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/resume_user_mode.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 #if defined(USER_SUPPORT_WINDOWED)
49 /*
50 * Flush register windows stored in pt_regs to stack.
51 * Returns 1 for errors.
52 */
53
54 static int
flush_window_regs_user(struct pt_regs * regs)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(&SPILL_SLOT_CALL8(sp, 4),
94 ®s->areg[(base + 1) * 4], 16))
95 goto errout;
96 inc = 2;
97
98 } else if (m & 8) { /* call12 */
99 if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
100 ®s->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(&SPILL_SLOT(sp, 0), ®s->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 #else
126 static int
flush_window_regs_user(struct pt_regs * regs)127 flush_window_regs_user(struct pt_regs *regs)
128 {
129 return 0;
130 }
131 #endif
132
133 /*
134 * Note: We don't copy double exception 'regs', we have to finish double exc.
135 * first before we return to signal handler! This dbl.exc.handler might cause
136 * another double exception, but I think we are fine as the situation is the
137 * same as if we had returned to the signal handerl and got an interrupt
138 * immediately...
139 */
140
141 static int
setup_sigcontext(struct rt_sigframe __user * frame,struct pt_regs * regs)142 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
143 {
144 struct sigcontext __user *sc = &frame->uc.uc_mcontext;
145 struct thread_info *ti = current_thread_info();
146 int err = 0;
147
148 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x)
149 COPY(pc);
150 COPY(ps);
151 COPY(lbeg);
152 COPY(lend);
153 COPY(lcount);
154 COPY(sar);
155 #undef COPY
156
157 err |= flush_window_regs_user(regs);
158 err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
159 err |= __put_user(0, &sc->sc_xtregs);
160
161 if (err)
162 return err;
163
164 #if XTENSA_HAVE_COPROCESSORS
165 coprocessor_flush_release_all(ti);
166 err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
167 sizeof (frame->xtregs.cp));
168 #endif
169 err |= __copy_to_user(&frame->xtregs.opt, ®s->xtregs_opt,
170 sizeof (xtregs_opt_t));
171 err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
172 sizeof (xtregs_user_t));
173
174 err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
175
176 return err;
177 }
178
179 static int
restore_sigcontext(struct pt_regs * regs,struct rt_sigframe __user * frame)180 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
181 {
182 struct sigcontext __user *sc = &frame->uc.uc_mcontext;
183 struct thread_info *ti = current_thread_info();
184 unsigned int err = 0;
185 unsigned long ps;
186
187 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x)
188 COPY(pc);
189 COPY(lbeg);
190 COPY(lend);
191 COPY(lcount);
192 COPY(sar);
193 #undef COPY
194
195 /* All registers were flushed to stack. Start with a pristine frame. */
196
197 regs->wmask = 1;
198 regs->windowbase = 0;
199 regs->windowstart = 1;
200
201 regs->syscall = NO_SYSCALL; /* disable syscall checks */
202
203 /* For PS, restore only PS.CALLINC.
204 * Assume that all other bits are either the same as for the signal
205 * handler, or the user mode value doesn't matter (e.g. PS.OWB).
206 */
207 err |= __get_user(ps, &sc->sc_ps);
208 regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
209
210 /* Additional corruption checks */
211
212 if ((regs->lcount > 0)
213 && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
214 err = 1;
215
216 err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
217
218 if (err)
219 return err;
220
221 /* The signal handler may have used coprocessors in which
222 * case they are still enabled. We disable them to force a
223 * reloading of the original task's CP state by the lazy
224 * context-switching mechanisms of CP exception handling.
225 * Also, we essentially discard any coprocessor state that the
226 * signal handler created. */
227
228 #if XTENSA_HAVE_COPROCESSORS
229 coprocessor_release_all(ti);
230 err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
231 sizeof (frame->xtregs.cp));
232 #endif
233 err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
234 sizeof (xtregs_user_t));
235 err |= __copy_from_user(®s->xtregs_opt, &frame->xtregs.opt,
236 sizeof (xtregs_opt_t));
237
238 return err;
239 }
240
241
242 /*
243 * Do a signal return; undo the signal stack.
