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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/freezer.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 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
 33 
 34 asmlinkage int do_signal(struct pt_regs *regs, sigset_t *oldset);
 35 
 36 extern struct task_struct *coproc_owners[];
 37 
 38 struct rt_sigframe
 39 {
 40         struct siginfo info;
 41         struct ucontext uc;
 42         struct {
 43                 xtregs_opt_t opt;
 44                 xtregs_user_t user;
 45 #if XTENSA_HAVE_COPROCESSORS
 46                 xtregs_coprocessor_t cp;
 47 #endif
 48         } xtregs;
 49         unsigned char retcode[6];
 50         unsigned int window[4];
 51 };
 52 
 53 /* 
 54  * Flush register windows stored in pt_regs to stack.
 55  * Returns 1 for errors.
 56  */
 57 
 58 int
 59 flush_window_regs_user(struct pt_regs *regs)
 60 {
 61         const unsigned long ws = regs->windowstart;
 62         const unsigned long wb = regs->windowbase;
 63         unsigned long sp = 0;
 64         unsigned long wm;
 65         int err = 1;
 66         int base;
 67 
 68         /* Return if no other frames. */
 69 
 70         if (regs->wmask == 1)
 71                 return 0;
 72 
 73         /* Rotate windowmask and skip empty frames. */
 74 
 75         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
 76         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
 77                 
 78         /* For call8 or call12 frames, we need the previous stack pointer. */
 79 
 80         if ((regs->wmask & 2) == 0)
 81                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
 82                         goto errout;
 83 
 84         /* Spill frames to stack. */
 85 
 86         while (base < XCHAL_NUM_AREGS / 4) {
 87 
 88                 int m = (wm >> base);
 89                 int inc = 0;
 90 
 91                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
 92 
 93                 if (m & 2) {                    /* call4 */
 94                         inc = 1;
 95 
 96                 } else if (m & 4) {             /* call8 */
 97                         if (copy_to_user((void*)(sp - 32),
 98                                            &regs->areg[(base + 1) * 4], 16))
 99                                 goto errout;
100                         inc = 2;
101 
102                 } else if (m & 8) {     /* call12 */
103                         if (copy_to_user((void*)(sp - 48),
104                                            &regs->areg[(base + 1) * 4], 32))
105                                 goto errout;
106                         inc = 3;
107                 }
108 
109                 /* Save current frame a0..a3 under next SP */
110 
111                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
112                 if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
113                         goto errout;
114 
115                 /* Get current stack pointer for next loop iteration. */
116 
117                 sp = regs->areg[base * 4 + 1];
118                 base += inc;
119         }
120 
121         regs->wmask = 1;
122         regs->windowstart = 1 << wb;
123 
124         return 0;
125 
126 errout:
127         return err;
128 }
129 
130 /*
131  * Note: We don't copy double exception 'regs', we have to finish double exc. 
132  * first before we return to signal handler! This dbl.exc.handler might cause 
133  * another double exception, but I think we are fine as the situation is the 
134  * same as if we had returned to the signal handerl and got an interrupt 
135  * immediately...
136  */
137 
138 static int
139 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
140 {
141         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
142         struct thread_info *ti = current_thread_info();
143         int err = 0;
144 
145 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
146         COPY(pc);
147         COPY(ps);
148         COPY(lbeg);
149         COPY(lend);
150         COPY(lcount);
151         COPY(sar);
152 #undef COPY
153 
154         err |= flush_window_regs_user(regs);
155         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
156         err |= __put_user(0, &sc->sc_xtregs);
157 
158         if (err)
159                 return err;
160 
161 #if XTENSA_HAVE_COPROCESSORS
162         coprocessor_flush_all(ti);
163         coprocessor_release_all(ti);
164         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
165                               sizeof (frame->xtregs.cp));
166 #endif
167         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
168                               sizeof (xtregs_opt_t));
169         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
170                               sizeof (xtregs_user_t));
171 
172         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
173 
174         return err;
175 }
176 
177 static int
178 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
179 {
180         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
181         struct thread_info *ti = current_thread_info();
182         unsigned int err = 0;
183         unsigned long ps;
184 
185 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
186         COPY(pc);
187         COPY(lbeg);
188         COPY(lend);
189         COPY(lcount);
190         COPY(sar);
191 #undef COPY
192 
193         /* All registers were flushed to stack. Start with a prestine frame. */
194 
195         regs->wmask = 1;
196         regs->windowbase = 0;
197         regs->windowstart = 1;
198 
199         regs->syscall = -1;             /* disable syscall checks */
200 
201         /* For PS, restore only PS.CALLINC.
