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TOMOYO Linux Cross Reference
Linux/arch/cris/arch-v32/kernel/signal.c

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  1 /*
  2  * Copyright (C) 2003, Axis Communications AB.
  3  */
  4 
  5 #include <linux/sched.h>
  6 #include <linux/mm.h>
  7 #include <linux/slab.h>
  8 #include <linux/kernel.h>
  9 #include <linux/signal.h>
 10 #include <linux/errno.h>
 11 #include <linux/wait.h>
 12 #include <linux/ptrace.h>
 13 #include <linux/unistd.h>
 14 #include <linux/stddef.h>
 15 #include <linux/syscalls.h>
 16 #include <linux/vmalloc.h>
 17 
 18 #include <asm/io.h>
 19 #include <asm/processor.h>
 20 #include <asm/ucontext.h>
 21 #include <asm/uaccess.h>
 22 #include <arch/hwregs/cpu_vect.h>
 23 
 24 extern unsigned long cris_signal_return_page;
 25 
 26 /*
 27  * A syscall in CRIS is really a "break 13" instruction, which is 2
 28  * bytes. The registers is manipulated so upon return the instruction
 29  * will be executed again.
 30  *
 31  * This relies on that PC points to the instruction after the break call.
 32  */
 33 #define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->erp -= 2;
 34 
 35 /* Signal frames. */
 36 struct signal_frame {
 37         struct sigcontext sc;
 38         unsigned long extramask[_NSIG_WORDS - 1];
 39         unsigned char retcode[8];       /* Trampoline code. */
 40 };
 41 
 42 struct rt_signal_frame {
 43         struct siginfo *pinfo;
 44         void *puc;
 45         struct siginfo info;
 46         struct ucontext uc;
 47         unsigned char retcode[8];       /* Trampoline code. */
 48 };
 49 
 50 void do_signal(int restart, struct pt_regs *regs);
 51 void keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
 52                       struct pt_regs *regs);
 53 
 54 static int
 55 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 56 {
 57         unsigned int err = 0;
 58         unsigned long old_usp;
 59 
 60         /* Always make any pending restarted system calls return -EINTR */
 61         current->restart_block.fn = do_no_restart_syscall;
 62 
 63         /*
 64          * Restore the registers from &sc->regs. sc is already checked
 65          * for VERIFY_READ since the signal_frame was previously
 66          * checked in sys_sigreturn().
 67          */
 68         if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
 69                 goto badframe;
 70 
 71         /* Make that the user-mode flag is set. */
 72         regs->ccs |= (1 << (U_CCS_BITNR + CCS_SHIFT));
 73 
 74         /* Don't perform syscall restarting */
 75         regs->exs = -1;
 76 
 77         /* Restore the old USP. */
 78         err |= __get_user(old_usp, &sc->usp);
 79         wrusp(old_usp);
 80 
 81         return err;
 82 
 83 badframe:
 84         return 1;
 85 }
 86 
 87 asmlinkage int sys_sigreturn(void)
 88 {
 89         struct pt_regs *regs = current_pt_regs();
 90         sigset_t set;
 91         struct signal_frame __user *frame;
 92         unsigned long oldspc = regs->spc;
 93         unsigned long oldccs = regs->ccs;
 94 
 95         frame = (struct signal_frame *) rdusp();
 96 
 97         /*
 98          * Since the signal is stacked on a dword boundary, the frame
 99          * should be dword aligned here as well. It it's not, then the
100          * user is trying some funny business.
101          */
102         if (((long)frame) & 3)
103                 goto badframe;
104 
105         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
106                 goto badframe;
107 
108         if (__get_user(set.sig[0], &frame->sc.oldmask) ||
109             (_NSIG_WORDS > 1 && __copy_from_user(&set.sig[1],
110                                                  frame->extramask,
111                                                  sizeof(frame->extramask))))
112                 goto badframe;
113 
114         set_current_blocked(&set);
115 
116         if (restore_sigcontext(regs, &frame->sc))
117                 goto badframe;
118 
119         keep_debug_flags(oldccs, oldspc, regs);
120 
121         return regs->r10;
122 
123 badframe:
124         force_sig(SIGSEGV, current);
125         return 0;
126 }
127 
128 asmlinkage int sys_rt_sigreturn(void)
129 {
130         struct pt_regs *regs = current_pt_regs();
131         sigset_t set;
132         struct rt_signal_frame __user *frame;
133         unsigned long oldspc = regs->spc;
134         unsigned long oldccs = regs->ccs;
135 
136         frame = (struct rt_signal_frame *) rdusp();
137 
138         /*
139          * Since the signal is stacked on a dword boundary, the frame
140          * should be dword aligned here as well. It it's not, then the
141          * user is trying some funny business.
