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Linux/arch/xtensa/kernel/signal.c

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  1 /*
  2  * arch/xtensa/kernel/signal.c
  3  *
  4  * Default platform functions.
  5  *
  6  * This file is subject to the terms and conditions of the GNU General Public
  7  * License.  See the file "COPYING" in the main directory of this archive
  8  * for more details.
  9  *
 10  * Copyright (C) 2005, 2006 Tensilica Inc.
 11  * Copyright (C) 1991, 1992  Linus Torvalds
 12  * 1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 13  *
 14  * Chris Zankel <chris@zankel.net>
 15  * Joe Taylor <joe@tensilica.com>
 16  */
 17 
 18 #include <linux/signal.h>
 19 #include <linux/errno.h>
 20 #include <linux/ptrace.h>
 21 #include <linux/personality.h>
 22 #include <linux/tracehook.h>
 23 
 24 #include <asm/ucontext.h>
 25 #include <asm/uaccess.h>
 26 #include <asm/cacheflush.h>
 27 #include <asm/coprocessor.h>
 28 #include <asm/unistd.h>
 29 
 30 #define DEBUG_SIG  0
 31 
 32 extern struct task_struct *coproc_owners[];
 33 
 34 struct rt_sigframe
 35 {
 36         struct siginfo info;
 37         struct ucontext uc;
 38         struct {
 39                 xtregs_opt_t opt;
 40                 xtregs_user_t user;
 41 #if XTENSA_HAVE_COPROCESSORS
 42                 xtregs_coprocessor_t cp;
 43 #endif
 44         } xtregs;
 45         unsigned char retcode[6];
 46         unsigned int window[4];
 47 };
 48 
 49 /* 
 50  * Flush register windows stored in pt_regs to stack.
 51  * Returns 1 for errors.
 52  */
 53 
 54 int
 55 flush_window_regs_user(struct pt_regs *regs)
 56 {
 57         const unsigned long ws = regs->windowstart;
 58         const unsigned long wb = regs->windowbase;
 59         unsigned long sp = 0;
 60         unsigned long wm;
 61         int err = 1;
 62         int base;
 63 
 64         /* Return if no other frames. */
 65 
 66         if (regs->wmask == 1)
 67                 return 0;
 68 
 69         /* Rotate windowmask and skip empty frames. */
 70 
 71         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
 72         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
 73                 
 74         /* For call8 or call12 frames, we need the previous stack pointer. */
 75 
 76         if ((regs->wmask & 2) == 0)
 77                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
 78                         goto errout;
 79 
 80         /* Spill frames to stack. */
 81 
 82         while (base < XCHAL_NUM_AREGS / 4) {
 83 
 84                 int m = (wm >> base);
 85                 int inc = 0;
 86 
 87                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
 88 
 89                 if (m & 2) {                    /* call4 */
 90                         inc = 1;
 91 
 92                 } else if (m & 4) {             /* call8 */
 93                         if (copy_to_user((void*)(sp - 32),
 94                                            &regs->areg[(base + 1) * 4], 16))
 95                                 goto errout;
 96                         inc = 2;
 97 
 98                 } else if (m & 8) {     /* call12 */
 99                         if (copy_to_user((void*)(sp - 48),
100                                            &regs->areg[(base + 1) * 4], 32))
101                                 goto errout;
102                         inc = 3;
103                 }
104 
105                 /* Save current frame a0..a3 under next SP */
106 
107                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
108                 if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
109                         goto errout;
110 
111                 /* Get current stack pointer for next loop iteration. */
112 
113                 sp = regs->areg[base * 4 + 1];
114                 base += inc;
115         }
116 
117         regs->wmask = 1;
118         regs->windowstart = 1 << wb;
119 
120         return 0;
121 
122 errout:
123         return err;
124 }
125 
126 /*
127  * Note: We don't copy double exception 'regs', we have to finish double exc. 
128  * first before we return to signal handler! This dbl.exc.handler might cause 
129  * another double exception, but I think we are fine as the situation is the 
130  * same as if we had returned to the signal handerl and got an interrupt 
131  * immediately...
132  */
133 
134 static int
135 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
136 {
137         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
138         struct thread_info *ti = current_thread_info();
139         int err = 0;
140 
141 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
142         COPY(pc);
143         COPY(ps);
144         COPY(lbeg);
145         COPY(lend);
146         COPY(lcount);
147         COPY(sar);
148 #undef COPY
149 
150         err |= flush_window_regs_user(regs);
151         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
152         err |= __put_user(0, &sc->sc_xtregs);
153 
154         if (err)
155                 return err;
156 
157 #if XTENSA_HAVE_COPROCESSORS
158         coprocessor_flush_all(ti);
159         coprocessor_release_all(ti);
160         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
161                               sizeof (frame->xtregs.cp));
162 #endif
163         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
164                               sizeof (xtregs_opt_t));
165         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
166                               sizeof (xtregs_user_t));
167 
168         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
169 
170         return err;
171 }
172 
173 static int
174 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
175 {
176         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
177         struct thread_info *ti = current_thread_info();
178         unsigned int err = 0;
179         unsigned long ps;
180 
181 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
182         COPY(pc);
183         COPY(lbeg);
184         COPY(lend);
185         COPY(lcount);
186         COPY(sar);
187 #undef COPY
188 
189         /* All registers were flushed to stack. Start with a prestine frame. */
190 
191         regs->wmask = 1;
192         regs->windowbase = 0;
193         regs->windowstart = 1;
194 
195         regs->syscall = -1;             /* disable syscall checks */
196 
197         /* For PS, restore only PS.CALLINC.