202          * Assume that all other bits are either the same as for the signal
203          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
204          */
205         err |= __get_user(ps, &sc->sc_ps);
206         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
207 
208         /* Additional corruption checks */
209 
210         if ((regs->lcount > 0)
211             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
212                 err = 1;
213 
214         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
215 
216         if (err)
217                 return err;
218 
219         /* The signal handler may have used coprocessors in which
220          * case they are still enabled.  We disable them to force a
221          * reloading of the original task's CP state by the lazy
222          * context-switching mechanisms of CP exception handling.
223          * Also, we essentially discard any coprocessor state that the
224          * signal handler created. */
225 
226 #if XTENSA_HAVE_COPROCESSORS
227         coprocessor_release_all(ti);
228         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
229                                 sizeof (frame->xtregs.cp));
230 #endif
231         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
232                                 sizeof (xtregs_user_t));
233         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
234                                 sizeof (xtregs_opt_t));
235 
236         return err;
237 }
238 
239 
240 /*
241  * Do a signal return; undo the signal stack.
242  */
243 
244 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
245                                     long a4, long a5, struct pt_regs *regs)
246 {
247         struct rt_sigframe __user *frame;
248         sigset_t set;
249         int ret;
250 
251         if (regs->depc > 64)
252                 panic("rt_sigreturn in double exception!\n");
253 
254         frame = (struct rt_sigframe __user *) regs->areg[1];
255 
256         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
257                 goto badframe;
258 
259         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
260                 goto badframe;
261 
262         sigdelsetmask(&set, ~_BLOCKABLE);
263         set_current_blocked(&set);
264 
265         if (restore_sigcontext(regs, frame))
266                 goto badframe;
267 
268         ret = regs->areg[2];
269 
270         if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->areg[1]) == -EFAULT)
271                 goto badframe;
272 
273         return ret;
274 
275 badframe:
276         force_sig(SIGSEGV, current);
277         return 0;
278 }
279 
280 
281 
282 /*
283  * Set up a signal frame.
284  */
285 
286 static int
287 gen_return_code(unsigned char *codemem)
288 {
289         int err = 0;
290 
291         /*
292          * The 12-bit immediate is really split up within the 24-bit MOVI
293          * instruction.  As long as the above system call numbers fit within
294          * 8-bits, the following code works fine. See the Xtensa ISA for
295          * details.
296          */
297 
298 #if __NR_rt_sigreturn > 255
299 # error Generating the MOVI instruction below breaks!
300 #endif
301 
302 #ifdef __XTENSA_EB__   /* Big Endian version */
303         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
304         err |= __put_user(0x22, &codemem[0]);
305         err |= __put_user(0x0a, &codemem[1]);
306         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
307         /* Generate instruction:  SYSCALL */
308         err |= __put_user(0x00, &codemem[3]);
309         err |= __put_user(0x05, &codemem[4]);
310         err |= __put_user(0x00, &codemem[5]);
311 
312 #elif defined __XTENSA_EL__   /* Little Endian version */
313         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
314         err |= __put_user(0x22, &codemem[0]);
315         err |= __put_user(0xa0, &codemem[1]);
316         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
317         /* Generate instruction:  SYSCALL */
318         err |= __put_user(0x00, &codemem[3]);
319         err |= __put_user(0x50, &codemem[4]);
320         err |= __put_user(0x00, &codemem[5]);
321 #else
322 # error Must use compiler for Xtensa processors.
