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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 #include <linux/sched/task_stack.h>
 24 
 25 #include <asm/ucontext.h>
 26 #include <linux/uaccess.h>
 27 #include <asm/cacheflush.h>
 28 #include <asm/coprocessor.h>
 29 #include <asm/unistd.h>
 30 
 31 extern struct task_struct *coproc_owners[];
 32 
 33 struct rt_sigframe
 34 {
 35         struct siginfo info;
 36         struct ucontext uc;
 37         struct {
 38                 xtregs_opt_t opt;
 39                 xtregs_user_t user;
 40 #if XTENSA_HAVE_COPROCESSORS
 41                 xtregs_coprocessor_t cp;
 42 #endif
 43         } xtregs;
 44         unsigned char retcode[6];
 45         unsigned int window[4];
 46 };
 47 
 48 /* 
 49  * Flush register windows stored in pt_regs to stack.
 50  * Returns 1 for errors.
 51  */
 52 
 53 int
 54 flush_window_regs_user(struct pt_regs *regs)
 55 {
 56         const unsigned long ws = regs->windowstart;
 57         const unsigned long wb = regs->windowbase;
 58         unsigned long sp = 0;
 59         unsigned long wm;
 60         int err = 1;
 61         int base;
 62 
 63         /* Return if no other frames. */
 64 
 65         if (regs->wmask == 1)
 66                 return 0;
 67 
 68         /* Rotate windowmask and skip empty frames. */
 69 
 70         wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
 71         base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
 72                 
 73         /* For call8 or call12 frames, we need the previous stack pointer. */
 74 
 75         if ((regs->wmask & 2) == 0)
 76                 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
 77                         goto errout;
 78 
 79         /* Spill frames to stack. */
 80 
 81         while (base < XCHAL_NUM_AREGS / 4) {
 82 
 83                 int m = (wm >> base);
 84                 int inc = 0;
 85 
 86                 /* Save registers a4..a7 (call8) or a4...a11 (call12) */
 87 
 88                 if (m & 2) {                    /* call4 */
 89                         inc = 1;
 90 
 91                 } else if (m & 4) {             /* call8 */
 92                         if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4),
 93                                          &regs->areg[(base + 1) * 4], 16))
 94                                 goto errout;
 95                         inc = 2;
 96 
 97                 } else if (m & 8) {     /* call12 */
 98                         if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
 99                                          &regs->areg[(base + 1) * 4], 32))
100                                 goto errout;
101                         inc = 3;
102                 }
103 
104                 /* Save current frame a0..a3 under next SP */
105 
106                 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
107                 if (copy_to_user(&SPILL_SLOT(sp, 0), &regs->areg[base * 4], 16))
108                         goto errout;
109 
110                 /* Get current stack pointer for next loop iteration. */
111 
112                 sp = regs->areg[base * 4 + 1];
113                 base += inc;
114         }
115 
116         regs->wmask = 1;
117         regs->windowstart = 1 << wb;
118 
119         return 0;
120 
121 errout:
122         return err;
123 }
124 
125 /*
126  * Note: We don't copy double exception 'regs', we have to finish double exc. 
127  * first before we return to signal handler! This dbl.exc.handler might cause 
128  * another double exception, but I think we are fine as the situation is the 
129  * same as if we had returned to the signal handerl and got an interrupt 
130  * immediately...
131  */
132 
133 static int
134 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
135 {
136         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
137         struct thread_info *ti = current_thread_info();
138         int err = 0;
139 
140 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
141         COPY(pc);
142         COPY(ps);
143         COPY(lbeg);
144         COPY(lend);
145         COPY(lcount);
146         COPY(sar);
147 #undef COPY
148 
149         err |= flush_window_regs_user(regs);
150         err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
151         err |= __put_user(0, &sc->sc_xtregs);
152 
153         if (err)
154                 return err;
155 
156 #if XTENSA_HAVE_COPROCESSORS
157         coprocessor_flush_all(ti);
158         coprocessor_release_all(ti);
159         err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
160                               sizeof (frame->xtregs.cp));
161 #endif
162         err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
163                               sizeof (xtregs_opt_t));
164         err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
165                               sizeof (xtregs_user_t));
166 
167         err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
168 
169         return err;
170 }
171 
172 static int
173 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
174 {
175         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
176         struct thread_info *ti = current_thread_info();
177         unsigned int err = 0;
178         unsigned long ps;
179 
180 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
181         COPY(pc);
182         COPY(lbeg);
183         COPY(lend);
184         COPY(lcount);
185         COPY(sar);
186 #undef COPY
187 
188         /* All registers were flushed to stack. Start with a pristine frame. */
189 
190         regs->wmask = 1;
191         regs->windowbase = 0;
192         regs->windowstart = 1;
193 
194         regs->syscall = NO_SYSCALL;     /* disable syscall checks */
195 
196         /* For PS, restore only PS.CALLINC.