142          */
143         if (((long)frame) & 3)
144                 goto badframe;
145 
146         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
147                 goto badframe;
148 
149         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
150                 goto badframe;
151 
152         set_current_blocked(&set);
153 
154         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
155                 goto badframe;
156 
157         if (restore_altstack(&frame->uc.uc_stack))
158                 goto badframe;
159 
160         keep_debug_flags(oldccs, oldspc, regs);
161 
162         return regs->r10;
163 
164 badframe:
165         force_sig(SIGSEGV, current);
166         return 0;
167 }
168 
169 /* Setup a signal frame. */
170 static int
171 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
172                  unsigned long mask)
173 {
174         int err;
175         unsigned long usp;
176 
177         err = 0;
178         usp = rdusp();
179 
180         /*
181          * Copy the registers. They are located first in sc, so it's
182          * possible to use sc directly.
183          */
184         err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
185 
186         err |= __put_user(mask, &sc->oldmask);
187         err |= __put_user(usp, &sc->usp);
188 
189         return err;
190 }
191 
192 /* Figure out where to put the new signal frame - usually on the stack. */
193 static inline void __user *
194 get_sigframe(struct ksignal *ksig, size_t frame_size)
195 {
196         unsigned long sp = sigsp(rdusp(), ksig);
197 
198         /* Make sure the frame is dword-aligned. */
199         sp &= ~3;
200 
201         return (void __user *)(sp - frame_size);
202 }
203 
204 /* Grab and setup a signal frame.
205  *
206  * Basically a lot of state-info is stacked, and arranged for the
207  * user-mode program to return to the kernel using either a trampiline
208  * which performs the syscall sigreturn(), or a provided user-mode
209  * trampoline.
210   */
211 static int
212 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
213 {
214         int err;
215         unsigned long return_ip;
216         struct signal_frame __user *frame;
217 
218         err = 0;
219         frame = get_sigframe(ksig, sizeof(*frame));
220 
221         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
222                 return -EFAULT;
223 
224         err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
225 
226         if (err)
227                 return -EFAULT;
228 
229         if (_NSIG_WORDS > 1) {
230                 err |= __copy_to_user(frame->extramask, &set->sig[1],
231                                       sizeof(frame->extramask));
232         }
233 
234         if (err)
235                 return -EFAULT;
236 
237         /*
238          * Set up to return from user-space. If provided, use a stub
239          * already located in user-space.
240          */
241         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
242                 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
243         } else {
244                 /* Trampoline - the desired return ip is in the signal return page. */
245                 return_ip = cris_signal_return_page;
246 
247                 /*
248                  * This is movu.w __NR_sigreturn, r9; break 13;
249                  *
250                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
251                  * reasons and because gdb uses it as a signature to notice
252                  * signal handler stack frames.
253                  */
254                 err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
255                 err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
256                 err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
257         }
258 
259         if (err)
260                 return -EFAULT;
261 
262         /*
263          * Set up registers for signal handler.
264          *
265          * Where the code enters now.
266          * Where the code enter later.
267          * First argument, signo.
268          */
269         regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
270         regs->srp = return_ip;
271         regs->r10 = ksig->sig;
272 
273         /* Actually move the USP to reflect the stacked frame. */
274         wrusp((unsigned long)frame);
275 
276         return 0;
277 }
278 
279 static int
280 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
281 {
282         int err;
283         unsigned long return_ip;
284         struct rt_signal_frame __user *frame;
285 
286         err = 0;
287         frame = get_sigframe(ksig, sizeof(*frame));
288 
289         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
290                 return -EFAULT;
291 
292         err |= __put_user(&frame->info, &frame->pinfo);
293         err |= __put_user(&frame->uc, &frame->puc);
294         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
295 
296         if (err)
297                 return -EFAULT;
298 
299         /* Clear all the bits of the ucontext we don't use.  */
300         err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
301         err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
302         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
303         err |= __save_altstack(&frame->uc.uc_stack, rdusp());
304 
305         if (err)
306                 return -EFAULT;
307 
308         /*
309          * Set up to return from user-space. If provided, use a stub
310          * already located in user-space.