198          * Assume that all other bits are either the same as for the signal
199          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
200          */
201         err |= __get_user(ps, &sc->sc_ps);
202         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
203 
204         /* Additional corruption checks */
205 
206         if ((regs->lcount > 0)
207             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
208                 err = 1;
209 
210         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
211 
212         if (err)
213                 return err;
214 
215         /* The signal handler may have used coprocessors in which
216          * case they are still enabled.  We disable them to force a
217          * reloading of the original task's CP state by the lazy
218          * context-switching mechanisms of CP exception handling.
219          * Also, we essentially discard any coprocessor state that the
220          * signal handler created. */
221 
222 #if XTENSA_HAVE_COPROCESSORS
223         coprocessor_release_all(ti);
224         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
225                                 sizeof (frame->xtregs.cp));
226 #endif
227         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
228                                 sizeof (xtregs_user_t));
229         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
230                                 sizeof (xtregs_opt_t));
231 
232         return err;
233 }
234 
235 
236 /*
237  * Do a signal return; undo the signal stack.
238  */
239 
240 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
241                                     long a4, long a5, struct pt_regs *regs)
242 {
243         struct rt_sigframe __user *frame;
244         sigset_t set;
245         int ret;
246 
247         /* Always make any pending restarted system calls return -EINTR */
248         current_thread_info()->restart_block.fn = do_no_restart_syscall;
249 
250         if (regs->depc > 64)
251                 panic("rt_sigreturn in double exception!\n");
252 
253         frame = (struct rt_sigframe __user *) regs->areg[1];
254 
255         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
256                 goto badframe;
257 
258         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
259                 goto badframe;
260 
261         set_current_blocked(&set);
262 
263         if (restore_sigcontext(regs, frame))
264                 goto badframe;
265 
266         ret = regs->areg[2];
267 
268         if (restore_altstack(&frame->uc.uc_stack))
269                 goto badframe;
270 
271         return ret;
272 
273 badframe:
274         force_sig(SIGSEGV, current);
275         return 0;
276 }
277 
278 
279 
280 /*
281  * Set up a signal frame.
282  */
283 
284 static int
285 gen_return_code(unsigned char *codemem)
286 {
287         int err = 0;
288 
289         /*
290          * The 12-bit immediate is really split up within the 24-bit MOVI
291          * instruction.  As long as the above system call numbers fit within
292          * 8-bits, the following code works fine. See the Xtensa ISA for
293          * details.
294          */
295 
296 #if __NR_rt_sigreturn > 255
297 # error Generating the MOVI instruction below breaks!
298 #endif
299 
300 #ifdef __XTENSA_EB__   /* Big Endian version */
301         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
302         err |= __put_user(0x22, &codemem[0]);
303         err |= __put_user(0x0a, &codemem[1]);
304         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
305         /* Generate instruction:  SYSCALL */
306         err |= __put_user(0x00, &codemem[3]);
307         err |= __put_user(0x05, &codemem[4]);
308         err |= __put_user(0x00, &codemem[5]);
309 
310 #elif defined __XTENSA_EL__   /* Little Endian version */
311         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
312         err |= __put_user(0x22, &codemem[0]);
313         err |= __put_user(0xa0, &codemem[1]);
314         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
315         /* Generate instruction:  SYSCALL */
316         err |= __put_user(0x00, &codemem[3]);
317         err |= __put_user(0x50, &codemem[4]);
318         err |= __put_user(0x00, &codemem[5]);
319 #else
320 # error Must use compiler for Xtensa processors.
321 #endif
322 
323         /* Flush generated code out of the data cache */
324 
325         if (err == 0) {
326                 __invalidate_icache_range((unsigned long)codemem, 6UL);
327                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
328         }
329 
330         return err;
331 }
332 
333 
334 static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
335                        sigset_t *set, struct pt_regs *regs)
336 {
337         struct rt_sigframe *frame;
338         int err = 0;
339         int signal;
340         unsigned long sp, ra, tp;
341 
342         sp = regs->areg[1];
343 
344         if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
345                 sp = current->sas_ss_sp + current->sas_ss_size;
346         }
347 
348         frame = (void *)((sp - sizeof(*frame)) & -16ul);
349 
350         if (regs->depc > 64)
351                 panic ("Double exception sys_sigreturn\n");
352 
353         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
354                 goto give_sigsegv;
355         }
356 
357         signal = current_thread_info()->exec_domain
358                 && current_thread_info()->exec_domain->signal_invmap
359                 && sig < 32
360                 ? current_thread_info()->exec_domain->signal_invmap[sig]
361                 : sig;
362 
363         if (ka->sa.sa_flags & SA_SIGINFO) {
364                 err |= copy_siginfo_to_user(&frame->info, info);
365         }
366 
367         /* Create the user context.  */
368 
369         err |= __put_user(0, &frame->uc.uc_flags);
370         err |= __put_user(0, &frame->uc.uc_link);
371         err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
372         err |= setup_sigcontext(frame, regs);
373         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
374 
375         if (ka->sa.sa_flags & SA_RESTORER) {
376                 ra = (unsigned long)ka->sa.sa_restorer;
377         } else {
378 
379                 /* Create sys_rt_sigreturn syscall in stack frame */
380 
381                 err |= gen_return_code(frame->retcode);
382 
383                 if (err) {
384                         goto give_sigsegv;
385                 }
386                 ra = (unsigned long) frame->retcode;
387         }
388 
389         /* 
390          * Create signal handler execution context.