197          * Assume that all other bits are either the same as for the signal
198          * handler, or the user mode value doesn't matter (e.g. PS.OWB).
199          */
200         err |= __get_user(ps, &sc->sc_ps);
201         regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
202 
203         /* Additional corruption checks */
204 
205         if ((regs->lcount > 0)
206             && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
207                 err = 1;
208 
209         err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
210 
211         if (err)
212                 return err;
213 
214         /* The signal handler may have used coprocessors in which
215          * case they are still enabled.  We disable them to force a
216          * reloading of the original task's CP state by the lazy
217          * context-switching mechanisms of CP exception handling.
218          * Also, we essentially discard any coprocessor state that the
219          * signal handler created. */
220 
221 #if XTENSA_HAVE_COPROCESSORS
222         coprocessor_release_all(ti);
223         err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
224                                 sizeof (frame->xtregs.cp));
225 #endif
226         err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
227                                 sizeof (xtregs_user_t));
228         err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
229                                 sizeof (xtregs_opt_t));
230 
231         return err;
232 }
233 
234 
235 /*
236  * Do a signal return; undo the signal stack.
237  */
238 
239 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
240                                     long a4, long a5, struct pt_regs *regs)
241 {
242         struct rt_sigframe __user *frame;
243         sigset_t set;
244         int ret;
245 
246         /* Always make any pending restarted system calls return -EINTR */
247         current->restart_block.fn = do_no_restart_syscall;
248 
249         if (regs->depc > 64)
250                 panic("rt_sigreturn in double exception!\n");
251 
252         frame = (struct rt_sigframe __user *) regs->areg[1];
253 
254         if (!access_ok(frame, sizeof(*frame)))
255                 goto badframe;
256 
257         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
258                 goto badframe;
259 
260         set_current_blocked(&set);
261 
262         if (restore_sigcontext(regs, frame))
263                 goto badframe;
264 
265         ret = regs->areg[2];
266 
267         if (restore_altstack(&frame->uc.uc_stack))
268                 goto badframe;
269 
270         return ret;
271 
272 badframe:
273         force_sig(SIGSEGV, current);
274         return 0;
275 }
276 
277 
278 
279 /*
280  * Set up a signal frame.
281  */
282 
283 static int
284 gen_return_code(unsigned char *codemem)
285 {
286         int err = 0;
287 
288         /*
289          * The 12-bit immediate is really split up within the 24-bit MOVI
290          * instruction.  As long as the above system call numbers fit within
291          * 8-bits, the following code works fine. See the Xtensa ISA for
292          * details.
293          */
294 
295 #if __NR_rt_sigreturn > 255
296 # error Generating the MOVI instruction below breaks!
297 #endif
298 
299 #ifdef __XTENSA_EB__   /* Big Endian version */
300         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
301         err |= __put_user(0x22, &codemem[0]);
302         err |= __put_user(0x0a, &codemem[1]);
303         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
304         /* Generate instruction:  SYSCALL */
305         err |= __put_user(0x00, &codemem[3]);
306         err |= __put_user(0x05, &codemem[4]);
307         err |= __put_user(0x00, &codemem[5]);
308 
309 #elif defined __XTENSA_EL__   /* Little Endian version */
310         /* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
311         err |= __put_user(0x22, &codemem[0]);
312         err |= __put_user(0xa0, &codemem[1]);
313         err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
314         /* Generate instruction:  SYSCALL */
315         err |= __put_user(0x00, &codemem[3]);
316         err |= __put_user(0x50, &codemem[4]);
317         err |= __put_user(0x00, &codemem[5]);
318 #else
319 # error Must use compiler for Xtensa processors.
