig, struct k_sigaction *ka, sigset_t *set,
358  struct pt_regs *regs)
359 {
360  unsigned long oldsp, r26, err = 0;
361  struct sigframe __user *frame;
362 
363  oldsp = rdusp();
364  frame = get_sigframe(ka, oldsp, sizeof(*frame));
365  if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
366  return -EFAULT;
367 
368  err |= setup_sigcontext(&frame->sc, regs, set->sig[0], oldsp);
369  if (err)
370  return -EFAULT;
371 
372  /* Set up to return from userspace. If provided, use a stub
373  already in userspace. */
374  if (ka->ka_restorer) {
375  r26 = (unsigned long) ka->ka_restorer;
376  } else {
377  err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
378  err |= __put_user(INSN_LDI_R0+__NR_sigreturn, frame->retcode+1);
379  err |= __put_user(INSN_CALLSYS, frame->retcode+2);
380  imb();
381  r26 = (unsigned long) frame->retcode;
382  }
383 
384  /* Check that everything was written properly. */
385  if (err)
386  return err;
387 
388  /* "Return" to the handler */
389  regs->r26 = r26;
390  regs->r27 = regs->pc = (unsigned long) ka->sa.sa_handler;
391  regs->r16 = sig; /* a0: signal number */
392  regs->r17 = 0; /* a1: exception code */
393  regs->r18 = (unsigned long) &frame->sc; /* a2: sigcontext pointer */
394  wrusp((unsigned long) frame);
395 
396 #if DEBUG_SIG
397  printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
398  current->comm, current->pid, frame, regs->pc, regs->r26);
399 #endif
400  return 0;
401 }
402 
403 static int
404 setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
405  sigset_t *set, struct pt_regs *regs)
406 {
407  unsigned long oldsp, r26, err = 0;
408  struct rt_sigframe __user *frame;
409 
410  oldsp = rdusp();
411  frame = get_sigframe(ka, oldsp, sizeof(*frame));
412  if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
413  return -EFAULT;
414 
415  err |= copy_siginfo_to_user(&frame->info, info);
416 
417  /* Create the ucontext. */
418  err |= __put_user(0, &frame->uc.uc_flags);
419  err |= __put_user(0, &frame->uc.uc_link);
420  err |= __put_user(set->sig[0], &frame->uc.uc_osf_sigmask);
421  err |= __put_user(current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
422  err |= __put_user(sas_ss_flags(oldsp), &frame->uc.uc_stack.ss_flags);
423  err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
424  err |= setup_sigcontext(&frame->uc.uc_mcontext, regs,
425  set->sig[0], oldsp);
426  err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
427  if (err)
428  return -EFAULT;
429 
430  /* Set up to return from userspace. If provided, use a stub
431  already in userspace. */
432  if (ka->ka_restorer) {
433  r26 = (unsigned long) ka->ka_restorer;
434  } else {
435  err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
437  frame->retcode+1);
438  err |= __put_user(INSN_CALLSYS, frame->retcode+2);
439  imb();
440  r26 = (unsigned long) frame->retcode;
441  }
442 
443  if (err)
444  return -EFAULT;
445 
446  /* "Return" to the handler */
447  regs->r26 = r26;
448  regs->r27 = regs->pc = (unsigned long) ka->sa.sa_handler;
449  regs->r16 = sig; /* a0: signal number */
450  regs->r17 = (unsigned long) &frame->info; /* a1: siginfo pointer */
451  regs->r18 = (unsigned long) &frame->uc; /* a2: ucontext pointer */
452  wrusp((unsigned long) frame);
453 
454 #if DEBUG_SIG
455  printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
456  current->comm, current->pid, frame, regs->pc, regs->r26);
457 #endif
458 
459  return 0;
460 }
461 
462 
463 /*
464  * OK, we're invoking a handler.