311          */
312         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
313                 return_ip = (unsigned long) ksig->ka.sa.sa_restorer;
314         } else {
315                 /* Trampoline - the desired return ip is in the signal return page. */
316                 return_ip = cris_signal_return_page + 6;
317 
318                 /*
319                  * This is movu.w __NR_rt_sigreturn, r9; break 13;
320                  *
321                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
322                  * reasons and because gdb uses it as a signature to notice
323                  * signal handler stack frames.
324                  */
325                 err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));
326 
327                 err |= __put_user(__NR_rt_sigreturn,
328                                   (short __user*)(frame->retcode+2));
329 
330                 err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
331         }
332 
333         if (err)
334                 return -EFAULT;
335 
336         /*
337          * Set up registers for signal handler.
338          *
339          * Where the code enters now.
340          * Where the code enters later.
341          * First argument is signo.
342          * Second argument is (siginfo_t *).
343          * Third argument is unused.
344          */
345         regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
346         regs->srp = return_ip;
347         regs->r10 = ksig->sig;
348         regs->r11 = (unsigned long) &frame->info;
349         regs->r12 = 0;
350 
351         /* Actually move the usp to reflect the stacked frame. */
352         wrusp((unsigned long)frame);
353 
354         return 0;
355 }
356 
357 /* Invoke a signal handler to, well, handle the signal. */
358 static inline void
359 handle_signal(int canrestart, struct ksignal *ksig, struct pt_regs *regs)
360 {
361         sigset_t *oldset = sigmask_to_save();
362         int ret;
363 
364         /* Check if this got called from a system call. */
365         if (canrestart) {
366                 /* If so, check system call restarting. */
367                 switch (regs->r10) {
368                         case -ERESTART_RESTARTBLOCK:
369                         case -ERESTARTNOHAND:
370                                 /*
371                                  * This means that the syscall should
372                                  * only be restarted if there was no
373                                  * handler for the signal, and since
374                                  * this point isn't reached unless
375                                  * there is a handler, there's no need
376                                  * to restart.
377                                  */
378                                 regs->r10 = -EINTR;
379                                 break;
380 
381                         case -ERESTARTSYS:
382                                 /*
383                                  * This means restart the syscall if
384                                  * there is no handler, or the handler
385                                  * was registered with SA_RESTART.
386                                  */
387                                 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
388                                         regs->r10 = -EINTR;
389                                         break;
390                                 }
391 
392                                 /* Fall through. */
393 
394                         case -ERESTARTNOINTR:
395                                 /*
396                                  * This means that the syscall should
397                                  * be called again after the signal
398                                  * handler returns.
399                                  */
400                                 RESTART_CRIS_SYS(regs);
401                                 break;
402                 }
403         }
404 
405         /* Set up the stack frame. */
406         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
407                 ret = setup_rt_frame(ksig, oldset, regs);
408         else
409                 ret = setup_frame(ksig, oldset, regs);
410 
411         signal_setup_done(ret, ksig, 0);
412 }
413 
414 /*
415  * Note that 'init' is a special process: it doesn't get signals it doesn't
416  * want to handle. Thus you cannot kill init even with a SIGKILL even by
417  * mistake.
418  *
419  * Also note that the regs structure given here as an argument, is the latest
420  * pushed pt_regs. It may or may not be the same as the first pushed registers
421  * when the initial usermode->kernelmode transition took place. Therefore
422  * we can use user_mode(regs) to see if we came directly from kernel or user
423  * mode below.
424  */
425 void
426 do_signal(int canrestart, struct pt_regs *regs)
427 {
428         struct ksignal ksig;
429 
430         canrestart = canrestart && ((int)regs->exs >= 0);
431 
432         /*
433          * The common case should go fast, which is why this point is
434          * reached from kernel-mode. If that's the case, just return
435          * without doing anything.