244 */
245
xtensa_rt_sigreturn(void)246 asmlinkage long xtensa_rt_sigreturn(void)
247 {
248 struct pt_regs *regs = current_pt_regs();
249 struct rt_sigframe __user *frame;
250 sigset_t set;
251 int ret;
252
253 /* Always make any pending restarted system calls return -EINTR */
254 current->restart_block.fn = do_no_restart_syscall;
255
256 if (regs->depc > 64)
257 panic("rt_sigreturn in double exception!\n");
258
259 frame = (struct rt_sigframe __user *) regs->areg[1];
260
261 if (!access_ok(frame, sizeof(*frame)))
262 goto badframe;
263
264 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
265 goto badframe;
266
267 set_current_blocked(&set);
268
269 if (restore_sigcontext(regs, frame))
270 goto badframe;
271
272 ret = regs->areg[2];
273
274 if (restore_altstack(&frame->uc.uc_stack))
275 goto badframe;
276
277 return ret;
278
279 badframe:
280 force_sig(SIGSEGV);
281 return 0;
282 }
283
284
285
286 /*
287 * Set up a signal frame.
288 */
289
290 static int
gen_return_code(unsigned char * codemem)291 gen_return_code(unsigned char *codemem)
292 {
293 int err = 0;
294
295 /*
296 * The 12-bit immediate is really split up within the 24-bit MOVI
297 * instruction. As long as the above system call numbers fit within
298 * 8-bits, the following code works fine. See the Xtensa ISA for
299 * details.
300 */
301
302 #if __NR_rt_sigreturn > 255
303 # error Generating the MOVI instruction below breaks!
304 #endif
305
306 #ifdef __XTENSA_EB__ /* Big Endian version */
307 /* Generate instruction: MOVI a2, __NR_rt_sigreturn */
308 err |= __put_user(0x22, &codemem[0]);
309 err |= __put_user(0x0a, &codemem[1]);
310 err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
311 /* Generate instruction: SYSCALL */
312 err |= __put_user(0x00, &codemem[3]);
313 err |= __put_user(0x05, &codemem[4]);
314 err |= __put_user(0x00, &codemem[5]);
315
316 #elif defined __XTENSA_EL__ /* Little Endian version */
317 /* Generate instruction: MOVI a2, __NR_rt_sigreturn */
318 err |= __put_user(0x22, &codemem[0]);
319 err |= __put_user(0xa0, &codemem[1]);
320 err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
321 /* Generate instruction: SYSCALL */
322 err |= __put_user(0x00, &codemem[3]);
323 err |= __put_user(0x50, &codemem[4]);
324 err |= __put_user(0x00, &codemem[5]);
325 #else
326 # error Must use compiler for Xtensa processors.