465  */
466 static inline void
467 handle_signal(int sig, struct k_sigaction *ka, siginfo_t *info,
468  struct pt_regs * regs)
469 {
470  sigset_t *oldset = sigmask_to_save();
471  int ret;
472 
473  if (ka->sa.sa_flags & SA_SIGINFO)
474  ret = setup_rt_frame(sig, ka, info, oldset, regs);
475  else
476  ret = setup_frame(sig, ka, oldset, regs);
477 
478  if (ret) {
479  force_sigsegv(sig, current);
480  return;
481  }
482  signal_delivered(sig, info, ka, regs, 0);
483 }
484 
485 static inline void
486 syscall_restart(unsigned long r0, unsigned long r19,
487  struct pt_regs *regs, struct k_sigaction *ka)
488 {
489  switch (regs->r0) {
490  case ERESTARTSYS:
491  if (!(ka->sa.sa_flags & SA_RESTART)) {
492  case ERESTARTNOHAND:
493  regs->r0 = EINTR;
494  break;
495  }
496  /* fallthrough */
497  case ERESTARTNOINTR:
498  regs->r0 = r0; /* reset v0 and a3 and replay syscall */
499  regs->r19 = r19;
500  regs->pc -= 4;
501  break;
503  regs->r0 = EINTR;
504  break;
505  }
506 }
507 
508 
509 /*
510  * Note that 'init' is a special process: it doesn't get signals it doesn't
511  * want to handle. Thus you cannot kill init even with a SIGKILL even by
512  * mistake.
513  *
514  * Note that we go through the signals twice: once to check the signals that
515  * the kernel can handle, and then we build all the user-level signal handling
516  * stack-frames in one go after that.
517  *
518  * "r0" and "r19" are the registers we need to restore for system call
519  * restart. "r0" is also used as an indicator whether we can restart at
520  * all (if we get here from anything but a syscall return, it will be 0)
521  */
522 static void
523 do_signal(struct pt_regs *regs, unsigned long r0, unsigned long r19)
524 {
525  siginfo_t info;
526  int signr;
527  unsigned long single_stepping = ptrace_cancel_bpt(current);
528  struct k_sigaction ka;
529 
530  /* This lets the debugger run, ... */
531  signr = get_signal_to_deliver(&info, &ka, regs, NULL);
532 
533  /* ... so re-check the single stepping. */
534  single_stepping |= ptrace_cancel_bpt(current);
535 
536  if (signr > 0) {
537  /* Whee! Actually deliver the signal. */
538  if (r0)
539  syscall_restart(r0, r19, regs, &ka);
540  handle_signal(signr, &ka, &info, regs);
541  if (single_stepping)
542  ptrace_set_bpt(current); /* re-set bpt */
543  return;
544  }
545 
546  if (r0) {
547  switch (regs->r0) {
548  case ERESTARTNOHAND:
549  case ERESTARTSYS:
550  case ERESTARTNOINTR:
551  /* Reset v0 and a3 and replay syscall. */
552  regs->r0 = r0;
553  regs->r19 = r19;
554  regs->pc -= 4;
555  break;
557  /* Force v0 to the restart syscall and reply. */
558  regs->r0 = __NR_restart_syscall;
559  regs->pc -= 4;
560  break;
561  }
562  }
563 
564  /* If there's no signal to deliver, we just restore the saved mask. */
565  restore_saved_sigmask();
566  if (single_stepping)
567  ptrace_set_bpt(current); /* re-set breakpoint */
568 }
569 
570 void
571 do_work_pending(struct pt_regs *regs, unsigned long thread_flags,
572  unsigned long r0, unsigned long r19)
573 {
574  do {
575  if (thread_flags & _TIF_NEED_RESCHED) {
576  schedule();
577  } else {
579  if (thread_flags & _TIF_SIGPENDING) {
580  do_signal(regs, r0, r19);
581  r0 = 0;
582  } else {
583  clear_thread_flag(TIF_NOTIFY_RESUME);
584  tracehook_notify_resume(regs);
585  }
586  }
588  thread_flags = current_thread_info()->flags;
589  } while (thread_flags & _TIF_WORK_MASK);
590 }