391          * Return context not modified until this point.
392          */
393 
394         /* Set up registers for signal handler; preserve the threadptr */
395         tp = regs->threadptr;
396         start_thread(regs, (unsigned long) ka->sa.sa_handler,
397                      (unsigned long) frame);
398 
399         /* Set up a stack frame for a call4
400          * Note: PS.CALLINC is set to one by start_thread
401          */
402         regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
403         regs->areg[6] = (unsigned long) signal;
404         regs->areg[7] = (unsigned long) &frame->info;
405         regs->areg[8] = (unsigned long) &frame->uc;
406         regs->threadptr = tp;
407 
408         /* Set access mode to USER_DS.  Nomenclature is outdated, but
409          * functionality is used in uaccess.h
410          */
411         set_fs(USER_DS);
412 
413 #if DEBUG_SIG
414         printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
415                 current->comm, current->pid, signal, frame, regs->pc);
416 #endif
417 
418         return 0;
419 
420 give_sigsegv:
421         force_sigsegv(sig, current);
422         return -EFAULT;
423 }
424 
425 /*
426  * Note that 'init' is a special process: it doesn't get signals it doesn't
427  * want to handle. Thus you cannot kill init even with a SIGKILL even by
428  * mistake.
429  *
430  * Note that we go through the signals twice: once to check the signals that
431  * the kernel can handle, and then we build all the user-level signal handling
432  * stack-frames in one go after that.
433  */
434 static void do_signal(struct pt_regs *regs)
435 {
436         siginfo_t info;
437         int signr;
438         struct k_sigaction ka;
439 
440         task_pt_regs(current)->icountlevel = 0;
441 
442         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
443 
444         if (signr > 0) {
445                 int ret;
446 
447                 /* Are we from a system call? */
448 
449                 if ((signed)regs->syscall >= 0) {
450 
451                         /* If so, check system call restarting.. */
452 
453                         switch (regs->areg[2]) {
454                                 case -ERESTARTNOHAND:
455                                 case -ERESTART_RESTARTBLOCK:
456                                         regs->areg[2] = -EINTR;
457                                         break;
458 
459                                 case -ERESTARTSYS:
460                                         if (!(ka.sa.sa_flags & SA_RESTART)) {
461                                                 regs->areg[2] = -EINTR;
462                                                 break;
463                                         }
464                                         /* fallthrough */
465                                 case -ERESTARTNOINTR:
466                                         regs->areg[2] = regs->syscall;
467                                         regs->pc -= 3;
468                                         break;
469 
470                                 default:
471                                         /* nothing to do */
472                                         if (regs->areg[2] != 0)
473                                         break;
474                         }
475                 }
476 
477                 /* Whee!  Actually deliver the signal.  */
478                 /* Set up the stack frame */
479                 ret = setup_frame(signr, &ka, &info, sigmask_to_save(), regs);
480                 if (ret)
481                         return;
482 
483                 signal_delivered(signr, &info, &ka, regs, 0);
484                 if (current->ptrace & PT_SINGLESTEP)
485                         task_pt_regs(current)->icountlevel = 1;
486 
487                 return;
488         }
489 
490         /* Did we come from a system call? */
491         if ((signed) regs->syscall >= 0) {
492                 /* Restart the system call - no handlers present */
493                 switch (regs->areg[2]) {
494                 case -ERESTARTNOHAND:
495                 case -ERESTARTSYS:
496                 case -ERESTARTNOINTR:
497                         regs->areg[2] = regs->syscall;
498                         regs->pc -= 3;
499                         break;
500                 case -ERESTART_RESTARTBLOCK:
501                         regs->areg[2] = __NR_restart_syscall;
502                         regs->pc -= 3;
503                         break;
504                 }
505         }
506 
507         /* If there's no signal to deliver, we just restore the saved mask.  */
508         restore_saved_sigmask();
509 
510         if (current->ptrace & PT_SINGLESTEP)
511                 task_pt_regs(current)->icountlevel = 1;
512         return;
513 }
514 
515 void do_notify_resume(struct pt_regs *regs)
516 {
517         if (test_thread_flag(TIF_SIGPENDING))
518                 do_signal(regs);
519 
520         if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
521                 tracehook_notify_resume(regs);
522 }
523 

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