323 #endif
324 
325         /* Flush generated code out of the data cache */
326 
327         if (err == 0) {
328                 __invalidate_icache_range((unsigned long)codemem, 6UL);
329                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
330         }
331 
332         return err;
333 }
334 
335 
336 static int setup_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
337                        sigset_t *set, struct pt_regs *regs)
338 {
339         struct rt_sigframe *frame;
340         int err = 0;
341         int signal;
342         unsigned long sp, ra;
343 
344         sp = regs->areg[1];
345 
346         if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
347                 sp = current->sas_ss_sp + current->sas_ss_size;
348         }
349 
350         frame = (void *)((sp - sizeof(*frame)) & -16ul);
351 
352         if (regs->depc > 64)
353                 panic ("Double exception sys_sigreturn\n");
354 
355         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
356                 goto give_sigsegv;
357         }
358 
359         signal = current_thread_info()->exec_domain
360                 && current_thread_info()->exec_domain->signal_invmap
361                 && sig < 32
362                 ? current_thread_info()->exec_domain->signal_invmap[sig]
363                 : sig;
364 
365         if (ka->sa.sa_flags & SA_SIGINFO) {
366                 err |= copy_siginfo_to_user(&frame->info, info);
367         }
368 
369         /* Create the user context.  */
370 
371         err |= __put_user(0, &frame->uc.uc_flags);
372         err |= __put_user(0, &frame->uc.uc_link);
373         err |= __put_user((void *)current->sas_ss_sp,
374                           &frame->uc.uc_stack.ss_sp);
375         err |= __put_user(sas_ss_flags(regs->areg[1]),
376                           &frame->uc.uc_stack.ss_flags);
377         err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
378         err |= setup_sigcontext(frame, regs);
379         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
380 
381         if (ka->sa.sa_flags & SA_RESTORER) {
382                 ra = (unsigned long)ka->sa.sa_restorer;
383         } else {
384 
385                 /* Create sys_rt_sigreturn syscall in stack frame */
386 
387                 err |= gen_return_code(frame->retcode);
388 
389                 if (err) {
390                         goto give_sigsegv;
391                 }
392                 ra = (unsigned long) frame->retcode;
393         }
394 
395         /* 
396          * Create signal handler execution context.
397          * Return context not modified until this point.
398          */
399 
400         /* Set up registers for signal handler */
401         start_thread(regs, (unsigned long) ka->sa.sa_handler, 
402                      (unsigned long) frame);
403 
404         /* Set up a stack frame for a call4
405          * Note: PS.CALLINC is set to one by start_thread
406          */
407         regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
408         regs->areg[6] = (unsigned long) signal;
409         regs->areg[7] = (unsigned long) &frame->info;
410         regs->areg[8] = (unsigned long) &frame->uc;
411 
412         /* Set access mode to USER_DS.  Nomenclature is outdated, but
413          * functionality is used in uaccess.h
414          */
415         set_fs(USER_DS);
416 
417 #if DEBUG_SIG
418         printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
419                 current->comm, current->pid, signal, frame, regs->pc);
420 #endif
421 
422         return 0;
423 
424 give_sigsegv:
425         force_sigsegv(sig, current);
426         return -EFAULT;
427 }
428 
429 /*
430  * Atomically swap in the new signal mask, and wait for a signal.