320 #endif
321 
322         /* Flush generated code out of the data cache */
323 
324         if (err == 0) {
325                 __invalidate_icache_range((unsigned long)codemem, 6UL);
326                 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
327         }
328 
329         return err;
330 }
331 
332 
333 static int setup_frame(struct ksignal *ksig, sigset_t *set,
334                        struct pt_regs *regs)
335 {
336         struct rt_sigframe *frame;
337         int err = 0, sig = ksig->sig;
338         unsigned long sp, ra, tp;
339 
340         sp = regs->areg[1];
341 
342         if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
343                 sp = current->sas_ss_sp + current->sas_ss_size;
344         }
345 
346         frame = (void *)((sp - sizeof(*frame)) & -16ul);
347 
348         if (regs->depc > 64)
349                 panic ("Double exception sys_sigreturn\n");
350 
351         if (!access_ok(frame, sizeof(*frame))) {
352                 return -EFAULT;
353         }
354 
355         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
356                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
357         }
358 
359         /* Create the user context.  */
360 
361         err |= __put_user(0, &frame->uc.uc_flags);
362         err |= __put_user(0, &frame->uc.uc_link);
363         err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
364         err |= setup_sigcontext(frame, regs);
365         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
366 
367         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
368                 ra = (unsigned long)ksig->ka.sa.sa_restorer;
369         } else {
370 
371                 /* Create sys_rt_sigreturn syscall in stack frame */
372 
373                 err |= gen_return_code(frame->retcode);
374 
375                 if (err) {
376                         return -EFAULT;
377                 }
378                 ra = (unsigned long) frame->retcode;
379         }
380 
381         /* 
382          * Create signal handler execution context.
383          * Return context not modified until this point.
384          */
385 
386         /* Set up registers for signal handler; preserve the threadptr */
387         tp = regs->threadptr;
388         start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler,
389                      (unsigned long) frame);
390 
391         /* Set up a stack frame for a call4
392          * Note: PS.CALLINC is set to one by start_thread
393          */
394         regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
395         regs->areg[6] = (unsigned long) sig;
396         regs->areg[7] = (unsigned long) &frame->info;
397         regs->areg[8] = (unsigned long) &frame->uc;
398         regs->threadptr = tp;
399 
400         pr_debug("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08lx\n",
401                  current->comm, current->pid, sig, frame, regs->pc);
402 
403         return 0;
404 }
405 
406 /*
407  * Note that 'init' is a special process: it doesn't get signals it doesn't
408  * want to handle. Thus you cannot kill init even with a SIGKILL even by
409  * mistake.
410  *
411  * Note that we go through the signals twice: once to check the signals that
412  * the kernel can handle, and then we build all the user-level signal handling
413  * stack-frames in one go after that.
414  */
415 static void do_signal(struct pt_regs *regs)
416 {
417         struct ksignal ksig;
418 
419         task_pt_regs(current)->icountlevel = 0;
420 
421         if (get_signal(&ksig)) {
422                 int ret;
423 
424                 /* Are we from a system call? */
425 
426                 if (regs->syscall != NO_SYSCALL) {
427 
428                         /* If so, check system call restarting.. */
429 
430                         switch (regs->areg[2]) {
431                                 case -ERESTARTNOHAND:
432                                 case -ERESTART_RESTARTBLOCK:
433                                         regs->areg[2] = -EINTR;
434                                         break;
435 
436                                 case -ERESTARTSYS:
437                                         if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
438                                                 regs->areg[2] = -EINTR;
439                                                 break;
440                                         }
441                                         /* fallthrough */
442                                 case -ERESTARTNOINTR:
443                                         regs->areg[2] = regs->syscall;
444                                         regs->pc -= 3;
445                                         break;
446 
447                                 default:
448                                         /* nothing to do */
449                                         if (regs->areg[2] != 0)
450                                         break;
451                         }
452                 }
453 
454                 /* Whee!  Actually deliver the signal.  */
455                 /* Set up the stack frame */
456                 ret = setup_frame(&ksig, sigmask_to_save(), regs);
457                 signal_setup_done(ret, &ksig, 0);
458                 if (current->ptrace & PT_SINGLESTEP)
459                         task_pt_regs(current)->icountlevel = 1;
460 
461                 return;
462         }
463 
464         /* Did we come from a system call? */
465         if (regs->syscall != NO_SYSCALL) {
466                 /* Restart the system call - no handlers present */
467                 switch (regs->areg[2]) {
468                 case -ERESTARTNOHAND:
469                 case -ERESTARTSYS:
470                 case -ERESTARTNOINTR:
471                         regs->areg[2] = regs->syscall;
472                         regs->pc -= 3;
473                         break;
474                 case -ERESTART_RESTARTBLOCK:
475                         regs->areg[2] = __NR_restart_syscall;
476                         regs->pc -= 3;
477                         break;
478                 }
479         }
480 
481         /* If there's no signal to deliver, we just restore the saved mask.  */
482         restore_saved_sigmask();
483 
484         if (current->ptrace & PT_SINGLESTEP)
485                 task_pt_regs(current)->icountlevel = 1;
486         return;
487 }
488 
489 void do_notify_resume(struct pt_regs *regs)
490 {
491         if (test_thread_flag(TIF_SIGPENDING))
492                 do_signal(regs);
493 
494         if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
495                 tracehook_notify_resume(regs);
496 }
497 

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