327 #endif
328
329 /* Flush generated code out of the data cache */
330
331 if (err == 0) {
332 __invalidate_icache_range((unsigned long)codemem, 6UL);
333 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
334 }
335
336 return err;
337 }
338
339
setup_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)340 static int setup_frame(struct ksignal *ksig, sigset_t *set,
341 struct pt_regs *regs)
342 {
343 struct rt_sigframe *frame;
344 int err = 0, sig = ksig->sig;
345 unsigned long sp, ra, tp, ps;
346 unsigned int base;
347
348 sp = regs->areg[1];
349
350 if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
351 sp = current->sas_ss_sp + current->sas_ss_size;
352 }
353
354 frame = (void *)((sp - sizeof(*frame)) & -16ul);
355
356 if (regs->depc > 64)
357 panic ("Double exception sys_sigreturn\n");
358
359 if (!access_ok(frame, sizeof(*frame))) {
360 return -EFAULT;
361 }
362
363 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
364 err |= copy_siginfo_to_user(&frame->info, &ksig->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 (ksig->ka.sa.sa_flags & SA_RESTORER) {
376 ra = (unsigned long)ksig->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 return -EFAULT;
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 ps = regs->ps;
397 start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler,
398 (unsigned long) frame);
399
400 /* Set up a stack frame for a call4 if userspace uses windowed ABI */
401 if (ps & PS_WOE_MASK) {
402 base = 4;
403 regs->areg[base] =
404 (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
405 ps = (ps & ~(PS_CALLINC_MASK | PS_OWB_MASK)) |
406 (1 << PS_CALLINC_SHIFT);
407 } else {
408 base = 0;
409 regs->areg[base] = (unsigned long) ra;
410 }
411 regs->areg[base + 2] = (unsigned long) sig;
412 regs->areg[base + 3] = (unsigned long) &frame->info;
413 regs->areg[base + 4] = (unsigned long) &frame->uc;
414 regs->threadptr = tp;
415 regs->ps = ps;
416
417 pr_debug("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08lx\n",
418 current->comm, current->pid, sig, frame, regs->pc);
419
420 return 0;
421 }
422
423 /*
424 * Note that 'init' is a special process: it doesn't get signals it doesn't
425 * want to handle. Thus you cannot kill init even with a SIGKILL even by
426 * mistake.
427 *
428 * Note that we go through the signals twice: once to check the signals that
429 * the kernel can handle, and then we build all the user-level signal handling
430 * stack-frames in one go after that.
431 */
do_signal(struct pt_regs * regs)432 static void do_signal(struct pt_regs *regs)
433 {
434 struct ksignal ksig;
435
436 task_pt_regs(current)->icountlevel = 0;
437
438 if (get_signal(&ksig)) {
439 int ret;
440
441 /* Are we from a system call? */
442
443 if (regs->syscall != NO_SYSCALL) {
444
445 /* If so, check system call restarting.. */
446
447 switch (regs->areg[2]) {
448 case -ERESTARTNOHAND:
449 case -ERESTART_RESTARTBLOCK:
450 regs->areg[2] = -EINTR;
451 break;
452
453 case -ERESTARTSYS:
454 if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
455 regs->areg[2] = -EINTR;
456 break;
457 }
458 fallthrough;
459 case -ERESTARTNOINTR:
460 regs->areg[2] = regs->syscall;
461 regs->pc -= 3;
462 break;
463
464 default:
465 /* nothing to do */
466 if (regs->areg[2] != 0)
467 break;
468 }
469 }
470
471 /* Whee! Actually deliver the signal. */
472 /* Set up the stack frame */
473 ret = setup_frame(&ksig, sigmask_to_save(), regs);
474 signal_setup_done(ret, &ksig, 0);
475 if (test_thread_flag(TIF_SINGLESTEP))
476 task_pt_regs(current)->icountlevel = 1;
477
478 return;
479 }
480
481 /* Did we come from a system call? */
482 if (regs->syscall != NO_SYSCALL) {
483 /* Restart the system call - no handlers present */
484 switch (regs->areg[2]) {
485 case -ERESTARTNOHAND:
486 case -ERESTARTSYS:
487 case -ERESTARTNOINTR:
488 regs->areg[2] = regs->syscall;
489 regs->pc -= 3;
490 break;
491 case -ERESTART_RESTARTBLOCK:
492 regs->areg[2] = __NR_restart_syscall;
493 regs->pc -= 3;
494 break;
495 }
496 }
497
498 /* If there's no signal to deliver, we just restore the saved mask. */
499 restore_saved_sigmask();
500
501 if (test_thread_flag(TIF_SINGLESTEP))
502 task_pt_regs(current)->icountlevel = 1;
503 return;
504 }
505
do_notify_resume(struct pt_regs * regs)506 void do_notify_resume(struct pt_regs *regs)
507 {
508 if (test_thread_flag(TIF_SIGPENDING) ||
509 test_thread_flag(TIF_NOTIFY_SIGNAL))
510 do_signal(regs);
511
512 if (test_thread_flag(TIF_NOTIFY_RESUME))
513 resume_user_mode_work(regs);
514 }
515