431  */
432 
433 asmlinkage long xtensa_rt_sigsuspend(sigset_t __user *unewset, 
434                                      size_t sigsetsize,
435                                      long a2, long a3, long a4, long a5, 
436                                      struct pt_regs *regs)
437 {
438         sigset_t saveset, newset;
439 
440         /* XXX: Don't preclude handling different sized sigset_t's.  */
441         if (sigsetsize != sizeof(sigset_t))
442                 return -EINVAL;
443 
444         if (copy_from_user(&newset, unewset, sizeof(newset)))
445                 return -EFAULT;
446 
447         sigdelsetmask(&newset, ~_BLOCKABLE);
448         saveset = current->blocked;
449         set_current_blocked(&newset);
450 
451         regs->areg[2] = -EINTR;
452         while (1) {
453                 current->state = TASK_INTERRUPTIBLE;
454                 schedule();
455                 if (do_signal(regs, &saveset))
456                         return -EINTR;
457         }
458 }
459 
460 asmlinkage long xtensa_sigaltstack(const stack_t __user *uss, 
461                                    stack_t __user *uoss,
462                                    long a2, long a3, long a4, long a5,
463                                    struct pt_regs *regs)
464 {
465         return do_sigaltstack(uss, uoss, regs->areg[1]);
466 }
467 
468 
469 
470 /*
471  * Note that 'init' is a special process: it doesn't get signals it doesn't
472  * want to handle. Thus you cannot kill init even with a SIGKILL even by
473  * mistake.
474  *
475  * Note that we go through the signals twice: once to check the signals that
476  * the kernel can handle, and then we build all the user-level signal handling
477  * stack-frames in one go after that.
478  */
479 int do_signal(struct pt_regs *regs, sigset_t *oldset)
480 {
481         siginfo_t info;
482         int signr;
483         struct k_sigaction ka;
484 
485         if (!user_mode(regs))
486                 return 0;
487 
488         if (try_to_freeze())
489                 goto no_signal;
490 
491         if (!oldset)
492                 oldset = &current->blocked;
493 
494         task_pt_regs(current)->icountlevel = 0;
495 
496         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
497 
498         if (signr > 0) {
499                 int ret;
500 
501                 /* Are we from a system call? */
502 
503                 if ((signed)regs->syscall >= 0) {
504 
505                         /* If so, check system call restarting.. */
506 
507                         switch (regs->areg[2]) {
508                                 case -ERESTARTNOHAND:
509                                 case -ERESTART_RESTARTBLOCK:
510                                         regs->areg[2] = -EINTR;
511                                         break;
512 
513                                 case -ERESTARTSYS:
514                                         if (!(ka.sa.sa_flags & SA_RESTART)) {
515                                                 regs->areg[2] = -EINTR;
516                                                 break;
517                                         }
518                                         /* fallthrough */
519                                 case -ERESTARTNOINTR:
520                                         regs->areg[2] = regs->syscall;
521                                         regs->pc -= 3;
522                                         break;
523 
524                                 default:
525                                         /* nothing to do */
526                                         if (regs->areg[2] != 0)
527                                         break;
528                         }
529                 }
530 
531                 /* Whee!  Actually deliver the signal.  */
532                 /* Set up the stack frame */
533                 ret = setup_frame(signr, &ka, &info, oldset, regs);
534                 if (ret)
535                         return ret;
536 
537                 block_sigmask(&ka, signr);
538                 if (current->ptrace & PT_SINGLESTEP)
539                         task_pt_regs(current)->icountlevel = 1;
540 
541                 return 1;
542         }
543 
544 no_signal:
545         /* Did we come from a system call? */
546         if ((signed) regs->syscall >= 0) {
547                 /* Restart the system call - no handlers present */
548                 switch (regs->areg[2]) {
549                 case -ERESTARTNOHAND:
550                 case -ERESTARTSYS:
551                 case -ERESTARTNOINTR:
552                         regs->areg[2] = regs->syscall;
553                         regs->pc -= 3;
554                         break;
555                 case -ERESTART_RESTARTBLOCK:
556                         regs->areg[2] = __NR_restart_syscall;
557                         regs->pc -= 3;
558                         break;
559                 }
560         }
561         if (current->ptrace & PT_SINGLESTEP)
562                 task_pt_regs(current)->icountlevel = 1;
563         return 0;
564 }
565 
566 

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