436          */
437         if (!user_mode(regs))
438                 return;
439 
440         if (get_signal(&ksig)) {
441                 /* Whee!  Actually deliver the signal.  */
442                 handle_signal(canrestart, &ksig, regs);
443                 return;
444         }
445 
446         /* Got here from a system call? */
447         if (canrestart) {
448                 /* Restart the system call - no handlers present. */
449                 if (regs->r10 == -ERESTARTNOHAND ||
450                     regs->r10 == -ERESTARTSYS ||
451                     regs->r10 == -ERESTARTNOINTR) {
452                         RESTART_CRIS_SYS(regs);
453                 }
454 
455                 if (regs->r10 == -ERESTART_RESTARTBLOCK){
456                         regs->r9 = __NR_restart_syscall;
457                         regs->erp -= 2;
458                 }
459         }
460 
461         /* if there's no signal to deliver, we just put the saved sigmask
462          * back */
463         restore_saved_sigmask();
464 }
465 
466 asmlinkage void
467 ugdb_trap_user(struct thread_info *ti, int sig)
468 {
469         if (((user_regs(ti)->exs & 0xff00) >> 8) != SINGLE_STEP_INTR_VECT) {
470                 /* Zero single-step PC if the reason we stopped wasn't a single
471                    step exception. This is to avoid relying on it when it isn't
472                    reliable. */
473                 user_regs(ti)->spc = 0;
474         }
475         /* FIXME: Filter out false h/w breakpoint hits (i.e. EDA
476            not within any configured h/w breakpoint range). Synchronize with
477            what already exists for kernel debugging.  */
478         if (((user_regs(ti)->exs & 0xff00) >> 8) == BREAK_8_INTR_VECT) {
479                 /* Break 8: subtract 2 from ERP unless in a delay slot. */
480                 if (!(user_regs(ti)->erp & 0x1))
481                         user_regs(ti)->erp -= 2;
482         }
483         sys_kill(ti->task->pid, sig);
484 }
485 
486 void
487 keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
488                  struct pt_regs *regs)
489 {
490         if (oldccs & (1 << Q_CCS_BITNR)) {
491                 /* Pending single step due to single-stepping the break 13
492                    in the signal trampoline: keep the Q flag. */
493                 regs->ccs |= (1 << Q_CCS_BITNR);
494                 /* S flag should be set - complain if it's not. */
495                 if (!(oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT)))) {
496                         printk("Q flag but no S flag?");
497                 }
498                 regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
499                 /* Assume the SPC is valid and interesting. */
500                 regs->spc = oldspc;
501 
502         } else if (oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT))) {
503                 /* If a h/w bp was set in the signal handler we need
504                    to keep the S flag. */
505                 regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
506                 /* Don't keep the old SPC though; if we got here due to
507                    a single-step, the Q flag should have been set. */
508         } else if (regs->spc) {
509                 /* If we were single-stepping *before* the signal was taken,
510                    we don't want to restore that state now, because GDB will
511                    have forgotten all about it. */
512                 regs->spc = 0;
513                 regs->ccs &= ~(1 << (S_CCS_BITNR + CCS_SHIFT));
514         }
515 }
516 
517 /* Set up the trampolines on the signal return page. */
518 int __init
519 cris_init_signal(void)
520 {
521         u16* data = kmalloc(PAGE_SIZE, GFP_KERNEL);
522 
523         /* This is movu.w __NR_sigreturn, r9; break 13; */
524         data[0] = 0x9c5f;
525         data[1] = __NR_sigreturn;
526         data[2] = 0xe93d;
527         /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
528         data[3] = 0x9c5f;
529         data[4] = __NR_rt_sigreturn;
530         data[5] = 0xe93d;
531 
532         /* Map to userspace with appropriate permissions (no write access...) */
533         cris_signal_return_page = (unsigned long)
534           __ioremap_prot(virt_to_phys(data), PAGE_SIZE, PAGE_SIGNAL_TRAMPOLINE);
535 
536         return 0;
537 }
538 
539 __initcall(cris_init_signal);
540 

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